Nonpharmacologic validation of the intrinsic heart rate in cardiac transplant recipients

Background: The maximum sinus rate during exertion in humans is inversely r elated to age. However, the sinus rate at rest Is quite variable. The intri nsic heart (MR) following pharmacologic blockade of autonomic tone with pro pranolol and atropine has been proposed as a test of sinus node function an d is related to age by the linear regression equation: IHR = 118.1 - (0.57 x age). Whether this relationship exists for transplanted hearts for which the donor sinus node is denervated has not been determined. Methods: The re lationship between the resting heart rate and the age of the donor heart wa s examined in 103 patients 1 year following orthotopic cardiac transplantat ion in the absence of rejection or intercurrent illness. Patients receiving beta-blockers, calcium blockers, antiarrhythmic drugs, digitalis, theophyl line, or with biopsy evidence of rejection or abnormal coronary arteriogram s were excluded from analysis. Results: The recipient age, left ventricular ejection fraction, pulmonary capillary pressure, cardiac index, donor hear t ischemic time and cardiopulmonary bypass time did not correlate with the rate of the resting donor sinus node. The resting heart rate was inversely related to age of the donor heart by the linear regression equation: HR = 1 12.0 - (046 x age). Conclusion: The resting rate of the denervated sinus no de is related to donor age with a regression equation that is similar, thou gh slightly slower, than that predicted after pharmacologic autonomic block ade.