CA1324461C - Correction of incompetent venous valves - Google Patents
Correction of incompetent venous valvesInfo
- Publication number
- CA1324461C CA1324461C CA000542284A CA542284A CA1324461C CA 1324461 C CA1324461 C CA 1324461C CA 000542284 A CA000542284 A CA 000542284A CA 542284 A CA542284 A CA 542284A CA 1324461 C CA1324461 C CA 1324461C
- Authority
- CA
- Canada
- Prior art keywords
- band
- cuff
- vein
- venous
- cuff according
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
Links
Classifications
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B17/00—Surgical instruments, devices or methods, e.g. tourniquets
- A61B17/12—Surgical instruments, devices or methods, e.g. tourniquets for ligaturing or otherwise compressing tubular parts of the body, e.g. blood vessels, umbilical cord
- A61B17/12009—Implements for ligaturing other than by clamps or clips, e.g. using a loop with a slip knot
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
- A61F2/00—Filters implantable into blood vessels; Prostheses, i.e. artificial substitutes or replacements for parts of the body; Appliances for connecting them with the body; Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents
- A61F2/02—Prostheses implantable into the body
- A61F2/24—Heart valves ; Vascular valves, e.g. venous valves; Heart implants, e.g. passive devices for improving the function of the native valve or the heart muscle; Transmyocardial revascularisation [TMR] devices; Valves implantable in the body
- A61F2/2475—Venous valves
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
- A61F2/00—Filters implantable into blood vessels; Prostheses, i.e. artificial substitutes or replacements for parts of the body; Appliances for connecting them with the body; Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents
- A61F2/02—Prostheses implantable into the body
- A61F2/24—Heart valves ; Vascular valves, e.g. venous valves; Heart implants, e.g. passive devices for improving the function of the native valve or the heart muscle; Transmyocardial revascularisation [TMR] devices; Valves implantable in the body
- A61F2/2442—Annuloplasty rings or inserts for correcting the valve shape; Implants for improving the function of a native heart valve
Abstract
ABSTRACT OF THE DISCLOSURE
A cuff for restoring competence to an in-competent venous valve comprises a band of biocom-patible implantable material that is not stretchable at blood flow pressures, the band being of sufficient length to encompass the vein at the site of the venous valve, with portions of the band overlapping, the overlapping portions being joinable together to form a cuff of desired circumference small enough to restore competence yet not too tight to decrease blood flow;
in particular the band of the cuff may be notched to accommodate application at a venous juncture or may include loop means adjacent an end portion of the band to which the overlapping end portion of the band is joined.
A cuff for restoring competence to an in-competent venous valve comprises a band of biocom-patible implantable material that is not stretchable at blood flow pressures, the band being of sufficient length to encompass the vein at the site of the venous valve, with portions of the band overlapping, the overlapping portions being joinable together to form a cuff of desired circumference small enough to restore competence yet not too tight to decrease blood flow;
in particular the band of the cuff may be notched to accommodate application at a venous juncture or may include loop means adjacent an end portion of the band to which the overlapping end portion of the band is joined.
Description
CORRECTION OF INCOMPETENT VENOUS VALVES j:
FIELD OF INVENTIO~
This invention relates to the correction of incompetent venous valves.
venous ~alves in mammals are usually bicuspid valves, with each ~usp forming a sack or reservoir for blood which, under pressure, forces the free edges of the CUSp9 together to prevent retrograde flow of the blood and allow only antegrade flow to the heart. When an incompetent valve attempts to close in response to a pressure gradient across the valve, the cusps do not seal properly and retrograde flow of blood occurs.
There are~two chronic venous diseases in which inco~petence of venous valves is thought to be an important factor in the pathophysiology. These are varicose veins and chronic deep venous insuf ficiency.
~he varicose vein condition consists of dilatation and tortuosity of the superficial veins of the lower limb and resulting cosmetic impairment, pain and ulceration. Primary ,`
varicose veins are the result of primary incompetence of the venous valves separating the superficial venous system from ;
the deep venous system. Secondary varicose veins occur as ~ `
the result of deep venous hypertension which has damaged the valves of the perforating veins.
Chronic deep venous insufficiency consists of deep hypertension of the lower limb with associated pigmentation, ~ .
.. .~. .
.
FIELD OF INVENTIO~
This invention relates to the correction of incompetent venous valves.
venous ~alves in mammals are usually bicuspid valves, with each ~usp forming a sack or reservoir for blood which, under pressure, forces the free edges of the CUSp9 together to prevent retrograde flow of the blood and allow only antegrade flow to the heart. When an incompetent valve attempts to close in response to a pressure gradient across the valve, the cusps do not seal properly and retrograde flow of blood occurs.
There are~two chronic venous diseases in which inco~petence of venous valves is thought to be an important factor in the pathophysiology. These are varicose veins and chronic deep venous insuf ficiency.
~he varicose vein condition consists of dilatation and tortuosity of the superficial veins of the lower limb and resulting cosmetic impairment, pain and ulceration. Primary ,`
varicose veins are the result of primary incompetence of the venous valves separating the superficial venous system from ;
the deep venous system. Secondary varicose veins occur as ~ `
the result of deep venous hypertension which has damaged the valves of the perforating veins.
Chronic deep venous insufficiency consists of deep hypertension of the lower limb with associated pigmentation, ~ .
.. .~. .
.
-2- 1 324~
pain, swelling, ulceration and varicose veins.
For the sake of convenience, the invention will be described in relation to the correction of incompetent valves in the venous system of the lower limb in man, but, it is to be understood that the invention is not limited thereto.
The venous system of the lower limb consists essentially of the superf icial venous system and the deep venous system. The superficial system includes the great saphenous vein and the small saphenous vein~ The deep venous system includes the anterior and posterior tibial veins which unite to form the popliteal vein which in turn becomes the femoral vein when joined by the small saphenous vein~ `
The initial defect in primary varicose veins often involves localised imcompetence of a venous valve thus allowing reflux of blood from the deep venous sytem to the ' ~
superficial venous system. ~bis incompetence is ,, :`
traditionally thought to arise at the saphenofemoral junction but may also start at the perforators~ Thus, gross saphenofemoral valvular dys~unction may be present in even mild~varicose veins with competent distal veins~ Even in the presence of incompetent perforators, occlusion of the sap~enofemoral junction usually normalises venous pressure~
~he initial defect in secondary varicose veins is often incompetence of a venous valve secondary to hypertension in ?5 the deep venous system~ Since this increased pressure is manifested at many points, correction of one site of :
. . .
~ ~ incompetence could clearly be insufficient as other sites of : -....... .. ..
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. .. . .
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_3_ 1 32446~
incompetence will be prone to develop. Apart from the initial defect, the pathophysiology is similar to that of varicose veins.
Once the initial incompetence occurs, incompetence in other valves in the system will tend to occur secondary to the venous hypertension.
Apparently, incompetence of venous valves is caused by dilatation of the vein wall. The evidence for this is as follows:-i? The valv~s in varicose veins are normal macroscopically and histologically in most cases.
The vein wall is more distensible in apparenely ~-normal veins in people with varicose veins~
ii) The valve cusps have a much greaeer tensile strength than the vein wall~ ` `
iii) Venous function deteriorates during the day as the venous system becomes more dilated. ` `
iv) Saphenofemoral va~lves which are incompetent can .. .
become competent again at operation when the diameter is decreased by spasm. A similar occurence has been noted in the superficial femoral vein.
v) Varicose veins may temporarily appear during pregnancy before the uterus is large enough eO --cause venous obstruction.
; ~ vi) Forearm veins ~hich are incompetent when full and distended can become competent again when the ., ;,`~."`','' 1 3~4b$
. .
distal segment is emptied thus reducing the diame~er. Valves which are competent can be made incompetent by injection of local anaesthetic which caused venodilatation~
s Thus, it appears that dila ation of the vein wall, whether idiopathic (primary varicose veins) or secondary to venous hypertension ~secondary varicose veins) leads to valvular incompetence. This dilatation may eventually lead to stretching and sclerosis of the valve. Other valves in the system will tend to become incompetent as ~he reflux of ,~
blood causes dilataeion of the vein wall. We have found that `
it is possible to reverse or prevent the destructive process by overcoming this dilatation. Even if tbe vein wall wea~ness is generalised as appears to be the case with `
primary varicose veins, correction of the initial defect will delay or prevent stress being placed on that wall and thus ~"` `;
hind progression of the disease.
The fundamental change in flow in primary varicose veins is raflux of blood from the deep venous system into the ~20 superfici~l venous system, usually the great saphenous vein.
Traaitionally, chronic deep venous insufficiency is reg~rded as being secondary eO deep venous thrombosis which either Obseructs the vein or is recanalised with associated ``
destruction of the deep venous valves. The obstruction is `' initially prominent but as recanalisation occurs and ;
collateral circulation develops, the obstruction is less prominent. Then the ~enou-~ incompetence becomes more :, . .:
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` ~5~ 1324461 prominent. This syndrome follows deep venous thrombosis in a majority of ~ases .
Deep venous thrombosis is involved in the majority of cases of post-phlebetic syndrome but other factors such as site of deep venous thrombosis, obesity, muscle activity, posture and genetic predisposition may be involved. A
primary inco~petence of the venous valves appears to be -involved in a significant number of cases~ ~`
BACKGROUND ART
In the main, prior art approaches to restoring competency of incompetent valves has involved venous reconstruction surgery of three basic kinds, namely, venous valve transplants, venous transposition and venous valvuloplasty.
As the tera implies, the venous valve transplant approach involves the replacement of the segment of the vein having the incompetent valve with a segment of another vein having a competent valve. The venous transposition approach ``
~ ~involves the redirection o~ the venous system so as to bypass an incompetent ~alve and venous valvuloplasty involves venous ~alve reconstructive surgery in which the free length of the valve cusps is reduced by plicating sutures. ~ - `
These approaches to the prior art are well documented in A RATIONAL APPROACH TO 5URGERY OF THE CHRONIC VENOUS STAS IS `-~ SYNDROME by Harry Schan~er AND E Converse Peirce ANNALS OF
SURGERY 1982, 195: 25 - 29 as well as in VALVULOPLASTY AND .``
VALVE TRANSF~R by Seshadri Raju Inter. Angio. 4 1985 419-424. ~ ---6- 1 32446~
A single example on one patient of an experimental technique for treating an incompetent venous valve not involving the above types of venous surgery is described in an article by Dag Hallberg in ACTA CHIR SCAND 138: 193-145, 1972. Hallberg placed a band two to three millimetres larger than the diameter of the view around the vein.
