WO2007066344A1

WO2007066344A1 - Implantable extra-cardiac compression device for left ventricular assistance in severe heart failure

Info

Publication number: WO2007066344A1
Application number: PCT/IN2005/000400
Authority: WO
Inventors: Baskaran Chandrasekar
Original assignee: Baskaran Chandrasekar
Priority date: 2005-12-07
Filing date: 2005-12-07
Publication date: 2007-06-14

Abstract

A device for assisting the dilated left ventricle in a patient with severe heart failure. Extra-cardiac compression of the left ventricle is achieved by a simple, implantable device consisting of metal flanges (2) that are passively flexed at springed-hinges (5) by a vertically moving metal cup (1) . The vertical movements of the metal cup are achieved by means, such as a motor driven rack-and-pinion mechanism, or, a linear induction motor system. The motor is controlled by a micro-controller (16) that is external to the patient's body and worn, preferably on a waist belt along with the external battery system. The device can be synchronized to the patient's cardiac cycle by using commercially available standard three-lead surface electrocardiogram (11) . The flanges (2) are connected to each other by a high-tensile, elastic polymer membrane (3). The phosphorylcholine-containing polymer membrane may be used as a carrier of drugs or other agents to be delivered locally directly onto the myocardium.

Description

FIELD OF THE INVENTION

The invention relates generally to a device for assisting the dilated left ventricle in a patient with severe heart failure. More specifically, the invention relates to extra-cardiac compression of the left ventricle by an implantable device to augment the ejection of blood from the left ventricle.

BACKGROUND OF THE INVENTION

The prevalence and incidence of heart failure is of great concern. Heart failure is estimated to affect 5 million patients in the United States (Stevenson LW, Rose EA. Left ventricular assist devices: bridges to transplantation, recovery, and destination for whom? Circulation 2003;108:3059-63). In the United States, approximately 5,50,000 new patients of heart failure are diagnosed annually (2001 Heart and Stroke Statistical Update. Dallas, Tex: American Heart Association; 2000). In European countries, at least 10 million patients are estimated to be affected by heart failure (European Society of Cardiology guidelines for the diagnosis and treatment of chronic heart failure (update 2005), www.eurheartj.com.).

Patients with mild to moderate heart failure derive significant benefit from medications, implantable cardioverter-defibrillator therapy, and biventricular pacing, and have an annual mortality ranging from 8% to 18% (Hunt SA, Baker DW, Chin MH, et al. ACC/AHA guidelines for the evaluation and management of chronic heart failure in the adult: executive summary. A report of the American College of Cardiology/ American Heart Association Task Force on Practice Guidelines (Committee to revise the 1995 Guidelines for the Evaluation and Management of Heart Failure). J Am Coll Cardiol. 2001 ; 38: 2101-2113.). Patients with severe heart failure have a poorer prognosis, with an annual mortality rate of more than 50%. In such patients, heart transplantation is the only treatment providing significant benefit. However, less than 3000 donor hearts are available worldwide per year (Hosenpud JD, Bennett LE, Keck BM, et al. The Registry of the International Society for Heart and Lung Transplantation: seventeenth official report-2000. J Heart Lung Transplant 2000;19:909-931); In the United States less than 2200 donor hearts are available per year where an estimated 1,00,000 patients are considered eligible for heart transplantation (Willman V. Expert panel review of NHLBI Total Artificial Heart Program- 1999. Available at: http://www.nhlbi.nih.gov/resources/docs/tah-rpt.htm.). Therefore, a large number of patients with severe heart failure in need of heart transplantation are unable to receive the therapy. Such patients are increasingly being treated with left ventricular assist device (LVAD) therapy either as a "bridge" to heart transplantation until a suitable donor heart becomes available, or, as long-term "destination" therapy (Smart FW, Palanichamy N. Left ventricular assist device therapy for end-stage congestive heart failure: from REMATCH to the future. Congest Heart Fail 2005;l 1 :188-91.).

