US 20060135962 A1
Disclosed is an expandable transluminal sheath, for introduction into the body while in a first, low cross-sectional area configuration, and subsequent expansion of at least a part of the distal end of the sheath to a second, enlarged cross-sectional configuration. The sheath is configured for use in the vascular system. The access route is through the inferior vena cava to the right atrium, where a trans-septal puncture, followed by advancement of the catheter is completed. The distal end of the sheath is maintained in the first, low cross-sectional configuration during advancement through the atrial septum into the left atrium. The distal end of the sheath is expanded using a radial dilator. In one application, the sheath is utilized to provide access for a diagnostic or therapeutic procedure such as electrophysiological mapping of the heart, radio-frequency ablation of left atrial tissue, placement of atrial implants, valve repair, or the like.
1. An expandable endovascular access sheath for providing minimally invasive access to a left atrium, comprising:
an axially elongate sheath tube with a proximal end, a distal end, and a central through lumen, the sheath having a distal region which is expandable in circumference in response to outward pressure applied therein;
a hub coupled to the proximal end of the sheath tube, the hub configured to facilitate the passage of instrumentation;
an obturator that extend through the central lumen and which is configured to occlude the central lumen of the sheath during insertion, the obturator comprising an obturator hub that is releasably couples to the hub of the sheath; and
a guidewire lumen within the obturator;
wherein. the obturator is a balloon dilator capable of expanding the distal region of the sheath from a collapsed configuration to an expanded configuration.
2. The endovascular access sheath of
3. The endovascular access sheath of
4. The endovascular access sheath of
5. The endovascular access sheath of
6. The endovascular access sheath of
7. The endovascular access sheath of
8. The endovascular access sheath of
9. A method of instrumenting a left atrium of a patient comprising the steps of:
routing a guidewire into the right atrium from a peripheral vein,
inserting a sheath with a collapsed distal region and a pre-inserted dilator into the patient over the guidewire;
advancing the sheath to a treatment or diagnostic site within the right atrium of the heart;
performing a trans-septal puncture between the right and left atrium and advancing the collapsed distal region through the puncture into the left atrium;
dilating the distal region of the sheath so that the distal region of the sheath is expanded;
collapsing the dilator;
removing the dilator from the sheath,
inserting instrumentation through the lumen of the sheath into the left atrium,
performing therapy or diagnosis with the instrumentation, and
removing the sheath from the patient.
10. The method of
11. The method of
12. The method of
13. The method of
14. The method of
15. The method of
16. The method of
17. The method of
18. A sheath adapted for insertion into the right or left atrium of the heart comprising:
a diametrically collapsed distal end;
means for tracking the sheath over an already placed guidewire to a target treatment site in the right or left atrium of the heart,
means for articulating the distal end of the sheath,,
means for dilating at least a portion of the distal end of the sheath, and
means for removal of the sheath from the patient.
19. The sheath of
20. The sheath of
21. The sheath of
22. The sheath of
This application claims priority to U.S. application Ser. No. 60/709,240, filed Aug. 18, 2005, U.S. application Ser. No. 60/674,226, filed Apr. 22, 2005, U.S. application Ser. No. 60/660,512, filed on Mar. 9, 2005, and U.S. Provisional Application Ser. No. 60/608,355, filed on Sep. 9, 2004, the entirety of which are hereby incorporated by reference herein.
1. Field of the Invention
The invention relates to medical devices and, more particularly, to methods and devices for accessing the cardiovascular system.
2. Description of the Related Art
A wide variety of diagnostic or therapeutic procedures involves the introduction of a device into the vasculature through a percutaneous incision at an access site. Such regions of the vasculature, preferred for access, include both the arteries and veins, typically at peripheral locations in the body. Typical access sites include the jugular vein, the subclavian artery, the subclavian vein, the brachial artery, the femoral arteries and the femoral veins. Techniques commonly known for such vascular access include the Seldinger technique. The Seldinger technique involves using a hollow needle to puncture the skin and gain access to the selected artery or vein. A guidewire is next placed through the hollow needle into the selected region of vasculature. The guidewire may be advanced to a target location in the vasculature, often more than 100 cm away from the access site. The needle is removed and a tapered dilator with a sheath and a central lumen in the dilator is advanced over the guidewire into the vasculature. The dilator is next removed and a guide catheter is advanced through the sheath over the guidewire. The guide catheter can be advanced all the way, or part way, to the target site. The guide catheter, following, or without, removal of the guidewire can be used for directing therapeutic or diagnostic catheters to regions of the vasculature and central circulation, including external and internal structures of the heart. A general objective of access systems, which have been developed for this purpose, is to minimize the cross-sectional area of the access lumen, while maximizing the available space for the diagnostic or therapeutic catheter placement therethrough. These procedures are especially suited for coronary angioplasty, stent placement, cerebrovascular coil placement, diagnostic cardiac catheterization, and the like.
