Right Ventricle-to-Pulmonary Artery Conduit Versus Blalock-Taussig Shunt: A Hemodynamic Comparison

Background: A comprehensive assessment of 48 hour postoperative hemodynamics in neonates randomized to the right ventricle-to-pulmonary artery (RV-PA) conduit or modified Blalock-Taussig (BT) shunt for stage 1 palliation of hypoplastic left heart syndrome was performed to determine the potential benefits of the modified technique. Methods: Randomization to either RV-PA conduit or BT shunt was stratified by surgeon and the presence of aortic atresia. The designated procedure was performed by using hypothermic cardiopulmonary bypass with phenoxybenzamine, continuous cerebral perfusion, pH-stat blood gas management, and continuous postoperative venous oximetry. Differences between treatments were analyzed by time-series generalized least-squares regression, χ² tests, two-way repeated measures analysis of variance, and the Levene variance ratio test for variability in parameters, as appropriate. Results: All patients underwent the procedure to which they were randomized. There were no differences in age, weight, deep hypothermic circulatory arrest, or cardiopulmonary bypass times between patients receiving the BT shunt (n = 8) or the RV-PA conduit (n = 9). There was one early and one late death in the RV-PA conduit group, and one interstage death in the BT shunt group. Other than diastolic blood pressure (39 mm Hg in BT shunt versus 46 mm Hg in RV-PA conduit, p < 0.001), there were no differences in the mean values of arterial saturation, venous oximetry, mean arterial blood pressure, pulmonary-to-systemic flow ratio (Qp/Qs), or any other physiologic or inotropic support variable between groups. The variability of physiologic values related to pulmonary blood flow was greater in the RV-PA group (Qp/Qs coefficient of variation, 0.91 versus 2.50, p < 0.001). Conclusions: In this randomized prospective study, no hemodynamic benefits of the RV-PA modification for stage 1 palliation of hypoplastic left heart syndrome were found. Pulmonary blood flow was more variable, and the diastolic blood pressure was higher. These findings did not influence indicators of systemic oxygen delivery with our afterload reduction strategy.