The band was made of DACRON polyester and polyester and was applied when the patient was in the horizontal ~`
position~ The band was retained loosely in position by several sutures in the venous adventitia~ ;
Hallberg's method could not restore competence to the majority of the incompetent venous valves~ In patients with venous disease, incompetent valve~ will usually be -incompetent in the horisontal as well as the vertical positions~ See, for example, FENORAL VEIN RECONSTRUCTION IN
THE MANAGENENT OF CHRONIC VENOUS INSU~FICIENCY by Ferris E.B~ -and Ristner R., ARCHIVES OF SURGERY, 1982, 117:1571 - 1579. ``
~erris and Ristner operated on 53 femoral veins in which the valves had been demonstrated pre-operatively to be -`
incompetent. In only one case was the valve noted to be co~petent when tbe patient was horizontal at the time of operation. Risener's approach was to suture the vein to prevent post-operative dilatation. `
It is ~ell known that by itself DACRON ~Registered Trade ~5 Mark) polyester material causes marked fibrosis as well as foreign body reaction. Therefore, DACRON polyester cannot alone be conridered bioco~patible. In fact, DACRON polyester "~
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~7~ 1 324~6~
has been employed to stimulate fibrotic reactions which incorporate the synthetic fabric into tissue (see: s. Raju, .
ANN. SURG. (1983) 197, 688-697).
The article REVASCULATION OF SEVERELY ISCHEMIC
EXTR~MI~IES WITH AN ARTERIOVENOUS FISTULA by F.W. slaisdell et al in AMERICAN JOURNAL OF SURGERY, Volume 112, pages 166-173 discloses problems associated with the use of DACRON -polyester as an implantable material. In a number of cases, gradual narrowing of arteriovenous fistulas under a woven DACRON polyester sleeve was demonstrated.
In physical terms, Hallberg approach was a static one.
Once the cuff was sutured into position, no attempt was made to reduce the diameter of the vein at the valve site to restore competency of the valve. Indeed, Nallberg's single patient experiment was concerned with further dilatation of ~ "
the vein at the valve site rather than reduction in the dia~eter of the dilated valve to restore competency.
DISCLOSUR~ OF T~E INV~NTIO~
It is an object of this invention to provide a method ` `
for restoring competence of incompetent venous valves by reducing the diameter of the appropriate vein at the valve site.
It is a further ob~ect of the invention to provide a method for restoring competence of incompetent venous valves in ~hich the diameter of the vein at the valve site is ad~u~ted to achieve proper competence of the valve and which : `
permits clinical testing at the time of diameter reduction. ~ ~
. ., ~ . `' ~ ~ ~ ' ` ;;` `"
-8- t324461 It is a yet another object of the invention to provide a device for restoring competence of an incompetent venous valve which is biocompatible and which does not require suturing to the vein itself.
According to one aspect of the invention there is provided a cuff for restoring competence to an incomptetent '; -.
venous valve, said cuff comprising a band of biocompatible `~
implantable material that is not strètchable at blood flow . -pressures, the band being of sufficient length to emcompass the vein at the site of the venous valve, with portions of ` .:
the strap overlapping, the overlapping portions being .
joinable together to form a cuff of desired circumference ``
small enough to restore competence yet not too tight to ..
decrease blood flow~
According to anot~er aspect of the invention there is ` `:
provided a method of restoring compeeency to incompetent `-`
venous-valves co~prising the steps of ~
: . ` .
i) placing a cuff of biocompatible material around the vein at the site of the valve, ii) reducing the circum~erence of the cuff ~and hence ~i ~:~ ehe diamter of the vein at the valve site) until ~ "
competency of the valve in the vein is restored, `.:
. ~ ,~ and, ..
: ~ iii) fixing the circumference of the CUff at the point ~ where the diameter of the vein is reduced to ::.
restore competency of the valve without impairing :-~- blood flow. . ;`
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If necessary, the cuff is then secured to the surrounding. tissue. Preferably, the circumference of the cuff around the vein is reduced in a stepwise fashion with the competency of the valve being tested between each stepped reduction in the circumference of the cuff.
Competency of the valve may be tested by milking the vein, by the use of appropriate pressure detectors or by Doppler Techniques.
BRIEF DESCRIPTION OF THE DRAWINGS
In order that the invention may be more readily understood and put into practical effect, reference will now .
be made to ehe accompanying drawings in which:-Fig. 1 is a cutaway diagrammatic perspective view of one side of a vein at a valve ` :
. .
site with the valve in its closed disposition, ; Fig~ 2 is a plan view from above of the venous valve shown~in Fig. 1, Fig. 3 is a schematic view of a competent venous valve in its closed disposition, : ~ Fig. ~ is a schematic view~similar to Fig~ 3 but of an inoompetent valve, Fig. 5 is a perspective view of a venous cuff according to one embodiment of the invention, Fig. 6 is a perspective view of the cuff shown in Fig. X encircled around a vein, ~ Fig. 7 ls a p}an view of a second embodiment of a ~ -: venous cuff, ;: ' '; ' - " ' ";: ',~:' " -lo- 1 324461 Fig. 8 is a side elevational view of the cuff j, ~' shown in Fig. 3 in place at the junction of :
two veins, -'.
~ig. 9 is a plan view of a third embodiment of a ,.. ~.:
5venous cuff, .``'`~, Fig. 10 is a side elevational view of the cuff ~--shown in Fiq. 5 in place at the junction of two veins, ' .`.
Fig. 11 is a view similar to Fig. 6 but with : :.
10the strap position over the loop of the cuff, Fig. 12 is a graph of distal blood pressure against ,.", ;:
circumference of a vein at a valve site, and, ~`.i''~
Fig~ 13 is a graph of retrograde resistance against ```
.~ .
~ vein circumference at a valve site. ~ ~`.
- ~ 15~ ~ ESCRIPTION OF PREFERRED EMBODIMENTS `~`.
:. ~The valves in the venous system of man are almost .~' invariably bicuspid as is shown diagramatically in Fig. 1.
chlcusp 10, 11 i-Q semi-lunar ànd is àttàched to the wall of '`
` , the -ein 12 by its convex edge 13~. The concave edges 14 lie ~ `
20~free~io the direction of normal blood flow indicated by arrow .~
IF~ be~attaçhment~of each cusp approaches that of the other : :
- cusp~proximally to form the commissure 15. Proximai to the `.,`.
e,~ the ~ein is`more distens}ble for about l~cm. to form ,the -inus. In cross-section, whon closed, the cusps 10, 11 `25.~of~the~v~lve ~eet in a ~taight llne in the centre of the vein `
`1`2 as~sho~n:in Fig. 2. ~
~?~`It ~11 be appreciated that the venous valve is normally open with the free concave edges 14 separated by the upward flow of blood in the direction of arrow F. ~s will be apparent from Fig. 1, each cusp 10, 11 forms a sack or reservoir 16 for blood which, under pressure, in the direction of arrow R, forces the concave edges 14 together to prevent retrograde flow of blood - see Figs. 1 and 3.
There are 10 to 20 valves in the great saphenous vein and 7 to 13 in the small saphenous vein. The perorating veins also have valves except for the feet where they`are unusual. .~ -On standing at rest, the pressure in both the superficial and deep venous system correlates closely with the hydrostatic pressure of a column of blood at the height of the atrium, about 80-90mm. Flow in both superficial and deep systems is slow and is directed towards the heart ~antegrade)~ ~low in the perforators is also slow but tends to be from the superficial venous system to the deep venous ~syste~. The ~low in the foot is ehe reverse of that just ~ described - from the deep ~eins in the sole of the foot to the superficial ~eins on the dorsum of the foot.
The position changes markedly on exercise. On`calf contraction ~systole) the pressure and flow in the deep ~ ~ system increases and flo~ through the perforators ceases. On - ~ calf relaxation (diastole) the pressure and flow in the deep Jystem decrease and there is increased flow in the perforators from the superficial venous sytem to the deep venous system. Tbe mean venous pressure drops during ,.
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exercise by about 60-70mmHg. ~-These changes are the result of the musculo-venous pump, As the muscle contracts, blood is expelled towards the heart. The blood is prevented from moving into the superficial system by the valves in the perforating system.
On relaxation of ehe muscle the pressure drops but blood is prevented from reflux by the valves of the deep venous system and flow recommences from tbe superficial venous system to ;~
the deep venous system, through the perforators. The ~
musculo-venous pump is responsible for efficient venous -return in combination with the vis a tergo effect and of ~
intra-tboracic and intra-abdominal pressure. `
~ competent valve is shown diagramatically in Fig. 3 in ;~
its closed disposition and an incompetent valve in Fig. 4. " `
Tbe ~usps 10 and 11 of the competent valve in Fig. 3 form the blood sac~s 16. The length of vein 12 at the valve si~e is ` ``
indicated by ~L~ and the diameter of tbe vein, when the valve is competent, is indicated by ~d~. The extent of contact of the upper edges of the cusps when the valve is closed is `~
indicated by ~
When the diameter of the vein 12 is increased to "D" as " ;
sho~n in Fig. 4, the concave edges 14 of the cusps no longer meet and retrograde flow of blood can occur. The cusps 10a, lla shown in dotted outline in Fig. 4 represent the normal disposition of the cusps and thus it can be seen that ;;~
dilatation of the vein has led not only to separation of the cusps but also to a decrease in the general angle of the ~, `''~ .
: '`,"'.. , : '''' ` ; :' -13- 1 324~61 cusps to one another with a consequent lessening of the possible area of contact between the cusps should contact be possible at some diameter less than "Dn.
According to the present invention, it is possible to restore competence to an incompetent valve by decreasing the diameter of the vein wall at the valve site from the valve ~D~ of Fig. 4 towards but not necessarily to the diameter ~d"
of Fig. 3 by the use of a venous cuff.
The venous cuff 20 shown in Figs. 5 and 6 is made of a bio-compatible material that does not significantly react with a vein or its surrounds and which in this instance, is flexible but does not stretch at the pressures encountered in blood ~low. A preferred material is silicone rubber sheeting reinforced with embedded polyester fibres.
The venous cuff 20 consists of an elongated band 21 having a free end 22 and a loop 23 at its other end 24. As :
can be seen in Fig~ 5, the loop 23 extends above the upper ` "
face 25 of the band 21 so that it may receive the free end 22 ~
as shown in Fig. 6 ;
The loop 23 may be formed as a separate item that is glued to ~he band 2~. In this instance, the loop 23 is formed from a flat rectangular strap 26 of polyester ~`
reinforced, Do~ Corning Medical Grade silicone rubber sheet No. 501-1. The flat strap 26 has two straight slits 27 extending in~ardly from the opposite edges of the strap and cut parallel to and 2mm from the longitudinal side 28. The dimenJions of the strap 26 accordinq to one embodi~ent Iwhich `
-14- ~ 3z~
are given for ilLustrative purposes only) are as follows:-~ength 48.0 (~ 0.5) mm --sreadth 5.0 (~ 0.2) mm Thickness 0.178 ~ 0.076) mm Slit length 16.7 (~2-0.0) mm The slits 27 divide the loop 23 into an inner attachment portion 29 that is 2mm wide and an outer deformable portion 30 that is 3mm wide. The free ends of th~ attachment portion 29 are folded over one another to provide the loop 23. The free ends of the deformable portion 30 are each folded over -themselves and secured between each folded portion by means of a suitable adhesive is a securing tab 31 by means of which the cuff may be sutured to neighbouring tissue.
