SINUS NODE FUNCTION AFTER CARDIAC TRANSPLANTATION

Objectives. This study aimed to examine changes over time in sinus nod e function after cardiac transplantation; to determine the incidence, natural history and etiology of sinus node dysfunction in transplant r ecipients; and to identify any early predictors of long-term sinus nod e function. Background. Bradyarrhythmias caused by sinus node dysfunct ion are common immediately after cardiac transplantation. Existing ele ctrophysiologic studies have been limited by small numbers and have re ported an unexpectedly high incidence of sinus node dysfunction (simil ar to 50%) compared with the incidence of bradyarrhythmias in other st udies. There have been no previous studies reporting serial electrophy siologic data, Thus, the natural history of sinus node dysfunction aft er 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. Resul ts. The overall incidence of sinus node dysfunction was 17.5% (7 of 40 ). Six patients (15%) had sinus node dysfunction from week 1; one deve loped sinus node dysfunction at 3 months. Sinus node recovery time ret urned to normal by 6 weeks in all six patients with early sinus node d ysfunction, but abnormalities of sinoatrial conduction persisted in tw o. 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 week s and continued to require pacing 6 months after transplantation. Conc lusions, The incidence of sinus node dysfunction after cardiac transpl antation is lower than has been previously reported in electrophysiolo gic studies. Sinus node automaticity improves with time, although abno rmalities of sinoatrial conduction may persist. The best predictor of permanent pacing requirements is the temporary pacing requirements dur ing 24-h Holter monitoring 2 and 3 weeks after transplantation, with t emporary pacing set at 50 beats/min on demand.