Cardiac Failure

Some 15 to 20 percent of patients with AMI present in some degree of congestive heart failure. One-third of these patients have circulatory shock. In the setting of AMI, congestive heart failure can occur through either diastolic dysfunction alone or a combination of systolic and diastolic dysfunction. Left ventricular diastolic dysfunction leads to pulmonary congestion. Systolic dysfunction is responsible for decreased forward flow, reduced cardiac output, and reduced ejection fraction. In general, the more severe the degree of left ventricular dysfunction, the higher the mortality. The degree of left ventricular dysfunction in any single patient is dependent upon the net effect of prior myocardial dysfunction (prior AMI), baseline myocardial hypertrophy, acute myocardial necrosis, and acute reversible myocardial dysfunction ("stunned myocardium").

Patients with AMI can be classified into four subsets based upon hemodynamic status (Forrester-Diamond classification) and clinical status (Killip classification), shown in Ta.b.!ยง...4.Z.-9 and Table. ...4Z.zl0. These classifications are useful to guide therapy and predict response to treatment. Patients with decreasing cardiac outputs or increasing pulmonary congestion have an increasingly higher mortality in the setting of AMI. Class I patients have a mortality of 2 to 5 percent. Class IV patients, (i.e., those with cardiogenic shock), are at very high risk of mortality (50 to 80 percent).

TABLE 47-9 Forrester-Diamond-Swan Hemodynamic Classification

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Essentials of Human Physiology

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