Postcardioversion atrial electrophysiologic changes induced by oral verapamil in patients with persistent atrial fibrillation

OBJECTIVES The aim of our study was to verify the effect of oral administra tion of verapamil on atrial electrophysiologic characteristics after cardio version of persistent atrial fibrillation (AF) in humans. BACKGROUND Discordant findings have been reported regarding the efficacy of verapamil in preventing the electrical remodeling induced by AF. METHODS We determined the effective refractory periods (ERPs) at five pacin g cycle lengths (300 to 700 ms) and in five right atrial sites after intern al cardioversion of persistent AF (mean duration 238.1 +/- 305.9 days) in 1 9 patients. Nine patients received oral verapamil (240 mg/day) starting fou r weeks before the electrophysiologic study, whereas the other 10 patients were in pharmacologic washout. RESULTS The mean ERPs were 202.0 +/- 22.7 ms in the washout group and 189.3 +/- 18.5 ms in the verapamil group (p < 0.0001). The degree of adaptation of refractoriness to rate was similar in the two groups (mean slope value i n the washout group and verapamil group: 0.07 +/- 0.03 and 0.08 +/- 0.05, r espectively), showing a normal or nearly normal adaptation to rate in the m ajority of the paced sites in both groups. The mean ERP was slightly longer in the septum than in the lateral wall and in the roof, both in the washou t and verapamil groups. CONCLUSIONS In patients with persistent AF, long-term administration of ver apamil before internal cardioversion resulted in 1) shortening of atrial ER Ps; 2) no change in refractoriness dispersion within the right atrium; and 3) no change in atrial ERP adaptation to rate. (C) 2000 by the American Col lege of Cardiology.