Prognosis and predictors of right ventricular dysfunction by quantitative cardiac magnetic resonance in non-ischaemic cardiomyopathy

Pathophysiology and prognostic implications of right ventricle (RV) dysfunction in heart failure are complex and incompletely elucidated. Cardiac magnetic resonance imaging (CMR) is the reference standard for RV quantification, but its clinical implications in non-ischaemic cardiomyopathy (NICM), in the context of myocardial fibrosis and functional mitral regurgitation are not well defined. We evaluated predictors, prognostic impact, and thresholds for defining significant RV dysfunction in NICM. NICM patients (n = 624) undergoing CMR assessment during 2002-2017 were retrospectively studied. CMR's quantification of right ventricular ejection fraction (RVEF) was evaluated against the primary outcome of all-cause mortality, heart transplant, and/or left ventricular assist device implantation in threshold and multivariable analyses. Mean RVEF was 43 ± 13%, and factors associated with reduced RVEF were male sex, New York Heart Association (NYHA) class III-IV, right bundle branch block, lower left ventricular ejection fraction, higher mitral regurgitant fraction (MR-RF) and right ventricle size in NICM. RVEF per 5% increase was independently associated with the primary endpoint hazards ratio (95% confidence interval) 0.80 (0.73-0.88), P < 0.001. RVEF ≤40% was the optimal threshold associated with worse prognosis, regardless of late gadolinium enhancement (LGE) or MR-RF quantification. On the other hand, higher LGE was associated with primary endpoint in patients with RVEF ≤ 40% only, while risk associated with MR-RF was significant dampened after adjusting for RVEF. RVEF provides powerful risk stratification, with RVEF ≤ 40% defining significant RV dysfunction associated with adverse outcomes in NICM. The integration of quantitative CMR measurements for RVEF, LGE, and MR-RF provides comprehensive NICM risk prognostication.