Association of secondary mitral regurgitation and right ventricular dysfunction among patients with non-ischaemic cardiomyopathy

Aims: The association between secondary mitral regurgitation (MR) and right ventricular (RV) dysfunction in heart failure patients with non-ischaemic cardiomyopathy (NICM) is unclear. Hence, our objective was to study the association between secondary MR and the occurrence of RV dysfunction among patients with NICM using cardiac magnetic resonance (CMR). Methods and results: Patients with NICM were enrolled in a prospective observational registry between 2008 and 2019. CMR was used to quantify MR severity along with RV function. The RV dysfunction was defined as RV ejection fraction <45%. The outcome of the study was a composite event of all-cause death, heart transplantation, or left ventricular assist device implantation at follow-up. In the study cohort of 241 patients, RV dysfunction (RVEF < 45%) was present in 148 (61%). In comparison with patients without RV dysfunction, those with RV dysfunction had higher median MR volume {23 mL [interquartile range (IQR) 16-31 mL] vs. 18 mL (IQR 12-25 mL), P = 0.002} and MR fraction [33% (IQR 25-43%) vs. 22% (IQR 15-29%), P < 0.001]. Furthermore, secondary MR was independently associated with RV dysfunction: MR volume ≥ 24 mL (OR 3.21, 95% CI 1.26-8.15, P = 0.01) and MR fraction ≥ 30% (OR 5.46, 95% CI 2.23-13.35, P = 0.002). Increasing RVEF (every 1% increase) was independently associated with lower risk of adverse events (HR 0.98; 95% CI 0.95, 1.00; P = 0.047). Conclusion: In patients with NICM, the severity of secondary MR is associated with an increased prevalence of RV dysfunction. The RV dysfunction is not only associated with the severity of LV dysfunction but also with the severity of secondary MR. Clinical Trial Registration: https://clinicaltrials.gov/ct2/show/NCT04281823.