, In this instance, the band 21 is formed from a flat piece of polyester reinforced Dow Corning Medical Grade ~15 silicone rubbar sheet No~ 501-3. A hole 32 may be cut in the , `
"` tapered end 22 of the band 21 for attaching the band 21 to a mechanical applicator. The dimensions of the band 21 àccotding to one embodimen~ which are given for illustrative `
purposes only are as follows~
20~ Length 68.0~0.5) mm `~
Breadth l5.0t~0.5) mm ~ , ~ ; Thickness0.503~0.Q~6) mm ~ i .
Taper Length20.0(~0.5) mm Taper Breadth10.0(~0.5) mm ~ .
25 ~ Hole diameter3.0(~0.2) mm `' As will be apparent from the above dimensions, the ::
: :
deformable portion 30 is made from thinner material than the band 21 in order to decrease any possible effects that cuff surface discontinuities may have on the vein wall. ~he use of thinner material for the deformable portion 16 allows a smooth overlap inner surface on the cuff when implanted around a vein as is shown in Fiq. 7 and allows the cuff to assume the shape of the vein.
AS will be apparent from Fig. 6, with manual application of the cu~f, the loop end 24 of the band 21 is placed on the vein 33. The band 21 is then encircled around the vein 33 s and the free end 22 of the band 21 is passed through the loop "
23. When the circumference of the cuff has been reduced to the poin~ whereat the diameter of the vein is reduced to restore competency of the valve within the vein 33, the overlapping portions of the band 21 are fixed together by ~ ;
stapiing or suturing and, if necessary, the free end 22 of `
the band 21 beyond the suture or staple is removed by any ~``
convenient means~ The tabs 31 are then sutured to tissue ; `~
surrounding tbe vein to prevent the cuff from sliding along the vèin. ~
In an alternative method of application, the band could ` `
be looped in the other direction so that the free end of the ` `
.
band overlies the top of the loop as shown in Fig. 7.
~ he modified form of the venous cuff shown in Fig. 8 is ; 25 ~ particularly suitable for restoring the competence of a valve .
in a fir-qt vein having a junction with a second vein of the kind shown in Fig. 9. She cuff is substantially similar to .
.
-~ 1 324461 that shown in Fig. 5 and thus common elements share the same numerals.
A CUt out portion 40 in the uppèr edge 41 of the band 21 is so dimensioned to enable the cuff to assume the shape s shown in Fig. 9 when the cuff is positioned around a first veln 42 adjacent to its junction with a second vein 43.
The portions 44 of the band 21 adjacent to the cut-out 40 engage the vein as shown in Fig. 9 and the cuff is secured ~ -in position by means of one tab 31 being sutured to the tissue surrounding the vein 42 and the other tab 31 being , , `
sutured t~ tissue surrounding the vein 43. ;
The cuff shown in Fig~ 10 is substantially similar to `:
that shown in Fig. 8 except that the cut-out 50 is in the lower edge 51 of the band 21. The cut-out 50 is so di~ensioned to enable the cuff to assume the shape shown in Fig. 11 when the cuff is positioned around a first vein 52 adjacent to its junction with a second vein 53. `
~he portions 54 of the band 21 adjacent to the cut-out ;`
50 engage the vein 53 as shown in Fig. 11 and the cuff is ` ;.
secured into position by means of one tab 31 being`sutured to tiJsue surrounding the vein 52 and the other tab 31 being sutured to tissue surrounding the vein 53. `
It will be appreciated that the venous cuff may be made of any appropriate bio-compatible material that will not give `~ rl-e to any significant~adverse reactions within the body uch as thrombosis, stenosis ~i.e. narrowing of the vein) or perforation of the vein wall through wear and tear, The `
` -17- 132~461 overlapping portions of the band 21 may be secured together in any convenient way - with or without the loop or buckle arrangement shown in the drawings. ~he overlapping portions may be secured together by s~apling or suturing as described above, or by mechanical interlocking of parts of one portion with part o~ the other portion of the stap at the overlap, or by adhesive, or by heat sensitive or pressure sensitive means.
If the overlapping portions of the band 21 are secured together by means external of thè band such as by staples, sutures or adhesi`ves, the external means should be selected so that there is no adverse interaction between the fastening means and the cuff or therein or surrounding tissue. It is prèferred that neither the band nor the fastening means be - `
secured to the vein. -Although the above described cuffs incorporate tabs for `
securing the cuff to tissue surrounding the vein, such tabs àre not essential~ Anchoring of the cuff may not always be required - for example, the location of the cuff may not permit movement of the cuff along the vein or the material of the cuff may possess sufficient friction with respect to the vein so as to prevent movement of the cuff along the vein.
~he cuff may, of course, be of any convenient shape or configuration. As to its breadth ti.e. its dimension along the vein~, the minimum requirement is that the cuff should cover substantially all of the cusps of the vaive, preferably ': `
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with some 1 to 1~ 5mm excess at each end of the valve. The maximum breadth is limited by the general consideration that a single cuff should not span two venous valves.
The band is to be long enough to encircle the vein to `
which it is to be applied and to provide sufficient overlap to facilitate joining of the overlapping portions. As will be explained in more detail below, the overlapping arrangement of the band portions enables the circumference of -the cuff to be reduced to the desired value at which competence is restored. That is to say, the cuff is applied i in a dynamic way - the cuff circumference is initially larger than the diameter of the dilated ~rein and the circumference o~ the cuff is reduced until competency of the valve is detected.
The cuff may be manufactured from components as described above or formed as a one piece moulding~ -A use of the cuff will now be described in relation to incompetence of the sapheno-femoral valve. The function of the sapheno-femoral valve is to decrease the pressure in the long saphenous system.
When the sapheno-femoral valve becomes incompetent, the vein distal to this point is exposed to abnormally high :- ~
- ~ pressure ~hich in turn causes dilatation of the vein below ~ the ~apheno-femoral valve and incompetence of the corresponding valve. ~his sequence continues until the thin-walled tributaries of the internal saphenous vein are also : ~ . :' .''`
' '.," ,'`:~' , ~ .
: ~ ,,.''' :' 132446!
exposed to pressures that cause them to dilate, elongate and become tortuous - that is to say, they become varicose.
The above described sequential process commences because of the incompetence of the valve at the sapheno-femoral _ s junction. Thus, if the functional defect of the valve is corrected by surgery, the patient will be substantially free from risk of further varicose veins.
~he unction of the cu~f is to decrease the size of the sapheno-femoral vein at the valve site which pathologically ~-dilates and, as described above, the consequence incompetence of the valve causes varicose veins. The cuff is tightened around the vein at the valve site until the valve is assessed, during the operation, as being competent~ `
The standard surgical approach to the sapheno-femoral junction is used and the tributaries of the saphenous system are ~ied off be~ore placing the cuff in position. ` `
The sapheno-femoral valve band is so dimensioned as to encircle the sapheno-femoral vein at the valve site with the ends of the band overlapping so that they can be secured together in any convenient way. The sapheno-femoral valvè
can usually be seen through the vein wall and thus the cuff ; `~
can be correctly located by inspec~ion.
An integral securing tab may be provided in the mid , , .
portion of the strap that is preferably larger than the ``~
~ diameter of the vein at the valve. The securing tab may conveniently be of semi-circular shape and may be sutured to ~ ;~
the cribriform fascia above the sapheno-femoral valve using '::
: ~, :;` '.
,,'"~, ' fine non-absorbable sutures.
The use of the valve repairing cuff enables the main saphenous system to be left intact so that it may be used for coronary artery by-pass grafting, femoro-popliteal by-pass grafting and any of the other different types of by-pass grafting used in standard vascular surgery.
~he varicose veins that actually appear in the legs are tributaries of the main long saphenous system and are dilated and become tortuous because the walls of these veins are exceedingly thin. On the other hand, the main long saphenous system itself has thick walls three to four times as thic~ as its tribùtaries and indeed has more muscle in its walls than any other vein in the body. Thus, this vein may be relatively normal whilst its tributaries become dilated.
The insertion of the venous cuff at the sapheno-femoral junction preserves the long saphenous system and a standard removal of varicose tributaries can be performed at the same -proc dure.
It has been noted while using the venous cuff of the invention that the restoration of competence to a valve `
occurred rapidly at a critical circumference. A small ,` ~-increase in circumference resulted in a large increase in ``
inco~petence. Two studies examined this phenomenon, one in vivo and one in vitro.
The first study Wa# performed on the left internal jugular vein o~ a sheep. A side to side arteriovenous ~ ', ,' '- ' , . '' ', :' .. ~ . . .
-` 1 324461 anastamosis was performed proximal to a minimally incompetent valve. The vein was re-explored 2 weeks later and the pressure gradient was measured across the valve. The proximal pressure was a mean of 90 mmHg. The distal pressure was measured across the valve at different circumferences of the venous cuff. The initial circumference was 4cm. This is a refleceion of the degree of competence of the valve. The results were as follows~
- "~'",. . ` ,..
,,".: '":
TAB~E 1 .. _ .
venous Cuff Circumference Distal Pressure (cm) (mmHg) _ _ _ .
4.0 55 3.6 36 3.4 30 3.3 24 3.0 25 2.8 22 2.6 21 _ 2.5 1 24_ ~ he venous pressure when the vein occluded was 23mmHc which is the minimum pressure that the distal vein can achieve with a fully competent valve or with a circumference of Ocm.
Fig. 12 is a graph of the results in Table 1. It can be seen that only minimal improvement in competence can be made by reducing circumference below 3~3cm~ That is, a 17~5 reduction in circumference produced a near maximal effect on co~petence. Any further reduction in circumference is `
unnecessary and increases the risk of obstruction. The use ~' -of a special applicator allows a~fine adjustment in circumference to be made and for competence to be continuously tested with successive small decreases in circumference~
, ,.'',','''' ,`'"'''~
"
.
The second study was on the right internal jugular vein of the same sheep. An in vitro set-up was used for this study. 8art~ann's solution (~inger's lactate) was perfused retrogradely from a standard intravenous infusion set at a height of approximately 1 metre~ The distal vein was also connected to plastic tubing which was raised to run into a reservoir so that the distal pressure was a constant 5 mmHg. Pressures were measured lcm above and below the valve using the same equipment and methods as in the previous studies except that l9G needles rather than cannulae were used.
The flow was measured using a measuring flask to measure outflow from the distal vein over 30 seconds. The results were as follows:-TABLE II
_. . ., Venous Cuff Flow Pressure Retrograde Circumference ~ml/min) Gradient Resistance _ ~cm~ (mmHg) _ 3.6 146 2 0.01 ` ~ ;
3.0 81 5 0.06 `
2.6 5 80 16~0 `
2.5 3 90 30.0 ` ` ``~
~here was no increase in competence with urther decreases in circumference unless the vein was occluded. The ~-results sho~n in Table II are graphed in Fig. 13. Although insufficient points are plotted to be confident as to the `~
exact best fitting curve, it is apparent that a large change -2~- 1 32446 1 in retrograde resistance is produced within a small range of change in circumference.