Electrophysiology (EP) mapping and cardiac tissue ablation procedures are examples of diagnostic or therapeutic interventional procedures that are commonly performed on the heart. The procedure involves the steps of inserting a hollow needle, with a hemostasis valve affixed to its proximal end, into the femoral vein via a percutaneous puncture. A guidewire is next inserted through the hemostasis valve and the central lumen of the needle into the femoral vein. The guidewire is routed, under fluoroscopic control, cranially toward the heart until it reaches the right atrium via the inferior vena cava. The hollow needle is removed and a sheath with a tapered tip central obturator further including a central guidewire lumen, termed a dilator, is routed over the guidewire, through the skin puncture, through the wall of the femoral vein, and into the central lumen of the femoral vein. The central obturator or dilator is next removed. A Mullins catheter is next routed through the sheath, over the guidewire, and advanced to the right atrium. The guidewire is removed and a Brockenbrough™ (Trademark of C. R. Bard, Inc.)-type needle is inserted through the proximal end of the Mullins™ catheter and routed to the right atrium. The Mullins catheter is positioned, under fluoroscopic guidance, so that its distal end is located in the Foramenal valley, a feature in the septal wall of myocardium that divides the right atrium from the left atrium. The Foramenal valley is the remains of a communication between the right and left atrium, which exists prior to birth, but which closes following birth due to the pressures imposed by the beating heart of the newborn infant. The Brockenbrough needle is next advanced through the atrial septum in the general region of the Foramenal valley. The Mullins catheter is next advanced over the Brockenbrough needle until its distal end resides within the left atrium. Hemostatic valves at the proximal end of all hollow devices permit sealing around catheters and devices inserted therethrough with corresponding prevention or minimization of blood loss and the entry of air.
The procedure continues with the Brockenbrough needle being withdrawn and replaced with a 0.032 to 0.038 inch diameter guidewire, generally of the stiff variety. This guidewire may have a bifurcated distal end to prevent inadvertent retraction once the guidewire has been advanced and expanded into the left atrium. The Mullins catheter is next withdrawn and replaced with a guide catheter having internal dimensions generally around 8 French and a tapered, removable obturator. The guide catheter is advanced into the right atrium and across the atrial septum, following which the obturator is removed. At this time, diagnostic and therapeutic catheters can be advanced into the left atrium so that appropriate EP mapping and ablation can occur. However, problems sometime arise, when trying to pass the guide catheter across the atrial septum, in that the tract generated by the Brockenbrough needle and Mullins catheter closes too tightly to allow passage of the guide catheter. At this point, a balloon catheter is advanced over the guidewire and through the guide catheter. The balloon catheter is advanced so that its dilatation balloon traverses the atrial septum. The balloon catheter is next inflated to stretch the tissues surrounding the atrial septal puncture. At this time, the guide catheter can have its dilator re-inserted and the entire assembly advanced over the guidewire through the atrial septum and into the left atrium.
Current therapeutic techniques may involve advancing an EP mapping catheter through the guide catheter and positioning the EP mapping catheter at various locations within the left atrium. Electrocardiogram signals are sensed by the EP mapping catheter. These signals are conducted or transmitted from the distal tip to the proximal end over electrical lines routed along the length of the EP catheter. The signals are analyzed by equipment electrically connected to the proximal end of the EP mapping catheter. Catheter guidance is generally accomplished using X-ray fluoroscopy, ultrasound imaging such as ICE, TEE, and the like. Therapy generally involves radio-frequency (RF) electromagnetic wave generation by external equipment electrically connected to an EP therapeutic catheter. The EP therapeutic catheter is advanced into the left atrium into regions of foci of electrical interference of the hearts normal electrical conduction. Application of such radio-frequency energy at the tip of the EP therapeutic catheter, which is brought into contact with the myocardium, causes tissue ablation and the elimination of the sources of these spurious signals or re-entry waveforms. A primary area targeted for RF tissue ablation is the area surrounding the origin of the pulmonary veins. Often a ring-type electrode is beneficial in performing this procedure. Such tissue ablation can be performed using RF energy to generate heat, but it can also be performed using microwaves, Ohmic heating, high-intensity focused ultrasound (HIFU), or even cryogenic cooling. The cryogenic cooling may have certain advantages relative to heating methodologies in that tissue damage is lessened. Although a single atrial septal puncture may be adequate for electrophysiological mapping of the left atrium, therapeutic systems, including RF ablation devices often require that two atrial septal punctures be performed. A risk of atrial septal punctures includes potentially perforating the aorta, a high-pressure outlet line, which resides quite close to the atrial septum.
Provision is generally made to deflect instrumentation through substantial angles, between 20 and 90 degrees, within the right atrium to gain access to the atrial septum from a catheter routed cranially within the inferior vena cava. To address this situation, the Brockenbrough needle, the Mullins catheter, or both, are substantially curved and significant skill is required, on the part of the cardiologist or electrophysiologist to negotiate the path to the atrial septum and into the left atrium.
One of the primary issues that arise during electrophysiology procedures in the heart is the need to remove and replace multiple instruments multiple times, which is highly expensive and adds substantial time to the conduct of the procedure. A reduction in the number of catheter and guidewire passes and interchanges would reduce procedure time, reduce the risk of complications, improve patient outcomes, reduce procedural cost, and increase the number of cases that could be performed at a given catheterization lab. Current procedures involving multiple atrial septal penetrations would be reduced in frequency or become less time consuming and less risky if only a single atrial septal penetration was necessary. Additional benefit could be derived if larger catheters could be used, thus enabling the use of more sophisticated, powerful, and accurate instruments to improve patient outcomes. The limitations of current systems are accepted by physicians but the need for improved instrumentation is clear. Furthermore, placement of implants within the left atrium, such as the Atritech Watchman™ or the Microvena PLAATO™ would be facilitated if a larger working channel could be made available.
