US RE41394 E1
A device, potentially implantable in a living organism, intended to utilize at least a part of the hydraulic energy generated by the heart (10)—the primary unit—at the natural phases of work when the cavities of the heart (11, 12 and 16, 17) are filed with blood. The device includes at least one secondary unit (24), which is connectable to the cardiovascular system of the organism and arranged to utilize said hydraulic energy. The secondary unit is represented by at least one hydraulic motor (24a) arranged to transfer the hydraulic energy to a transferal organ (28). The transferal organ (28) is arranged to influence at least one tertiary unit, for example an executive device (29), which is constructed in order to convert the transferred energy to an alternative form of energy, with the purpose to influence certain defined functions within the organism. Preferably is arranged a regulating device (30) in order to control running parameters of the unit.
1. A device for implantation, able to make use of at least part of the hydraulic energy generated by a heart at its natural phases of work, said device including at least one actuator connected to the cardiovascular system of an organism, said actuator arranged in order to transfer the hydraulic energy to an executive organs, said executive organ arranged to influence certain defined functions within or outside the organisms, characterised by the actuator consisting of a hydraulic motor located outside the cardiovascular system of the organism, said hydraulic motor arranged to conduct at least part of the hydraulic fluid to and fro between the hydraulic motor and its connecting site to the organism, and/or between arteries and/or veins and that the executive organ consists of at least one pump powered by the hydraulic motor, said pump delivering hydraulic fluid to and fro vessels synchronously or asynchronously in relation to the rhythm of the heart with or without pressure amplification.
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This application is a continuation of PCT International Application No. PCT/SE00/01355 filed Jun. 26, 2000 which PCT Application claims priority to Swedish Application No. 990238 1-4 filed June 23, 1999.
The present invention refers to a device, implantable in a living organisms, for the utilisation of at least part of the hydraulic energy developed by the heart (the primary unit), which is acquired by the natural work of the heart i.e. by the contraction of the heart (the systolic phase) where the blood is put under pressure, followed by the relaxation phase (the diastole), where the ventricles of the heart are filled with blood. The device comprises at least one secondary unit connected to the cardiovascular system.
The heart is well known to work as two deplacement pumps which are functionally separated apart, and which work sycncronously, in the way that the right pump transports blood to the pulmonary circulation, whereafter the oxygenated blood returns to the left pump. Thereafter, the left side ejects the oxygenated blood to the peripheral circulation of the body i.e. to the vascular system of the entire organism. Finally, the blood returns to the inlet of the right pump.
The force of the pump is generated by the contraction of the cells of the myocardium, which surrounds the atria and the ventricles of the heart. The direction of the circulation is controlled by unidirectionally acting valves. The energy delivered by the heart to the surrounding, mainly to the blood consists primarily of pressure-volume work against the blood, kinetic work and heat.
It is previously known to assist the circulation, when the heart is fainting, by external force. Such assist is typically powered by pressurized air or electricity as energy source located outside the body. It has even been suggested to utilize energy converted from muscle, other than the heart, for example muscle of the legs, or from the back, as energy for the circulating blood via some sort of converting mechanism.
To add energy, from outside the body, to implanted assist devices has previously been used and is principally not difficult. But it may cause discomfort and be complicated for the patient due to tubings and cables penetrating the skin. Such connections limit the patient's degree of freedom to special rooms or to trolleys equipped with batteries and computers. If therefore, one could use energy existing within the body, the patient would experience a new degree of freedom. The circulation of living creatures, including man, is normally kept in balance between the cardiac output and the resistance of the peripheral arteries, in the way that blood pressure is kept within narrow limits. This is necessary since several organs cannot work and/or survive if the blood pressure drops below, or increases above extreme levels. The kidneys and the brain are organs known to be sensitive to variations in blood pressure. Thus, if the heart in a human being faints, and cannot pump out the blood with enough force to keep the arterial mean blood pressure slightly above 50 mm Hg, the person will loose consciousness. If the kidneys are exposed for a similarly low arterial pressure, at least if exposed for a considerable long time, the urine production will cease. When the heart is fainting, and for some reason or another cannot generate a sufficiently high blood pressure, the person will die. This is through for left side fainting, but also for right side fainting if the right pump cannot overcome the resistance of the lungs.
The fact that the heart sometimes cannot pump out the blood to the circulation with a sufficiently high pressure does not necessarily mean that the heart cannot deliver enough energy to the circulation, if mechanical, and other conditions, where correct. In contrary, several examples can be given, where the heart is extremely powerful and has hypertrophied to a size 2-3 times the normal, over years, but still the pressure is low. One typical example for such a situation, is a heart with one or more valves leaking, or a dilated heart, which cannot deliver a sufficiently high pressure to the circulation. The energy consumption of such a heart is much higher than the normal delivery to the circulation at rest (1 watt). The efficiency, i.e. the PV-energy+the kinetic energy/ the total energy for a normal heart is around 15%, while for a diseased heart, especially if dilated the efficiency is considerably lower than that.