Published randomized studies with left ventricular assist device therapy in patients with severe heart failure report a significant 48% reduction in 1-year mortality with left ventricular assist device therapy compared to optimal medical management (Rose EA, Gelijns AC, Moskowitz AJ, et al. Long-term left ventricular assistance for end-stage heart failure. N Engl J Med 2001;345: 1435-43.). Devices such as reported in the published study work as follows: an inflow cannula is inserted into the apex of the left ventricle, and an outflow cannula is anastomosed to the ascending aorta. Blood exits the left ventricle through the left ventricular apex and across an inflow valve into a prosthetic pumping chamber. Blood is then actively pumped through an outflow valve into the ascending aorta (Rose EA, Gelijns AC, Moskowitz AJ, et al. Long-term left ventricular assistance for end-stage heart failure. N Engl J Med 2001;345: 1435-43.).

Such devices expose a patient to potentially serious complications arising from direct contact of the patient's circulation to artificial surfaces. A high incidence of infection with fatal sepsis, and bleeding have been reported (Rose EA₅ Gelijns AC, Moskowitz AJ, et al. Long-term left ventricular assistance for end-stage heart failure. N Engl J Med 2001,345:1435-43.). A neurological complication rate more than four times that of medical treatment group have been reported with such devices (Lazar RM, Shapiro PA, Jaski BE, et al. Neurological events during long-term mechanical circulatory support for heart failure: the Randomized Evaluation of Mechanical Assistance for the Treatment of Congestive Heart Failure (REMATCH) experience. Circulation 2004; 109:2423-7.). Other reported complications of such devices include activation of coagulation and fibrinolytic pathways (Spanier T, Oz M, Levin H, et al. Activation of coagulation and fibrinolytic pathways in patients with left ventricular assist devices. J Thorac Cardiovasc Surg 1996; 112: 1090-7.), changes in the immune system (Kasirajan V, McCarthy PM, Hoercher KJ, et al. Clinical experience with long-term use of implantable left ventricular assist devices: indications, implantation, and outcomes. Semin Thorac Cardiovasc Surg 2000; 12:229-37.), and predisposition to left ventricular arrhythmias (Ziv O, Dizon J, Thosani A, et al. Effects of left ventricular assist device therapy on ventricular arrhythmias. J Am Coll Cardiol 2005;45: 1428-34; Harding JD, Piacentino V 3^rd, Rothman S, et al. Prolonged repolarization after ventricular assist device support is associated with arrhythmias in humans with congestive heart failure. J Card Fail 2005;l 1 :227-32.). A left ventricular assist device that functions without exposing the patient's circulation to artificial surfaces, therefore, could potentially avoid the occurrence of above complications.

The proposed invention works by extra-cardiac heart compression mechanism, thereby avoiding direct contact of the patient's circulation with artificial surfaces.

In a US patent No. 6,464,655 for an external compression device to Shahinpoor, the invention consisted of multiple, resilient soft fingers connected to a base platform. The apparatus contains a central platform attached to a stem (cable guide). The fingers contain pressure sensors on bumps located on the fingers. A robotically controlled pulling cable located inside the cable guide actively pulls the central platform against the base platform thus closing the attached fingers and squeezing the heart. In another embodiment of the invention, an assembly of electroactive polymer fingers or patches are sutured to the myocardium and are directly electrically flexed to squeeze the heart. In yet another embodiment of the invention, an assembly of bladder-like fingers is inflated by hydrogen gas from an electrically controlled metal-hydride actuator to create compression of the heart.

Another external compression device, the MYO-VAD™, consists of a polymer sac-like structure that surrounds the heart and is pneumatically activated to compress and expand bi-directionally (Source: http://www.biophan.com/myo-vad/. Accessed on October 3, 2005). SUMMARY OF THE INVENTION

The present invention is an implantable left ventricular assist device designed for patients with severe heart failure. Most patients with severe heart failure have a dilated left ventricle with low ejection fraction. The present invention is designed for compression of the left ventricle by an extra-cardiac mechanism, thereby avoiding direct contact between artificial surfaces and the patient's circulation, unlike currently available left ventricular assist devices. Therefore, potential complications arising from direct contact between artificial surfaces and patient's circulation are avoided with the present invention.

Another important advantage of the present invention is that the implantation process does not require the heart to be stopped during the surgery. Therefore, there is no need for a heart-lung machine during surgery, unlike currently available left ventricular assist devices which require a heart-lung machine to be used during the implantation process.

Another advantage of the present invention is that the device can also be implanted by an abdominal approach without the need for a thoracotomy (opening of the chest). This can be achieved by approaching the heart from the abdomen through the diaphragm.

