Surgical procedures and devices for increasing cardiac...

Details Surgical procedures and devices for increasing cardiac... Surgical procedures and devices for increasing cardiac...

1998-07-16

2003-04-15

Snow, Bruce (Department: 3738)

Prosthesis (i.e., artificial body members), parts thereof, or ai

Corporeal artificial heart, heart assist , control...

C600S016000

Reexamination Certificate

active

06547821

ABSTRACT:

Diseases of the cardiovascular system affect millions of people each year and are a leading cause of death in the United States and throughout the world. The costs to society from such diseases is enormous both in terms of the lives lost and in terms of the cost of treating patients through surgery. A particularly deadly form of heart disease which afflicts an estimated 3 million Americans is Congestive Heart Failure (CHF). Congestive heart failure is a syndrome caused by a failing heart, with congestion in the pulmonary or systemic circulation or both. It afflicts males more often than females, blacks more often than whites, and the elderly more often than younger persons. It is one of the most frequent causes of hospitalization of people aged 65 and older. Despite improvements in the management of patients with CHF, there appears to be no decline in mortality, presumably because of the aging of the population and the improved survival of patients with predisposing conditions, such as chronic ischemic heart disease.
The most common cause of congestive failure is coronary artery disease—narrowing of the arteries supplying blood to the heart muscle. Although coronary disease often starts at an early age, congestive failure occurs most often in the elderly. Among people more than 70 years old, about 8 out of 1,000 are diagnosed with congestive heart failure each year. The majority of these patients are women, probably because men are more likely to die from coronary artery disease before it progresses to heart failure.
Heart failure is also associated with untreated hypertension, alcohol abuse, and drug abuse (primarily cocaine and amphetamines) at any age. Hyperthyroidism and various abnormalities of the heart valves (particularly aortic and mitral) are among the other disorders that can cause heart failure. In addition, viral infection or inflammation of the heart (myocarditis) or primary heart muscle disease (cardiomyopathy), and in rare instances, extreme vitamin deficiencies, can result in heart failure.
Heart failure may occur suddenly, or it may develop gradually. When heart function deteriorates over years, one or more conditions may exist. The strength of muscle contractions may be reduced, and the ability of the heart chambers to fill with blood may be limited by mechanical problems, resulting in less blood to pump out to tissues in the body. Conversely, the pumping chambers may enlarge and fill with too much blood when the heart muscle is not strong enough to pump out all the blood it receives. In addition, as the architecture of the heart changes as it enlarges, regurgitation of the mitral valve may develop, making the heart failure even worse. An enlarged heart, called cardiomyopathy, is a particularly debilitating form of heart disease which effects as many as 40% of patients with congestive heart failure.
Traditional therapeutic techniques for the treatment of congestive heart failure have been less than completely effective for a majority of patients treated. Drug therapy is one of the most widely used means of reducing the debilitating effects of CHF and for improving the quality of life of patients. Diuretics are often prescribed to help the kidneys eliminate excess water and sodium, thereby reducing the blood volume and the heart's workload. Digitalis may be prescribed to increase the heart's pumping action and increase the work done by the heart. Vasodilators, including angiotensin converting enzyme (ACE) inhibitors, may be used, along with diuretics, in patients with mild-to-moderate or severe congestive failure. ACE inhibitors, which include captopril (Capoten) and enalapril (Vasotec), block the production of a substance called angiotensin II, a potent constrictor of blood vessels. By causing the dilation of blood vessels, vasodilators decrease the amount of work that must be done by the heart as the blood pressure of the patient is decreased with increased vessel diameter. Nitrates and glycosides are also widely utilized in the treatment of heart failure to improve cardiac function and decrease symptoms.
Drug therapy has proved to be ineffective in completely treating more severe forms of CHF. Although ACE inhibitors and newer drug combinations have provided some relief for many patients, drugs often do not attack the root of the problem: a weak heart. Although workload on the heart is decreased through drug therapy, the pumping action of the heart is generally not improved long term in the case of most drugs. Also, in the case of drugs like digitalis, nitrates and glycosides, researchers remain unsure as to the long term debilitating affects that these drugs may have on an already weakened heart. Many believe that enhancement of the heart's performance through drug therapy further damages the weakened muscles of the heart in the long term. Drug therapy may also be less than desirable for patients who suffer from moderate to severe side effects. For example, the use of ACE inhibitors often is accompanied by a persistent cough. Angioedema is another potential side effect of ACE inhibitors which can be potentially life threatening. Diuretics may dangerously decrease the body's supply of potassium and other important vitamins and require additional corrective measures to maintain proper body chemistry. Finally, drug therapy often results in only short term gains to the patient. Although short term mortality of patients may be reduced in patients using aggressive drug therapy, after 3 to 5 years, drugs often offer little reduction in the rate of mortality for CHF patients.
Surgical intervention is another means for improving the condition of weakened hearts. When heart failure is due to valvular disease, the patient may have surgical implantation of an artificial heart valve or valve repair to help increase cardiac function. Surgery may also be helpful in correcting congenital heart defects that can lead to heart failure. Coronary artery bypass graft surgery or catheterization using balloon angioplasty are among the therapeutic techniques used to prevent and treat heart failure caused by occluded, or blocked, arteries. Additionally, newer techniques for myocardial revascularization and improved cardiac functioning include transmyocardial laser revascularization, implantation of mechanical assist devices, implantable cardioverters/defibrillators and dynamic cardiomyoplasty.
Implantation of permanent or temporary mechanical assist devices is one method by which ventricular function can be augmented in a diseased heart. A number of devices and methods are known in the art for compensating mechanically for the reduced ventricular output. Such devices include rotary blood flow pumps, intraaortic balloon pumps, axial flow pumps, external mechanical assist devices, and centrifugal blood flow pumps. The pump devices are traditionally used to augment the functioning of the left or right side of the heart by removing blood from one portion of the heart into a downstream portion of the patient's vasculature. For example, for ventricular “unloading” of the left heart, an axial flow pump may be inserted into the left ventricle via the aortic arch of the patient. The pump will remove blood from the ventricle and pump it into the aortic arch where it will flow normally to the remainder of the patient's arterial system. Right heart unloading is similarly accomplished except that blood is typically removed from the right atrium or ventricle and pumped into the pulmonary artery. In contrast, external ventricular assist devices are generally surgically attached to the external surface of the heart and compress the ventricle of the heart during contraction so as to augment the contraction and improve cardiac output.
Mechanically assisting the functioning of the heart often presents substantial practical problems which prevent this method of CHF treatment from being the most desirable therapeutic option. Mechanical assist devices are often very expensive and difficult to install. Devices which have components external to the patient can detract signi

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