A normal heart has a relatively low efficiency as a pump, compared to industrial pumps. Energy losses do arise (among other things) since the ventricles, at each contraction, as first step, have to generate a contraction of the ventricular wall, which allows the ventricular pressure to reach the aortic pressure (or the pressure of the pulmonary artery for the right pump); the ventricle wall is pre-tightened. This contraction leads to energy losses, which are proportional to the diameter of the ventricles in square, and therefore, these losses are great when the ventricles are dilated. In the second phase of the contraction, the ventricles have to increase the tension of the ventricular wall further, resulting in a ventricular pressure higher than the aortic pressure whereby the ejection of the blood takes place. During the ejection, the volume of the ventricles decreases, and therefore, the wall thickness of the ventricles increases. This remodeling of the muscle mass also leads to energy losses which in some diseases (for example at extremely hypertrophic hearts) may be considerable.
The way more than normal energy can be extracted from a fainting heart, is realized by comparing the pressure volume relation demonstrated in
It is noted that the area of the surface PE (in
The fact that retained blood within the ventricle after each contraction does lead to energy loss should not be considered as if the retained blood should possess potential energy released in diastole. This is not the case since the blood is not compressible. In contrast, energy is lost since the ventricle must be pre-tightened before it can create a pressure high enough to start the ejection of the blood. This pre-tightening is well known energy consuming and is proportional to the volume of the ventricle.
Besides this factor, there are several other important factors that decide the oxygen consumption of the heart and thereby the energy consumption, the magnitude of the lost energy and the efficiency of the heart. These are described in the book “The Heart Arteries and Veins” 8 Edition. McGraw-Hill Inc., being for example the mass of the heart, the level of the pre-tightening, the frequency of the heart and the hormones influencing the heart. In contrast, as a paradox, the external work of the heart is not the main factor to decide the oxygen consumption since maximally 15% of the energy of the heart is converted to external work (for a healthy heart). When a heart wakens, often first step is a dilatation of the ventricle, later through an increase of its mass whereby the losses increase dramatically.
The idea to take out more blood at the contraction of the ventricles (systolic phase) is old and used every day. Pharmacologically it is easy to dilate the capacitance vessels of the arterial system (i.e. an afterload reduction) and thereby increase the stroke volume and the minute volume. But the price is low blood pressure and the limits within one operates are narrow. Likewise, one can influence the heart mechanically to eject more blood in each cycle. This may for example be achieved by diastolic counterpulsating, and one example of such pumps is the aortic balloon pump.
A diastolic counterpulsator works in its simplest form in the way that when the heart in systolic phase ejects its contained blood, the counterpulsator accumulates part of this volume outside the cardiovascular system for example in a pump cylinder connected to the artery in a groin. Thereby, the systolic resistance is reduced and the systolic blood pressure is kept low which ameliorates the ejection of the blood from the heart.
In diastolic phase, when the valve between the heart and the arterial system is closed, an external force, i.e. a motor, is used to press back the blood from the counterpulsator to the arterial system. The diastolic pressure is increased, as is the mean pressure. It is noted that this way of pumping results in a mirrored arterial blood pressure curve. This is true for external counterpulsators as described above, but also for internally located counterpulsators like the aortic balloon pump, which is the most commonly used assist pump in modern cardiac surgery. The mechanism is simple and intelligent—bit it needs externally added energy.
The counterpulsator is a device well described in the medical literature i.e. “Cardiopulmonary Bypass” by Kenneth M. Taylor, 1986. Chapman and Hall Ltd., 9 chapter.
By U.S. Pat. No. 4,938,766—R. Jarvik—is known an implantable prosthesis—a device—for amelioration of the perfusion of the natural cardiovascular system without adding energy from outside the body. However, the device cannot store the energy for more than part of a cardiac cycle. Nor can it render the arterial pressure curve in mirrored version, which is the case for the counterpulsator. It flattens out the blood pressure curve. It may increase the mean pressure in the arterial system, and it may enhance the take out of more energy from the heart (more than before connecting the device), but it will decrease the maximum systolic pressure. Thus, the device cannot solve the pressure demand from peripheral organs like the brain and the kidneys, which have an absolute pressure demand in order to survive.
The Purpose Of The Invention And The Solution Of The Problem
The purpose of the present invention is to achieve a device which, as mentioned in the introduction, without adding external—from outside the body—energy, can utilize energy created within the body, for different purposes and in different ways, depending on which disease is actual. Some examples of possibilities to be opened are given:
The purpose is among other to bring back the modus operandi of the heart to a normal pump modus and thereby reduce the lost energy, while the energy delivered to the surrounding (at rest) is constant. These purposes have been solved by the characteristics mentioned in the patent claims.
