Ventricular fibrillation complicating acute myocardial infarction. Two distinct clinical and electrocardiographic features.

Two distinct electrocardiographic patterns of ventricular fibrillation (VF) complicating acute myocardial infarction (AMI) were observed in 34 patients during the first 24 hours from initial symptoms. Type 1 (seven patients) was characterized by fast disorganized ventricular activity, small voltage, and no clear identifiable QRS complexes (fine VF). Type 2 (27 patients) was defined as multiform QRS configuration (greater than 300/min) with marked changes in the amplitude (polymorphous VF). Type 1 rhythm was seen mostly during the hyperacute ischemic phase, probably associated with total coronary vessel occlusion; type 2 was observed when Q waves were already present in the electrocardiogram.