Further reading related to the diagnosis and treatment of atrial fibrillation (AF) includes Hocini, M, et al., Techniques for Curative Treatment of Atrial Fibrillation, J. Cardiovasc Electrophysiol, 15(12): 1467-1471, 2004 and Pappone, C and Santinelli, V, The Who, What, Why, and How-to Guide for Circumferential Pulmonary Vein Ablation, J. Cardiovasc Electrophysiol, 15(10): 1226-1230, 2004. Further reading on RF ablation includes Chandrakantan, A, and Greenberg, M, Radiofrequency Catheter Ablation, eMedicine, topic 2957 Oct. 28, 2004. Further reading regarding catheter approaches to treating pathologies of the left atrium include Ross, et al, Transseptal Left Atrial Puncture; New Technique for the Measurement of Left Atrial Pressure in Man, Am J. Cardiol, 653-655, May 1959 and Changsheng M, et al., Transseptal Approach, an Indispensable Complement to Retrograde Aortic Approach for Radiofrequency Catheter Ablation of Left-Sided Accessory Pathways, J. HK Coll Cardiol, 3: 107-111,1995.
A need, therefore, remains for improved access technology, which allows a device to be percutaneously or surgically introduced, endovascularly advanced to the right atrium, and enabled to cross the atrial septum by way of a myocardial puncture and Dotter-style follow-through. The device would further permit dilation of the myocardial puncture in the region of the atrial septum so that the sheath could pass relatively large diameter instruments or catheters, or multiple catheters through the same puncture. Such large dilations of the tissues of the atrial septum need to be performed in such a way that the residual defect is minimized when the device is removed. It would be beneficial if a cardiologist or hospital did not need to inventory and use a range of catheter diameters. It would be far more useful if one catheter or sheath diameter could fit the majority of patients or devices. Ideally, the catheter or sheath would be able to enter a vessel or body lumen with a diameter of 3 to 12 French or smaller, and be able to pass instruments through a central lumen that is 14 to 30 French. The sheath or catheter would be capable of gently dilating the atrial septum using radially outwardly directed force and of permitting the exchange of instrumentation therethrough without being removed from the body. The sheath or catheter would also be maximally visible under fluoroscopy and would be relatively inexpensive to manufacture. The sheath or catheter would be kink resistant, provide a stable or stiff platform for atrial septum penetration, and minimize abrasion and damage to instrumentation being passed therethrough. The sheath or catheter would further minimize the potential for injury to body lumen or cavity walls or surrounding structures. The sheath or catheter would further possess certain steering capabilities so that it could be negotiated through substantial curves or tortuosity and permit instrument movement within the sheath.
Accordingly, an embodiment of the present invention comprises an expandable endovascular access sheath for providing minimally invasive access to a left atrium. An axially elongate sheath tube includes a proximal end, a distal end, and a central through lumen. The sheath has a distal region which is expandable in circumference in response to outward pressure applied therein. A hub is coupled to the proximal end of the sheath tube. The hub is configured to facilitate the passage of instrumentation. An obturator extends through the central lumen and is configured to occlude the central lumen of the sheath during insertion. The obturator comprises an obturator hub that is releasably coupled to the hub of the sheath. A guidewire lumen is within the obturator. The obturator is a balloon dilator capable of expanding the distal region of the sheath from a collapsed configuration to an expanded configuration.
Another embodiment of the present invention is a method of instrumenting a left atrium of a patient. A guidewire is routed into the right atrium from a peripheral vein. A sheath is inserted with a collapsed distal region and a pre-inserted dilator into the patient over the guidewire. The sheath is advanced to a treatment or diagnostic site within the right atrium of the heart. A trans-septal puncture is made between the right and left atrium. The collapsed distal region is advanced through the puncture into the left atrium. The distal region of the sheath is dilated so that the distal region of the sheath is expanded. The dilator is collapsed and removed from the sheath. Instrumentation is inserted through the lumen of the sheath into the left atrium. A therapy or diagnosis procedure is performed with the instrumentation. The sheath is removed from the patient.
Another embodiment of the invention is a sheath adapted for insertion into the right or left atrium of the heart. The sheath has a diametrically collapsed distal end and means for tracking the sheath over an already placed guidewire to a target treatment site in the right or left atrium of the heart. The sheath also includes means for articulating the distal end of the sheath, means for dilating at least a portion of the distal end of the sheath, and means for removal of the sheath from the patient.
