WO1995009660A1

WO1995009660A1 - Artificial heart

Info

Publication number: WO1995009660A1
Application number: PCT/FR1994/001134
Authority: WO
Inventors: Didier Chatel
Original assignee: Didier Chatel
Priority date: 1993-10-06
Filing date: 1994-09-28
Publication date: 1995-04-13
Also published as: FR2710847A1

Abstract

The device comprises an external bag (1) of synthetic material and shaped like a warhead cap, provided with a rigid shell (2), configured like a hull, and covering the inside of the bag (1) only on a portion of its surface, and supporting two individual ventricles made of synthetic material (3). Each individual ventricle (3) comprises an external rigid envelope (8) which is also shaped like a warhead cap, and carries at its apical extremity an actuator (4) acting on an intermediary synthetic bag (9) having a shape similar to that of the rigid envelope (8) in order to cause the cyclic deformation of a pericardial bag (10) contained in the intermediary bag (9).

Description

ARTIFICIAL HEART

The present invention relates to an artificial heart device, that is to say a biventricular complex for an electro-hydraulic total artificial heart (CAT).

The growing clinical needs of CAT on the one hand and the limits of therapeutic performance of CAT currently available in current practice on the other led to the conception of the new biventricular complex according to. Indeed the total artificial heart represents a therapeutic solution whose needs are great and justified by:

- the large number of patients with heart failure for whom surgical myocardial substitution remains the only therapeutic alternative (estimate of at least 17,000 to 35,000 patients per year in the USA); - the financial and human costs of CAT considered completely competitive compared to the financial and human costs of the necessary hospitalizations in the cardiac intensive care unit of patients who cannot benefit from myocardial substitution;

- the relative defect of the cardiac grafts necessary for cardiac transplants which still remain the dominant form of surgical myocardial substitution. This pre-eminence of heart transplantation can be explained by the limits of the performance of monoventricular assistive devices and CATs developed and known to date. Indeed the most recent CATs, called second generation, most electric (developed on the basis of knowledge acquired with older CATs called first generation, most often pneumatic), which are the most experienced and the most used clinically , have only solved the specific problems linked to the source and transmission of pneumatic energy (infections by pneumatic transmission lines, limited autonomy of the patient, noise pollution) but did not solve the problems related to the configuration of CATs.

A known electromechanical CAT has a closed rigid outer shell which determines a cylindrical outer shape. This CAT is equipped with two fully synthetic ventricular bags (right and left) containing the blood and connected to the corresponding atria by converging valve ear connectors and to the corresponding arteries by valve arterial connectors. The valve ports of these connectors are oriented in the same plane. Each ventricular bag has a discoid shape with a fixed face and a face mobilized by a pusher actuated by a motor and a mechanical system of transfer of rotary energy into linear energy. A compliance chamber is associated with this CAT to allow variations in internal volume in the rigid shell of this CAT, variations due to the pulsed nature of the flow generated by this CAT.

Another known electrohydraulic CAT is composed of two artificial ventricles juxtaposed to each other and connected together by a common hydraulic compartment. Each artificial ventricle is equipped with a rigid envelope determining a lenticular shape and a completely synthetic bag containing blood and connected to the corresponding atrium by a converging valve connector and to the corresponding artery by a valve connector. The valve ports of these connectors are oriented in substantially similar planes with one another. Each bag has a fixed face and a face mobilized by the oil itself mobilized in the hydraulic compartment of the CAT by a pump.

The disadvantages of these CAT are:

- inadequacy of the volume and especially of the shape of these CAT with the volume and shape of the pericardial space reserved for the implantation of

CAT;

In the first case,

- regular external shape of the CAT, but cylindrical and therefore responsible for the formation of dead spaces at the apex of the pericardium; - limits of the mechanical and functional durability of the compliance chamber associated with the cited CAT, compliance chamber which is necessary to allow variations in the internal volume of the closed rigid shell of this CAT, variations generated by the pulsed nature of the flow generated by this CAT; In the second case, - CAT more spherical but irregular external shape with reliefs and crevices also responsible for the formation of dead spaces which are sources of infectious foci; this mismatch is also responsible for the compression of the neighboring bodies and therefore detrimental to the proper functioning of the CATs; for each of the two CATs:

- arrangement almost in the same plane of the ear and arterial connectors, arrangement which is hardly compatible with the orientation of the cardiovascular structures to which the connectors are attached;

- convergent nature of the synthetic ear connectors which therefore have a large contact surface with the blood, thus exposing to the risk of thromboembolism and pannus;

- synthetic nature of the bags of artificial ventricles, exposing despite their hemocompatible nature, to the risk of thromboembolism even with anticoagulant treatment;

- discoid form of the ventricles of the first CAT and lenticular form of the ventricles of the second, both conditioning the intra-ventricular blood flows in circular and turbulent currents conducive to thromboembolism and not very favorable for good blood filling of these artificial ventricles;

- small diameter (25 to 29 mm) of the inlet valves of the artificial ventricles imposing the convergent nature of the ear connectors and making discomfort in the blood filling of these artificial ventricles.

