Retrograde ventriculoatrial conduction in patients with acute myocardial infarction.

Temporary transvenous pacemakers were inserted in ten patients with acute myocardial infarction complicated by atrioventricubu (A-V) block. With return of sinus rhythm, the ventricular rate was intentionally increased above sinus rate by graded increases of the pacemaker rate and stimulus amplitude to a maximum of 120 beats/minute and to 12 milliamperes for each paced rate. Four patients had ventriculoatrial (V-A) conduction at paced rates greater than the sinus rate. Two of four had V-A conduction at slower rates (80-100 beats/minute), but A-V dissociation developed with more rapid rates (100-140). Three of six patients who had sinus rhythm with normal PR interval demonstrated V-A conduction while only one of four with first degree block showed rehconduction. The pattern of conduction was independent of stimulus amplitude. Retrograde V-A conduction occurs commonly in patients with acute myocardial infarction with slow ventricular rates (80-100 beats/minute) and less commonly with rapid rates.