Atrial flutter associated with acute myocardial infarction.

Between 1966 and 1968, 35 of 340 patients (10.3 percent) admitted to the Los Angeles County-University of Southern California Medical Center with documented myocardial infarctions were noted to have atrial flutter while being monitored in the coronary care unit. This incidence is higher than that found in most previous studies. Patients with atrial flutter had significantly higher mortality than infarction patients without flutter (P <0.05). The increased mortality for those with flutter was apparently the result of concurrent complications and probably not because of the arrhythmia alone. Atrial flutter recurring for more than one day was associated with further increase in mortality (P <0.02). Also, there was a higher death rate among patients with flutter who had anterior infarctions than among those with inferior infarctions, but the difference was not statistically significant. Most patients responded to treatment with antiarrhythmic drugs, but prior digitalis therapy apparently did not prevent the onset of atrial flutter.