The invention aims to overcome these drawbacks by producing a device forming a CAT, characterized in that it comprises an external plastic bag of general shape in a warhead, provided with a rigid shell internally covering the bag only on a part of its surface, supporting two individual ventricles in synthetic material, and in that each individual ventricle comprises a rigid outer envelope which also has a pointed shape and carries at its apical end an actuator acting on a synthetic intermediate bag, having the form of a warhead identical to that of the rigid envelope, to cause cyclic deformation of a pericardial sac contained in said intermediate bag. According to a particular embodiment of the invention, the synthetic intermediate bag is fixed to the corresponding rigid envelope in at least two locations, the apex and the posterior base. The connection to the apex is made by semi-rigid links at the apical opening of the rigid envelope corresponding to the electro-hydraulic actuator.

According to the invention, at the posterior base of each ventricle, the pericardial bag is fixed to a part covered with synthetic material having a small surface of contact with the blood and on which is applied the ring of a valve prosthesis, which is also applied to the respective part of a bi-annular ear connector sutured to the surgically respected atria.

This bi-annular ear connector consists, according to the invention, of two atrioventricular rings joined together at an obtuse angle. With the proposed device, the drawbacks of existing devices are eliminated thanks to the specific external shape of the device and to the also specific configuration of the artificial ventricles which equip it:

- external shape in a warhead similar to the shape of the pericardial space reserved for the implantation of CAT, allowing a good adequacy with this space and consequently respecting the neighboring organs;

- partial attachment of the outer bag to the shell allowing both the maintenance of the external shape of the device (thanks to the shell) and variations in the internal volume of the device (thanks to the non-attached part of the outer bag) due to the pulsed nature of the flow generated by said device and therefore no need for an associated compliance chamber;

- specific arrangement of the ear and arterial connectors designed according to anatomical criteria to best respond to the orientations of the cardiovascular structures to which they are attached;

- ear connectors with a small contact surface with blood; - biological characteristics (animal pericardium treated with glutaraldehyde recognized as the least thrombogenic biomaterial even without anticoagulant treatment) and homogeneous without continuity solution of the intraventricular coating in contact with the blood; - pointed shape of the artificial ventricles with a wide base allowing full-flow and therefore non-circular filling blood flows from the atria to the artificial ventricles;

- large diameter (60 mm) of the inlet valves of the artificial ventricles justifying the absence of convergence of the ear connectors and eliminating any discomfort in the blood filling of the artificial ventricles.

The invention will be explained in more detail below thanks to the description of an embodiment shown in the accompanying drawing, in which there is shown:

Figure 1: a three-dimensional view of the shape of the various components of the device according to the invention;

Figure 2: a section of the device along the plane P of Figure 1.

The biventricular assembly comprises an external bag 1 which contains all the other components of the CAT, including the electro-hydraulic actuator, and the oil useful for the operation of the actuator. A specific shell 2 determining the external shape of the CAT is placed inside the bag 1 and supports the two artificial ventricles.

The shape of the outer bag 1 defines the shape of the CAT which is ogive, with an anterior apex and a posterior base 5; this double bevel and vertical base corresponds to the biannular ear connector. The outer bag 1 is synthetic, flexible, and covered with Dacron double velvet. This Dacron coating must facilitate the adhesion of this bag to the surgically respected native pericardium. Through the underside of this bag pass the electrical connection lines (not shown), and through its upper side pass the arterial connectors.

The lower part of the internal face of this bag is fixed to the shell 2 which is included in this bag 1. The hull 2 has the shape of a boat hull with an anterior apex 6 similar to a bow of a boat, and a biannular rear base 5 which corresponds to the biannular ear connector. It covers the bag 1 internally only over part of its surface, approximately the lower half. Thus, with the exception of the connectors, all the components are included in the external bag 1. This bag 1 must be watertight for hydraulic oil and is therefore fixed to the rear base 5 of the hull with a clamp. It is also fixed on the upper wall of each ventricle 3 around the respective arterial connector and on the underside of the shell 2 around the electrical connection lines. The biventricular assembly can be applied to the biannular ear connector with a tensioned system between the peripheral part of the biannular ear connector and the above-mentioned clamp. Two ventricles 3, each consisting of a rigid envelope 8 and two bags, an internal pericardial bag 10 and a synthetic intermediate bag 9, are arranged inside the external bag 1 and supported by the shell 2; these 3 ventricular components have an identical shape in warhead, which determines the size, the position, and the orientation of the connectors of the CAT, ie a biannular ear connector and two distinct arterial connectors.

