To date, pump failure and its extreme manifestation,
cardiogenic shock are the most common cause of death in patients with acute
myocardial infarction. Post-mortem studies have shown that primary (myocardial)
cardiogenic shock does not occur until some 40 to 50% of the myocardium has been rendered nonfunctional. Not infrequently,
cardiogenic shock is mainly the result of a mechanical lesion (
mitral regurgitation secondary to papillary muscle dysfonction or
rupture, or
ventricular septal defect) superimposed upon an ischemic and infarcted ventricle. In both situations medical
therapy usually produces only a limited effect. Numerous physiological studies have shown that balloon pumping can reduce the workload and
oxygen demands of the heart while increasing coronary blood flow and cardiac output. Most patients with
cardiogenic shock can be at least temporarily stabilized, but many patients are balloon-dependent in the sense that when circulatory support is temporarily discontinued,
shock or severe
heart failure recurs. In these patients, some attempt to correct the underlying anatomic abnormalities appears necessary if they are to survive. Early
intra-aortic balloon pumping (IABP) and surgery is much more effective in patients with
cardiogenic shock secondary to mechanical complications. Finally, the combination of IABP and surgery has resulted in survival of approximately 50% of patients with
cardiogenic shock either primary or secondary.