The present invention consists of 3 flanges (or more, depending on the degree of enlargement of the left ventricle) each of which is attached by springed-hinges to separate stalks. The three stalks pass through respective slots in a metal cup-like structure that slides vertically upwards and downwards over the stalks. The metal cup and its shaft, the three stalks and the flanges are preferably made of surgical-grade stainless steel, or, titanium, or, other biocompatible metal alloys. Alternatively, the cup and its shaft, the stalks, and the flanges could also be made of anodized aluminum, tantalum, a composite, or ceramic In the normal position, the springed-hinges keep the flanges open. Upon activation of the device, the metal cup slides upward over the metal stalks thus bending the flanges inwards at the hinges. The closing flanges compress the left ventricle aiding in ejection of blood from the left ventricle. When the metal cup slides downward over the stalks, the flanges spring open at the springed-hinges, thus allowing the left ventricle to expand and fill with blood. The closing and opening of the flanges can be synchronized to occur with the natural cardiac cycle of contraction (systole) and relaxation (diastole).

The flanges are connected to each other by a continuous, high-tensile, elastic polymer membrane that may form a continuous broad band, or, could also be in the form of a polymer "cup". The high-tensile elastic polymer membrane is preferably made of phosphorylcholine-containing polyurethane. The phosphorylcholine present will reduce possible inflammatory reaction to the polymer membrane and increase bio-compatibility of the membrane. An important function of the polymer membrane would be to act as a restraint to prevent prolapse of the left ventricle between the flanges during the diastole phase (relaxation or filling phase) of the heart. An important application of the phosphorylcholine-containing polymer membrane will be as a carrier of drugs or agents to be delivered locally directly onto the myocardium. One such application would be to deliver anti-inflammatory agents such as dexamethasone directly onto the myocardium to further reduce inflammatory reaction that may occur due to the polymer membrane. Many patients with severe heart failure have a failing heart due to ischemic heart disease that critically reduces blood flow to the failing myocardium. Another potential application of the phosphorylcholine-containing polymer membrane would be tυ uGiiver drugs or agents locally directly onto the myocardium that induce new blood vessel formation, thereby increasing blood supply to the ischemic myocardium. Such agents include 17beta-estradiol or other hormones or their derivatives, growth factors which may include but not limited to fibroblast growth factor and vascular endothelial growth factor, pharmacological agents, or genetic material, or any agent that can be delivered locally directly onto the myocardium for the purpose of neovascularization (angiogenesis and arteriogenesis). In another important application, the phosphorylcholine- containing polymer membrane could be used as a carrier to deliver stem cells or myoblasts locally directly onto the myocardium in patients with severe heart failure. The membrane could also be made of other high-tensile, elastic, biocompatible polymers with, or, without phosphorylcholine.

The vertical upwards and downwards movement of the metal cup is achieved by a rack-and-pinion motor mechanism, where the pinion is stationary and the rack moves vertically up and down. The rack-and-pinion system assembly may be of a straight tooth, or, of a helical tooth configuration. To eliminate backlash between the rack-and-pinion, mechanical or electrical preloading systems may be used. The rack-and-pinion motor mechanism is powered by an external battery system worn around the patient's waist. The external battery system may be recharged, or, replaced as and when deemed necessary. The external battery system will be connected trans cutaneous Iy to the motor assembly placed inside the patient's abdomen through commercially available special conduits that encourage normal tissue growth around the skin incision. Another embodiment of the invention will be the use of a linear induction motor system instead of a rack-and-pinion mechanism. In this embodiment, the stator will be fixed while the reaction plate will be mobile. The linear induction motor system will be powered by an external battery along with an inverter. The motor is controlled by a micro-controller that is housed along with the external battery system worn around the patient's waist. Synchronization of the motor with the patient's cardiac contraction (systole) and relaxation (diastole) cycles can be easily achieved by the micro-controller which receives input from a standard three-lead surface electrocardiogram of the patient.

In another embodiment of the invention, the device will have additional functions of management of life-threatening tachyarrhythmias and bradyarrhythmias. In such an embodiment, the device will have the ability to deliver small direct-current shocks (defibrillator function) directly to the myocardium upon recognition of a life-threatening tachyarrhythmia, and, to stimulate the heart (pacemaker function) upon recognition of a life-threatening bradyarrhythmia. The recognition of life-threatening tachyarrhythmias and bradyarrhythmias can be easily achieved from the standard three-lead surface electrocardiogram of the patient which sends input to the micro-controller.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG 1. shows a perspective view of the device of the present invention; FIG 2. shows a cross-section view of the device of the present invention;

FIG 3. Diagramatic representation of the device of the present invention inside a patient's body.

