Multiscale Modeling of Superior Cavopulmonary Circulation: Hemi-Fontan and Bidirectional Glenn Are Equivalent

Superior cavopulmonary circulation (SCPC) can be achieved by either the Hemi-Fontan (hF) or Bidirectional Glenn (bG) connection. Debate remains as to which results in best hemodynamic results. Adopting patient-specific multiscale computational modeling, we examined both the local dynamics and global physiology to determine if surgical choice can lead to different hemodynamic outcomes. Six patients (age: 3-6 months) underwent cardiac magnetic resonance imaging and catheterization prior to SCPC surgery. For each patient: (1) a finite 3-dimensional (3D) volume model of the preoperative anatomy was constructed to include detailed definition of the distal branch pulmonary arteries, (2) virtual hF and bG operations were performed to create 2 SCPC 3D models, and (3) a specific lumped network representing each patient's entire cardiovascular circulation was developed from clinical data. Using a previously validated multiscale algorithm that couples the 3D models with lumped network, both local flow dynamics, that is, power loss, and global systemic physiology can be quantified. In 2 patients whose preoperative imaging demonstrated significant left pulmonary artery (LPA) stenosis, we performed virtual pulmonary arterioplasty to assess its effect. In one patient, the hF model showed higher power loss (107%) than the bG, while in 3, the power losses were higher in the bG models (18-35%). In the remaining 2 patients, the power loss differences were minor. Despite these variations, for all patients, there were no significant differences between the hF and bG models in hemodynamic or physiological outcomes, including cardiac output, superior vena cava pressure, right-left pulmonary flow distribution, and systemic oxygen delivery. In the 2 patients with LPA stenosis, arterioplasty led to better LPA flow (5-8%) while halving the power loss, but without important improvements in SVC pressure or cardiac output. Despite power loss differences, both hF and bG result in similar SCPC hemodynamics and physiology outcome. This suggests that for SCPC, the pre-existing patient-specific physiology and condition, such as pulmonary vascular resistance, are more deterministic in the hemodynamic performance than the type of surgical palliation. Multiscale modeling can be a decision-assist tool to assess whether an extensive LPA reconstruction is needed at the time of SCPC for LPA stenosis.