Induced fibrillation is equally effective as crystalloid cardioplegia in the protection of fetal myocardial function.

BACKGROUND Fetal cardiac intervention represents a potential advance in the treatment of congenital cardiac lesions that increase in complexity during development. Prenatal repair of a primary defect might prevent pathologic blood-flow patterns that can result in hypoplasia of a cardiac chamber or great vessel. However, strategies to optimize fetal myocardial protection have not been studied. A biventricular working fetal heart preparation was used to evaluate the cardioprotective properties of induced fibrillation and crystalloid cardioplegia. METHODS Hearts from 16 fetal lambs at 115 to 125 days' gestation were harvested and perfused with Krebs-Henseleit solution. The descending aorta was ligated distal to the ductal insertion and the branch pulmonary arteries were ligated to simulate the parallel circulation of the fetus. Hearts were arrested with normothermic fibrillation (n = 8) or hypothermic crystalloid cardioplegia (n = 8) before reperfusion with Krebs-Henseleit solution. Baseline and postarrest myocardial function measurements were obtained from analysis of pressure-dimension relationships. RESULTS Fibrillatory and cardioplegic arrest were equally effective at preserving postarrest systolic function (left ventricle, 70% +/- 5% vs 68% +/- 15%, P =.52; right ventricle, 68% +/- 4.5% vs 65% +/- 4.5%, P =.26) and preventing increased diastolic stiffness (left ventricle, 32% +/- 5.3% vs 38% +/- 11%, P =.24; right ventricle, 25% +/- 3.3% vs 27% +/- 2.1%, P =.46). Myocardial water content was unchanged in hearts arrested with fibrillation and cardioplegia (84% +/- 1.5% vs 83.7% +/- 0.9%, P =.71). CONCLUSIONS Normothermic fibrillation and hypothermic crystalloid cardioplegia provide equal protection of the fetal myocardium. In the setting of diminished fetal myocardial reserve and because of the limited ability to manipulate the surrounding temperature in the fetus, normothermic fibrillation may be preferable for in utero repairs of selected congenital heart defects.