Left ventricular diastolic inflow and myocardial flow reserve in patients with coronary artery disease: simultaneous analysis of 4D-Flow and myocardial perfusion using hybrid PETMR.

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This study aimed to simultaneously evaluate the association between diastolic left ventricular (LV) inflow and myocardial flow reserve (MFR) using a hybrid PET/MR system in patients with coronary artery disease (CAD). Sixty-seven patients (mean 66 ± 15 years, male 55) with CAD who underwent rest-pharmacological stress 13N-ammonia PET/MR were included. MFR, perfusion defect, and peak filling rate (PFR) were obtained through rest-stress PET. MR acquisition was performed simultaneously during the PET scan to obtain rest-stress 4D flow. Diastolic LV inflow volume (LVinf)(mL/s), peak velocity (peakV)(cm/s), and the change from the rest scan (Δvalue) were computed. Diastolic LV inflow parameters were compared based on the presence or absence of preserved MFR and perfusion defects. In all patients, diastolic LV inflow parameters significantly increased in the stress scan compared to the rest (53.7 ± 23.1 vs. 64.1 ± 32.9ml/s, p = 0.0002; 68.1 ± 15.1 vs. 76.4 ± 20.6cm/s, p = 0.0001 for LVinf and peakV, respectively). PeakV and PFR showed a significant correlation for rest and stress (r = 0.4, p = 0.01; r = 0.3, p = 0.03 for rest and stress, respectively).ΔpeakV significantly correlated to stress MBF, and MFR (r = 0.3, p = 0.007; r = 0.3, p = 0.04 for stress MBF, and MFR, respectively). Among patients with preserved LVEF (n = 47), when were divided into 4 subgroups based on the median myocardial flow reserve (MFR, 1.86) and the presence of perfusion defect, ΔpeakV was significantly higher in those with MFR above median and without abnormal perfusion compared to the other groups (21.8 ± 13.6 vs. 13.5 ± 17.0, 13.0 ± 13.5, and 4.6 ± 19.1; p = 0.04, 0.04, and 0.04 for MFR ≥ 1.86 or < 1.86 with or without abnormal perfusion, respectively). Non-invasive assessment of diastolic intra-LV hemodynamics derived from 4D flow MR demonstrated a significant association with coronary vasodilation.