Electrophysiologic differences in young patients with atrial fibrillation. Influence of preexcitation

Paroxysmal atrial fibrillation is a common arrhythmia, which may occur in young patients without known structural heart disease, with or without preexcitation. Elimination of an accessory pathway in these patients may prevent not only orthodromic and antidromic tachycardia but also atrial fibrillation. However, abnormalities of atrial conduction and refractoriness have been reported, suggesting that atrial fibrillation may still recur in these patients. In a review of all electrophysiologic studies performed at the authors' institution since January 1990 in patients under age 60 years of age without identifiable heart disease, 24 patients with atrial fibrillation were identified whose electrophysiologic measurements of a right atrial conduction and effective refractory period of the right atrium and accessory pathway were in sinus rhythm. Of these patients, 12 had preexcitation and the other 12 did not. These patients were compared with age- and sex-matched control subjects, 12 with preexcitation without atrial fibrillation and 13 without preexcitation or atrial fibrillation, respectively. Electrophysiologic abnormalities were noted in patients with atrial fibrillation depending on the presence or absence of preexcitation. In patients with preexcitation, these abnormalities were a shorter refractory period of the right atrium (212 +/- 33 ms) and of the accessory pathway (251 +/- 27 ms), compared with control subjects (241 +/- 27 ms, P < .05 and 306 +/- 61 ms, P < .02, respectively). In patients without preexcitation, conduction abnormality in the form of prolonged atrial conduction time when compared with control subjects (48 +/- 26 ms vs 31 +/- 10 ms, P < .05) was noted. These findings may influence the type of antiarrhythmic drug used in these patients, and if confirmed in a larger study, they may lead to a better understanding of factors influencing the development of atrial fibrillation in young patients.