Clinical spectrum of mechanical circulatory assistance.

Mechanical blood pumps can provide effective circulatory support in a variety of clinical settings. Ventricular assist devices are single ventricle blood pumps designed to work in parallel with the natural heart. These devices can be powered by air pulses or an electric motor to provide temporary or permanent circulatory assistance, respectively. Unlike ventricular assist devices, artificial hearts replace the natural heart. In doing so, they provide complete support of both the systemic and pulmonary circulation. Air-driven artificial hearts will primarily support patients with profound biventricular failure prior to heart transplantation. Electrically assisted artificial hearts with their implantable energy converters are in the earliest stages of development. These devices will ultimately serve as permanent heart replacements in patients who do not qualify for heart transplantation.