The biventricular assembly according to the invention is described here as it would be in the orthotopic position in a standing patient. It is represented arbitrarily in the figures with an actuator 4 for each artificial ventricle 3.

The two artificial ventricles (right and left) 3 are included in the outer bag 1 and the shell 2 described above. They are immersed in the hydraulic oil necessary for the operation of the electro-hydraulic actuators. The two ventricles 3 have a pointed shape with an anterior apex and a posterior base 7 in a single bevel. The ventricles 3 are placed side by side so that their respective bases correspond together to the posterior base 5 in double bevel of the external bag and therefore of the CAT.

The rigid envelope 8 of each ventricle 3 also has a vertical base in a single bevel which corresponds to the respective part of the biannular ear connector. The apex of the rigid envelope is open. The actuator 4 is placed opposite the open apex and produces the oil flow on either side of the rigid casing (intake oil flow in the rigid envelope during systole, flow of ejection oil out of the rigid envelope during diastole). The upper wall of the rigid envelope 8 has a circular opening 11 for the arterial valve connector; the opening 11 of the right artificial ventricle is earlier than that for the arterial valve connector of the left artificial ventricle. The exact position and orientation of the arterial valve connectors on the upper wall of each ventricle can be determined by the results of anatomical measurements. Three or four Hall effect sensors 12 are placed on the internal face of each rigid envelope 8 to detect at the end of the diastole three or four magnets 13 placed similarly on the external face of each synthetic intermediate bag 9.

Each synthetic intermediate bag 9 is fixed to three parts of its respective rigid envelope: at the rear base, at the circular opening on the upper wall for the arterial valve connector and at the apex. Small deflectors 14 are placed on the external face of the apex of the bag. The apex is fixed to the internal face of the apex of its respective rigid envelope with semi-rigid links placed between the deflectors and the circumference of the apical opening of the rigid envelope 8. In this way can be produced a systolic centripetal compression of the ventricular bags with relative mobility of their apex thanks to the systolic flow of oil admission into the rigid envelope, and the apical opening of each rigid envelope 8 is not closed by the apex of the bag respective synthetic intermediate 9 during the diastole, thus allowing the diastolic flow of oil to flow out of the rigid envelope. Each synthetic intermediate bag 9 carries on its external face three or four magnets 13 specifically placed to be detected at the end of the diastole by the three or four respective Hall effect sensors 12 placed on the internal face of the rigid envelope.

Each internal pericardial sac 10 is treated with glutaraldehyde. It is also fixed to two parts of the rigid envelope 8: at the rear base and at the opening on the upper wall for the arterial valve connector. It is in permanent contact with the synthetic intermediate bag 9 because of the "virtual" space between these two bags. This "virtual" space is very small and only intended to allow the presence of a lubricant to facilitate the sliding of each bag over one another during the cardiac cycle. The internal pericardial sac 10 is in continuity with the atrial and arterial connectors so that the blood tightness is perfect and that the surface of contact with the blood is homogeneous without solution of continuity. At the posterior base of each ventricle 3, the internal pericardial sac 10 is fixed to a part 18 covered with synthetic material (Dacron) on which is applied the ring 15 of a valve prosthesis 16; for each artificial ventricle 3, the valve prosthesis 16 is also applied to the respective part of the biannular ear connector sutured to the auricles surgically observed.

This biannular ear connector corresponds to the posterior base 7 in double bevel of the biventricular assembly. Thus, this connector is composed of two rings 19 (right and left atrioventricular rings for the native atria and the respective artificial ventricles). These two rings 19 are joined to each other at an obtuse angle: this angle between the rings is anterior and equal to 160 ° according to the results of anatomical measurements. The internal diameter of each ring can be at least 60 mm. Thus, on the anterior face of this connector, the rings of the atrioventricular valve prostheses are applied by virtue of the system already mentioned stretched between the biannular ear connector and the already mentioned clamping collar. Thus the diameter of atrioventricular valve prostheses can be equal to 60 mm. The posterior side of this connector is sutured to the surgically respected native atria. In this way the surface of contact with the blood of such a connector is almost similar to the surface of contact with the blood of a conventional valve prosthesis.

Each arterial connector is separate and is placed on the upper wall of the respective rigid envelope; these connectors are valved vascular prostheses. The right arterial connector is earlier than the left arterial connector. The exact position and orientation of these arterial valve connectors can be determined with the results of anatomical measurements.

At the end of diastole the artificial ventricle is completely filled with blood in the internal pericardial sac. During the systole the actuator 3 transfers the hydraulic oil from the external bag 1 into the rigid envelope 8 so that the synthetic intermediate bag 9 and the internal pericardial bag 10 are compressed together and the blood is ejected towards the respective arterial connector 17 and the downstream arteries. During the diastole the actuator 4 transfers into the external bag 1 all the oil contained in the rigid envelope 8, so that the intermediate bag 9 and the internal pericardial bag 10 are subjected together to a centrifugal expansion allowing an admission of blood in the bag internal pericardial until full filling detected by Hall signal detectors 12. As soon as Hall signals are detected a new systole can be generated.

