Impaired sinus node function and global atrial conduction time after high rate atrial pacing in dogs.

In animal and human studies, it has been shown that atrial fibrillation shortens the atrial refractory period and impairs its rate adaptation. The objective of this study was to evaluate the effects of high-rate pacing on sinus node function and intra-atrial conduction. Eight dogs were subjected to rapid atrial pacing (AP) at 400 bpm for 16 days. Sinus node recovery time (SNRT) and P-wave duration were measured at baseline, immediately after AP and four weeks after the termination of AP. SNRT immediately after AP was significantly prolonged at all pacing rates compared to the baseline values. P-wave duration was significantly longer after AP relative to the baseline values. All the variables were completely reversible four weeks after the termination of pacing. Rapid AP induces sinus node dysfunction and prolongs the intra-atrial conduction time. It is possible that the electrical remodelling extends to the sinus node as well.