VENTRICULAR PARTITIONING DEVICE
FIELD OF THE INVENTION
The present invention relates generally to the field of treat- 5 ing congestive heart failure and more specifically, to a device and method for partitioning a patient's heart chamber and a system for delivering the treatment device.
BACKGROUND OF THE INVENTION 10
Congestive heart failure (CHF) is characterized by a progressive enlargement of the heart, particularly the left ventricle and is a major cause of death and disability in the United States. Approximately 500,000 cases occur annually in the 15 U.S. alone. As the patient's heart enlarges, it cannot efficiently pump blood forward with each heart beat. In time, the heart becomes so enlarged the heart cannot adequately supply blood to the body. Even in healthy hearts only a certain percentage of the blood in a patient's left ventricle is pumped 20 out or ejected from the chamber during each stroke of the heart. The pumped percentage, commonly referred to as the "ejection fraction", is typically about sixty percent for a healthy heart. A patient with congestive heart failure can have an ejection fraction of less than 40% and sometimes lower. As 25 a result of the low ejection fraction, a patient With congestive heart failure is fatigued, unable to perform even simple tasks requiring exertion and experiences pain and discomfort. Further, as the heart enlarges, the internal heart valves such as the mitral valve, cannot adequately close. An incompetent mitral 30 valve allows regurgitation of blood from the left ventricle back into the left atrium, further reducing the heart's ability to pump blood forewardly.
Congestive heart failure can result from a variety of conditions, including viral infections, incompetent heart valves 35 (e.g. mitral valve), ischemic conditions in the heart wall or a combination of these conditions. Prolonged ischemia and occlusion of coronary arteries can result in myocardial tissue in the ventricular wall dying and becoming scar tissue. Once the myocardial tissue dies, it is less contractile (sometimes 40 non-contractile) and no longer contributes to the pumping action of the heart. It is referred to as hypokinetic. As the disease progresses, a local area of compromised myocardium may bulge out during the heart contractions, further decreasing the heart's ability to pump blood and further reducing the 45 ejection fraction. In this instance, the heart wall is referred to as dyskinetic or akinetic. The dyskinetic region of the heart wall may stretch and eventually form an aneurysmic bulge.
Patients suffering from congestive heart failure are commonly grouped into four classes, Classes I, II, III and IV. In 50 the early stages, Classes I and II, drug therapy is presently the most commonly prescribed treatment. Drug therapy typically treats the symptoms of the disease and may slow the progression of the disease, but it can not cure the disease. Presently, the only permanent treatment for congestive heart disease is 55 heart transplantation, but heart transplant procedures are very risky, extremely invasive and expensive and are performed on a small percentage of patients. Many patient's do not qualify for heart transplant for failure to meet any one of a number of qualifying criteria, and, Furthermore, there are not enough 60 hearts available for transplant to meet the needs of CHF patients who do qualify.
Substantial effort has been made to find alternative treatments for congestive heart disease. For example, surgical procedures have been developed to dissect and remove weak- 65 ened portions of the ventricular wall in order to reduce heart volume. This procedure is highly invasive, risky and expen
sive and is commonly only done in conjunction with other procedures (such as heart valve replacement or coronary artery by-pass graft). Additionally, the surgical treatment is usually limited to Class IV patients and, accordingly, is not an option for patients facing ineffective drug treatment prior to Class IV. Finally, if the procedure fails, emergency heart transplant is the only presently available option.
Other efforts to treat CHF include the use of an elastic support, such as an artificial elastic sock placed around the heart to prevent further deleterious remodeling.
Additionally, mechanical assist devices have been developed as intermediate procedures for treating congestive heart disease. Such devices include left ventricular assist devices and total artificial hearts. A left ventricular assist device includes a mechanical pump for increasing blood flow from the left ventricle into the aorta. Total artificial heart devices, such as the Jarvik heart, are usually used only as temporary measures while a patient awaits a donor heart for transplant.
Recently, improvements have been made in treating patient's with CHF by implanting pacing leads in both sides of the heart in order to coordinate the contraction of both ventricles of the heart. This technique has been shown to improve hemodynamic performance and can result in increased ejection fraction from the right ventricle to the patient's lungs and the ejection fraction from the left ventricle to the patient's aorta. While this procedure has been found to be successful in providing some relief from CHF symtoms and slowed the progression of the disease, it has not been able to stop the disease.
SUMMARY OF INVENTION
The present invention is directed to a ventricular partitioning device and method of employing the device in the treatment of a patient with congestive heart failure. Specifically, the ventricular chamber of the CHF patient is partitioned by the device so as to reduce its total volume and to reduce the stress applied to the heart and, as a result, improve the ej ection fraction thereof.
A ventricular partitioning device embodying features of the invention has a reinforced membrane component, preferably self expanding, which is configured to partition the patient's ventricular heart chamber into a main productive portion and a secondary non-productive portion, and a support or spacing component extending from the distal side of the reinforced membrane for non-traumatically engaging a region of the patient's ventricular wall defining in part the secondary non-productive portion to space a central portion of the reinforced membrane from the heart wall. The partitioning device preferably includes a centrally located hub secured to the reinforced membrane. The partitioning membrane of the device may be reinforced by a radially expandable frame component formed of a plurality of ribs.
The ribs of the expandable frame have distal ends secured to the central hub, preferably secured to facilitate abduction of the free proximal ends of the ribs away from a centerline axis. The distal ends of the ribs may be pivotally mounted or formed of material such as superelastic NiTi alloy which allow for compressing the ribs into a contracted configuration and when released allow for their self expansion. The ribs also have free proximal ends configured to engage and preferably penetrate the tissue of the heart wall so as to secure the peripheral edge of the membrane to the heart wall and fix the position of the membrane with respect thereto. The free proximal ends of the ribs may have tissue penetrating tips such as barbs or hooks. The partitioning membrane is secured