Assessment of left ventricular mechanical synchrony and intraventricular blood flow energy in ischemic heart disease using a hybrid positron emission tomography-magnetic resonance system

BACKGROUNDS We aimed to simultaneously investigate the relationship between left ventricular (LV) mechanical synchrony and intra-LV blood flow energy in patients with ischemic heart disease (IHD) using hybrid PET/MR. METHODS Sixty-six patients (mean age 67 years, male 54) who underwent rest-pharmacological stress 13N ammonia PET and 4D flow MR were included. Left ventricular ejection fraction (LVEF), phase analysis (PA) parameters including histogram bandwidth (BW), phase standard deviation (PSD), and entropy were obtained from gated PET. Perfusion defect was assessed as summed defect score from static PET images. Intra-LV 4D flow MR acquisition was simultaneously performed for rest and stress. Intra-LV blood flow kinetic energy (KE mJ) was obtained from dynamic flow curve, and indexed with end-diastolic volume (KEi mJ/mL). RESULTS A significant positive correlation was observed between LVEF and KEi at rest and stress (r = 0.30, p = 0.014; r = 0.42, p < 0.0001 for rest and stress, respectively). In contrast, summed defect score did not show a significant correlation to KEi. All PA parameters demonstrated a weak inverse correlation with KEi at rest (BW: r = -0.26, p = 0.019; PSD r = -0.27, p = 0.026; entropy r = -0.27, p = 0.031) and stress (BW: r = -0.29, p = 0.016; PSD r = -0.37, p = 0.0021; entropy r = -0.33, p = 0.0062). CONCLUSION PET derived PA was associated with intra-LV blood flow energy, suggesting impaired LV mechanical synchrony is linked to intra-LV blood flow insufficiency. These findings highlight the novel assessment of PA in clinical practice for IHD.