These studies on the biomechanics of the valve confirm the critical nature of circumference on competence. A narrow optimal range is apparent in these studies and can be observed by the surgeon while applying the venous cuff. If the vein is narrowed beyond this point, then a relative obstruction may be produced for no gain in competence. The choosing of the optimal circumference is aided by the use of an applicator which enable small increments in decreasing the circumference of the band and allows the surgeon to test competence by the ~milking~ technique. An optimal circumference can thus be found without narrowing the vein unnecessarily.
EXAMPL~ 4 A venous cuff according ~o the invention has been used to restore competence to incompetent valves in ten internal jugular veins of sheep. All ten valves required a reduction in circumference of the dilated vein to produce a satis~actory degree of competence as is shown in the following table:-` ' ' :, ' ' ' ' ' ~ .... ... ~ . . . .....
TABLE III
S~EEP JUGULAR CIRCUMFERENCE PERCENTAGE DECREASE .
NO VEIN _ IN CMS _ _ IN
INITIAL WITH CUFFCIRC.AREA .
-_ _ 86 LEFT 2.9 1.9 34 57 . : .
RIGHT 2.5 2.1 16 29 : .
87 RIGHT 3.5 2.2 37 60 88 L~FT 4.0 2.8 30 51 .;
RIGHT 3.9 2.8 28 48 ~:
89 LEFT 2.6 2.2 15 28 RIGHT 2.7 2.0 26 25 '::
RIGHT 1.9 1.5 21 38 `: :
gl LEFT 2.0 1.7 15 28 RIGHT 2.4 2.0 17 31 : -_ _ ,. _. ~` :;'~."'';
The average reduction of circumference was 24 with a range of 15% to 34%. This is a moderate degree of narrowing but it must be placed in the context that veins are normally ~-`
in a partially collapsed state when compressed by surrouding tissue~ One vein ~as made incompetent by creating an arterio-venous fistula which caused dilatation of the valve ring~ The reduction in circumference necessary to restore competence was 52~
The animal model of venous valve incompetence is a `
useful one because, :`.
i) The venous valves in the internal jugular vein in sheep appear macroscopically identical to `;
the venous valves in humans. The histology of the vein wall is also similar. ..
. ", "..
. ;;.,-" ' " ' ' ii) The cause of the incompetence is the same as that which applies in over 90~ of cases of varicose veins in at leas~ 50% of cases of deep venous disease in humans, that is, hydrostatic pressure overcoming the strength of the vein.
iii) An arteri~venous fistula has been found to mimic venous insufficiency in dogs, and has ~:
been used with proximal venous occlusion in dogs and rats. The arteriovenous fistula alone is sufficient to produce swelling of the limb in dogs and lymph changes which are similar to the disease o~ hùmans~ It is also well known that an arteriovenous fistula can produce varicosities in humans and ulceration ..
even of the upper limb~ `
iv) The response of the ~ein wall histologically :
to a fistula has similarities to changes observed in saphenous veins in humans when used as an arterial graft particularly in the intimal prolifera~ion, vein wall fibrosis and variable damage to the internal elastic : :
lamina~ The changes are, however, less severe~ `
v) Destructive changes on the valve aod vein wall .`
are hastened both by the continuous applicat;ion of a very high pressure to the -`-.
, ,"
valve and also by the pulsatile nature of the pressure which is thought to have an adverse affect on collagen.
In two sheep, incompetence of the valves developed quickly twithin 5 days). This is despite the fact that these valves managed to remain competent for years (depending upon the age of the sbeep) of normal function. The pressures on these valves nor~ally would increase on grazing, when the head is lowered. The valves would be subjected to the hydrostatic pressure from the right atrium to the valve. The valves would also be subjected to pressures associated with coughing and Valsalva type maneuvers.
The implantation of the venous cuff protected the distal vein from the high pressure of the arteriovenous ~istula. `
This ~as demonstrated convincingly by the measured pressure `
gradient and circumferences before and after implantation.
In one sheep, this protective effect was still present nearly `
9 ~ee~s la~er at harvesting of the vein. From the results in ` ~-this sheep it could reasonably be expected that this ` `
protective effect would last many years in the normal `
situation. ~his can be seen from the fact that the fistula ^- `
had a destructive effect in five days greater than the life of the animal to that stage. ~espite 9 weeks of this stress, `
the valve functioned well with the venous cuff implanted.
The venous cuff is very effective in preventing venous ;~
valve incompetence even in the presence of abnormally high pressures. These pressu;res created incompetence in the ~ `
controls within two weeks yet this did not happen with the venous cuff in situ at a mean of 20 weeks. The importance of prevention of movement of the venous cuff along the vein led to the addition of tags or ears to the venous cuff to facilitate attachment to the surrounding fascia.
There was minimal damage to the vein wall and no complication attributable to the venous cuff itself.
Comparison of light microscopy control and implant results showed that negligible effects on the vein wall are attributable to the venous cuff.
The silicone rubber sheet venous cuffs produced a similar reaction in all cases of implants. The macriscopic reaction to silicone rubber sheet around the adventitia of the vein was a smooth fine fibrous opaque white reaction.
The silicone rubber sheet lifted easily away from the vein.
There was no incorporation of the silicone rubber sheet into the vein wall and there was a small amount of clear serous fluid between the wall of the vein and the silicone rubber sheet.
The macroscopic appearance was that of serous membrane. When the vessel lumen was opened underneath the silicone rubber sheet cuff, there was minimal thickening of the wall.
The inti~al lining itself appeared macroscopically identical to the surrounding intima. ~here was no evidence of any thrombotic process, no ulceration, no fibrotic obstruction, no haemorrhage into the wall and no thickening -~ 1 32446 1 of the vein w~ll. One sheep had a decrease in the diameter of the wall distal to the implant. This appeared to be related to a subcutaneous suture distally which was compressing the vein. This was not associated with the silicone cuffs themselves.
Based on microscopic observation, light microscopy, scanning electron microscopy and pressure measurements, the following conclusions can be drawn from the above animal studies.
The venous cuff is made from a material with , favourable biocompatibility characteristics in terms of -interactions with veins. There was minimal or no difference in histology of implant specimens and control specimens on the vein wall. Out of 50 implants in animals, there have `
1~ only been three complications with two implants. There were : .....
two infections and one thrombosis. This thrombosis was probably caused by the pressure measurement technique. The .
two infections would be expected with any operation. The , silicone cuff has not caused complications beyond those expected with any similar operation with no implant. Thus no `
complication can be directly attributed to the cuff.
The venous cuff is highly successful at restoring competence to incompeeent venous valves which are not ~ -destroyed by thrombophlebitis. Competence was markedly improved in all 20 of 20 valves in animal models. The improvement is maintained at a mean implant time of 12 weeks. This is also supported by six implaats which ~
',' ;`: ' ' `
','``. `~' prevented incompetence despite very high retrograde pressure gradient for a mean implant time of 20 weeks and a maximum of 28 wee~s implant time.
The animal models are confirmed by the human work. The only complication out of 16 implants was one infection which had no long-term morbidity after removal of the cuff. There were two prophylactic implants. The implant of the cuff produced com-petence in twelve out of the remaining thirteen valves. The other valve was affected by thrombophle-bitis, which is now regarded as a relative contra-indiction to the procedure. Of these thirteen valves, ten were for varicose veins and all patients had resolution of symptoms. The mean implant time was 25 weeks. The longest implant was 15 months.
This long-term implant has had no recurrence of an ulcer which was present five months continuous preoperativaly. The remaining three implants were on a patient with deep venous disease. He had healing o$ his ulcers and has minimal symptoms three months postoperatively.
The venous cu$$ of the invention is a sa$e, reliable device for producing long-term competence in incompetent venous valves. This produces a corres-ponding resolution of symptoms in people with vari-cose veins and chronic deep venous insu$$iciency.
The venous cuff may be placed into position and tightened around the vein by the use of an appli-cator. A suitable applicator has an .
:. ~,. .
A
-` 1 324461 upstanding tab which receives the loop of the cu~f. The cuff is then passed around the vein and the free end of the cuff connected to a cuff adjus~or mounted on the applicator body with a ratchet mechanism which allows the adjustor to be -moved relative to the applicator and to be held in any ~-selected position. A stapling gun incorporatea within the applicator is used to secure the overlapping end of the cuff '`
to the loop 13.
As will be apparent from the above description, the applicator allows a single surgeon to apply the cuff to a .-i vein. With one hand, the surgeon using the applicator can adjust the cuff to the desired diameter and then test the valve for competence~ After final adjustment of the diameter, the surgeon then staples the overlapping portions of the cuff together. If need be, the free end af the band is trimmed and the cuff removed from the applicator.
Various modifications may be made in deta~ls of the cuff and the method of restoring venous valve competency without departing from the scope and ambit of the invention.
,.` .','. :`:
. ..: .
~ . ....
~, .
pain, swelling, ulceration and varicose veins.
For the sake of convenience, the invention will be described in relation to the correction of incompetent valves in the venous system of the lower limb in man, but, it is to be understood that the invention is not limited thereto.
The venous system of the lower limb consists essentially of the superf icial venous system and the deep venous system. The superficial system includes the great saphenous vein and the small saphenous vein~ The deep venous system includes the anterior and posterior tibial veins which unite to form the popliteal vein which in turn becomes the femoral vein when joined by the small saphenous vein~ `
The initial defect in primary varicose veins often involves localised imcompetence of a venous valve thus allowing reflux of blood from the deep venous sytem to the ' ~
superficial venous system. ~bis incompetence is ,, :`
traditionally thought to arise at the saphenofemoral junction but may also start at the perforators~ Thus, gross saphenofemoral valvular dys~unction may be present in even mild~varicose veins with competent distal veins~ Even in the presence of incompetent perforators, occlusion of the sap~enofemoral junction usually normalises venous pressure~
~he initial defect in secondary varicose veins is often incompetence of a venous valve secondary to hypertension in ?5 the deep venous system~ Since this increased pressure is manifested at many points, correction of one site of :
. . .
~ ~ incompetence could clearly be insufficient as other sites of : -....... .. ..
; ... ..
. .. . .
~.... ~
_3_ 1 32446~
incompetence will be prone to develop. Apart from the initial defect, the pathophysiology is similar to that of varicose veins.
Once the initial incompetence occurs, incompetence in other valves in the system will tend to occur secondary to the venous hypertension.
Apparently, incompetence of venous valves is caused by dilatation of the vein wall. The evidence for this is as follows:-i? The valv~s in varicose veins are normal macroscopically and histologically in most cases.