In another embodiment, a radially expanding access sheath is used to provide access to the left atrium by way of a tran's-septal puncture and advancement in the atrial septum dividing the right and left atriums. In an particular embodiment, the sheath can have an introduction outside diameter that ranges from 3 to 12 French with a preferred range of 5 to 10 French. The diameter of the sheath can be expandable to permit instruments ranging up to 30 French to pass therethrough, with a preferred range of between 3 and 20 French. The sheath can have a working length ranging between 40-cm and 200-cm with a preferred length of 75-cm to 150-cm. The ability to pass the traditional electrophysiology therapeutic and diagnostic catheters and instruments as well as larger, more innovative, instruments through a catheter introduced with a small outside diameter is derived from the ability to atraumatically expand the distal end of the catheter or sheath to create a larger through lumen to access the cardiac chambers. The ability to pass multiple catheters through a single sheath with a single septal penetration is inherently safer and less time-consuming than a multiple septal puncture procedure. The expandable distal end of the catheter can comprise between 5% and 95% of the overall working length of the catheter. The proximal end of the catheter is generally larger than the distal end to provide for pushability, torqueability (preferably approximately 1:1 torqueability), steerability, control, and the ability to easily pass large diameter instruments therethrough. In an embodiment, the sheath can be routed to its destination over one or more already placed guidewires with a diameter ranging from 0.010 inches up to 0.040 inches and generally approximating 0.035 inches in diameter. An advantage of approaching the treatment site by the veins, instead of the arteries, is that the venous pressure is lower than that in the arterial system, thus reducing the potential for catastrophic hemorrhage during the procedure.
Another embodiment of the invention comprises an endovascular access system for providing minimally invasive access to atrial structures of the mammalian heart. The system includes an access sheath comprising an axially elongate tubular body that defines a lumen extending from the proximal end to the distal end of the sheath. At least a portion of the distal end of the elongate tubular body is expandable from a first, smaller cross-sectional profile to a second, greater cross-sectional profile. In an embodiment, the first, smaller cross-sectional profile is created by making axially oriented folds in the sheath material. These folds may be located in only one circumferential position on the sheath, or there may be a plurality of such folds or longitudinally oriented crimps in the sheath. The folds or crimps may be made permanent or semi-permanent by heat-setting the structure, once folded. In an embodiment, a releasable or expandable jacket is carried by the access sheath to restrain at least a portion of the elongate tubular structure in the first, smaller cross-sectional profile during insertion and up to or during inflation of the distal region. In another embodiment, the jacket is removed prior to inserting the sheath into the patient. In an embodiment, the elongate tubular body is sufficiently pliable to allow the passage of objects having a maximum cross-sectional size larger than an inner diameter of the elongate tubular body in the second, greater cross-sectional profile. The adaptability to objects of larger dimension is accomplished by pliability or re-shaping of the cross-section to the larger dimension in one direction accompanied by a reduction in dimension in a lateral direction. The adaptability may also be generated through the use of malleable or elastomerically deformable sheath material. This re-shaping or non-round cross-section can be beneficial in passing two or more catheters through a single sheath with a minimum lateral cross-sectional area.
In another embodiment of the invention, a transluminal access sheath assembly for providing minimally invasive access comprises an elongate tubular member having a proximal end and a distal end and defining a working inner lumen. In this embodiment, the tubular member comprises a folded or creased sheath that can be expanded by a dilatation balloon. The dilatation balloon, if filled with fluids, preferably liquids and further preferably radiopaque liquids, at appropriate pressure, can generate the force to radially dilate or expand the sheath. The dilatation balloon is removable to permit subsequent instrument passage through the sheath. Longitudinal runners may be disposed within the sheath to serve as tracks for instrumentation, which further minimize friction while minimizing the risk of catching the instrument on the expandable plastic tubular member. Such longitudinal runners are preferably circumferentially affixed within the sheath so as not to shift out of alignment. In yet another embodiment, the longitudinal runners may be replaced by longitudinally oriented ridges and valleys, termed flutes. The flutes, or runners, can be oriented along the longitudinal axis of the sheath, or they can be oriented in a spiral, or rifled, fashion.
In many of the embodiments, the proximal end of the access assembly, apparatus, or device is preferably fabricated as a structure that is flexible, resistant to kinking, and further retains both column strength and torqueability. Such structures include tubes fabricated with coils or braided reinforcements and preferably comprise inner walls that prevent the reinforcing structures from protruding, poking through, or becoming exposed to the inner lumen of the access apparatus. Such proximal end configurations may be single lumen, or multi-lumen designs, with a main lumen suitable for instrument, guidewire, endoscope, or obturator passage and additional lumens being suitable for control and operational functions such as balloon inflation. Such proximal tube assemblies can be affixed to the proximal end of the distal expandable segments described heretofore. In an embodiment, the proximal end of the catheter includes an inner layer of thin polymeric material, an outer layer of polymeric material, and a central region comprising a coil, braid, stent, plurality of hoops, or other reinforcement. It is beneficial to create a bond between the outer and inner layers at a plurality of points, most preferably at the interstices or perforations in the reinforcement structure, which is generally fenestrated. Such bonding between the inner and outer layers causes a braided structure to lock in place. In another embodiment, the inner and outer layers are not fused or bonded together in at least some, or all, places. When similar materials are used for the inner and outer layers, the sheath structure can advantageously be fabricated by fusing of the inner and outer layer to create a uniform, non-layered structure surrounding the reinforcement. The polymeric materials used for the outer wall of the jacket are preferably elastomeric to maximize flexibility of the catheter. The polymeric materials used in the composite catheter inner wall may be the same materials as those used for the outer wall, or they may be different. In another embodiment, a composite tubular structure can be co-extruded by extruding a polymeric compound with a stent, braid, or coil structure embedded therein. The reinforcing structure is preferably fabricated from annealed metals, such as fully annealed stainless steel, titanium, or the like. In this embodiment, once expanded, the folds or crimps can be held open by the reinforcement structure embedded within the sheath, wherein the reinforcement structure is malleable but retains sufficient force to overcome any forces imparted by the sheath tubing.
