Intra-Ventricular Diastolic Hemodynamics under Pharmacological Stress in Patients with Ischemic Heart Disease: Analysis of 4D-Flow and Myocardial Flow Reserve using hybrid 13N-ammonia Positron Emission Tomography/Magnetic Resonance

Objectives: This study aimed to explore the linkage between intra-left ventricular (LV) diastolic hemodynamics and coronary endothelial function, utilizing four-dimensional (4D) flow magnetic resonance imaging (MR) and myocardial flow reserve (MFR) through simultaneous acquisition using hybrid PETMR system in patients with ischemic heart disease (IHD). Methods: Sixty-eight patients (mean 66 ± 15 years, male 55) with IHD who underwent rest-pharmacological stress 13N-ammonia PET/MR were included. MFR and summed defect score (SSS and SRS for stress and rest) were obtained thorough rest-stress PET images. MR acquisition was performed simultaneously during PET scan to obtain rest-stress 4D flow datasets and followed by cine-MRI for the LV volume measurement. LV diastolic inflow(mL/s), peak velocity(cm/s), and averaged diastolic kinetic energy (KEi)(μJ/mL) indexed with endo-diastolic volume were computed. Results: Diastolic LV inflow parameters and KEi significantly increased in stress scan compared to the rest (74.8 ± 17.5 cm/s vs. 64.5 ± 14.4 cm/s, p<0.0001; 10.1 ± 5.2 vs. 13.3 ± 7.8, p=0.0004 for peak velocity and KEi, respectively). Stress KE showed a significant and weak correlation to MFR and SSS (r = 0.3, p=0.004; r=-0.4, p=0.002 for MFR and SSS, respectively). In patients with MFR above median value (1.76), stress KE significantly elevated from rest KE, while no significant change was observed for the patients with MFR below median (11.0 ± 4.6 vs. 16.2 ± 8.8, p=0.0002; 9.7 ± 5.4 vs. 10.3 ± 5.1 for rest vs. stress, respectively). Conclusion: Non-invasive estimation of diastolic dysfunction derived from 4D-flow demonstrated a significant association with myocardial ischemia and coronary endothelial dysfunction.