The invention will be described in detail below together with some examples with referral to enclosed drawings.
The main purpose of the invention is to utilize and/or to convert at least part of the energy delivered by the heart—also called the primary unit—to the blood for specific or other purposes, primarily within the body, but in some specific cases even outside the body. The device needed to extract energy from the pump work of the heart via the blood depends on the purpose the energy is intended to be used for and consists in most cases a conventional hydraulic motor—even called the secondary unit—which has been adjusted according to its specific purpose. The hydraulic motor, which is powered by the pressurized blood, converts the hydraulic energy back to mechanical or electric energy. After this conversion, the energy can be used immediately, stored for a short period (a cycle of the heart) or stored for a longer time. The energy can be used to run different apparatus i.e. one or more pumps, an electric motor, a control mechanism or a regulator etc. The actual equipment will decrease the pressure within the heart, Ph and the residual volume Vr after the contraction of the ventricle/ventricles.
If the hydraulic energy is converted within the body to electricity, new possibilities will appear for self supply with limited amounts of electric power, to be used for several purposes, for example to run pumps to maintain the circulation, to generate blood pressure higher than the normal pressure, generated by the normal or by the diseased heart etc.
The energy delivered by the heart to a hydraulic motor is V*dp where V is volume and dp is reduction in pressure of the blood when passing the hydraulic motor. The energy spent by the heart to deliver V*dp is much higher than V*dp itself.
One way to absorb energy from the pressurized blood is by help of a hydraulic motor connected to the heart directly, normally to one or both ventricles, and most frequently to the left ventricle. But principally, any of the atria and ventricles of the heart may be connected to each its motor and work independently or more or less interconnected.
By adjusting the characteristics of the hydraulic motor, more blood may be ejected the natural way and to the motor than before connection to the device. The pressure in the heart may be same as normal—or lower, depending on the characteristics of the motor. At diastole, the ventricle needs to be filled with blood, and the most natural way to do this is to empty the motor directly through the inflow connection, which in that case will be the outflow connection as well. Thus, the blood from the motor is mixed with the blood filling the ventricle the natural way. But emptying an filling of the motor does necessarily have to take place by the same route. If the motor empties its blood “upstream” in the circulation, the blood will automatically find its way down to the same ventricle (although it may be a burden for the circulatory system to a certain degree on its way back).
As mentioned, the energy absorbed from the heart by the motor may be used for several purposes. One example is to lead back the energy directly to the circulation—or later, at the same time as electricity is generated and stored in an accumulator. Arranged in this way, the net amount of energy transferred to the circulation will be the same, less or more than before connection to the motor. The profile of the blood pressure can be manipulated and the mean blood pressure can be increased.
It is even possible with this device to take out a maximum of blood volume for the ventricle at a pressure so low that the valve between the ventricle and the circulation never opens, which normally is inconsistent with life, and still absorb energy at this low pressure. The device may give back the energy to the circulation and thereby generate a sufficiently high pressure to guarantee life —without adding energy from the surrounding.
To get e better understanding of the invention,
The blood is pumped from the circulatory system of the body (the periphery) via the two caval veins 21 to the right atrium 16, passes through the tricuspid valve 18 to the right ventricle 17 and is pumped through the pulmonary valve 19 to the pulmonary artery. In the lungs the blood absorbs oxygen and continues its flow to the pulmonary veins 22 to the left atrium 11 and further via the mitral valve 13 to the left ventricle 12, which pumps out the blood through the aortic valve 14 to the main body artery 15.
To the lower part of the left ventricle 12 is connected, i.e. by an operation, a connection tube 23, which connects the heart 10—the primary unit—with an implanted secondary unit 24. This is illustrated in a considerably greater scale than the heart and is in this example a hydraulic motor 24a. Its plus side is a variable volume chamber i.e. a cylinder 25 and within the cylinder is an axially movable piston 26, which on its minus side is influenced by a return spring 27. This spring tends to move the piston to its one end at the opening of the connection tube 23, when the hydraulic pressure of the heart comes to an end. In stead of a cylinder the hydraulic motor may consist of a bellows cylinder or a similar device. To the piston 26 is connected a transferal organ 28, which in
In most applications it is an advantage if the return spring 27 is adjustable concerning spring force as well as other spring characteristics, which in
In systolic phase, when the heart contracts, blood is pumped from both ventricles of the heart 12 and 17 to each its hydraulic cylinder 24a, and the pistons are pressed back while the return spring 27 is compressed. In diastolic phase (the relaxation phase of the heart where the pressure of the ventricles drops) the pistons are pressed back by the spring 27 and the blood returns to the heart. Depending on the adjustment of the gear, the quote of energy extracted from the two ventricles may be varied.
