Prognostic Impact of Ischemic Mitral Regurgitation Severity and Myocardial Infarct Quantification by Cardiovascular Magnetic Resonance

Objectives: This study sought to evaluate the role of cardiac magnetic resonance (CMR) for the quantification of ischemic mitral regurgitation (IMR) and myocardial infarct size (MIS) in patients with ischemic cardiomyopathy (ICM). This study also sought to explore the interaction between IMR severity and MIS and its association with outcomes in patients with ICM.

Background: IMR occurs secondary to a disease of the left ventricle and is associated with poor outcomes. The role of CMR for the evaluation and risk stratification of patients with ICM and IMR remains uncertain.

Methods: Consecutive patients with ICM who underwent baseline CMR were included. MIS was quantified on late gadolinium enhancement imaging as the proportion of left ventricular mass. IMR was quantified with CMR by calculating the mitral regurgitant fraction (MRFraction). Cox proportional hazards models were built to assess the association of IMR and MIS quantification with the combined endpoint of all-cause death or heart transplant.

Results: We evaluated 578 patients (mean age: 62 ± 11 years, 76% males). The mean left ventricular ejection fraction was 25 ± 11%, with an MIS of 24 ± 16% and MRFraction of 18 ± 17%. Over a median follow-up time of 4.9 years, 198 (34%) patients experienced death or cardiac transplant. On multivariable analysis, after comprehensive medical risk score, subsequent revascularization, implantable cardioverter-defibrillator insertion, and surgical mitral valve intervention were controlled for, the interaction of IMR severity and MIS emerged as a powerful predictor of adverse outcomes (p = 0.008). For patients with significant IMR (MRFraction: ≥35%), the hazard ratio comparing moderate MIS (15% to 29%) versus small MIS (<15%) was 1.51 (0.57 to 3.98), and the hazard ratio comparing large MIS (≥30%) versus small MIS was 5.41 (2.34 to 12.7).

Conclusions: Risk associated with IMR is more comprehensively described as an interaction between IMR severity and MIS. Further studies in patients IMR using comprehensive CMR evaluation are needed to verify whether this approach can improve patient selection and procedural outcomes to address IMR.