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Background: The hybrid comprehensive stage 2 (HCS2) procedure is a novel palliative operation applicable to a select subset of single ventricle patients with adequate native antegrade aortic flow to the upper body. Flow to the descending aorta, through the pulmonary outlet and ductal arch, is influenced by a stented intrapulmonary baffle connecting the branch pulmonary arteries. We used computational fluid dynamics (CFD) to elucidate the hemodynamic characteristics of this reconstruction. Methods: We used multiscale CFD analysis of a synthetic, patient-derived HCS2 anatomic configuration with unsteady laminar flow conditions and a non-Newtonian blood model to quantify the resultant hemodynamics. The 3-dimensional CFD model was coupled to a 0-dimensional lumped parameter model of the peripheral circulation to determine the required boundary conditions. Results: For the specific anatomy studied, the intrapulmonary baffle did not obstruct flow from the pulmonary trunk to ductal arch as long as the distance between the anterior pulmonary artery wall and baffle wall exceeded ∼7 mm. Vortex shedding off of the baffle wall did not develop, because of the short distance to the ductal arch. The stented baffle experienced significantly uneven “inward” loading from the systemic side. Pulmonary outlet flow separation distal to the baffle produced a low-speed recirculation region. Conclusions: Hemodynamic patterns in this complex anatomy are generally favorable. Low flow recirculation could be mitigated by preoperative shape optimization. Calculated inward stresses on the pulmonary baffle can be used in the future to study baffle stent deformation, which is expected to be small.

Objective: We previously described the hybrid comprehensive stage II operation as an alternate surgical procedure for a subset of patients with single ventricle congenital heart disease with adequate native ascending aortic outflow. Here we provide a clinical update on the 4 patients who have undergone this procedure. Methods: After undergoing a hybrid approach to the stage I Norwood palliation, the hybrid comprehensive stage II procedure was performed with an incision to the main pulmonary artery (PA), dilation of the ductal stent, creation of a stented baffle between the branch PAs, and a bidirectional Glenn connection. With this approach, dissection of the distal arch and creation of a Damus-Kaye-Stansel anastomosis was avoided. A standard Fontan procedure was planned after the usual period of growth. Results: The first patient, who had trisomy 21 and elevated PA pressures, died postoperatively due to left PA thrombosis. The subsequent 3 patients survived the procedure and remain clinically well. All have required catheterizations for reintervention on their stented intrapulmonary baffles and ductal arches, and all have undergone successful completion of their Fontan procedures. Conclusions: The hybrid comprehensive stage II is a feasible, less complex alternative to the conventional comprehensive stage II operation in a subset of patients with single ventricle physiology. Early postoperative anticoagulation therapy to avoid PA thrombosis is recommended, and restenting of the ductal arch is anticipated. Although the long-term consequences of separate outflow tracts supplying the upper and lower body is unknown, the 3 surviving patients with this circulation are doing well with their Fontan circulation at midterm follow-up.