The vein wall is more distensible in apparenely ~-normal veins in people with varicose veins~
ii) The valve cusps have a much greaeer tensile strength than the vein wall~ ` `
iii) Venous function deteriorates during the day as the venous system becomes more dilated. ` `
iv) Saphenofemoral va~lves which are incompetent can .. .
become competent again at operation when the diameter is decreased by spasm. A similar occurence has been noted in the superficial femoral vein.
v) Varicose veins may temporarily appear during pregnancy before the uterus is large enough eO --cause venous obstruction.
; ~ vi) Forearm veins ~hich are incompetent when full and distended can become competent again when the ., ;,`~."`','' 1 3~4b$
. .
distal segment is emptied thus reducing the diame~er. Valves which are competent can be made incompetent by injection of local anaesthetic which caused venodilatation~
s Thus, it appears that dila ation of the vein wall, whether idiopathic (primary varicose veins) or secondary to venous hypertension ~secondary varicose veins) leads to valvular incompetence. This dilatation may eventually lead to stretching and sclerosis of the valve. Other valves in the system will tend to become incompetent as ~he reflux of ,~
blood causes dilataeion of the vein wall. We have found that `
it is possible to reverse or prevent the destructive process by overcoming this dilatation. Even if tbe vein wall wea~ness is generalised as appears to be the case with `
primary varicose veins, correction of the initial defect will delay or prevent stress being placed on that wall and thus ~"` `;
hind progression of the disease.
The fundamental change in flow in primary varicose veins is raflux of blood from the deep venous system into the ~20 superfici~l venous system, usually the great saphenous vein.
Traaitionally, chronic deep venous insufficiency is reg~rded as being secondary eO deep venous thrombosis which either Obseructs the vein or is recanalised with associated ``
destruction of the deep venous valves. The obstruction is `' initially prominent but as recanalisation occurs and ;
collateral circulation develops, the obstruction is less prominent. Then the ~enou-~ incompetence becomes more :, . .:
. , ; ':
~: ` . ~,.,',- . :.
~' '` ,:
~ ..
` ~5~ 1324461 prominent. This syndrome follows deep venous thrombosis in a majority of ~ases .
Deep venous thrombosis is involved in the majority of cases of post-phlebetic syndrome but other factors such as site of deep venous thrombosis, obesity, muscle activity, posture and genetic predisposition may be involved. A
primary inco~petence of the venous valves appears to be -involved in a significant number of cases~ ~`
BACKGROUND ART
In the main, prior art approaches to restoring competency of incompetent valves has involved venous reconstruction surgery of three basic kinds, namely, venous valve transplants, venous transposition and venous valvuloplasty.
As the tera implies, the venous valve transplant approach involves the replacement of the segment of the vein having the incompetent valve with a segment of another vein having a competent valve. The venous transposition approach ``
~ ~involves the redirection o~ the venous system so as to bypass an incompetent ~alve and venous valvuloplasty involves venous ~alve reconstructive surgery in which the free length of the valve cusps is reduced by plicating sutures. ~ - `
These approaches to the prior art are well documented in A RATIONAL APPROACH TO 5URGERY OF THE CHRONIC VENOUS STAS IS `-~ SYNDROME by Harry Schan~er AND E Converse Peirce ANNALS OF
SURGERY 1982, 195: 25 - 29 as well as in VALVULOPLASTY AND .``
VALVE TRANSF~R by Seshadri Raju Inter. Angio. 4 1985 419-424. ~ ---6- 1 32446~
A single example on one patient of an experimental technique for treating an incompetent venous valve not involving the above types of venous surgery is described in an article by Dag Hallberg in ACTA CHIR SCAND 138: 193-145, 1972. Hallberg placed a band two to three millimetres larger than the diameter of the view around the vein.
The band was made of DACRON polyester and polyester and was applied when the patient was in the horizontal ~`
position~ The band was retained loosely in position by several sutures in the venous adventitia~ ;
Hallberg's method could not restore competence to the majority of the incompetent venous valves~ In patients with venous disease, incompetent valve~ will usually be -incompetent in the horisontal as well as the vertical positions~ See, for example, FENORAL VEIN RECONSTRUCTION IN
THE MANAGENENT OF CHRONIC VENOUS INSU~FICIENCY by Ferris E.B~ -and Ristner R., ARCHIVES OF SURGERY, 1982, 117:1571 - 1579. ``
~erris and Ristner operated on 53 femoral veins in which the valves had been demonstrated pre-operatively to be -`
incompetent. In only one case was the valve noted to be co~petent when tbe patient was horizontal at the time of operation. Risener's approach was to suture the vein to prevent post-operative dilatation. `
It is ~ell known that by itself DACRON ~Registered Trade ~5 Mark) polyester material causes marked fibrosis as well as foreign body reaction. Therefore, DACRON polyester cannot alone be conridered bioco~patible. In fact, DACRON polyester "~
' ":' .
, .
~7~ 1 324~6~
has been employed to stimulate fibrotic reactions which incorporate the synthetic fabric into tissue (see: s. Raju, .
ANN. SURG. (1983) 197, 688-697).
The article REVASCULATION OF SEVERELY ISCHEMIC
EXTR~MI~IES WITH AN ARTERIOVENOUS FISTULA by F.W. slaisdell et al in AMERICAN JOURNAL OF SURGERY, Volume 112, pages 166-173 discloses problems associated with the use of DACRON -polyester as an implantable material. In a number of cases, gradual narrowing of arteriovenous fistulas under a woven DACRON polyester sleeve was demonstrated.
In physical terms, Hallberg approach was a static one.
Once the cuff was sutured into position, no attempt was made to reduce the diameter of the vein at the valve site to restore competency of the valve. Indeed, Nallberg's single patient experiment was concerned with further dilatation of ~ "
the vein at the valve site rather than reduction in the dia~eter of the dilated valve to restore competency.
DISCLOSUR~ OF T~E INV~NTIO~
It is an object of this invention to provide a method ` `
for restoring competence of incompetent venous valves by reducing the diameter of the appropriate vein at the valve site.
It is a further ob~ect of the invention to provide a method for restoring competence of incompetent venous valves in ~hich the diameter of the vein at the valve site is ad~u~ted to achieve proper competence of the valve and which : `
permits clinical testing at the time of diameter reduction. ~ ~
. ., ~ . `' ~ ~ ~ ' ` ;;` `"
-8- t324461 It is a yet another object of the invention to provide a device for restoring competence of an incompetent venous valve which is biocompatible and which does not require suturing to the vein itself.
According to one aspect of the invention there is provided a cuff for restoring competence to an incomptetent '; -.
venous valve, said cuff comprising a band of biocompatible `~
implantable material that is not strètchable at blood flow . -pressures, the band being of sufficient length to emcompass the vein at the site of the venous valve, with portions of ` .:
the strap overlapping, the overlapping portions being .
joinable together to form a cuff of desired circumference ``
small enough to restore competence yet not too tight to ..
decrease blood flow~
According to anot~er aspect of the invention there is ` `:
provided a method of restoring compeeency to incompetent `-`
venous-valves co~prising the steps of ~
: . ` .
i) placing a cuff of biocompatible material around the vein at the site of the valve, ii) reducing the circum~erence of the cuff ~and hence ~i ~:~ ehe diamter of the vein at the valve site) until ~ "
competency of the valve in the vein is restored, `.:
. ~ ,~ and, ..
: ~ iii) fixing the circumference of the CUff at the point ~ where the diameter of the vein is reduced to ::.
restore competency of the valve without impairing :-~- blood flow. . ;`
; :. -;,~..
:.' ., ~ ,':
-g- ~ 3~44~6~
If necessary, the cuff is then secured to the surrounding. tissue. Preferably, the circumference of the cuff around the vein is reduced in a stepwise fashion with the competency of the valve being tested between each stepped reduction in the circumference of the cuff.
Competency of the valve may be tested by milking the vein, by the use of appropriate pressure detectors or by Doppler Techniques.
BRIEF DESCRIPTION OF THE DRAWINGS
In order that the invention may be more readily understood and put into practical effect, reference will now .
be made to ehe accompanying drawings in which:-Fig. 1 is a cutaway diagrammatic perspective view of one side of a vein at a valve ` :
. .
site with the valve in its closed disposition, ; Fig~ 2 is a plan view from above of the venous valve shown~in Fig. 1, Fig. 3 is a schematic view of a competent venous valve in its closed disposition, : ~ Fig. ~ is a schematic view~similar to Fig~ 3 but of an inoompetent valve, Fig. 5 is a perspective view of a venous cuff according to one embodiment of the invention, Fig. 6 is a perspective view of the cuff shown in Fig. X encircled around a vein, ~ Fig. 7 ls a p}an view of a second embodiment of a ~ -: venous cuff, ;: ' '; ' - " ' ";: ',~:' " -lo- 1 324461 Fig. 8 is a side elevational view of the cuff j, ~' shown in Fig. 3 in place at the junction of :
two veins, -'.
~ig. 9 is a plan view of a third embodiment of a ,.. ~.:
5venous cuff, .``'`~, Fig. 10 is a side elevational view of the cuff ~--shown in Fiq. 5 in place at the junction of two veins, ' .`.
Fig. 11 is a view similar to Fig. 6 but with : :.
10the strap position over the loop of the cuff, Fig. 12 is a graph of distal blood pressure against ,.", ;:
circumference of a vein at a valve site, and, ~`.i''~
Fig~ 13 is a graph of retrograde resistance against ```
.~ .
~ vein circumference at a valve site. ~ ~`.
- ~ 15~ ~ ESCRIPTION OF PREFERRED EMBODIMENTS `~`.
:. ~The valves in the venous system of man are almost .~' invariably bicuspid as is shown diagramatically in Fig. 1.
chlcusp 10, 11 i-Q semi-lunar ànd is àttàched to the wall of '`
` , the -ein 12 by its convex edge 13~. The concave edges 14 lie ~ `
20~free~io the direction of normal blood flow indicated by arrow .~
IF~ be~attaçhment~of each cusp approaches that of the other : :
- cusp~proximally to form the commissure 15. Proximai to the `.,`.
e,~ the ~ein is`more distens}ble for about l~cm. to form ,the -inus. In cross-section, whon closed, the cusps 10, 11 `25.~of~the~v~lve ~eet in a ~taight llne in the centre of the vein `
`1`2 as~sho~n:in Fig. 2. ~
~?~`It ~11 be appreciated that the venous valve is normally open with the free concave edges 14 separated by the upward flow of blood in the direction of arrow F. ~s will be apparent from Fig. 1, each cusp 10, 11 forms a sack or reservoir 16 for blood which, under pressure, in the direction of arrow R, forces the concave edges 14 together to prevent retrograde flow of blood - see Figs. 1 and 3.
