Cardiovascular disease (CVD) is the leading cause of morbidity and mortality in the United States and a significant public health problem in most industrialized nations. Since 1900, it has been the leading cause of death in the United States every year except 1918.1 In 2005, CVD afflicted 80 million Americans and caused 864,500 deaths. Meanwhile, the number of people with CVD, and especially its advanced forms, has been increasing. There are two main reasons for this. First, although there is still no cure for CVD, palliative therapy has improved to the point that more people are surviving past their initial episodes of CVD to live on with some form of the disease. Second, the average age of the US population is rising as the “baby boom” generation ages.
An increasingly prevalent form of advanced CVD is heart failure (HF). Almost 5.7 million Americans (approximately 3.2 million men and 2.5 million women) are living with HF.1 Its etiology can be ischemic, idiopathic, or viral. More than $37.2 billion is spent each year on the care of HF patients, and many therapeutic advances have been made. In 2005, HF directly caused 53,000 deaths and indirectly caused another 250,000. As large as the problem is now, its magnitude is expected to worsen as more cardiac patients are able to survive and live longer with their disease and thus increase their chances of developing end-stage HF.
At present, treatment of advanced HF takes three forms: medical therapy, surgical therapy, and cardiac support or replacement.2,3 Medical therapy (eg, intravenous inotropes and vasodilators) relieves symptoms by reducing cardiac work and increasing myocardial contractility. However, although advances in medical therapy have helped improve quality of life for those with heart failure, mortality remains unaffected. Surgical therapy (eg, revascularization and valve replacement or repair) relieves symptoms of ischemia and valvular dysfunction, but in most cases does not stop the underlying disease process from progressing. When conventional medical and surgical therapies for HF are exhausted, cardiac support or replacement (ie, heart transplantation or implantation of an artificial heart or ventricular assist device) may in some cases become the only therapeutic alternative.
Heart transplantation has evolved into a suitable treatment for advanced HF. However, it has severe limitations related to patient selection, organ procurement and distribution, and cost-effectiveness. Slightly more than 2000 patients with end-stage heart failure receive heart transplants each year in the United States. However, about 3000 patients are on the active heart transplant waiting list at any given time, and as many as 40,000 more are potential candidates for heart transplantation.4,5 Heart transplantation for the relatively young (<40 years old) is not very promising because the life expectancy of a donor heart recipient is about 10 years on average and 20 years at most. In 2004, 460 patients on the active waiting list died while awaiting a donor heart. Heart transplantation is also associated with continuous, lifelong, expensive medical therapy.
To help overcome these limitations, engineers and physicians have continued efforts begun over four decades ago to develop systems for providing either temporary or permanent mechanical circulatory support (MCS). Originally, such systems were intended to support patients indefinitely because other forms of heart replacement did not ...