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Objective: Post-Norwood mortality remains high and unpredictable. Current models for mortality do not incorporate interstage events. We sought to determine the association of time-related interstage events, along with (pre)operative characteristics, with death post-Norwood and subsequently predict individual mortality. Methods: From the Congenital Heart Surgeons' Society Critical Left Heart Obstruction cohort, 360 neonates underwent Norwood operations from 2005 to 2016. Risk of death post-Norwood was modeled using a novel application of parametric hazard analysis, in which baseline and operative characteristics and time-related adverse events, procedures, and repeated weight and arterial oxygen saturation measurements were considered. Individual predicted mortality trajectories that dynamically update (increase or decrease) over time were derived and plotted. Results: After the Norwood, 282 patients (78%) progressed to stage 2 palliation, 60 patients (17%) died, 5 patients (1%) underwent heart transplantation, and 13 patients (4%) were alive without transitioning to another end point. In total, 3052 postoperative events occurred and 963 measures of weight and oxygen saturation were obtained. Risk factors for death included resuscitated cardiac arrest, moderate or greater atrioventricular valve regurgitation, intracranial hemorrhage/stroke, sepsis, lower longitudinal oxygen saturation, readmission, smaller baseline aortic diameter, smaller baseline mitral valve z-score, and lower longitudinal weight. Each patient's predicted mortality trajectory varied as risk factors occurred over time. Groups with qualitatively similar mortality trajectories were noted. Conclusions: Risk of death post-Norwood is dynamic and most frequently associated with time-related postoperative events and measures, rather than baseline characteristics. Dynamic predicted mortality trajectories for individuals and their visualization represent a paradigm shift from population-derived insights to precision medicine at the patient level.

Background: In single-ventricle physiology, focus on pulmonary vascular resistance neglects the resistance in the conduit supplying the pulmonary inflow. Methods: Conduit length and diameter, which can approximate conduit resistance, are available in the public dataset of Single Ventricle Reconstruction (SVR) trial. Conduit resistance was then calculated for SVR trial participants and the relationship with clinically important variables (death or transplant at 1 year, pulmonary artery size at second-stage palliation, pulmonary-to-systemic blood flow ratio, and supplemental oxygen requirement) was explored. To validate this calculated resistance, calculated resistance was compared with catheterization measurements at a single institution (not included in the SVR trial). Results: In the institutional dataset, calculated and measured resistances had an intraclass correlation of 0.78 for modified Blalock–Taussig shunts (MBTS). Within the SVR trial, transplant-free survivors had a lower MBTS resistance (median, 8.3 Woods Units [WU]. interquartile range [IQR], 6.5-11.1 WU) than patients who died or required transplantation (median, 13.0 WU; IQR, 9.4-16.6 WU, P = .0001). When we controlled for left pulmonary artery diameter after the Norwood procedure in the SVR trial, for each unit increase in MBTS resistance, the left pulmonary artery diameter at stage II decreased (–0.006 ± 0.002 cm, P = .005). When we controlled for pulmonary vascular resistance, greater MBTS resistance was associated with a decrease in log pulmonary-to-systemic blood flow ratio (–0.04 ± 0.015, P = .0048) in the SVR trial. Patients in the SVR trial requiring supplemental oxygen on admission for stage II palliation had greater MBTS resistance (median. 11.1 WU; IQR, 6.6-16.6 WU) than patients not requiring oxygen (median 8.3, WU; IQR, 6.5-11.1 WU, P = .015). Conclusions: Conduit resistance is associated with important clinical outcomes after Norwood; however, further studies are required to guide conduit resistance optimization.