Short-term effect of atrial fibrillation on atrial contractile function inhumans

Background-Conversion of chronic atrial fibrillation (AF) is associated wit h atrial stunning, but the short-term effect of a brief episode of AF on le ft atrial appendage (LAA) emptying velocity is unknown. The purpose of this study was to determine whether a short episode of AF affects left atrial f unction and whether verapamil modifies this effect, Methods and Results-The subjects of this study were 19 patients without str uctural heart disease undergoing an electrophysiology procedure. Ln 13 pati ents, LAA emptying velocity was measured by transesophageal echocardiograph y in the setting of pharmacological autonomic blockade before, during, and after a short episode of AF, During sinus rhythm, the baseline LAA emptying velocity was measured 5 times and averaged. AF was then induced by rapid r ight atrial pacing. After either spontaneous or electrical conversion, LAA emptying velocity was measured immediately on resumption of sinus rhythm an d every minute thereafter. The mean duration of AF was 15.3+/-3.8 minutes. The mean baseline emptying velocity was 70+/-20 cm/s. The first post-AF emp tying velocity was 63+/-20 cm/s (P=0.02 versus baseline emptying velocity), The post-AF emptying velocity returned to the baseline emptying velocity v alue after 3.0 minutes. The mean percent reduction in post-AF emptying velo city was 9.7+/-21% (range, 15% increase to 56% decrease). A second group of 6 patients were pretreated with verapamil (0.1-mg/kg IV bolus followed by an infusion of 0.005 mg.kg(-1).min(-1)). In these patients, the first post- AF emptying velocity, 58+/-14 cm/s, was not significantly different from th e pre-AF emptying velocity, 60+/-13 cm/s (P=0.08). Conclusions-In humans, several minutes of AF may be sufficient to induce at rial contractile dysfunction after cardioversion. When atrial contractile d ysfunction occurs, then is recovery of AF within several minutes. AF-induce d contractile dysfunction is attenuated by verapamil and may be at least pa rtially mediated by cellular calcium overload.