Transient giant R waves in the early phase of acute myocardial infarction: association with ventricular fibrillation.

An unusual electrocardiographic (ECG) pattern was observed in five patients who suffered an acute anterior myocardial infarction. Early in their illness and following resuscitation from ventricular fibrillation (three patients), in the midst of recurrent ventricular irritability prior to development of ventricular fibrillation (one patient), and following a period of seizures (one patient), the ECG showed ST-segment elevation, marked increase in the R-wave amplitude, disappearance of S waves and merging of QRS complexes with the elevated ST segments, ECG patterns noted in these patients were similar to the ones recorded from dogs immediately after ligation of a large coronary artery, and from patients with severe episodes of variant angina. Although these early electrocardiographic changes probably reflect either marked regional transmural blood flow deprivation or its aftermath, they could not be taken as indices of eventual massive myocardial necrosis since in most of these patients the alterations were followed by development of nontransmural myocardial infarction. The possible mechanisms and the implications of such discrepancy between early and late electrocardiographic indicators of injury or necrosis is discussed.