Twenty-Four Hour Cardiopulmonary Stability in a Model of Assisted Newborn Fontan Circulation

Abstract

Morbidity and mortality after stage-1 palliation of hypoplastic left heart syndrome is high as a result of adverse physiologic conditions imposed by the systemic-to-pulmonary arterial shunt. Conversion to a systemic venous source of pulmonary blood flow (Glenn/Fontan) substantially decreases instability and mortality risk. Cavopulmonary assist has the potential to eliminate critical dependence on the problematic systemic arterial shunt. We studied this support modality during a 24-hour period in a neonatal animal model of univentricular Fontan circulation. Lambs (8.1 +/- 0.9 kg, 8.3 +/- 2.1 days, n = 7) underwent total cavopulmonary diversion. A miniature centrifugal pump was used to assist cavopulmonary flow. Control animals (6.6 +/- 1.0 kg, 7.3 +/- 2.1 days, n = 11) underwent placement of monitoring lines only. Hemodynamic and gas exchange data were measured. Within-group and between-group comparisons were made using two-way repeated measures analysis of variance. After an initial phase of reactivity, pulmonary vascular resistance returned to low levels and was not significantly different from baseline values after hour 13 or significantly different from control values after hour 4. Systemic venous pressure remained low. Oxygenation and ventilation remained normal with no histologic evidence of parenchymal lung injury. Pump-assisted cavopulmonary diversion is well tolerated up to 24 hours in the neonatal period. Despite initial reactivity, pulmonary vascular resistance trended toward normal and approached control values. Cavopulmonary assist holds the potential to serve as a bridge to neonatal Fontan repair of single ventricle. Chronic studies are warranted to determine the duration and rate of weaning of support to transition to an unassisted univentricular Fontan circulation.