ATRIAL-FIBRILLATION BEGETS ATRIAL-FIBRILLATION - A STUDY IN AWAKE CHRONICALLY INSTRUMENTED GOATS

Background In this study we tested the hypothesis that atrial fibrilla tion (AF) causes electrophysiological changes of the atrial myocardium which might explain the progressive nature of the arrhythmia. Methods and Results Twelve goats were chronically instrumented with multiple electrodes sutured to the epicardium of both atria. Two to 3 Weeks aft er implantation, the animals were connected to a fibrillation pacemake r which artificially maintained AF. Whereas during control episodes of AF were short lasting (6+/-3 seconds), artificial maintenance of AF r esulted in a progressive increase in the duration of AF to become sust ained (>24 hours) after 7.1+/-4.8 days (10 of 11 goats). During the fi rst 24 hours of AF the median fibrillation interval shortened from 145 +/-18 to 108+/-8 ms and the inducibility of AF by a single premature s timulus increased from 24% to 76%. The atrial effective refractory per iod (AERP) shortened from 146+/-19 to 95+/-20 ms (-35%) (S1S1, 400 ms) . At high pacing rates the shortening was less (-12%), pointing to a r eversion of the normal adaptation of the AERP to heart rate. In 5 goat s, after 2 to 4 weeks of AF, sinus rhythm was restored and all electro physiological changes were found to be reversible within 1 week. Concl usions Artificial maintenance of AF leads to a marked shortening of AE RP, a reversion of its physiological rate adaptation, and an increase in rate, inducibility and stability of AF. All these changes were comp letely reversible within 1 week of sinus rhythm.