FIG 4. Diagramatic representation of the device positioned around a dilated left ventricle. RV = Right ventricle, LV = Left ventricle. FIG 5. Illustration demonstrating upward movement of the cup that results in inward flexing of the flanges at the springed-hinges which in turn result in compression of the left ventricle.

FIG 6. Illustration demonstrating downward movement of the cup that results in opening of the flanges at the springed-hinges which will allow filling of the left ventricle.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG 1 illustrates the device schematically. The device consists of a metal cup-like structure 1 with a shaft. Three flanges 2 are attached to respective stalks 4 by means of springed-hinges 5. The stalks 4 pass through respective slots 6 in the cup 1. The base of the stalks 4 are attached to the case 7 housing the rack-and-pinion motor assembly. One end of the rack 8 is attached to the shaft of the cup 1. The flanges 2 are connected to each other by a polymer membrane 3. FIG 1 also shows the case 9 containing the micro-controller and battery assembly. Case 9 is located external to the patient's body and can be worn in a belt around the waist. An electric cable 10 arises from the case 9 and is connected to case 7. A three-lead standard surface electrocardiograph cable 11 for recording the patient's electrocardiogram is connected to case 9.

FIG 2 illustrates the device sectioned vertically. The metal stalks 4 pass through respective slots 6 in the cup 1. One end of the rack 8 is screwed onto the shaft of cup 1. The other end of the rack 8 that is inside the case 7 forms the rack-and-pinion assembly with the pinion 12. The pinion 12 is stationary and is driven by the motor 13. The rack-and-pinion system assembly may be of a straight tooth configuration as shown in FIG 2, or, of a helical tooth configuration (not shown). To eliminate backlash between the rack and pinion, mechanical or electrical preloading systems may be used (not shown). The rack has an attached lever 14 that activates a limiting switch 15 as the rack moves vertically upwards. The case 9 that is located external to the body houses the micro-controller 16 and the two battery systems 17(a) and 17(b). The external battery system may be recharged, or, replaced as and when deemed necessary. An electric cable 18 connects the battery system 17(a) to the micro-controller 16. Another electric cable 19 connects the micro-controller 16 to the battery system 17(b). The electric cable 10 connects the battery system 17(b) to the motor 13 housed in case 7. The three-lead standard surface electrocardiograph cable 11 is connected to the micro-controller 16 housed in case 9.

FIG 3 is a diagrammatic representation of the device as positioned inside a patient after implantation. The cup 1 is located beneath the dilated left ventricle and the flanges 2 are placed around the dilated left ventricle. The case 7 housing the rack-and-pinion motor assembly is positioned inside the abdominal cavity. The case 9 housing the micro-controller and battery assembly is external to the patient and worn in a belt around the waist. The electric cable

10 running from case 9 to case 7 enters the body transcutaneously at the incision site 20. The electric cable 10 can be covered by commercially available special conduits that encourage normal tissue growth around the skin incision. This will encourage healing at the entry site 20 thereby minimizing risk of infection at the entry site 20. The three-lead standard surface electrocardiograph cable 11 is attached by commercially available skin electrodes to the right side of the patient's abdomen 11 (a), to the right shoulder l l(b), and to the left shoulder

11 (C).

FIG 4 is an illustration of an enlarged view of FIG 3 showing the device position around the heart. The flanges 2 encircle the dilated left ventricle (LV). The three flanges are positioned around the left ventricle such that one flange is on the anterior surface of the left ventricle, another flange is positioned on the inferior surface of the left ventricle, and another flange on the lateral surface of the left ventricle, respectively. This arrangement will help to prevent any damage from the flanges to the epicardial coronary arteries supplying blood to the left ventricle. The high-tensile elastic polymer membrane 3 connecting the flanges 2 is shown as a broad band around the dilated left ventricle. The polymer membrane 3 could also be in the form of a "cup" (not shown) connecting the flanges.

