The relationship between sinoatrial conduction time and sinus cycle length during spontaneous sinus arrhythmia in adults.

It is well known that atrioventricular conduction varies as a function of atrial rate. However, rate related changes in sinoatrial conduction time (SACT) have not been examined. To determine the relationship between SACT and sinoatrial cycle length (SCL) in man, atrial and His bundle electrograms were recorded during atrial premature stimulation in each of nineteen patients with sinus arrhythmia. Ten of nineteen had asymptomatic, intermittent sinus bradycardia; 3/19 had persistent sinus bradycardia with nonspecific symptoms; 6/19 were felt to represent the sick sinus syndrome. In 18/19 individuals, there was a clearcut, in-