Incidence and significance of the low-voltage electrocardiogram in acute myocardial infarction.

In a retrospective study of 304 patients with acute transmural myocardial infarction admitted to the coronary care unit, 22 percent (67 patients) exhibited low voltage on their electrocardiograms within 72 hours of admission. The course of hospitalization of these patients was compared with an equal number of consecutive patients with transmural infarctions and normal electrocardiographic voltages. Among the patients with low voltage, there was a significantly higher incidence of previous infarction or present extensive infarction, congestive heart failure, and cardiogenic shock. This group of patients also demonstrated a markedly higher mortality. This study substantiates the clinical impression that acute myocardial infarction complicated by a low-voltage ECG implies a poor prognosis. It is speculated that this electrocardiographic pattern may reflect decreased ventricular performance as a result of widespread myocardial damage.