Thirteen patients with acute
myocardial infarction with multiform
accelerated idioventricular rhythm (
AIVR) occurring during the first 12 hours of monitoring in the coronary care unit are described. This
arrhythmia, similar to the more common uniform
AIVR, was intermittent, did not cause hemodynamic compromise, and was not related to more serious ventricular arrhythmias. There was no correlation between the
bundle branch block pattern of the multiform
AIVR and the electrocardiographic location of the
myocardial infarction, but there was a perfect correlation between the frontal plane electrical axis of the multiform
AIVR and the electrocardiographic location of the
myocardial infarction. The presence of fusion beats between the different forms of
AIVR suggests multifocality rather than multiformity. Intravenous
verapamil (3 to 5 mg bolus) was administered to 6 patients with multiform
AIVR in whom the arrhythmias were persistent enough to allow the evaluation of the effect of
verapamil on the
arrhythmia.
Verapamil caused no change in the rate of
AIVR in 1 patient, but in a second patient it decreased the rate by 20 beats/min. In 4 patients,
verapamil abolished the
arrhythmia: in 2 patients carotid sinus pressure (induced sinus slowing) allowed the emergence of the
AIVR at a lower rate, and in the remaining 2 patients the
arrhythmia was not observed.