Electrophysiologic characteristics of human atrial muscle in paroxysmal atrial fibrillation

There are several limitations in clinical electrophysiologic studies of PAF, mainly related to its mechanism, which is not an ordered reentry but a random reentry of multiple independent wavelets within the atrium. Recent investigations based on the recordings of local AAEs during sinus rhythm and their characteristic distribution within the right atrium of patients with PAF provide us with new information on the electrophysiologic properties of the diseased atrium. Moreover, several abnormal responses have been elicited by premature atrial stimulation, including repetitive atrial firing, fragmented atrial activity, and intraatrial conduction delay. Although these responses do not show the localization and characteristics of reentry circuits, they are found to be closely related to the development and maintenance of atrial fibrillation in predisposed patients. These indicators of atrial vulnerability and their corresponding zones, which are defined as the difference between the longest coupling interval eliciting the abnormal responses and the atrial effective refractory period, are useful parameters indicative of predisposition to atrial fibrillation. Electrophysiologic studies in patients with PAF have led to essential understanding of the underlying clinical pathophysiologic process of atrial fibrillation and would further contribute to future development of more suitable treatments.