Experiments and Simulations to Assess Exercise-Induced Pressure Drop Across Aortic Coarctations.

Blood pressure gradient (ΔP) across an aortic coarctation (CoA) is an important measurement to diagnose CoA severity and guide treatment. While invasive cardiac catheterization is the clinical gold-standard for measuring ΔP, it requires anesthesia and does not capture the effects of daily activity or exercise, potentially underestimating the disease's functional burden. This study aimed to identify patients with functionally significant CoA by evaluating exercise-induced ΔP using a hybrid mock circulatory loop (HMCL). Patient-specific aorta geometries (N = 5) of patients with CoA were generated from 4D-Flow magnetic resonance imaging (MRI) scans, then three dimensional (3D)-printed to create compliant aortic phantoms. The phantoms were incorporated into an HMCL with flow and pressure waveforms tuned to patient-specific rest and exercise states. Matched fluid-structure interaction (FSI) simulations were performed using simvascular for comparison. Results showed that mean ΔP increased nonlinearly with cardiac output (CO), with trends differing between patients. HMCL and FSI simulations exhibited excellent agreement in trends of ΔP change with CO, with minimal error of 1.6±1.1 mmHg. This study emphasizes the need for assessing exercise CoA hemodynamics beyond resting ΔP measurements. Overall, HMCLs and FSI simulations enable assessment of patient-specific hemodynamic response to exercise unattainable in clinical practice, thereby facilitating a comprehensive noninvasive assessment of CoA severity. Further, the excellent agreement between HMCL and FSI results indicates that our validated FSI approach can be used independently to assess exercise CoA hemodynamics hereafter, eliminating the need for repeated complex HMCL experiments.