EP0774984A1

EP0774984A1 - Method of training a skeletal muscle for a biomechanical heart and biomechanical heart using said muscle

Info

Publication number: EP0774984A1
Application number: EP94916281A
Authority: EP
Inventors: Norbert Guldner; Sylvain Thuaudet
Original assignee: Individual
Current assignee: Individual
Priority date: 1993-05-14
Filing date: 1994-05-13
Publication date: 1997-05-28
Also published as: WO1994026326A1; AU692770B2; CA2162585A1; JPH09506517A; US5814102A; AU6799894A

Abstract

A method for dynamically training a skeletal muscle (1) to be used for a biomechanical heart involves wrapping the skeletal muscle around a deformable training device (2) which can contract, resistance to contraction being provided, and recover its initial form. The skeletal muscle is stimulated by periodic electrical impulses. In a first stage, the skeletal muscle (1) is stimulated by electrical impulses at a frequency increasing with time, and in a second stage the contraction resistance of the deformable training device (2) is increased progressively, the first and second stages possibly overlapping slightly. A biomechanical heart operated by a skeletal muscle having undergone said dynamic training is also disclosed.

Description

METHOD FOR TRAINING A SKELETON MUSCLE FOR A BIOMECHANICAL HEART AND BIOMECHANICAL HEART USING SUCH A MUSCLE.

The present invention relates to a dynamic training process of a skeletal muscle for a biomechanical heart as well as a biomechanical heart using such a muscle.

It has already been envisaged to produce a biomechanical heart in the form of a circulatory pump capable of being completely implanted in the chest of a patient, in particular in cases of terminal heart failure. This pump is actuated by a skeletal muscle, for example the dorsal muscle, subjected to electrostimulation in such a way that all the pulsating energy of the pump comes from the metabolism of the muscle which in a way constitutes its motor. Such a biomechanical heart, using a skeletal muscle as a motor, offers the advantage that it does not cause a rejection reaction of the organism because the muscle is taken from the patient in which the biomechanical heart is implanted. .

In order to be able to use, as the motor of such a biomechanical heart, a non-tireable muscle, with so-called type I fibers, it has already been planned to subject the muscle to prior training. dynamic, as described in the publications:

N.W. Guldner et al .; "Development and training of skeletal muscle ventricle with low preload"; J.Card.Surg., 1991; vol. 6, No. 1.

N.W. Guldner et al.; "Dynamic training of skeletal muscle ventricles - a method to create high performance for muscle powered cardiac assist."; Fourth Vienna International Workshop on Functional Electrostimulation; Baden / Vienna, September 24-27, 1992; ISBN 3-900928-08-9 1992.

This type of dynamic training consists in wrapping the muscle around a training device comprising an elastically deformable element with an internal chamber filled with liquid and terminated at its ends by inflatable bladders, such a device being described in the document WO- A-9205813. To ensure the training of the muscle, it is connected to a myostimulator producing periodic electrical impulses of stimulation and when the muscle is thus excited by an electrical impulse, it contracts, which causes a retraction of the central chamber and an expulsion of the liquid to the side bladders which swell. When the muscle is no longer excited, between two successive electrical impulses and it relaxes, the bladders deflate and the liquid returns to the central chamber which increases in volume, and the cycle can then start again.

The present invention relates to improvements made to this method of training a muscle making it possible to obtain a significant increase in muscle mass and in developed power.

To this end, this dynamic training process for a skeletal muscle intended for use in a biomechanical heart, in which the skeletal muscle is wound around a deformable training device capable of being able to contract, by opposing resistance to the contraction, and then return to its initial shape and the skeletal muscle is stimulated, by means of periodic electrical pulses so as to cause its contraction and that of the deformable training apparatus and their subsequent relaxation, is characterized in that during a first step, the skeletal muscle is stimulated by means of electrical impulses having an increasing frequency as a function of time and during a second step, the resistance of the deformable training device is gradually increased. the contraction, the first and second stages possibly overlapping somewhat. The invention also relates to a biomechanical heart using as motor a skeletal muscle having been subjected to such dynamic training. Various embodiments of the present invention will be described below, by way of non-limiting examples, with reference to the appended drawings in which:

- Figure 1 is a diagram illustrating the method according to the invention, for the dynamic training of a skeletal muscle intended to be used in a biomechanical heart.