There are 10 to 20 valves in the great saphenous vein and 7 to 13 in the small saphenous vein. The perorating veins also have valves except for the feet where they`are unusual. .~ -On standing at rest, the pressure in both the superficial and deep venous system correlates closely with the hydrostatic pressure of a column of blood at the height of the atrium, about 80-90mm. Flow in both superficial and deep systems is slow and is directed towards the heart ~antegrade)~ ~low in the perforators is also slow but tends to be from the superficial venous system to the deep venous ~syste~. The ~low in the foot is ehe reverse of that just ~ described - from the deep ~eins in the sole of the foot to the superficial ~eins on the dorsum of the foot.
The position changes markedly on exercise. On`calf contraction ~systole) the pressure and flow in the deep ~ ~ system increases and flo~ through the perforators ceases. On - ~ calf relaxation (diastole) the pressure and flow in the deep Jystem decrease and there is increased flow in the perforators from the superficial venous sytem to the deep venous system. Tbe mean venous pressure drops during ,.
~:
;' ,' :" .
,: - .
exercise by about 60-70mmHg. ~-These changes are the result of the musculo-venous pump, As the muscle contracts, blood is expelled towards the heart. The blood is prevented from moving into the superficial system by the valves in the perforating system.
On relaxation of ehe muscle the pressure drops but blood is prevented from reflux by the valves of the deep venous system and flow recommences from tbe superficial venous system to ;~
the deep venous system, through the perforators. The ~
musculo-venous pump is responsible for efficient venous -return in combination with the vis a tergo effect and of ~
intra-tboracic and intra-abdominal pressure. `
~ competent valve is shown diagramatically in Fig. 3 in ;~
its closed disposition and an incompetent valve in Fig. 4. " `
Tbe ~usps 10 and 11 of the competent valve in Fig. 3 form the blood sac~s 16. The length of vein 12 at the valve si~e is ` ``
indicated by ~L~ and the diameter of tbe vein, when the valve is competent, is indicated by ~d~. The extent of contact of the upper edges of the cusps when the valve is closed is `~
indicated by ~
When the diameter of the vein 12 is increased to "D" as " ;
sho~n in Fig. 4, the concave edges 14 of the cusps no longer meet and retrograde flow of blood can occur. The cusps 10a, lla shown in dotted outline in Fig. 4 represent the normal disposition of the cusps and thus it can be seen that ;;~
dilatation of the vein has led not only to separation of the cusps but also to a decrease in the general angle of the ~, `''~ .
: '`,"'.. , : '''' ` ; :' -13- 1 324~61 cusps to one another with a consequent lessening of the possible area of contact between the cusps should contact be possible at some diameter less than "Dn.
According to the present invention, it is possible to restore competence to an incompetent valve by decreasing the diameter of the vein wall at the valve site from the valve ~D~ of Fig. 4 towards but not necessarily to the diameter ~d"
of Fig. 3 by the use of a venous cuff.
The venous cuff 20 shown in Figs. 5 and 6 is made of a bio-compatible material that does not significantly react with a vein or its surrounds and which in this instance, is flexible but does not stretch at the pressures encountered in blood ~low. A preferred material is silicone rubber sheeting reinforced with embedded polyester fibres.
The venous cuff 20 consists of an elongated band 21 having a free end 22 and a loop 23 at its other end 24. As :
can be seen in Fig~ 5, the loop 23 extends above the upper ` "
face 25 of the band 21 so that it may receive the free end 22 ~
as shown in Fig. 6 ;
The loop 23 may be formed as a separate item that is glued to ~he band 2~. In this instance, the loop 23 is formed from a flat rectangular strap 26 of polyester ~`
reinforced, Do~ Corning Medical Grade silicone rubber sheet No. 501-1. The flat strap 26 has two straight slits 27 extending in~ardly from the opposite edges of the strap and cut parallel to and 2mm from the longitudinal side 28. The dimenJions of the strap 26 accordinq to one embodi~ent Iwhich `
-14- ~ 3z~
are given for ilLustrative purposes only) are as follows:-~ength 48.0 (~ 0.5) mm --sreadth 5.0 (~ 0.2) mm Thickness 0.178 ~ 0.076) mm Slit length 16.7 (~2-0.0) mm The slits 27 divide the loop 23 into an inner attachment portion 29 that is 2mm wide and an outer deformable portion 30 that is 3mm wide. The free ends of th~ attachment portion 29 are folded over one another to provide the loop 23. The free ends of the deformable portion 30 are each folded over -themselves and secured between each folded portion by means of a suitable adhesive is a securing tab 31 by means of which the cuff may be sutured to neighbouring tissue.
, In this instance, the band 21 is formed from a flat piece of polyester reinforced Dow Corning Medical Grade ~15 silicone rubbar sheet No~ 501-3. A hole 32 may be cut in the , `
"` tapered end 22 of the band 21 for attaching the band 21 to a mechanical applicator. The dimensions of the band 21 àccotding to one embodimen~ which are given for illustrative `
purposes only are as follows~
20~ Length 68.0~0.5) mm `~
Breadth l5.0t~0.5) mm ~ , ~ ; Thickness0.503~0.Q~6) mm ~ i .
Taper Length20.0(~0.5) mm Taper Breadth10.0(~0.5) mm ~ .
25 ~ Hole diameter3.0(~0.2) mm `' As will be apparent from the above dimensions, the ::
: :
deformable portion 30 is made from thinner material than the band 21 in order to decrease any possible effects that cuff surface discontinuities may have on the vein wall. ~he use of thinner material for the deformable portion 16 allows a smooth overlap inner surface on the cuff when implanted around a vein as is shown in Fiq. 7 and allows the cuff to assume the shape of the vein.
AS will be apparent from Fig. 6, with manual application of the cu~f, the loop end 24 of the band 21 is placed on the vein 33. The band 21 is then encircled around the vein 33 s and the free end 22 of the band 21 is passed through the loop "
23. When the circumference of the cuff has been reduced to the poin~ whereat the diameter of the vein is reduced to restore competency of the valve within the vein 33, the overlapping portions of the band 21 are fixed together by ~ ;
stapiing or suturing and, if necessary, the free end 22 of `
the band 21 beyond the suture or staple is removed by any ~``
convenient means~ The tabs 31 are then sutured to tissue ; `~
surrounding tbe vein to prevent the cuff from sliding along the vèin. ~
In an alternative method of application, the band could ` `
be looped in the other direction so that the free end of the ` `
.
band overlies the top of the loop as shown in Fig. 7.
~ he modified form of the venous cuff shown in Fig. 8 is ; 25 ~ particularly suitable for restoring the competence of a valve .
in a fir-qt vein having a junction with a second vein of the kind shown in Fig. 9. She cuff is substantially similar to .
.
-~ 1 324461 that shown in Fig. 5 and thus common elements share the same numerals.
A CUt out portion 40 in the uppèr edge 41 of the band 21 is so dimensioned to enable the cuff to assume the shape s shown in Fig. 9 when the cuff is positioned around a first veln 42 adjacent to its junction with a second vein 43.
The portions 44 of the band 21 adjacent to the cut-out 40 engage the vein as shown in Fig. 9 and the cuff is secured ~ -in position by means of one tab 31 being sutured to the tissue surrounding the vein 42 and the other tab 31 being , , `
sutured t~ tissue surrounding the vein 43. ;
The cuff shown in Fig~ 10 is substantially similar to `:
that shown in Fig. 8 except that the cut-out 50 is in the lower edge 51 of the band 21. The cut-out 50 is so di~ensioned to enable the cuff to assume the shape shown in Fig. 11 when the cuff is positioned around a first vein 52 adjacent to its junction with a second vein 53. `
~he portions 54 of the band 21 adjacent to the cut-out ;`
50 engage the vein 53 as shown in Fig. 11 and the cuff is ` ;.
secured into position by means of one tab 31 being`sutured to tiJsue surrounding the vein 52 and the other tab 31 being sutured to tissue surrounding the vein 53. `
It will be appreciated that the venous cuff may be made of any appropriate bio-compatible material that will not give `~ rl-e to any significant~adverse reactions within the body uch as thrombosis, stenosis ~i.e. narrowing of the vein) or perforation of the vein wall through wear and tear, The `
` -17- 132~461 overlapping portions of the band 21 may be secured together in any convenient way - with or without the loop or buckle arrangement shown in the drawings. ~he overlapping portions may be secured together by s~apling or suturing as described above, or by mechanical interlocking of parts of one portion with part o~ the other portion of the stap at the overlap, or by adhesive, or by heat sensitive or pressure sensitive means.
If the overlapping portions of the band 21 are secured together by means external of thè band such as by staples, sutures or adhesi`ves, the external means should be selected so that there is no adverse interaction between the fastening means and the cuff or therein or surrounding tissue. It is prèferred that neither the band nor the fastening means be - `
secured to the vein. -Although the above described cuffs incorporate tabs for `
securing the cuff to tissue surrounding the vein, such tabs àre not essential~ Anchoring of the cuff may not always be required - for example, the location of the cuff may not permit movement of the cuff along the vein or the material of the cuff may possess sufficient friction with respect to the vein so as to prevent movement of the cuff along the vein.
~he cuff may, of course, be of any convenient shape or configuration. As to its breadth ti.e. its dimension along the vein~, the minimum requirement is that the cuff should cover substantially all of the cusps of the vaive, preferably ': `
": .':'~ ' ' .: -., .
' ' " ' '' ~
.....
.. " . ` ' .' g ~ 32446~
with some 1 to 1~ 5mm excess at each end of the valve. The maximum breadth is limited by the general consideration that a single cuff should not span two venous valves.
The band is to be long enough to encircle the vein to `
which it is to be applied and to provide sufficient overlap to facilitate joining of the overlapping portions. As will be explained in more detail below, the overlapping arrangement of the band portions enables the circumference of -the cuff to be reduced to the desired value at which competence is restored. That is to say, the cuff is applied i in a dynamic way - the cuff circumference is initially larger than the diameter of the dilated ~rein and the circumference o~ the cuff is reduced until competency of the valve is detected.
The cuff may be manufactured from components as described above or formed as a one piece moulding~ -A use of the cuff will now be described in relation to incompetence of the sapheno-femoral valve. The function of the sapheno-femoral valve is to decrease the pressure in the long saphenous system.
When the sapheno-femoral valve becomes incompetent, the vein distal to this point is exposed to abnormally high :- ~
- ~ pressure ~hich in turn causes dilatation of the vein below ~ the ~apheno-femoral valve and incompetence of the corresponding valve. ~his sequence continues until the thin-walled tributaries of the internal saphenous vein are also : ~ . :' .''`
' '.," ,'`:~' , ~ .
: ~ ,,.''' :' 132446!
exposed to pressures that cause them to dilate, elongate and become tortuous - that is to say, they become varicose.
The above described sequential process commences because of the incompetence of the valve at the sapheno-femoral _ s junction. Thus, if the functional defect of the valve is corrected by surgery, the patient will be substantially free from risk of further varicose veins.
