Sinus node function after cardiac transplantation.

Abstract

OBJECTIVES: This study aimed to examine changes over time in sinus mode function after cardiac transplantation; to determine the incidence, natural history and etiology of sinus node dysfunction in transplant recipients; and to identify any early predictors of long-term sinus node function. BACKGROUND: Bradyarrhythmias caused by sinus node dysfunction are common immediately after cardiac transplantation. Existing electrophysiologic studies have been limited by small numbers and have reported an unexpectedly high incidence of sinus node dysfunction (approximately 50%) compared with the incidence of bradyarrhythmias in other studies. There have been no previous studies reporting serial electrophysiologic data. Thus, the natural history of sinus node dysfunction after transplantation has not been adequately described. METHODS: Serial electrophysiologic studies of sinus node function and 24-h ambulatory electrocardiographic recordings were performed at 1, 2, 3 and 6 weeks and 3 and 6 months after transplantation in 40 adult recipients. RESULTS: The overall incidence of sinus node dysfunction was 17.5% (7 of 40). Six patients (15%) had sinus node dysfunction from week 1; one developed sinus node dysfunction at 3 months. Sinus node recovery time returned to normal by 6 weeks in all six patients with early sinus node dysfunction, but abnormalities of sinoatrial conduction persisted in two. Two patients who required pacing during ambulatory monitoring at 2 weeks after transplantation (temporary pacemaker 50 beats/min, demand) received a permanent pacemaker. One patient required pacing at 3 weeks and continued to require pacing 6 months after transplantation. CONCLUSIONS: The incidence of sinus node dysfunction after cardiac transplantation is lower than has been previously reported in electrophysiologic studies. Sinus node automaticity improves with time, although abnormalities of sinoatrial conduction may persist. The best predictor of permanent pacing requirements is the temporary pacing requirements during 24-h Holter monitoring 2 and 3 weeks after transplantation, with temporary pacing set at 50 beats/min on demand.