Abstract 2628: An Animal Model of Mechanical Lung Assist for Primary In-Series Palliation of Hypoplastic Left Heart Syndrome
Introduction: Single ventricle, in parallel physiology following the Norwood procedure, is inherently unstable. In series single ventricle physiology, seen with a bidirectional cavopulmo-nary connection (BCPS) as the source of pulmonary blood flow, would be more stable but is dependent on adequate lung maturation. Hypoplastic left heart syndrome (HLHS) outcomes may be improved if primary in series palliation can be performed.
Hypothesis: We hypothesized that mechanical lung assist by:
oxygenated superior vena cava to right atrium blood flow (SVC-RA+O2) or
unoxygenated SVC to pulmonary artery (SVC-PA) pump, would permit successful neonatal BCPS.
Methods: Two week-old piglets were randomized to single ventricle and BCPS without lung assist (n=8), BCPS plus SVC-RA+O2 (n=6) or BCPS plus SVC-PA pump (n=5). Surgery included atrial septectomy, tricuspid valve disruption, BCPS creation and pulmonary artery occlusion. Hemodynamic and blood gas analysis was performed regularly to a maximum of 6 hours postoperatively.
Results: No differences in mean arterial pressure, cardiac output, oxygen saturation or pulmonary vascular resistance were detected between groups at baseline. Median survival time for SVC-RA+O2 and SVC-PA vs BCPS groups was 270, 270 and 20 minutes respectively (log-rank test p=0.0006). Interestingly, there were no differences in arterial oxygen concentration or bicarbonate levels, however, arterial carbon dioxide was higher in the BCPS vs SVC-RA+O2 and SVC-PA pump pigs (increase of 7 mmHg/10min; p=0.007). Over time, BCPS pigs were more bradycardic (p<0.02) and had a decreased mean arterial pressure (4 mmHg/10min; p<0.02) compared to both lung assist groups. Left atrial pressure also rose more rapidly in BCPS vs SVC-RA+O2 pigs (3 mmHg/10min; p=0.018) with a similar trend vs SVC-PA pump animals (p=0.058).
Conclusions: This data demonstrates creation of a novel translational neonatal BCPS model in which mechanical lung assist augments survival. Early BCPS death was related to poor ventricular function and an inability to ventilate, issues that were improved with SVC-RA+O2 and SVC-PA pump lung assist. This strategy provides an animal model by which accelerated lung maturation and/or mechanical lung assist in the neonate may be studied.