In systolic phase, the pressurized blood is transferred from the ventricle 12/17 to first bellows 37 and to the transferal organ 28. First valve 39 is closed and bellows 37 expands. At the same time, blood is transferred from the second bellows 38 via the tube 41 to the artery 15/20 through the open valve 40. It is noted that the pressure in systolic phase is bigger in the second bellows 38 than in the heart 10 and bigger than in the first bellows 37, and that this difference is proportional to the difference in cross sectional area between the two bellows.
In diastolic phase, the valve 40 is closed and the return spring 27 will press the transferal organ 28 in return. The valve 39 opens passively and blood flows from the first bellows 37 to the second bellows 38, at the same time as blood flows back from the first bellows 37 to the heart 12/17 through the tube 23.
It is noted that the curve b of
The individual control units 31, 32 and 35, which are included in the regulating mechanism 30 according to
In the first control unit 31, the connector 98 of the regulator 36a is performed as a displaceable stop 93, limiting the stroke of the transferal organ 28 belonging to the hydraulic motor, which may be a piston rod. In this control unit 31 is included even a sensor of position 99 and a strain gauge 100.
The purpose of the second control unit 32 is to regulate the gear between the hydraulic motor 24a of the secondary unit and the piston pump 24b of the tertiary unit 29 or to regulate the gear between two secondary units. To do this, a lever 101 is arranged between the piston rods of the hydraulic motor and the pump. The pivot point is the connector 98, which is displaceable along the rail 94 in the way that a variable gear of the force from the hydraulic motor 24a to the pump 24b can be achieved. The regulation of the pivot point is performed with the adjusting means 26b. Depending on the preset parameters of the gear i.e. the pivot point of the lever 101, the quote of the energy extracted from the two ventricles may be varied, alternatively, the gear between the secondary and tertiary unit may be varied.
The third control unit 35, which controls the settings of the spring, has two adjusting devices 36c and 36d, of which the connector 98 of the first mentioned device 36c is displaceable along a spring 27 in order to adjust the tension of the spring. Using the second adjusting device 36d it is possible to adjust the zero point of the spring.
The components like the adjusting devices 36 and the sensors 99,100 in the different units 31, 32, 35 are all connected to a computer.
The transferal organ 28 consists in this example of a magnet connector 102, which runs a generator 53. The blood passing the turbine is returned to a vein 51.
The speed of the turbine can be regulated by means of for example adjustable flow devices (not given in the figure) and/or by rotating the wings of the propeller. The rotation energy can if necessary be stored temporarily by connecting a flywheel to the turbine shaft.
In some diseases it is necessary to drain compartments of the body for example the abdomen. This drainage is to day arranged by a tube passing out of the body through the skin. In
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A device according to the invention can also be used to power an implantable, or external apparatus for dialysis 61, as demonstrated in FIG. 19. Since a pressure approximately four times the mean pressure of the aorta is needed in a dialysis chamber, a pressure amplification unit 60 is needed, which is connected to the hydraulic motor 24a, thereby increasing the pressure to dialysis pressure level. The pressurized blood is transferred from the pressure amplifier to the blood side 62 of the dialysis device and thereafter to a suitable vein 51. The water side 63 of the dialysis device is via a drainage tube 71 connected with an external collector 64. Alternatively, the drainage tube is connected to the urinary bladder or to a urostomy (artificial urinary bladder/opening).
The dialysis apparatus according to the present invention results in water being lost from the body and this fluid must be replaced. Normally dialysis fluid of specific composition is added to the organism through a vein and/or by drinking. Since filtration in a dialysis filter results in the blood becoming more viscous on its way through the filter (since dialysed water is eliminated) in some dialysis apparatus extra dialysis liquid is added before the filter unit (i.e. predilution), Such predilution will enhance the flow through the filter.
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The invention is not limited to above described examples but several other variants and combinations are possible within the limits of the patent claims.
The device is not useful in all situations of heart failure. If a ventricle is little and stiff with a low compliance, the device for natural reasons cannot extract big volumes from the ventricle and therefore the absorbed energy is limited. In contrast, the device can absorb energy from one side of the circulation (left or right) and give back the energy to the opposite side without blood flow from one side to the other. This has so far been impossible with any known pump. The present pump thus can be connected to the contralaterat side of the heart as well as to the homolateral side. For natural reasons the extraction of energy from the left side of the circulation delivered to the right side can be higher and more powerful since the left side of the heart normally is 5 times as strong as the right side. But the opposite way around can also be of significant importance in critically ill patients.
Thus, the energy potentially delivered by the heart may therefore be: