The risk of myocardial ischemia in patients with Kawasaki Disease: Insights from patient-specific simulations of coronary hemodynamics

Background Pediatric patients with aneurysms due to Kawasaki disease require life-long and uninterrupted cardiology follow-up. Current AHA guidelines for risk stratification and long-term management are based primarily on maximal coronary artery luminal dimensions, normalized as Z-scores. Hemodynamic and functional significance of coronary arteries aneurysms on myocardial ischemic risk is not well studied. Methods We retrospectively studied a cohort of 15 patients who underwent coronary CT angiography imaging. We constructed patient-specific anatomic models from CT images and performed computational hemodynamic simulations incorporating pulsatile flow and deformable arterial walls. Simulation parameters were tuned to match patient-specific arterial pressure, ejection fraction, and cardiac output. From simulation results, we evaluated hemodynamic iscmemic risk metrics, including fractional flow reserve, wall shear stress, and residence time, in 153 coronary arteries. Results Fractional flow reserve (FFR) showed a weak correlation with aneurysm Z-scores. The slope of FFR significantly increased distal to the lumen narrowing at the end of aneurysms. Ischemic risk does not correlate well with aneurysm diameter measured by Z-score, but correlates much better with the ratio of maximum lumen diameter within aneurysms to minimum lumen diameter distal to aneurysms. Wall shear stress also correlates better with this diameter ratio, while residence can be stratified via Z-score. Conclusions Z-score alone is not a good indicator of abnormal FFR. Although FFR immediately distal to aneurysms is not critical, it starts to drop more rapidly distal to aneurysms and can therefore present an elevated risk of myocardial ischemia. Maximum-to-minimum lumen diameter is a good proxy for ischemic risk.