FIG. 2 is a diagram illustrating the variation, as a function of time, of the frequency of the electrical stimulation pulses and of the resistant mechanical load applied to the muscle during its training.

- Figure 3 is a diagram illustrating the range of variation of the pressure / volume characteristic for each of the inflatable bladders of the training apparatus. Figure 4 is an elevational view, partially in axial section, of a biomechanical ventricle according to the invention, with axial circulation of the blood flow. Figure 5 is a cross-sectional view, on a larger scale, taken along the line VV of FIG. 4, the upper half of the figure representing the biomechanical ventricle in the relaxed state while the lower half represents the ventricle in the contracted state. - Figure 6 is a diagram of an application of a biomechanical ventricle according to the invention, with axial circulation, for cardiac assistance.

- Figure 7 is a schematic sectional view of an alternative embodiment of a biomechanical ventricle with transverse circulation of the blood flow.

- Figure 8 is a schematic perspective view illustrating the different phases of training a muscle housed in a tubular envelope. - Figure 9 is a cross-sectional view of the muscle and its envelope wound around the dynamic training apparatus.

- Figure 10 is a perspective view of a motor muscle of Figures 8 and 9 wound around a spring cage constituting a pericardial device.

- Figure 11 is a diagram illustrating a muscle wound around the dynamic training apparatus with the interposition of an intermediate envelope. - Figure 12 is a schematic axial sectional view of the motor muscle and its intermediate envelope obtained after the training period.

- Figure 13 is a diagram of an alternative embodiment of a pericardial device comprising a hydraulic transmission system between the pump and the human heart.

- Figure 14 is a schematic sectional view of an alternative embodiment of the receptor associated with the human heart.

In Figure 1 is shown schematically the dynamic training process of a skeletal muscle 1, for example the back muscle, intended for use in a biomechanical heart according to the invention. This muscle 1 is wound around a dynamic training device 2 and more particularly around a central chamber 2a filled with liquid and extended, at its two ends, by inflatable bladders 2b. The material constituting the internal chamber 2a should not be elastic while the material forming the inflatable bladders 2b is. To train muscle 1, first of all, this muscle is electrostimulated by connecting it to a myostimulator 3 which is in fact a generator of periodic electrical pulses. When the muscle is excited by one of these impulses, it contracts, which leads to a reduction of the volume of the central chamber 2a and an expulsion of the liquid from this chamber towards the elastic lateral bladders 2b which inflate, so that the training apparatus 2 opposes a contraction resistance of the muscle 1. After the disappearance of the electrical excitation pulse, the muscle 1 relaxes and the elastic bladders 2b deflate by expelling the liquid which returns to the central chamber 2a. This central chamber 2a then inflates in turn, to return to at least its initial shape, by exerting a positive restoring force on the muscle 1, force directed towards the outside and oriented in the opposite direction to that exerted by the muscle during its contraction. . In the process according to the invention, on the one hand, an incremental variation of the frequency of the electrical pulses of the generator 3 is used, and, on the other hand, an incremental variation of the resistant mechanical load which opposes the contraction of the muscle 1. For this purpose, the internal volume of the training device 2 is connected to a catheter 5 communicating with an implantable chamber under the skin and making it possible to gradually increase the quantity of liquid found in the central chamber 2a and the inflatable bladders 2b. During a first stage of training muscle 1, indicated by I in FIG. 2, electrical stimulation pulses are applied to this muscle, the frequency of which f gradually increases over time. We start for example with a slow pulsation, of the order of one pulse per minute (corresponding to a frequency of about 0.017 Hz at the stimulator) and we then increase this frequency gradually, over a period of time of the order of 6 to 10 weeks, up to a normal heart rate of the order of 60 to 80 pulses per minute (frequency from 1 to 1.33 Hz with the pacemaker). This increase in frequency f as a function of time t is illustrated by curve A in FIG. 2. Furthermore the first step of electrical stimulation I is followed by a second step II during which the resistance r is gradually increased opposite by the training device 2 to the muscle contraction, as represented by the curve B. This increase in the resistant load is obtained by a progressive introduction of liquid into the device 2, by means of the device 5 .