The advantages of the device according to the present invention arise from the original characteristics of the biventricular assembly; these are:

The first is the consistency of the different solutions proposed with this biventricular set to improve anatomical, hemobiological and hemodynamic compatibility. Improvement of the anatomical compatibility is possible with the good adequacy of volume and especially of form between the CAT equipped with the biventricular system described above and the pericardial space available for a CAT implantation, with the small amplitude of the movement of the external bag. at its upper and lateral parts, the apex remaining immobile thanks to the shell 2 associated with the external bag 1, and with a favored adhesion of the native pericardium on the Dacron double velvet coating of the bag, all elements conducive to preventing the formation of spaces intrapericardial death source of possible infections.

Improvement of the anatomical compatibility is also possible by fixing the CAT by its apex to a rib according to anatomical criteria established in preoperative thanks to anatomical measurements modeled so that with closed chest the CAT respects the morphology and the function of the structures cardiovascular left in place (so no atrial, venous, arterial, or pulmonary compression); thus improving anatomical compatibility contributes to improving hemodynamic compatibility.

Improvement in hemobiological compatibility is possible with the biological nature of the internal coating of the ventricles demonstrated to be less thrombogenic, and above all its homogeneous nature without a solution of continuity; with the shape of the ventricles, the small surface in contact with the blood of the atrioventricular connector, and the large diameter of the admission valves to allow to reduce the turbulence and the vortex demonstrated with other classic CAT and made responsible for thromboembolic accidents and pannus development; thus improving hemobiological compatibility contributes to improving hemodynamic compatibility. Improvement in hemodynamic compatibility is possible with improvement in previous compatibilities, in particular with respect for the native atria representing true compliant reservoirs upstream for ventricular filling (average right and left atrial volumes calculated respectively at 250 and 260 cm-- ⁵ in 15 patients awaiting heart transplantation), such compliant upstream reservoirs promoting hemodynamic performance of CAT

Improvement of hemodynamic compatibility is also possible with the large diameter of the inlet valves and the pointed shape of the ventricles allowing a "full channel" flow from the atria to the artificial ventricles, with the homogeneous centrifugal diastolic expansion of the bags ventricular, all elements conducive to improving the overall compliance of the biventricular assembly and therefore to improving its hemodynamic performance. But the hemodynamic performance of a CAT is also determined by its controlled regulation, itself conditioned by the intrinsic mechanical properties of the CAT in question. However, the mechanical properties of the above-described biventricular assembly should not be a factor limiting the performance of a regulation but, on the contrary, allow a regulation capable of operating at variable systolic ejection volume and especially at variable frequency, which constitutes a additional advantage, being demonstrated the superiority of variable frequency regulations over fixed frequency regulations and variable ejection volume. Finally, the completely biological nature of the intraventricular coating in contact with the blood, and therefore the absence of blood contact with synthetic biomaterials, should make the manufacture of these biomaterials easier, less demanding and perhaps less costly. thus the constraints and possibly the manufacturing costs of the biventricular assembly.

Claims

1. Device forming an artificial heart, of the type comprising electro-hydraulic actuators, characterized in that the device comprises an external bag (1) of synthetic material of general shape in a warhead, provided with a rigid shell (2), in the form of hull, internally covering the bag (1) only on a part of its surface, supporting two individual ventricles in synthetic material (3), and in that each individual ventricle (3) comprises a rigid outer envelope (8) which has also a warhead shape and carries at its apical end an actuator (4) acting on a synthetic intermediate bag (9), having the shape of a warhead identical to that of the rigid outer casing (8), to cause deformation cyclic of a pericardial bag (10) contained in said intermediate bag (9).

2. Device according to claim 1 characterized in that the synthetic intermediate bag (9) is fixed to the corresponding rigid envelope (8) in at least two locations, the apex and the posterior base.

3. Device according to claim 2, characterized in that the connection to the apex is produced by semi-rigid links (13) at the apical opening of the rigid envelope (8) corresponding to the electro-hydraulic actuator (4).

4. Device according to any one of the preceding claims, characterized in that at the posterior base of each ventricle (3), the pericardial bag (10) is fixed to a part covered with synthetic material having a small surface for contact with the blood. and on which is applied the ring (15) of a valve prosthesis (16), which is also applied to the respective part of the bi¬ annular ear connector sutured to the auricles surgically respected.

5. Device according to claim 4, characterized in that the bi-annular ear connector consists of two atrioventricular rings joined together at an obtuse angle.