The etiology of sinus node (SN) dysfunction after orthotopic heart transplantation as assessed by the origin of rhythm, heart rate (HR), and, provided the origin of rhythm was sinus, by corrected sinus node recovery time (CSNRT) was studied in 50 patients. The possible influences on postoperative donor SN function of donor age, recipient age, underlying pretransplant heart disease, pretransplant amiodarone (AMIO) treatment, date of surgery, ischemic time, surgical technique of atrial incision, the use of different cardioplegic solutions during the study period, and rejection were evaluated. The results thus obtained indicate that SN dysfunction is common after cardiac transplantation and pinpoint to a different etiology of transient (restoration of normal SN function within 4 postoperative weeks) and persistent (SN function still impaired at 3 months) SN dysfunction. Of the several demographic and perioperative variables evaluated, only ischemic time had an influence on postoperative SN function in that ischemic times were significantly longer in patients with impaired SN function when compared with patients exhibiting normal SN function (148 +/- 39 min vs. 110.5 +/- 36 min, respectively, P = 0.001). Further stratification according to the duration of SN dysfunction revealed significantly longer ischemic times in patients with transiently impaired SN function only (156.3 +/- 35 min vs. 110.5 +/- 36 min, P = 0.0026). No relation to persistent SN dysfunction of ischemic time (130.5 +/- 36 min vs. 110.5 +/- 36 min, P = ns) or any other factor investigated was found.