FIGs 5 & 6 demonstrate the linear upward and downward movements of the cup resulting in closing and opening respectively of the flanges. In FIG 5, as the rack 8 moves upwards, it pushes the cup 1 which slides over the stalks 4. This upward movement of the cup 1 flexes the flanges 2 inwards at the springed-hinges 5. The encircled dilated left ventricle (not shown) is compressed by the closing flanges resulting in ejection of blood from the left ventricle. In FIG 6, as the rack 8 moves downwards, it pulls the cup 1 vertically downwards, releasing the flexed flanges 2 that spring open at the springed- hinges 5. The flanges 2 return to their open position, allowing filling of the left ventricle (not shown) with blood.

The operating mechanism of the device is defined in reference to FIGs 1 and 2. The movement of the cup 1 and hence the movement of the flanges 2 are synchronized with the patient's cardiac cycle using input from the three-lead standard surface electrocardiograph cable 11. The micro-controller 16 receives input of the patient's electrocardiogram from the three-lead standard surface electrocardiograph cable 11. The speed of the motor 13 driving the rack-and- pinion system is determined by the micro-controller 16 from the R-R interval (interval between two R waves) of the electrocardiogram. The micro-controller 16 receives its power supply from the battery system 17(a) through the cable 18. The micro-controller 16 processes the received electrocardiograph signals and, through cable 19 determines the amount of current flowing from the battery system 17(b) to the motor 13. The amount of current flowing from the battery system 17(b) to the motor 13 through the electric cable 10 determines the speed of the motor 13 which drives the pinion 12 and rack 8 that controls the movement of the cup 1. Upon signal from the micro-controller 16, the motor 13 drives the pinion 12 which moves the rack 8 in a linearly upward direction that in turn pushes the cup 1 vertically upwards. The degree of upward movement of the rack 8 (and hence of the cup 1) is determined by the limiting switch 15 housed in the case 7. As the rack 8 moves upwards, the lever 14 attached to the rack activates the limiting switch 15. The limiting switch 15 then reverses the polarity of the motor 13, which reverses the direction of movement of the pinion 12 and the rack 8. The rack 8 then moves linearly downwards to its original position, pulling the cup 1 vertically downwards to its original position.

Although the invention has been described in detail with particular reference to these preferred embodiments, other embodiments can achieve the same results. Variations and modifications of the present invention will be obvious to those skilled in the art and it is intended to cover in the appended claims all such modifications and equivalents.

Claims

CLAIMS :

1. An implantable extra cardiac compression device for left ventricular assistance in severe heart failure, the device comprising a cup shaped member made of metal with a shaft extending downwardly; at least three flanges joined with each other by a polymer membrane; at least three stalks passing through the respective slots in the cup shaped member, the bottom end of the flange is connected to the front end of the stalk with a hinged spring; movement mechanism attached to the shaft of the cup shaped member for moving the cup up and down in a vertical direction so that the flanges are in closed position when the cup moves upward and the flanges are in open position when the cup moves downwards, the bottom end of the stalks are fixed to a casing which houses the said movement mechanism; a power source to supply power to the movement mechanism; a micro controller for controlling the movement mechanism so that the movement of the flange is in synchronization with the patient's cardiac cycle; the power source and the micro controller are housed in a casing which is kept external to the patient's body.

2. The device as claimed in claim I₃ wherein said metal cup member, flanges and stalks are made of surgical grade stainless steel, titanium or other bio compatible metal alloys.

3. The device as claimed in claim I₃ wherein said metal cup member, flanges and stalks are made of anodized aluminum, tantalum, a composite or ceramic.

4. The device as claimed in claim 1, wherein said polymer membrane is made of phosphorylcholine-containing polyurethane.

5. The device as claimed in claim 1, wherein the said movement mechanism includes a motor, rack and pinion assembly.

6. The device as claimed in claim 5, wherein the rack has a lever for activating a limiting switch in order to reverse the direction of the rotation of the motor.

7. The device as claimed in claim 1, wherein the motor is a linear induction motor.

8. The device as claimed in claim 1, wherein the patient's cardiac cycle is measured by a three lead surface electro cardiogram.

9. The device as claimed in claim 1, wherein the power source is connected to the movement mechanism using an electric cable.

10. The device as claimed in claim 1, wherein the power source is a rechargeable battery.

11. The device as claimed in claim 1, wherein the phosphorylcholine- containing polyurethane membrane is used as a carrier of drugs or other agents to be delivered locally directly on to the myocardium.