The combination of the first step of increasing frequency electrical stimulation and the second step of gradually increasing resistance to muscle contraction allows a noticeable increase in muscle mass and muscle power. Thus, following experiments carried out on the dorsal muscle of the calf, we were able to reach a power of 10 watts, whereas in healthy and resting man the maximum power of a left ventricle is approximately 3 watts.

It has been found, in certain subjects, that it is possible to make the two stages I and II partially simultaneous, that is to say that one can be led, at least for a certain time to overlap the two stages. , to increase both the frequency of excitation of the stimulator and the quantity of liquid introduced into the training device 2. Gradually, according to a complementary characteristic of the invention, the material constituting the two inflatable bladders 2b consists of a silicone of elastic type forming the wall of the bladders and by polymer threads embedded in this wall so that one obtains, for each of the inflatable bladders 2b, a pressure / volume characteristic included in the range delimited between the two limit curves a and b in Figure 3. In this figure the elasticity C of the inflatable bladders is given by the ratio between the volume V and the pressure P of each bladder. The best results have been obtained with a value of elasticity C between 1/4 (curve a) and 2 (curve b). In a particularly advantageous embodiment, the wall of each bladder 2b is made up of three layers, namely an inner layer and an outer layer of material known as "Rehau SI 1511" and a middle layer in material known as "Dow Corning Q3-8111" or "Dow Corning MDX4-4210".

FIGS. 4 and 5 illustrate an embodiment of a biomechanical heart according to the invention constituting a "ventricle" with axial circulation of the blood flow, using as a motor a skeletal muscle dynamically driven in the manner described above. This biomechanical ventricle comprises a muscle 1, previously trained as indicated above, which is connected to a myostimulator 3 and is wound around a tubular pumping cage, deformable 6. This cage 6, flexible and elastic, has a central part of large diameter extended by two opposite end portions of smaller diameter. The tubular pumping cage 6 comprises a flexible outer casing 7, for example made of silicone, and inside this casing several cambered spring leaves 8, with convexity facing outwards, extending over the entire length of the 'casing 7, from one end to the other of the cage 6, and distributed around the axis of this cage 6. The ends of the spring blades 8 are embedded in two transverse stiffening rings 9 housed respectively in the two ends open of the tubular cage 6. An internal membrane 11, athrombogenic, for example made of polyurethane, extends inside the cage 6, covering the spring leaves 8 to which it adheres so as to delimit, between the spring blades 8, sealed individual chambers filled with a fluid 12. When the muscle 1 is not excited, that is to say when it is released, the tubular cage 6 has a large diameter and in this case the membrane 11 delimits relatively flattened chambers, as shown in the upper part of FIG. 5. On the other hand, when the muscle 1 is excited, the tubular cage 6 is contracted, as well as 'It is shown in the lower part of Figure 5, the spring blades 8 are flattened and close to each other and the membrane 11 then forms chambers which extend inwardly projecting between the spring blades 8, substantially in radial directions. When the muscle relaxes, the spring blades 8 allow the distension, that is to say the return of the tubular pumping cage 6 to its initial shape at large volume.

