Investigating Biventricular Intracardiac Flow Remodeling in Marathon Athletes With <scp>4D</scp> Flow Cardiac <scp>MRI</scp>

BACKGROUND: Exercise-induced cardiac remodeling (EICR) may share features with early cardiomyopathy, thereby rendering differentiation challenging with conventional imaging modalities. Identification of novel imaging biomarkers would be useful. Given that intracardiac hemodynamics is closely associated with EICR, its assessment may hold clinical importance. Four-dimensional flow MRI (4D Flow MRI) enables quantification of ventricular flow components, which may provide a complementary hemodynamic perspective alongside conventional structural and functional assessment. PURPOSE: To characterize biventricular intracardiac flow components in marathon athletes and examine their associations with cardiac structural remodeling. STUDY TYPE: Prospective. POPULATION: Fifty-one marathon athletes and 51 age- and sex-matched sedentary controls. FIELD STRENGTH/SEQUENCE: Steady state free precession cine and 4D Flow MRI sequences at 3.0 T. ASSESSMENT: Left ventricular (LV) and right ventricular (RV) volumes, myocardial mass, cardiac function, geometry indices, and intracardiac flow components (direct flow, delayed ejection, retained inflow, and residual volume) were quantified and compared between athletes and controls. Exploratory path modeling was used to examine hypothesized relationships among group (athletes vs. controls), cardiac structure, and intracardiac hemodynamics after adjustment for age and sex. STATISTICAL TESTS: Univariable analysis; Correlation analysis; Exploratory path modeling. A p value < 0.05 was considered significant. RESULTS: Compared with controls, athletes exhibited significantly lower direct flow in both ventricles (LV: 28.18% ± 7.93% vs. 31.68% ± 6.24%; RV: 29.90% ± 7.04% vs. 33.60% ± 8.33%) and significantly higher residual volume (LV: 25.92% ± 5.30% vs. 22.02% ± 5.24%; RV: 32.45% ± 6.72% vs. 25.38% ± 6.50%). Multiple significant associations were observed between biventricular flow components and cardiac structural/functional metrics. In the path model, all path coefficients were significant and remained so after age/sex adjustment. CONCLUSION: EICR may involve an intracardiac hemodynamic phenotype characterized primarily by decreased direct flow and increased residual volume. Both of these hemodynamic features are coupled with cardiac structural remodeling. EVIDENCE LEVEL: 2. TECHNICAL EFFICACY: Stage 2.