Right ventricular-pulmonary arterial coupling in patients with tricuspid regurgitation: a new cardiac magnetic resonance quantification method

Background Right ventricular–pulmonary arterial (RV–PA) coupling is a key parameter in evaluating right heart function and adaptation of the RV to afterload. Current Cardiac Magnetic Resonance (CMR) RV-PA coupling evaluation requires from PA flow assessment. In the absence of tricuspid regurgitation (TR), the ratio of right ventricular stroke volume (RVSV) assessed with volumetric assessment over RV end-sistolic volume (RVESV) could be applied. However, this method has not been tested, specifically in presence of TR. Purpose To demonstrate a novel method for estimating RV–PA coupling using RV volumes derived from standard cine CMR sequences, without the need of phase-contrast sequences or flow-derived parameters and investigating the correlation with the traditional method according to the TR grade. Methods A retrospective, single-center, observational study was conducted including 404 patients (64.6% male, mean age of 55 years) who underwent CMR for any clinical indication and whose scans included phase-contrast sequences of PA between January 2020 and January 2025. RV–PA coupling was estimated using a novel approach that relies exclusively on RV volumes derived from steady-state free precession (SSFP) cine sequences, avoiding the need for phase-contrast imaging. Specifically, the RVSV was calculated as the difference between RV end-diastolic volume (RVEDV) and RVESV, and RV–PA coupling was defined as the ratio of this calculated as RVSV to RVESV. Results The mean indexed RVEDV was 78 ml/m², the mean indexed RVESV was 37 ml/m², the mean RVSV was 75 ml, and the mean RV ejection fraction was 53%. There were 89 patients without TR, 144 with mild TR, 74 with moderate TR, 33 with severe TR, and 8 patients with massive or torrential TR. RV-PA coupling was calculated using the traditional method with phase contrast sequence data, resulting in a mean value of 1.24; and using the new proposed method based on RV volumetry from cine sequences, yielding a mean value of 1.31. In the overall cohort of 404 patients, the correlation coefficient between both methods was 0.851 (p < 0.001). When excluding patients with massive and torrential TR, the correlation improved progressively as TR severity decreased, reaching a correlation of up to 0.990 (p < 0.001) in patients with no TR. Conclusions RV–PA coupling can be accurately estimated using CMR without the need for phase-contrast sequences, by relying solely on RV volumes obtained from cine imaging. This volume-based method demonstrated excellent agreement with the conventional approach, even in patients with significant TR.Correlation between both methods Correlation according to TR grade