FIG. 6 illustrates a use of the tubular pumping cage 6 produced in the manner illustrated in FIGS. 4 and 5, to constitute an extra-aortic counter-pulse device. The tubular pumping cage 6, the muscle 1 of which is electrically connected to a myostimulator 3, is connected to a conduit 13 bypass on the aorta 14 of a patient whose heart is represented at 15. When the aortic valve 16 is closed (diastole), the myostimulator 3 sends, in synchronism with the left ventricular diastole, an electrical impulse to muscle 1 to stimulate it. Synchronization is ensured by a sensor 17 for monitoring the cardiac pulses in contact with the heart 15 and connected to the myostimulator 3. Due to the excitation of the muscle 1, the tubular pumping cage 6 is compressed and the blood is pumped towards upstream and downstream, as indicated by the arrows. The backflow of blood results in an increase in circulation in the coronaries 18. On the other hand when the aortic valve is open (systole) the muscle 1 is not electrically stimulated, it relaxes and the tubular cage 6 expands creating a depression promoting blood circulation in the aorta. This biomechanical ventricle with axial circulation of the blood flow can also be used in other topographic configurations, such as between the left atrium and the aorta between the left ventricle and the aorta, between the right atrium and the pulmonary artery. In this case, these biomechanical ventricles will be provided with two connections, namely an inlet connection provided with an inlet valve and an outlet connection provided with a discharge valve.

In the alternative embodiment of a biomechanical "ventricle" represented in FIG. 7, which is intended for a transverse circulation of the blood flow, the muscle 1 surrounds a flexible pouch not expandable 19 extending outside a hollow body 21, through an opening of the latter. The body 21 is separated into two parts by a waterproof membrane 22 (or a piston) delimiting, on one side, a pumping chamber 23 inside the flexible bag 19, containing a liquid such as physiological saline, and , on the other side, a flushing chamber 24. The flushing chamber 24 is provided with two connections, namely an inlet connection 25 provided with an inlet valve 26, and an outlet connection 27 provided with '' a discharge valve 28.

The biomechanical "ventricle" shown in FIG. 7 can be used in partial or total assistance, both for the left heart, between the left ventricle and aortic artery, and for the right heart between the right atrium and the pulmonary artery. In this case, the inlet 25 and outlet 27 fittings are connected to the circulatory system. It can be used without inlet and outlet valves in an aorto-aortic configuration of extra-aortic counter-pulse.

The apparatus shown in FIG. 7 can also be used to ensure dynamic training of the muscle 1. In this case, the inlet 25 and outlet 27 connections are not connected in the circulatory system but they are interconnected by a conduit 29 which is then cut to remove it when from the transition to operation, in order to connect the fittings 25 and 27 to the circulatory system.

Also shown in FIG. 7 is a catheter 31 communicating the pumping chamber 23 with a device for filling this pumping chamber with propellant liquid, during the second step of the dynamic drive process, in order to gradually increase the amount of liquid in the pumping chamber 23, and to be able to regularly measure the pressure of this liquid to follow the evolution of muscle performance. The catheter 18 can optionally be removed during the transition to normal operation but it can also be left in place to serve to measure the pressure of the propellant liquid.

Figures 8 and 9 show an alternative embodiment in which the muscle 1 is previously housed, before the implementation of the dynamic training process, in a tubular sheath 32 constituted by a polymer membrane which protects the muscle during the process dynamic training and ensures its non-adhesion to surrounding tissues. The sheath 32 is made of any natural, artificial or synthetic polymer, but preferably it is constituted by a polymer substituted in particular by fluorine, such as polymers of the polytetrafluoroethylene type. FIG. 10 illustrates a pericardial device comprising a muscle 1, around a flexible and elastic tubular cage 30, open at its two ends. One of the openings of the cage 30 has a diameter large enough to allow the introduction of a human heart inside the cage 30. The stimulation of the muscle 1 then causes the contraction of the cage 30 and that of the human heart housed tightly in this cage. If the muscle is not long enough, we can provide an extension in Y 33, made of a resistant polymer, such as Dacron or PTFE.

