Abstract 4363697: Hybrid PET/MR Assessment of Left Ventricular Mechanical Synchrony and Intraventricular Blood Flow Energy in Ischemic Heart Disease

Background: The assessment of left ventricular (LV) mechanical synchrony using phase analysis (PA) provides incremental diagnostic value over conventional indicators and is widely used in clinical practice. Four-dimensional (4D) flow cardiovascular magnetic resonance (CMR) has emerged as an imaging technique to visualize blood flow dynamics. Intra-LV kinetic energy (KE) obtained from 4D-CMR is a novel parameter refers to the quantification of the energy associated with the motion of blood within LV. This study aimed to simultaneously investigate the relationship between LV mechanical synchrony and intra-LV blood flow energy in patients with ischemic heart disease (IHD), using hybrid PET/MR system. Methods: Sixty-six patients (mean age 67 years, male 54) who underwent rest-pharmacological stress 13 N ammonia PET and 4D flow CMR at our hospital between January 2022 and February 2024 were included. Left ventricular ejection fraction (LVEF), PA parameters including histogram bandwidth (BW), phase standard deviation (PSD), and entropy were obtained from rest and stress gated PET. Perfusion defect was assessed as summed defect score from rest and stress static PET images. Intra-LV 4D flow MR acquisition was simultaneously performed for rest and stress. Intra-LV blood flow KE indexed with end-diastolic volume (KEi mJ/mL) was obtained from dynamic 4D flow curve. Results: BW[KF1] was 24.6 ± 17.9 and 24.4 ± 15.4%, PSD was 6.2 ± 3.7 and 6.2 ± 3.5, entropy was 61.6 ± 7.9 and 60.3 ± 9.3 for rest and stress, respectively. Summed defect score was 6.1 ± 7.1 and 11.2 ± 9.4 for rest and stress. KEi[KF2] was 0.018 ± 0.01, and 0.019 ± 0.01 (mJ/mL) for rest and stress. A significant positive correlation was observed between LVEF and KEi at both rest (R=0.30, P=0.014) and stress (R=0.42, P<0.001). Summed defect score was not significantly correlated with KEi at either rest or stress. All PA parameters demonstrated a weak inverse correlation with KEi at rest (BW: R= –0.29, P=0.019; PSD R = –0.27, P=0.026; entropy R = –0.27, P=0.031) and stress (BW: R= –0.28, P=0.023; PSD R = –0.36, P=0.003; entropy R = –0.31, P=0.010). Conclusions: PET-derived PA parameters were significantly associated with intra-LV blood flow KE, suggesting impaired LV mechanical synchrony is linked to intra-LV blood flow energy insufficiency.