EFFECT OF VERAPAMIL AND PROCAINAMIDE ON ATRIAL FIBRILLATION-INDUCED ELECTRICAL REMODELING IN HUMANS

Background Atrial fibrillation (AF) shortens the atrial effective refr actory period (ERP) and predisposes to further episodes of AF. The pur pose of this study was to determine the effect of verapamil and procai namide on these manifestations of AF-induced electrical remodeling. Me thods and Results In adult patients without structural heart disease, the atrial ERP was measured before and after AF after pharmacological autonomic blockade and administration of verapamil (17 patients), proc ainamide (10 patients), or saline (20 patients). AF was then induced b y rapid pacing. Immediately on AF conversion, the post-AF ERP was meas ured at alternating drive cycle lengths of 350 and 500 ms. In the sali ne group, the pre-AF and first post-AF ERPs at the 350-ms drive cycle length were 206+/-19 and 179+/-27 ms (P<.0001), respectively, and at t he 500-ms drive cycle length, the values were Z17+/-16 and 153+/-23 ms , respectively (P<.0001). There was a similar significant shortening o f the first post-AF ERP in the procainamide group. In the verapamil gr oup, however, there was no difference between the pre-AF and the first post-AF ERP at the 350-ms (226+/-15 versus 227+/-72 ms, P=.8) or 500- ms (230+/-17 versus 232+/-20 ms, P=.6) drive cycle length. During dete rminations of the post-AF ERP, 105 secondary episodes of AF were unint entionally induced in 12% of verapamil patients compared with 90% and 80% of saline and procainamide patients (P<.01 versus verapamil). Conc lusions Pretreatment with the calcium channel antagonist verapamil, bu t not the sodium channel antagonist procainamide, markedly attenuates acute. AF-induced changes in atrial electro: physiological properties. These data suggest that calcium loading during AF may be at least par tially responsible for AF-induced electrical remodeling.