Correlates of Myocardial Performance with Rejection in Pediatric Heart Transplant Patients † 80

Abstract

In pediatric heart transplant patients, myocardial performance is an important determinant of outcome. However, correlates mediating systolic and diastolic function in these patients are incompletely understood. We determined left ventricular +dP/dtmax (an index of contractility);-dP/dtmax and Tau (measures of relaxation), and end diastolic pressure(EDP); and performed right ventricular endomyocardial biopsies, in 5 post-transplant patients undergoing 8 cardiac catheterizations. One patient(*) had 3, and another (†) 2 catheterizations because of severe rejection. Their ages ranged from 4 to 17 yrs., and the time from transplant to catheterization was 2.5 to 3 yrs. Mechanical parameters were determined from left ventricular pressure tracings recorded at 200 mm/sec, and sampled at 4.16 ms intervals. Tau, the relaxation time constant, was obtained by fitting the ventricular pressure data to the exponcntial function P(t) = Po e-t/Tau, where Po is the pressure at -dP/dtmax, and t the time. Myocardial rejection was classified as mild (open box), moderate (shaded box) or severe (black box), based upon the grading system of the International Society for Heart Transplantation. Positive- and -dP/dtmax were jointly evaluated to determine whether ventricular contraction and relaxation were coupled (Fig. 1). Tau and EDP were analyzed to examine the relationship between active relaxation and passive filling (Fig. 2). Both correlations were highly significant regardless of the patients' degree of rejection. In conclusion, for these pediatric heart transplant patients: 1) Contraction-relaxation coupling is preserved, 2) + and -dP/dtmax do not correlate with the degree of rejection, and 3) Tau and EDP correlate with each other, and, more importantly, with the degree of rejection.