~he unction of the cu~f is to decrease the size of the sapheno-femoral vein at the valve site which pathologically ~-dilates and, as described above, the consequence incompetence of the valve causes varicose veins. The cuff is tightened around the vein at the valve site until the valve is assessed, during the operation, as being competent~ `
The standard surgical approach to the sapheno-femoral junction is used and the tributaries of the saphenous system are ~ied off be~ore placing the cuff in position. ` `
The sapheno-femoral valve band is so dimensioned as to encircle the sapheno-femoral vein at the valve site with the ends of the band overlapping so that they can be secured together in any convenient way. The sapheno-femoral valvè
can usually be seen through the vein wall and thus the cuff ; `~
can be correctly located by inspec~ion.
An integral securing tab may be provided in the mid , , .
portion of the strap that is preferably larger than the ``~
~ diameter of the vein at the valve. The securing tab may conveniently be of semi-circular shape and may be sutured to ~ ;~
the cribriform fascia above the sapheno-femoral valve using '::
: ~, :;` '.
,,'"~, ' fine non-absorbable sutures.
The use of the valve repairing cuff enables the main saphenous system to be left intact so that it may be used for coronary artery by-pass grafting, femoro-popliteal by-pass grafting and any of the other different types of by-pass grafting used in standard vascular surgery.
~he varicose veins that actually appear in the legs are tributaries of the main long saphenous system and are dilated and become tortuous because the walls of these veins are exceedingly thin. On the other hand, the main long saphenous system itself has thick walls three to four times as thic~ as its tribùtaries and indeed has more muscle in its walls than any other vein in the body. Thus, this vein may be relatively normal whilst its tributaries become dilated.
The insertion of the venous cuff at the sapheno-femoral junction preserves the long saphenous system and a standard removal of varicose tributaries can be performed at the same -proc dure.
It has been noted while using the venous cuff of the invention that the restoration of competence to a valve `
occurred rapidly at a critical circumference. A small ,` ~-increase in circumference resulted in a large increase in ``
inco~petence. Two studies examined this phenomenon, one in vivo and one in vitro.
The first study Wa# performed on the left internal jugular vein o~ a sheep. A side to side arteriovenous ~ ', ,' '- ' , . '' ', :' .. ~ . . .
-` 1 324461 anastamosis was performed proximal to a minimally incompetent valve. The vein was re-explored 2 weeks later and the pressure gradient was measured across the valve. The proximal pressure was a mean of 90 mmHg. The distal pressure was measured across the valve at different circumferences of the venous cuff. The initial circumference was 4cm. This is a refleceion of the degree of competence of the valve. The results were as follows~
- "~'",. . ` ,..
,,".: '":
TAB~E 1 .. _ .
venous Cuff Circumference Distal Pressure (cm) (mmHg) _ _ _ .
4.0 55 3.6 36 3.4 30 3.3 24 3.0 25 2.8 22 2.6 21 _ 2.5 1 24_ ~ he venous pressure when the vein occluded was 23mmHc which is the minimum pressure that the distal vein can achieve with a fully competent valve or with a circumference of Ocm.
Fig. 12 is a graph of the results in Table 1. It can be seen that only minimal improvement in competence can be made by reducing circumference below 3~3cm~ That is, a 17~5 reduction in circumference produced a near maximal effect on co~petence. Any further reduction in circumference is `
unnecessary and increases the risk of obstruction. The use ~' -of a special applicator allows a~fine adjustment in circumference to be made and for competence to be continuously tested with successive small decreases in circumference~
, ,.'',','''' ,`'"'''~
"
.
The second study was on the right internal jugular vein of the same sheep. An in vitro set-up was used for this study. 8art~ann's solution (~inger's lactate) was perfused retrogradely from a standard intravenous infusion set at a height of approximately 1 metre~ The distal vein was also connected to plastic tubing which was raised to run into a reservoir so that the distal pressure was a constant 5 mmHg. Pressures were measured lcm above and below the valve using the same equipment and methods as in the previous studies except that l9G needles rather than cannulae were used.
The flow was measured using a measuring flask to measure outflow from the distal vein over 30 seconds. The results were as follows:-TABLE II
_. . ., Venous Cuff Flow Pressure Retrograde Circumference ~ml/min) Gradient Resistance _ ~cm~ (mmHg) _ 3.6 146 2 0.01 ` ~ ;
3.0 81 5 0.06 `
2.6 5 80 16~0 `
2.5 3 90 30.0 ` ` ``~
~here was no increase in competence with urther decreases in circumference unless the vein was occluded. The ~-results sho~n in Table II are graphed in Fig. 13. Although insufficient points are plotted to be confident as to the `~
exact best fitting curve, it is apparent that a large change -2~- 1 32446 1 in retrograde resistance is produced within a small range of change in circumference.
These studies on the biomechanics of the valve confirm the critical nature of circumference on competence. A narrow optimal range is apparent in these studies and can be observed by the surgeon while applying the venous cuff. If the vein is narrowed beyond this point, then a relative obstruction may be produced for no gain in competence. The choosing of the optimal circumference is aided by the use of an applicator which enable small increments in decreasing the circumference of the band and allows the surgeon to test competence by the ~milking~ technique. An optimal circumference can thus be found without narrowing the vein unnecessarily.
EXAMPL~ 4 A venous cuff according ~o the invention has been used to restore competence to incompetent valves in ten internal jugular veins of sheep. All ten valves required a reduction in circumference of the dilated vein to produce a satis~actory degree of competence as is shown in the following table:-` ' ' :, ' ' ' ' ' ~ .... ... ~ . . . .....
TABLE III
S~EEP JUGULAR CIRCUMFERENCE PERCENTAGE DECREASE .
NO VEIN _ IN CMS _ _ IN
INITIAL WITH CUFFCIRC.AREA .
-_ _ 86 LEFT 2.9 1.9 34 57 . : .
RIGHT 2.5 2.1 16 29 : .
87 RIGHT 3.5 2.2 37 60 88 L~FT 4.0 2.8 30 51 .;
RIGHT 3.9 2.8 28 48 ~:
89 LEFT 2.6 2.2 15 28 RIGHT 2.7 2.0 26 25 '::
RIGHT 1.9 1.5 21 38 `: :
gl LEFT 2.0 1.7 15 28 RIGHT 2.4 2.0 17 31 : -_ _ ,. _. ~` :;'~."'';
The average reduction of circumference was 24 with a range of 15% to 34%. This is a moderate degree of narrowing but it must be placed in the context that veins are normally ~-`
in a partially collapsed state when compressed by surrouding tissue~ One vein ~as made incompetent by creating an arterio-venous fistula which caused dilatation of the valve ring~ The reduction in circumference necessary to restore competence was 52~
The animal model of venous valve incompetence is a `
useful one because, :`.
i) The venous valves in the internal jugular vein in sheep appear macroscopically identical to `;
the venous valves in humans. The histology of the vein wall is also similar. ..
. ", "..
. ;;.,-" ' " ' ' ii) The cause of the incompetence is the same as that which applies in over 90~ of cases of varicose veins in at leas~ 50% of cases of deep venous disease in humans, that is, hydrostatic pressure overcoming the strength of the vein.
iii) An arteri~venous fistula has been found to mimic venous insufficiency in dogs, and has ~:
been used with proximal venous occlusion in dogs and rats. The arteriovenous fistula alone is sufficient to produce swelling of the limb in dogs and lymph changes which are similar to the disease o~ hùmans~ It is also well known that an arteriovenous fistula can produce varicosities in humans and ulceration ..
even of the upper limb~ `
iv) The response of the ~ein wall histologically :
to a fistula has similarities to changes observed in saphenous veins in humans when used as an arterial graft particularly in the intimal prolifera~ion, vein wall fibrosis and variable damage to the internal elastic : :
lamina~ The changes are, however, less severe~ `
v) Destructive changes on the valve aod vein wall .`
are hastened both by the continuous applicat;ion of a very high pressure to the -`-.
, ,"
valve and also by the pulsatile nature of the pressure which is thought to have an adverse affect on collagen.
In two sheep, incompetence of the valves developed quickly twithin 5 days). This is despite the fact that these valves managed to remain competent for years (depending upon the age of the sbeep) of normal function. The pressures on these valves nor~ally would increase on grazing, when the head is lowered. The valves would be subjected to the hydrostatic pressure from the right atrium to the valve. The valves would also be subjected to pressures associated with coughing and Valsalva type maneuvers.
The implantation of the venous cuff protected the distal vein from the high pressure of the arteriovenous ~istula. `
This ~as demonstrated convincingly by the measured pressure `
gradient and circumferences before and after implantation.
In one sheep, this protective effect was still present nearly `
9 ~ee~s la~er at harvesting of the vein. From the results in ` ~-this sheep it could reasonably be expected that this ` `
protective effect would last many years in the normal `
situation. ~his can be seen from the fact that the fistula ^- `
had a destructive effect in five days greater than the life of the animal to that stage. ~espite 9 weeks of this stress, `
the valve functioned well with the venous cuff implanted.
The venous cuff is very effective in preventing venous ;~
valve incompetence even in the presence of abnormally high pressures. These pressu;res created incompetence in the ~ `
controls within two weeks yet this did not happen with the venous cuff in situ at a mean of 20 weeks. The importance of prevention of movement of the venous cuff along the vein led to the addition of tags or ears to the venous cuff to facilitate attachment to the surrounding fascia.
There was minimal damage to the vein wall and no complication attributable to the venous cuff itself.
Comparison of light microscopy control and implant results showed that negligible effects on the vein wall are attributable to the venous cuff.
The silicone rubber sheet venous cuffs produced a similar reaction in all cases of implants. The macriscopic reaction to silicone rubber sheet around the adventitia of the vein was a smooth fine fibrous opaque white reaction.
The silicone rubber sheet lifted easily away from the vein.
There was no incorporation of the silicone rubber sheet into the vein wall and there was a small amount of clear serous fluid between the wall of the vein and the silicone rubber sheet.
The macroscopic appearance was that of serous membrane. When the vessel lumen was opened underneath the silicone rubber sheet cuff, there was minimal thickening of the wall.
The inti~al lining itself appeared macroscopically identical to the surrounding intima. ~here was no evidence of any thrombotic process, no ulceration, no fibrotic obstruction, no haemorrhage into the wall and no thickening -~ 1 32446 1 of the vein w~ll. One sheep had a decrease in the diameter of the wall distal to the implant. This appeared to be related to a subcutaneous suture distally which was compressing the vein. This was not associated with the silicone cuffs themselves.
Based on microscopic observation, light microscopy, scanning electron microscopy and pressure measurements, the following conclusions can be drawn from the above animal studies.
The venous cuff is made from a material with , favourable biocompatibility characteristics in terms of -interactions with veins. There was minimal or no difference in histology of implant specimens and control specimens on the vein wall. Out of 50 implants in animals, there have `
1~ only been three complications with two implants. There were : .....
two infections and one thrombosis. This thrombosis was probably caused by the pressure measurement technique. The .
two infections would be expected with any operation. The , silicone cuff has not caused complications beyond those expected with any similar operation with no implant. Thus no `
complication can be directly attributed to the cuff.