In an embodiment of the invention, it is beneficial that the sheath comprise a radiopaque marker or markers. The radiopaque markers may be affixed to the non-expandable portion or they may be affixed to the expandable portion. Markers affixed to the radially expandable portion preferably do not restrain the sheath or catheter from radial expansion or collapse. Markers affixed to the non-expandable portion, such as the catheter shaft of a balloon dilator can be simple rings that are not radially expandable. Radiopaque markers include shapes fabricated from malleable material such as gold, platinum, tantalum, platinum iridium, and the like. Radiopacity can also be increased by vapor deposition coating or plating metal parts of the catheter with metals or alloys of gold, platinum, tantalum, platinum-iridium, and the like. Expandable markers may be fabricated as undulated or wavy rings, bendable wire wound circumferentially around the sheath, or other structures such as are found commonly on stents, grafts, stent-grafts, or catheters used for endovascular access in the body. Expandable radiopaque structures may also include disconnected or incomplete surround shapes affixed to the surface of a sleeve or other expandable shape. Non-expandable structures include circular rings or other structures that completely surround the catheter circumferentially and are strong enough to resist expansion. In another embodiment, the polymeric materials of the catheter or sheath may be loaded with radiopaque filler materials such as, but not limited to, bismuth salts, or barium salts, or the like, at percentages ranging from 1% to 50% by weight in order to increase radiopacity. The radiopaque markers allow the sheath to be guided and monitored using fluoroscopy.
In order to enable radial or circumferential expansive translation of the reinforcement, it may be beneficial not to completely bond the inner and outer layers together, thus allowing for some motion of the reinforcement in translation as well as the normal circumferential expansion. Regions of non-bonding may be created by selective bonding between the two layers or by creating non-bonding regions using a slip layer fabricated from polymers, ceramics or metals. Radial expansion capabilities are important because the proximal end needs to transition to the distal expansive end and, to minimize manufacturing costs, the same catheter may be employed at both the proximal and distal end, with the expansive distal end undergoing secondary operations to permit radial or diametric expansion.
In another embodiment, the distal end of the catheter is fabricated using an inner tubular layer, which is thin and lubricious. This inner layer is fabricated from materials such as, but not limited to, FEP, PTFE, polyamide, polyethylene, polypropylene, Pebax, Hytrel, and the like. The reinforcement layer comprises a coil, braid, stent, or plurality of expandable, foldable, or collapsible rings, which are generally malleable and maintain their shape once deformed. Preferred materials for fabricating the reinforcement layer include but are not limited to, stainless steel, tantalum, gold, platinum, platinum-iridium, titanium, nitinol, and the like. The materials are preferably fully annealed or, in the case of nitinol, fully martensitic. The outer layer is fabricated from materials such as, but not limited to, FEP, PTFE, polyamide, polyethylene, polypropylene, polyurethane, Pebax, Hytrel, and the like. The inner layer is fused or bonded to the outer layer through holes in the reinforcement layer to create a composite unitary structure. The structure is crimped radially inward to a reduced cross-sectional area. A balloon dilator is inserted into the structure before crimping or after an initial crimping and before a final sheath crimping. The balloon dilator is capable of forced radial, or diametric, expansion of the reinforcement layer, which provides sufficient strength necessary to overcome any forces imparted by the polymeric tubing, thus controlling the cross-sectional shape of the polymeric tubing. The dilator is also capable of overcoming any forces imparted by tissues, including atrial or even ventricular myocardial tissue, through which the sheath is inserted.
Another embodiment of the invention comprises a method of providing endovascular access to the left atrium. The method first comprises percutaneously placing a hollow needle into the femoral vein, inserting a guidewire through the hollow needle into the vein, withdrawing the needle, and inserting a sheath with a tapered obturator into the puncture site and into the vein over the guidewire. The guidewire is next withdrawn, as is the tapered obturator and a 0.032 to 0.035-inch stiff guidewire is advanced into the vein and to the level of the right atrium or superior vena cava (SVC) through the inferior vena cava (IVC). A radially expandable sheath is next advanced into the femoral vein and advanced to the right atrium over the guidewire. The expandable sheath is articulated at its distal end so that it is turned toward and positioned against the Foramen Ovale of the atrial septum. The guidewire is next withdrawn and replaced with a Brockenbrough-type needle, which is advanced through the guidewire lumen of the expandable sheath. The Brockenbrough-type needle is advanced through the atrial septum into the left atrium while maintaining the expandable sheath in position against the septal wall, either by normal cardiac movement or by mechanical forward force on the Brockenbrough needle. The expandable sheath is next advanced axially through the septal wall, over the Brockenbrough-type needle and the needle, affixed to its control wire is withdrawn from the proximal end of the expandable sheath. A dilator, positioned within the expandable-sheath is next radially expanded causing the distal end of the sheath to expand radially so as to dilate the hole in the tissues of the atrial septum. The dilator is, next, deflated and removed form the sheath, leaving a large central lumen for the passage of instruments into the left atrium. The expanded sheath is capable of holding a single instrument or multiple instruments of, for example, 8 to 10 French diameter. Suitable hemostatic and anti-reflux valves and seals are affixed the distal end of all devices except guidewires to ensure maintenance of hemostasis and prevention of air entry into the vasculature. Following therapeutic or diagnostic procedures, or both, the sheath is withdrawn from the patient allowing the septal puncture to close, thus preventing communication of blood between the right and left atrium. Throughout substantially the entire procedure, heparinized saline or other anti-thrombogenic solution is infused through an infusion port operably connected to an infusion line at the proximal end of the sheath. The infusion line is operably connected to the central lumen of the sheath, generally in the region of the hub, and the infused fluid flows out through the distal end of the sheath. In another embodiment, the distal end of the expandable portion of the sheath comprises a plurality of fenestrations or holes so that the infused fluid can exit the sheath through these holes. The infusion of this fluid is beneficial in minimizing thrombosis within or about the sheath as well as minimizing the occurrence of thromboemboli that might be generated by a sheath in the venous or arterial circulation.
