Introduction: Depression of sinus node function occurs in dogs and in patients after cessation of atrial flutter and fibrillation. We tested whether transient atrial pacing might produce similar changes in humans.
Methods and results: We studied the impact of short-term rapid atrial pacing, simulating atrial tachyarrhythmias, on sinoatrial conduction time (SACT) and corrected sinus node recovery time (CS-NRT) in 10 patients undergoing electrophysiologic study. None had recognizable structural heart disease, history of atrial fibrillation or flutter, autonomic dysfunction, or any tachycardia for at least 24 hours before study. All cardiac drugs were discontinued >5 half-lives prior to study. No patient had significant hypotension during atrial stimulation. SACT and CSNRT were measured at baseline, and sinus node reset zone was determined. Right atrial pacing was performed for 10 to 15 minutes, after which SACT and CSNRT were measured again. Both parameters increased significantly, from 423+/-208 msec to 491+/-214 msec and from 80+/-50 msec to 96+/-53 msec, respectively (P = 0.02 and P < 0.001, respectively).
Conclusion: Rapid atrial pacing for only 10 to 15 minutes, simulating transient atrial tachyarrhythmias, alters sinus node function in humans. Additional studies are needed to evaluate the mechanism, but the clinical implication is that even transient episodes of atrial tachyarrhythmias can cause sinus node remodeling in patients.