The relation of sinus rate to the frequency of paroxysmal ventricular tachycardia during acute myocardial infarction in man.

Continuous tape recordings of cardiac rhythm were made in 51 male patients with acute myocardial infarction within 24 hours of their infarction. These tracings were analyzed for the incidence of paroxysmal ventricular tachycardia (PVT) and the sinus rate immediately preceding each episode of PVT. In 26 patients, 112 episodes of PVT at a rate greater than 100 beats/min were documented. Although 67 per cent of the episodes of PVT were preceded by sinus rates between 60 and 100 beats/min, 15 per cent occurred at sinus rates below 60 beats/min and 18 per cent occurred at sinus rates above 100 beats/min. The data remained essentially unchanged regardless of whether ventricular tachycardia was defined at rates in excess of 100, 120 or 140 beats/min. The results of this study show that during the early phases of acute myocardial infarction in man, PVT was most common during sinus rates generally thought to be within the normal range (60 to 100 beats/min). A lower, but close to equal incidence of PVT was observed during sinus bradycardia and sinus tachycardia.