Assessing reliability and comparability of 4D flow CMR whole heart measurements using retrospective valve tracking: A single-vendor study in the Berlin research network

INTRODUCTION: This study investigated intracardiac flow dynamics and assessed the comparability and reliability of 4D flow CMR measurements across multiple sites within the Berlin Research Network for Cardiovascular Magnetic Resonance (BER-CMR) using 3D cine phase-contrast imaging with three-directional velocity encoding in a healthy traveling cohort. METHODS: In a prospective multi-site cohort study, 20 healthy volunteers underwent CMR at different sites. Quantitative assessment of Forward flow Volume (FFV), Peak (PV) and Mean Velocity (MV) across the heart's valves were conducted using retrospective valve tracking. FFV of the aortic and pulmonary valves, measured via 4D flow CMR, was compared to each other and to Stroke Volume (SV) from cine imaging. Reliability was assessed using scan-rescan tolerance ranges from a single site, with equivalency assumed if other sites' confidence intervals fell within these ranges. Intra- and interobserver analyses evaluated measurement consistency. RESULTS: The final analysis included 19 healthy volunteers. Intersite comparability analysis across all four heart valves revealed a strong reliability for FFV, PV and MV, except for FFV at the mitral valve at two sites and PV at the tricuspid valve at one site. Correlation analysis of SV and FFV of the corresponding ventriculoarterial valves demonstrated good agreement (aortic valve: r = 0.89, P < 0.001; pulmonary valve: r = 0.88, p < 0.001). Inter- and intraobserver analyses yielded good to excellent agreement across all valves (ICC > 0.90, p < 0.001). CONCLUSION: 4D flow CMR whole-heart measurements in healthy volunteers were consistent across sites, showing strong agreement despite physiological and technical variability. These findings support future multicenter studies.