Figures 11 and 12 show an alternative embodiment in which, during the dynamic training of the muscle, there is interposed between the muscle 1 and the dynamic training apparatus 2 a membrane 34 wound around an axis, on the surface continuous, open at both ends. This membrane 34 is preferably made of a material "colonizable" by the connective tissue. After the training phase the flexible tubular "cage" 35 thus obtained comprises, on the outside, the muscle 1 and, on the inside, the membrane 34 adhering to the muscle and colonized by the cells of the connective tissue. The cage 35 can be used directly as a pumping chamber and it can be connected to arterial prostheses 36. FIG. 13 illustrates an embodiment of a pericardial device in which the muscle 1 is wound around a flexible and elastic cage 37, forming a pumping chamber or a transmitter of pressure pulses, the internal volume of which communicates , by a conduit 38, with a pocket 39 in the form of a bowl in which is housed a human heart 15. The pocket 39 which forms a receptor for pressure pulses, has a hollow wall and it includes an external non-expandable envelope 41 and a internal envelope 42 expandable in contact with the heart. The flexible and elastic cage 37, with variable pumping volume, is thus connected by a hydraulic transmission device to the pocket 39. When the cage 37 contracts, under the action of the electrically stimulated muscle 1, it expels liquid, by through the conduit 38, inside the pocket 39, in other words it creates a pressure pulse transmitted to the pocket 39. As its external envelope 41 is not expandable, the excess liquid arriving in the pocket causes an expansion of the internal envelope 42 and consequently a contraction of the human heart 15.

The conduit 38 is connected, by means of a bypass conduit 43, to a chamber 44 situated under the skin 45 of a patient and closed by a perforable membrane 46. Through this membrane can be introduced a needle 47 for replenishing propellant. Furthermore, a needle for measuring the pressure 48 can also be introduced through the membrane 46. In the alternative embodiment shown in FIG. 14, the conduit 38 of the hydraulic transmission device terminates in a pressure pulse receiver comprising an expandable envelope 49 housed inside an external non-expandable pocket 51, pocket inside which the human heart is also located 15. The expandable cover 49 is in contact on the one hand with the external pocket 51 and on the other hand with the human heart 15 so that the pressure pulses in the conduit 38 result in an increase in volume of the expandable envelope 49 and a contraction of the heart 15.

One can also provide, as shown in Figure 13, a pipe 52 connected to the hydraulic transmission circuit, for example to conduit 43 or 38. This pipe allows transcutaneous connection to a suction system (suction) during a short period. This transcutaneous connection can be removed after a few days when the internal surface of the hydraulic bag 39 (made of silicone, for example), adheres permanently to the epicardium.

Claims

1- Method for dynamic training of a skeletal muscle (1) intended for use in a biomechanical heart, in which the skeletal muscle is wound around a deformable training device (2) capable of being able to contract, in opposing a resistance to contraction, and then return to its initial shape and the skeletal muscle (1) is stimulated, by means of periodic electrical pulses (3) so as to cause its contraction and that of the deformable training apparatus ( 2) and their subsequent relaxation, characterized in that during a first step, the skeletal muscle (1) is stimulated by means of electrical impulses having a frequency increasing as a function of time and during a second step the resistance of the deformable training device (2) to contraction is gradually increased, the first and second steps possibly overlapping somewhat.

2- A method according to claim 1, characterized in that one applies to the muscle, during the relaxation phase following the phase of electrical stimulation or contraction, a distension force exerted in the opposite direction to that of the force of contraction. 3- Method according to any one of claims 1 and 2, characterized in that one applies, between the muscle (1) and the deformable training device (2), a layer of intermediate material (34) colonizable by connective tissue.

4- A method according to any one of claims 1 and 2, characterized in that the skeletal muscle (1) is housed beforehand inside a tubular sheath (32) avoiding the adhesion of the muscle to the surrounding tissues.

5- Implantable biomechanical heart operating from periodic contractions, under the effect of electrical stimulation pulses, of a skeletal motor muscle (1), characterized in that its motor muscle is a muscle (1) previously driven by the method according to any one of claims 1 to 4.

