Kinetic Energy of Left Ventricular Blood Flow Under Pharmacological Stress

This study aimed to simultaneously evaluate 4D cardiac magnetic resonance (MR)-derived kinetic energy (KE) of intra-left ventricular (LV) blood flow, wall kinetics, and myocardial perfusion under pharmacological stress in patients with coronary artery disease (CAD) using a hybrid PET/MR system. Sixty-five patients (mean 68±12 y; male, 53) with CAD who underwent rest-stress 13N-ammonia PET/MR were included. MR acquisition was performed simultaneously during the PET scan to obtain rest-stress 4D flow, and followed by cine MR to measure LV ejection fraction (LVEF) and myocardial strain, including global longitudinal strain (GLS). The maximum KE during the cardiac cycle was calculated and indexed to the end-diastolic LV volume (maxKEi, μJ/mL) at rest and during stress. Perfusion defect, myocardial flow (MBF), and flow reserve (MFR) were assessed through rest-stress PET. MaxKEi showed a significant correlation with LVEF and GLS for both rest and stress (r=0.3, P=0.01, r=-0.4, P=0.04 for rest LVEF and GLS; r=0.4, P=0.0009, r=-0.4, P=0.003, for stress LVEF and GLS, respectively). Stress maxKEi showed a significant correlation with stress MBF and MFR (r=0.3, P=0.006, and r=0.3, P=0.03, for stress MBF and MFR, respectively). Noninvasive assessment of 4D flow MR-derived intra-LV KE demonstrated a significant association with wall kinetics and endothelial function under pharmacological stress.