Friesen RM, et al. - The authors attempted to use a quantitative method of myocardial perfusion in children with Kawasaki disease (KD), with the aid of the stress cardiac magnetic resonance (MR)-derived myocardial perfusion reserve index (MPRI). They also undertook a comparative analysis of MPRI with ventricular mechanical performance evaluated by cardiac MR strain analysis. Impaired myocardial perfusion was illustrated by MPRI in the study cohort. MPRI could change over time. This was indicative of progressive coronary artery changes, which possibly preceded fibrosis and mechanical decline. Among these patients, MPRI could examine the segmental and global perfusion defects. MPRI was recommended as a part of routine cardiac MR evaluation in KD.