In many embodiments, the expandable access sheath is configured to bend, or flex, around sharp corners and be advanced into the right atrium so that the longitudinal axis of its distal end is perpendicular to the atrial septal wall. Provision can optionally be made to actively orient or steer the sheath through the appropriate angles of between 20 to 120 degrees or more and to bend in one or even two planes of motion. The steering mechanism, in various embodiments, can be a curved guidewire and straight catheter, curved catheter and straight guidewire, a movable core guidewire, or a combination of the aforementioned. The expandable sheath also needs to be able to approach the right atrium from a variety of positions. In one embodiment, radial expansion of the distal end of the access sheath from a first smaller diameter cross-section to a second larger diameter cross-section is next performed, using a balloon dilator. The balloon dilator is subsequently removed from the sheath to permit passage of instruments that may not normally have been able to be inserted into the atrium of the heart. Once the sheath is in place, the guidewire may be removed or, preferably, it may be left in place. The atrial septum is gently dilated with radial force, preferably to a diameter of 10 mm or less, rather than being axially or translationally dilated by a tapered dilator or obturator. In most embodiments, the use of the expandable trans-septal sheath eliminates the need for multiple access system components.
In another embodiment of the invention, the expandable sheath comprises steerable members that eliminate the need for a 0.038-inch guidewire to be placed prior to sheath insertion and advancement. In another embodiment, the Brockenbrough-type needle, or septal penetrator, is integrated into the expandable sheath so that it can be used to puncture the atrium but does not need to be advanced and withdrawn through the sheath. The integral septal penetrator is actuated by the operator at the proximal end of the sheath. The controls at the proximal end of the sheath are operably connected to the septal penetrator at the distal end of the sheath by linkages, pressure lumens, electrical lines, or the like, embedded within the sheath and routed from the proximal end to the distal end. The septal penetrator is capable of bending with the articulating sheath distal region. In yet another embodiment, a reversible fixation device, or safety cushion, is provided at the distal end of the expandable sheath. The reversible fixation device is actuated by the operator at the proximal end of the sheath. The controls at the proximal end of the sheath are operably connected to the fixation device at the distal end of the sheath by linkages, pressure lumens, electrical lines, or the like, embedded within the sheath and routed from the proximal end to the distal end. The reversible fixation device can be an inflatable structure such as a balloon, a moly-bolt expandable structure, an expandable mesh, an umbrella, or the like, preferably positioned to expand within the left atrium. In an embodiment, the structure of the catheter or sheath is such that it is able to maintain a selectively rigid operating structure sufficient to provide stability against the atrial septum to support the advancement of trans-septal needles or penetrators. The sheath can be selectively stiffened, at least at its distal end, to provide a non-deflecting platform for support of instrumentation, such as the septal penetrator, which is passed therethrough.
In another embodiment of the invention, the proximal end of the expandable sheath comprises hemostasis or backflow check seals or valves to prevent blood loss and retrograde flow of air into the circulatory system. The hub of the sheath comprises such hemostasis seal. The seal comprises an annular soft elastomeric gasket that seals against catheters, instruments, and the dilator, inserted therethrough. The seal can further comprise a valve such as a stopcock, one-way valve such as a duckbill or flap valve, or the like to prevent significant blood loss and air entry when an instrument or catheter is removed from the lumen of the expandable sheath. The soft annular seal can further comprise a mechanism to compress the inner diameter of the seal radially inward, such as the mechanisms found on Tuohy-Borst valves. The hub further comprises one or more sideport for injection of contrast media such as Omnipaque, Renografin, or other Barium-loaded solutions, for example, or anticoagulant solutions such as heparin, coumadin, persantin, or the like, or for the measurement of pressure at or near the distal end of the sheath. The dilator hub comprises a central lumen with a Tuohy-Borst valve and one or more sideports for balloon inflation, said sideports operably connected to lumens in the dilator catheter for injection or withdrawal of fluids from a balloon at the distal end of the dilator and optionally for measurement of pressure at or near the dilator distal end. The dilator hub can also comprise a slide knob, a trigger, or other lever to actuate a septal puncture device at the distal end of the dilator. The dilator hub, the sheath hub, or both, can also comprise a handle, lever, or trigger mechanism to enable steering mechanisms at the distal end of the dilator, the sheath, or both, respectively.