6- Biomechanical core according to claim 5, characterized in that it comprises a tubular cage (6, 30), elastically deformable, with open ends, having a central part of large diameter around which the muscle (1) is wound and extending by two opposite end portions of smaller diameter. 7- Biomechanical heart according to claim 6, characterized in that the tubular cage (6) which constitutes a pumping cage of a ventricle to axial circulation of the blood flow, comprises a flexible external envelope (7), several cambered spring blades (8), with convexity turned towards the outside, extending over the entire length of the envelope (7), of a end to end of the cage (6), and distributed around the axis of this cage (6), two transverse stiffening rings (9) respectively housed in the two open ends of the tubular cage (6) and in which the ends of the spring leaves (8) are embedded, an internal ahrombogenic membrane extending inside the cage (6), covering the spring leaves (8) to which it adheres so as to delimit, between the leaves spring (8), sealed individual chambers filled with a fluid (12).

8- Biomechanical core according to claim 6, characterized in that it comprises a membrane (34) wound around an axis, with a continuous surface, open at its two ends, interposed between the muscle (1) and the apparatus d dynamic training (2) during the training period, the membrane (34) being made of a material colonizable by the connective tissue to give, after the training period, a flexible tubular cage (35) comprising, on the outside , the muscle (1) and, inside, the membrane (34) adhering to the muscle and colonized by the cells of the connective tissue. 9- Biomechanical heart according to claim 6, characterized in that it constitutes a pericardial device comprising a flexible and elastic tubular cage (30), open at its two ends, surrounded by the muscle (1), one of the opening of the cage (30) having a diameter large enough to allow the introduction of a human heart inside this cage, the muscle surrounding the tubular cage can be extended if it is too short by a polymer element (33) resistant allowing it to completely surround this tubular cage.

10- Biomechanical heart according to claim 5, characterized in that it constitutes a ventricle with transverse circulation of the blood flow comprising a flexible non-expandable pocket (19) surrounded by the muscle (1) and extending outside of a hollow body (21) through an opening of this body, a waterproof membrane (22) or a piston separating the hollow body (21) into two parts so as to delimit, on one side a pumping chamber (23) to the interior of the flexible bag (19) containing a liquid, and, on the other side, a flushing chamber (24), this flushing chamber (24) being provided with two connections, namely an inlet connection ( 25) provided with an inlet valve (26) and an outlet fitting (27) provided with a discharge valve (28). 11- Biomechanical heart according to claim 5, characterized in that it constitutes a pericardial device comprising a flexible and elastic cage (37) forming a pumping chamber or a transmitter of pressure pulses, around which the muscle is wound ( 1), a pocket (39, 51) in which is housed a human heart (15) and forming a receiver of pressure pulses and an expandable means (42, 49) connected to the cage (37) by a hydraulic transmission conduit (38), to cause the heart (15) to contract when each pressure pulse is received.

12- Biomechanical core according to claim 11, characterized in that the pocket (39) in which is housed the heart (15), has a hollow wall and it comprises an external envelope (41) non-expandable and an internal envelope (42) expandable in contact with the heart.

13- Biomechanical core according to claim 11, characterized in that it comprises an external pocket

(51) non-expandable inside which are housed the human heart (15) and an expandable envelope (49) in contact on the one hand with the external pocket (51) and on the other hand with the human heart (15 ). 14- Biomechanical core according to any one of claims 11 to 13, characterized in that the conduit (38) extending between the flexible cage and elastic (37) forming the pumping chamber and the pocket (39, 51) in which the human heart (15) is housed, is connected, by means of a bypass duct (43), to a chamber (44 ) located under the skin (45) of the patient and closed by a perforable membrane (46) through which a needle (47) can be introduced for replenishing the propellant and possibly a needle for measuring the pressure (48). 15- Biomechanical core according to any one of claims 11 to 14, characterized in that a pipe (52) is connected to the hydraulic transmission conduit (38) to allow the transcutaneous connection to a suction system and to allow the internal surface of the hydraulic pocket (39) to adhere permanently to the epicardium.