Early mechanical function in the heterotopic heart transplant

The characteristics of left ventricular (LV) function in the nonimmunosuppressed heterotopic heart transplant (TX) with less than 3 hr of cold preservation, were studied in 12 awake chronically instrumented dogs prior to TX (control), 1-12 hr post TX (P₁), 12-24 hr post TX (P₂), and 24-48 hr post TX (P₃). Micromanometers measured LV transmural pressure and ultrasonic transducers measured ventricular dimension in order to allow calculations of myocardial mechanical properties. Immediately after transplant (P₁) there was significant (P < 0.05) depression noted in both diastolic function and systolic function (peak LV pressure, 137 ± 5 vs 80 ± 10 mm Hg; dp/dt_max, 2642 ± 170 vs 1038 ± 98 mm Hg/sec; maximum velocity of minor axis shortening, 4.46 ± 0.50 vs 2.41 ± 0.56; and E_max, 6.5 ± 1.2 vs 2.0 ± 1.4 mm Hg/ml). However, the contractility reserve (studied in six dogs) as estimated by postextrasystolic potentiation ratio was maintained (1.41 ± 0.07 vs 1.37 ± 0.15), suggesting reversibility of the depressed function. Over the next 2 days the diastolic function and the systolic function (at P₃: 109 ± 6 mm Hg, 1842 ± 450 mm Hg/sec, 5.54 ± 0.77 cm/sec, and 4.5 ± 1.3 mm Hg/ml, respectively) gradually improved toward control. Microscopic examination of the autopsied hearts did not show significant evidence of rejection. Thus, the early depression of function in the heart TX appeared to be the result of ischemia from preservation and surgical trauma. In spite of the depressed LV function immediately post TX, the contractility reserve of the transplanted heart appeared to be well maintained, and, in this study, recovery of function was observed. It is suggested that measurement of the cardiac contractility reserve may be of value in assessing various methods of long-term cardiac preservation for transplantation.