The expandable sheath, in an embodiment, comprises radiopaque markers to denote the beginning and end of the expandable region, and the middle of the expandable region. The middle of the expandable region is useful in that it can be aligned with the atrial septum during the sheath expansion procedure. The sheath can comprise radiopaque materials such as gold wire, platinum wire, tantalum wire, or coatings of the aforementioned over a malleable, stainless steel, deformable reinforcing layer. Such complete radiopaque markings are especially useful for sheath dilation insofar as they allow the operator to more clearly visualize the extent to which the sheath has been dilated once the dilator is activated. In a preferred embodiment, a radiopaque marker band is affixed to the dilator substantially near the distal tip of the dilator so that the position of the distal tip can be observed and controlled relative to the wall of the left atrium or other cardiac structures. This radiopaque marker band can be a non-expandable, axially elongate tubular structure that is adhered to the non-expandable dilator shaft. Another non-expandable radiopaque marker band can be adhered to the dilator shaft at a position substantially corresponding to the proximal most dilating portion of the dilator or sheath. Another non-expandable radiopaque marker band can be adhered to the dilator shaft at a position substantially corresponding to the distal most dilating portion of the dilator or sheath. Thus, the atrial septum can be positioned with confidence between the two dilator radiopaque markers and dilation will be assured. The radiopaque marker bands can further be configured to appear different under fluoroscopy, for example by making the distal tip marker a single band, the distal dilation marker two bands, and the proximal dilator marker, three bands. Yet another configuration of radiopaque marker bands can be achieved by using malleable wire windings of gold, tantalum, platinum alloys, or the like, which are embedded within the folded and expandable sheath, preferably at or near the distal end of the sheath and, optionally, at or near the proximal end of the expandable portion of the sheath. These wire windings can expand with the sheath and can help show the extents of the sheath even after the dilator has been removed.
Since in many embodiments the hub of a Trans-Septal sheath requires many hemostasis valves and fluid input connectors or ports, the hub can be a longer structure than that on current guide catheters. Therefore, it may be required that a longer Brockenbrough needle is used to allow sufficient working length to provide for maneuverability within the cardiac anatomy. It may be beneficial to use Brockenbrough needles, which are longer than the standard 60-71 cm length, preferably those of 80 to 90 cm in length. Furthermore, the sheath hub length can be advantageously foreshortened by use of tightly grouped ports and minimum length Tuohy-Borst valves as well as “Y” connectors that are integrated into the hub, rather than being separately attached. Thus, the working length of the entire system is between 50 and 90 cm and preferably between 60 and 80 cm. The sheath hub length, including the length of the dilator hub, is between 3 and 15 cm and preferably between 4 and 8 cm, the preferred length being appropriate if a shorter 70-cm or 71-cm long Brockenbrough needle is used. In an embodiment, the hub of the dilator comprises a “Y” or “T” connector operably connected to the guidewire lumen of the hub. The guidewire access port is controlled by and comprises a hemostasis valve or seal such as Tuohy-Borst connector. The side port is generally a luer port, luer lock port, or similar and is controlled by a stopcock, valve, Tuohy-Borst valve or other device to prevent unwanted fluid (including air) flow into or out of the guidewire port. The side port is beneficial in that it can be affixed to and operably connected to an infusion line for infusion of heparinized saline or other antithrombogenic material into the guidewire lumen of the sheath dilator. Such infusion of antithrombogenic fluid into the guidewire port during the procedure can help minimize thrombosis and thromboemboli generation.
In order to facilitate maneuvering the expandable trans-septal sheath into the right atrium and through the atrial septum, as well as for support of the sheath during catheter passage therethrough, it is beneficial in many embodiments to impart a curve into the trans-septal sheath, and optionally through the dilator. This curve is preferably a bend of between 20 to 120 degrees and preferably between 30 and 90 degrees. The bend can be in one plane or it can be in two orthogonal planes. An exemplary bend is to bend the sheath approximately 45 degrees out of plane 1 and approximately 50 degrees out of line in plane 2, which is orthogonal to plane 1. The radius of the curve can range between 2-cm and 12-cm and preferably between 3-cm and 10-cm in each of the two directions. Another example is a single plane curve of 90 degrees with a radius of around 3-cm to 12-cm. These bends are preferably imparted to the distal region of the non-expandable sheath tubing, just proximal to the expandable region. The bends can also be imparted through the expandable region but maintaining those bends in the expandable region may further require the use of a bent or curved shaped balloon, a resilient longitudinal support within the expandable region, a bent or curved dilator shaft, or both. The bending can be imparted to the tubing by placing the tubing over a curved mandrel and then heat-setting the tubing while over the mandrel. The tubing needs to be heated above glass-transition temperature, which is preferably above body temperature (37 degrees centigrade) for the heat set to be optimal. Materials used in the heat settable region can include, but not be limited to, polyethylene, PEN, PET, polyamide, polyimide, PEBAX, Hytrel, and the like. The expandable region of a trans-septal sheath need not be long and ranges between 0.5-cm and 20-cm with a preferred length of between 1-cm and 10-cm. By keeping the expandable region short, the region of the sheath comprising the bend, a bend, which makes the sheath have properties similar to those of a guiding catheter, is not in the expandable region, although methodologies of maintaining a bend within the expandable region are disclosed herein.
