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The heart may be unable to maintain a satisfactory circulation when part of its muscle has been permanently replaced by fibrous tissue or when the myocardium has been temporarily weakened by congestive heart failure of diverse etiology. Surgical successes that restore the normal mechanics of circulation are manifold. Replacement of stenosed and incompetent cardiac valves with prosthetic counterparts, the correction of congenital cardiac defects, the successful implantation of internal mammary and other arteries in cases of cardiac ischemia resulting from a coronary occlusion are today routine procedures in all cardiac units. The use of pacemakers has prolonged many lives in cases of auriculoventricular block caused by interference with conduction along the bundle of His. Despite the many triumphs of cardiac surgery, the problem of the inadequate or irreversibly damaged myocardium remains largely unsolved. The myocardium may only require temporary assistance in order to allow time for the natural restoration of tissues and function. It is, however, the case of progressive heart failure in which the myocardium is irreparably impaired, that is our most urgent and pressing concern. Replacement with a normal heart or some form of permanent assistance to the damaged heart become the only treatments of choice. [ABSTRACT FROM AUTHOR]