The Pattern of Onset and Spontaneous Cessation

The atrial electrocardiogram was studied in eight patients who developed intermittent atrial fibrillation following myocardial infarction. Thirty-two episodes of onset of atrial fibrillation and 28 episodes of spontaneous cessation were observed. An atrial premature beat followed by atrial tachycardia of variable duration always preceded the onset of atrial fibrillation. Spontaneous cessation of atrial fibrillation was preceded by a change of atrial wave form which suggested slowing of an ectopic focus. The time lapse between the cessation of atrial fibrillation and the onset of sinus rhythm exceeded the subsequent sinus cycle length which suggested overdrive and suppression of the sinoatrial node during the period of atrial fibrillation.