Exercise Chronotropy in Patients with Normal and Impaired Sinus Node Function After Cardiac Transplantation

The chronotropic response during graded, symptom limited exercise was investigoted in 32 cardiac transplant recipients a mean of 49 ± 18 days after transplantation. All patients had systematic evaluation of postoperative donor sinus node (SN) function and the cardioacceleratory response was compared according to the SN function. Twenty-one patients had normal postoperative SN studies (corrected SN recovery time < 520 msec, group I) while the SN function was impaired postoperatively in the remainder (n = 11, group II; corrected SN recovery time 4,149 ± 6,283 msec in 5 patients, junctionai escape rhythm in 6 patients). All patients had regained sinus rhythm at time of the exercise test Patients in group II had lower basal sinus rates at the beginning of exercise (91.5 ± 11 vs 101.4 ± 7 beats/min, P < 0.02). This lower chronotropy was maintained over every incremental step (F_{rato between groups}= 30, P = 0.0001, F_{rate vs workload}= 15, P = 0.0001 by two-way ANOVAJ and resulted in a significantly lower heart rate at individual peak exercise (108.3 ± 20 vs 124.2 ±13 beats/min, P < 0.02). A total of 14/16 patients in group I but only 2/16 patiejils in group 11 accomplished a peak heart rate ± 120 beats/min (P = 0.009). The workload achieved did not differ between the groups (107 ± 29 vs 102 ± 32 watts, P > 0.5). These data show a lower SN chronotropy during rest and at peak exercise in cardiac transplant recipients with postoperative SN deficiency and apparent normalization of SN fundion.