Hemodynamic Evaluation of Norwood Aortic Arch Geometry Compared to Native Arch Controls

Abstract

The Norwood procedure creates a reconstructed neo-aorta to provide unobstructed systemic cardiac output for hypoplastic left heart syndrome patients. We used patient-specific computational fluid dynamics (CFD) simulations incorporating physiologic boundary conditions to quantify hemodynamics for reconstructed aortic arch geometries versus native aortic arches from a control group of single ventricle patients. We hypothesized that reconstructed arches from Norwood patients (n = 5) would experience significant differences in time-averaged wall shear stress normalized to body surface area (TAWSSnBSA), oscillatory shear index (OSI), energy efficiency (Eeff), and energy loss (EL) versus controls (n = 3). CFD simulations were conducted using 3 T cardiac magnetic resonance imaging, blood flow, and pressure data. Simulations incorporated downstream vascular resistance and compliance to replicate patient physiology. TAWSSnBSA and OSI were quantified axially and circumferentially. Global differences in Eeff and EL were compared. Significance was assessed by Mann-Whitney U test. Norwood patients had higher TAWSSnBSA distal to the transverse arch at locations of residual narrowing presenting following coarctation correction, as well as higher OSI within ascending aorta and transverse arch regions (p < 0.05). EL correlated with patient features including cardiac output (r = 0.9) and BT-shunt resistance (r = -0.63) but did not correlate with arch measurements or morphology. These results indicate reconstructed arches from Norwood patients are exposed to altered wall shear stress and energy indices linked to cellular proliferation and inefficiency in prior studies. These results may help clinicians further understand what constitutes an optimally reconstructed arch after confirmation in larger studies.

Keywords: computational fluid dynamics; hypoplastic left heart syndrome; patient-specific modeling; pediatric cardiology.