Prognostic value of intracardiac blood kinetic energy assessed by four-dimensional flow cardiac magnetic resonance imaging in heart failure with reduced ejection fraction.

BACKGROUND: Cardiovascular magnetic resonance (CMR) four-dimensional (4D) flow has been introduced as a valuable technique for deriving intracardiac blood flow components and kinetic energy (KE), providing profound mechanistic insights into heart failure (HF) patients. This study aimed to explore the prognostic value of CMR 4D flow-derived intracardiac blood flow components and KEs in patients with heart failure with reduced ejection fraction (HFrEF). METHODS: A total of 420 HF patients underwent CMR examination between May 2019 and May 2022. Intracardiac left ventricular (LV) flow was divided into four components: direct flow (DF), retained inflow (RI), delayed ejection flow (DEF), and residual volume (RVo). Systolic KE and diastolic KE (early and late diastolic phases) were calculated throughout the cardiac cycle, and then normalized to LV end-diastolic volume (indexed KE, KEi). Clinical endpoints included cardiac-related death, HF-related rehospitalization, cardiac resynchronization therapy, implantable cardioverter defibrillator implantation, or revascularization. RESULTS: A total of 195 HFrEF patients and 16 controls were enrolled (55 ± 13 years vs 40 ± 9 years, p < 0.001) in the study. Among the 78 HFrEF patients who experienced adverse outcomes, DF, DEF, and peak systolic KEi were lower, whereas RVo and early diastolic KEi were higher compared to patients without adverse outcomes (all p < 0.05) during a 21-month follow-up period (range 10-36 months). In the multivariable logistic regression model, peak systolic KEi, LV end-systolic volume index, and late gadolinium enhancement (LGE %) independently predicted adverse outcomes. An optimal cut-off value of peak systolic KEi ≤11 μJ/mL predicted the adverse outcome in HFrEF patients. CONCLUSION: CMR 4D flow-derived peak systolic KEi is associated with adverse outcomes and has the potential to serve as a novel imaging biomarker for risk stratification in HFrEF patients.