Aorta size mismatch predicts decreased exercise capacity in patients with successfully repaired coarctation of the aorta

Objective: Coarctation of the aorta (CoA) is associated with decreased exercise capacity despite successful repair with no residual stenosis; however, the hemodynamic mechanism remains unknown. This study aims to correlate aortic arch geometry with exercise capacity in patients with successfully repaired CoA and explain hemodynamic changes using 3-dimensional–printed aorta models in a mock circulatory flow loop. Methods: A retrospective chart review identified patients with CoA repair who had cardiac magnetic resonance imaging and an exercise stress test. Measurements included aorta diameters, arch height to diameter ratio, left ventricular function, and percent descending aorta (%DAo) flow. Each aorta was printed 3-dimensionally for the flow loop. Flow and pressure were measured at the ascending aorta (AAo) and DAo during simulated rest and exercise. Measurements were correlated with percent predicted peak oxygen consumption (VO₂ max). Results: Fifteen patients (mean age 26.8 ± 8.6 years) had a VO₂ max between 47% and 126% predicted (mean 92 ± 20%) with normal left ventricular function. DAo diameter and %DAo flow positively correlated with VO₂ (P = .007 and P = .04, respectively). AAo to DAo diameter ratio (D_AAo/D_DAo) negatively correlated with VO₂ (P < .001). From flow loop simulations, the ratio of %DAo flow in exercise to rest negatively correlated with VO₂ (P = .02) and positively correlated with D_AAo/D_DAo (P < .01). Conclusions: This study suggests aorta size mismatch (D_AAo/D_DAo) is a novel, clinically important measurement predicting exercise capacity in patients with successful CoA repair, likely due to increased resistance and altered flow distribution. Aorta size mismatch and %DAo flow are targets for further clinical evaluation in repaired CoA.