Clinical behavior of paroxysmal atrial tachycardia

Paroxysmal atrial tachycardia is a familiar arrhythmia that has been studied extensively for the past decade using intracardiac recording and programmed electrical stimulation. These studies have thoroughly documented the mechanisms of this arrhythmia and its associated atrioventricular conduction abnormalities, but little is known about the spontaneous clinical behavior of this arrhythmia. A group of 34 patients with paroxysmal atrial tachycardia were studied using telephone transmission of the electrocardiogram to document recurrent tachycardia. When antiarrhythmic therapy was withdrawn, median time to the first recurrence of tachycardia was 19 days, mean heart rate during spontaneous tachycardia was 203.5 +/- 34.9 beats/min, and the median duration of an attack was 20 minutes. In a group of patients who were followed while many consecutive attacks were documented, the time intervals between attacks were found to be uncorrelated and to fit an exponential probability distribution (i.e., the occurrence of paroxysmal atrial tachycardia behaved like a Poisson process). Paroxysmal atrial tachycardia does not occur in a chaotic and unpredictable fashion; it is an event that occurs according to common probability models.