The venous cuff is highly successful at restoring competence to incompeeent venous valves which are not ~ -destroyed by thrombophlebitis. Competence was markedly improved in all 20 of 20 valves in animal models. The improvement is maintained at a mean implant time of 12 weeks. This is also supported by six implaats which ~
',' ;`: ' ' `
','``. `~' prevented incompetence despite very high retrograde pressure gradient for a mean implant time of 20 weeks and a maximum of 28 wee~s implant time.
The animal models are confirmed by the human work. The only complication out of 16 implants was one infection which had no long-term morbidity after removal of the cuff. There were two prophylactic implants. The implant of the cuff produced com-petence in twelve out of the remaining thirteen valves. The other valve was affected by thrombophle-bitis, which is now regarded as a relative contra-indiction to the procedure. Of these thirteen valves, ten were for varicose veins and all patients had resolution of symptoms. The mean implant time was 25 weeks. The longest implant was 15 months.
This long-term implant has had no recurrence of an ulcer which was present five months continuous preoperativaly. The remaining three implants were on a patient with deep venous disease. He had healing o$ his ulcers and has minimal symptoms three months postoperatively.
The venous cu$$ of the invention is a sa$e, reliable device for producing long-term competence in incompetent venous valves. This produces a corres-ponding resolution of symptoms in people with vari-cose veins and chronic deep venous insu$$iciency.
The venous cuff may be placed into position and tightened around the vein by the use of an appli-cator. A suitable applicator has an .
:. ~,. .
A
-` 1 324461 upstanding tab which receives the loop of the cu~f. The cuff is then passed around the vein and the free end of the cuff connected to a cuff adjus~or mounted on the applicator body with a ratchet mechanism which allows the adjustor to be -moved relative to the applicator and to be held in any ~-selected position. A stapling gun incorporatea within the applicator is used to secure the overlapping end of the cuff '`
to the loop 13.
As will be apparent from the above description, the applicator allows a single surgeon to apply the cuff to a .-i vein. With one hand, the surgeon using the applicator can adjust the cuff to the desired diameter and then test the valve for competence~ After final adjustment of the diameter, the surgeon then staples the overlapping portions of the cuff together. If need be, the free end af the band is trimmed and the cuff removed from the applicator.
Various modifications may be made in deta~ls of the cuff and the method of restoring venous valve competency without departing from the scope and ambit of the invention.
,.` .','. :`:
. ..: .
~ . ....
~, .
Claims (32)
1. A cuff for restoring competence to an incom-petent venous valve, said cuff comprising a band of biocompatible implantable material that is not stretchable at blood flow pressures, the band being of sufficient length to encompass the vein at the site of the venous valve, with portions of the band overlapping, the overlapping portions being joinable together to form a cuff of desired circumference small enough to restore competence yet not too tight to decrease blood flow, and said band being notched to accommodate application at a venous junction.
2. A cuff for restoring competence to an incompetent venous valve, said cuff comprising a band of biocompatible implantable material that is not stretchable at blood flow pressures, the band being of sufficient length to encompass the vein at the site of the venous valve, with portions of the band overlapping, and means for securing the overlapping portions together to form a cuff of desired circumference small enough to restore competence yet not too tight to decrease blood flow, and said band being notched to accommodate application at a venous juncture.
3. A cuff according to claim 1 or 2, and further including means for securing the cuff to the surrounding tissue.
4. A cuff according to claim 3, wherein the securing means comprises a pair of tabs secured one at each end of a transverse portion that extends outwardly from either side of the band.
5. A cuff according to claim 1 or 2, wherein one end of the band at the overlapping joint has deformable a portion of reduced thickness extending longitudinally from the bottom face of the band, whereby any inner surface discontinuities with respect to the wall of the vein at the overlap are reduced.
6. A cuff according to claim 5 wherein the reduced thickness portion also extends transversely each side of the strap and constitutes means for securing the cuff to the surrounding tissue.
7. A cuff according to claim 6 wherein the securing means includes tab secured to or integral with each transverse portion.
8. A cuff according to claim 1 or claim 2 and further including loop means at or adjacent one end of the band, said loop being spaced from the band so as to receive the other end of the band.
9. A cuff according to claim 8 wherein the band portion within the loop is secured to the loop to form the cuff of desired circumference.
10. A cuff according to claim 1 or claim 2 and further including means at or adjacent one end of the band for attaching the band to an applicator.
11. A cuff according to claim 10 wherein the free end of the band overlies the attachment means and is secured thereto to form the cuff of desired circumference.
12. A cuff according to claim 1 or claim 2 wherein the band has at one end connector means comprising an elongated strap of implantable material disposed transversely to the band, said strap having inwardly directed slits that divide the connector means into a band attachment portion and an outer deformable portion.
13. A cuff according to claim 12, wherein the deformable portion extends outwardly from each side of the band and constitutes means for securing the cuff to the surrounding tissue.
14. A cuff according to claim 13, wherein the securing means includes a tab secured to or integral with each transverse portion.
15. A cuff according to claim 13, wherein the band attachment portion includes a loop disposed above the band.
16. A cuff according to claim 1 or 2, wherein the implantable material comprises a composite including a reinforcing fabric.
17. A cuff according to claim 1 or 2, wherein the implantable material is cured silicon rubber sheeting.
18. A cuff according to claim 17, wherein the cured silicone rubber sheeting is reinforced with a woven polyester.
19. A venous valve competence-restoring cuff, said cuff comprising an elongated band, having one end and opposite overlapping end portions, of biocompatible implantable material, said material having an elasticity such that it is not stretchable at blood flow pressures, the band having a length to encompass the vein at the site of the venous valve, with said end portions of the band overlapping, the end portions being joinable together to form a cuff of desired circumference small enough to restore competence yet not too tight to decrease blood flow, and further including loop means adjacent said end portion of the band to which said overlapping end portion of the band is joined.
20. A venous valve competence-restoring cuff, said cuff comprising an elongated band, having one end and opposite overlapping end portions, of bicompatible implantable material, said material having an elasticity such that it is not stretchable at blood flow pressures, the band having a length to encompass the vein at the site of the venous valve, with said end portions of the band overlapping, and means for securing the end portions together to form a cuff of desired circumference small enough to restore competence yet not too tight to decrease blood flow and further including loop means adjacent said end portion of the band to which said overlapping end portion of the band is joined.
21. A cuff according to claim 19 or 20, and further including means for securing the cuff to the surrounding tissue.
22. A cuff according to claim 21, wherein the securing means comprises a pair of tabs secured one at each end of a transverse portion that extends outwardly from either side of the band.
23. A cuff according to claim 19 or 20, wherein said loop means adjacent said one end of the band is spaced from the band so as to receive said overlapping end of the band within the loop.
24. A cuff according to claim 23, wherein the band portion within the loop is secured to the loop to form the cuff of desired circumference.
25. A cuff according to claim 19 or 20, wherein said loop means adjacent said one end of the band is also used for attaching the band to an applicator.
26. A cuff according to claim 19 or 20, wherein the band has at said one end connector means comprising an elongated strap of implantable material disposed transversely to the band, said strap having inwardly directed slits that divide the connector means into a band attachment portion, free ends of the strap in the band attachment portion being folded over one another to provide the loop means and an outer deformable portion.
27. A cuff according to claim 26, wherein the outer deformable portion extends outwardly from each side of the band and constitutes means for securing the cuff to the surrounding tissue.
28. A cuff according to claim 27, wherein the securing means includes a tab secured to or integral with each transverse portion.
29. A cuff according to claim 27, wherein the band attachment portion includes a loop disposed above the band.
30. A cuff according to claim 19, wherein the implantable material comprises a composite including a reinforcing fabric.
31. A cuff according to claim 19, wherein the implantable material is cured silicone rubber sheeting.
32. A cuff according to claim 31, wherein the cured silicone rubber sheeting is reinforced with a woven polyester.
Applications Claiming Priority (6)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| AUPH6992 | 1986-07-17 | ||
| AUPH699286 | 1986-07-17 | ||
| AUPI0270 | 1987-02-10 | ||
| AUPI027087 | 1987-02-10 | ||
| AUPI1053 | 1987-03-24 | ||
| AUPI105387 | 1987-03-24 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1324461C true CA1324461C (en) | 1993-11-23 |
Family
ID=27157309
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000542284A Expired - Fee Related CA1324461C (en) | 1986-07-17 | 1987-07-16 | Correction of incompetent venous valves |
Country Status (9)
| Country | Link |
|---|---|
| US (2) | US4904254A (en) |
| EP (1) | EP0276254A4 (en) |
| JP (1) | JP2579655B2 (en) |
| AU (1) | AU608527B2 (en) |
| CA (1) | CA1324461C (en) |
| DK (1) | DK134588A (en) |
| FI (1) | FI881022A (en) |
| NO (1) | NO881176L (en) |
| WO (1) | WO1988000454A1 (en) |
Families Citing this family (53)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0302093A4 (en) * | 1987-02-10 | 1989-08-30 | Vaso Products Australia Pty Lt | Venous cuff applicator, cartridge and cuff. |
| AU646828B2 (en) * | 1987-02-10 | 1994-03-10 | Vaso Products, Inc | Venous cuff applicator |
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-
1987
- 1987-07-13 US US07/191,168 patent/US4904254A/en not_active Expired - Fee Related
- 1987-07-13 EP EP19870904669 patent/EP0276254A4/en not_active Withdrawn
- 1987-07-13 WO PCT/AU1987/000215 patent/WO1988000454A1/en not_active Application Discontinuation
- 1987-07-13 AU AU77068/87A patent/AU608527B2/en not_active Ceased
- 1987-07-13 JP JP62504331A patent/JP2579655B2/en not_active Expired - Lifetime
- 1987-07-16 CA CA000542284A patent/CA1324461C/en not_active Expired - Fee Related
-
1988
- 1988-03-04 FI FI881022A patent/FI881022A/en not_active IP Right Cessation
- 1988-03-11 DK DK134588A patent/DK134588A/en not_active Application Discontinuation
- 1988-03-17 NO NO881176A patent/NO881176L/en unknown
-
1991
- 1991-11-08 US US07/793,236 patent/US5147389A/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| NO881176D0 (en) | 1988-03-17 |
| WO1988000454A1 (en) | 1988-01-28 |
| DK134588A (en) | 1988-03-17 |
| EP0276254A1 (en) | 1988-08-03 |
| FI881022A0 (en) | 1988-03-04 |
| US4904254A (en) | 1990-02-27 |
| NO881176L (en) | 1988-03-17 |
| DK134588D0 (en) | 1988-03-11 |
| US5147389A (en) | 1992-09-15 |
| AU608527B2 (en) | 1991-04-11 |
| JPH01500246A (en) | 1989-02-02 |
| FI881022A (en) | 1988-03-04 |
| EP0276254A4 (en) | 1989-07-26 |
| JP2579655B2 (en) | 1997-02-05 |
| AU7706887A (en) | 1988-02-10 |
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