In yet another embodiment, the exterior of the sheath, and optionally the internal lumen of the sheath, can be coated with a lubricious coating comprising materials such as, but not limited to, silicone oil or a hydrophilic hydrogel comprising polyethylene glycol, polyether polyurethane, or the like.
In another embodiment, the proximal end of the sheath comprises a non-circular interior cross-section. The interior cross-section of the sheath can be oval, or it can comprise two or more completely walled off or partially walled off separate lumens. The sheath hub, which is affixed to the non-expandable proximal end of the sheath, can comprise two or more separate instrumentation ports, each of which are operably connected to a lumen or partial lumen within the sheath and which can advantageously comprise hemostasis valves. The instrumentation ports are especially useful for passage of, for example, multiple electrophysiology catheters, a mapping catheter and a therapeutic catheter, a ring catheter and an ablation catheter, or the like. Segregation of the multiple instrumentation can be useful to prevent binding or interference between the multiple catheters or instruments passed through the sheath. In yet another embodiment, the proximal end of the sheath has a non-circular cross-section that minimizes the overall cross-sectional area or circumference of a sheath configured to accept two or more catheters. This non-circular cross-section can be an oval, ellipse, rounded triangle, or the like. The non-circular cross section can, for example, reduce an 18 French OD catheter to around 15.5 French, using the same wall thickness and still retain the capability to accept two 8 French catheters within its internal lumen or lumens. Reduction in exterior cross-section is clearly useful in making the procedure as minimally invasive as possible and may make a procedure, which normally takes a cutdown, a percutaneous procedure.
For purposes of summarizing the invention, certain aspects, advantages and novel features of the invention are described herein. It is to be understood that not necessarily all such advantages may be achieved in accordance with any particular embodiment of the invention. Thus, for example, those skilled in the art will recognize that the invention may be embodied or carried out in a manner that achieves one advantage or group of advantages as taught herein without necessarily achieving other advantages as may be taught or suggested herein. These and other objects and advantages of the present invention will be more apparent from the following description taken in conjunction with the accompanying drawings.
A general architecture that implements the various features of the invention will now be described with reference to the drawings. The drawings and the associated descriptions are provided to illustrate embodiments of the invention and not to limit the scope of the invention. Throughout the drawings, reference numbers are re-used to indicate correspondence between referenced elements.
The invention may be embodied in other specific forms without departing from its spirit or essential characteristics. The described embodiments are to be considered in all respects only as illustrative and not restrictive. The scope of the invention is therefore indicated by the appended claims rather than the foregoing description. All changes that come within the meaning and range of equivalency of the claims are to be embraced within their scope.
In the description herein the terms catheter or sheath will be used to refer to being an axially elongate hollow tubular structure having a proximal end and a distal end. The structure can have any cross-sectional shape but in most embodiment the structure has a circular cross-sectional shape. The axially elongate structure further has a longitudinal axis and has an internal through lumen that extends from the proximal end to the distal end for the passage of instruments, fluids, tissue, or other materials. The axially elongate hollow tubular structure is generally flexible and capable of bending, to a greater or lesser degree, through one or more arcs in one or more directions perpendicular to the main longitudinal axis. As is commonly used in the art of medical devices, the proximal end of the device is that end that is closest to the user, typically a cardiologist, surgeon, or electrophysiologist. The distal end of the device is that end closest to the patient or that is first inserted into the patient. A direction being described as being proximal to a certain landmark will be closer to the user, along the longitudinal axis, and further from the patient than the specified landmark. The diameter of a catheter is often measured in “French Size” which can be defined as 3 times the diameter in millimeters (mm). For example, a 15 French catheter is 5 mm in diameter. The French size is designed to approximate the circumference of the catheter in mm and is often useful for catheters that have non-circular cross-sectional configurations. While the original measurement of “French” used π (3.14159 . . . ) as the conversion factor between diameters in millimeters (mm) and French, the system has evolved today to where the conversion factor is 3.0.
The present invention may be embodied in other specific forms without departing from its spirit or essential characteristics. For example, the sheath may include instruments affixed integrally to the interior central lumen of the sheath, rather than being separately inserted, for performing therapeutic or diagnostic functions. The hub may comprise tie downs or configuration changes to permit attaching the hub to the mouth, nose, or face of the patient. The dilatation means may be a balloon dilator as described in detail herein, it may rely on axial compression of a braid to expand its diameter, or it may be a translation dilator wherein an inner tube is advanced longitudinally to expand an elastomeric small diameter tube. Dilation may also occur as a result of unfurling a thin-film wrapped tube or by rotation of a series of hoops so that their alignment is at right angles to the long axis of the sheath. The embodiments described herein further are suitable for fabricating very small diameter catheters, microcatheters, or sheaths suitable for cardiovascular or neurovascular access. Various valve configurations and radiopaque marker configurations are appropriate for use in this device. The described embodiments are to be considered in all respects only as illustrative and not restrictive. The scope of the invention is therefore indicated by the appended claims rather than the foregoing description. All changes that come within the meaning and range of equivalency of the claims are to be embraced within their scope.