Left Ventricular Midwall Fibrosis as a Predictor of Mortality and Morbidity After Cardiac Resynchronization Therapy in Patients With Nonischemic Cardiomyopathy

Study Questions:

Does the presence of left ventricular mid-wall fibrosis in patients with nonischemic cardiomyopathy (NICM) undergoing cardiac resynchronization therapy (CRT) predict an increased risk of adverse events?

Methods:

This study examined 97 individuals with NICM and 161 patients with ischemic cardiomyopathy (ICM) undergoing both cardiac magnetic resonance imaging (MRI) and CRT. Comparisons of adverse events were evaluated between individuals with NICM and midwall hyperenhancement (MWHE), NICM without MWHE, and ICM.

Results:

Amongst the 97 patients with NICM, 26% had MWHE. In comparison to those without MWHE, these individuals had larger left ventricular volumes and reduced ejection fractions (p < 0.001 for both). After a median follow-up of 2.8 years, cardiovascular mortality was 45% for NICM with MWHE, 3% in NICM without MWHE, and 30% in ICM. After adjustment for baseline variables, the presence of MWHE in patients with NICM was associated with an increased risk of cardiovascular mortality (hazard ratio [HR], 18.1; p < 0.001), total mortality or hospitalization for major adverse cardiovascular events (HR, 7.6; p < 0.001), or cardiovascular mortality or heart failure hospitalization (HR, 9.9; p < 0.001). In those with MWHE, the scar burden was not an independent predictor of total or cardiovascular mortality. In adjusted analyses combining the cohorts, both NICM with MWHE (HR, 18.5; p < 0.001) and ICM (HR, 21.0; p < 0.001) were associated with increased cardiovascular mortality.

Conclusions:

The presence of MWHE in patients with NICM undergoing CRT identifies individuals with a markedly increased risk of adverse events.

Perspective:

The presence of mid-wall fibrosis has previously been observed to predict an increased risk of adverse events in patients with NICM. The present study examines a population undergoing CRT, and reports that the presence of mid-wall fibrosis in this cohort can be a powerful predictor of adverse events. While a minority of individuals with NICM had mid-wall fibrosis (26%), these patients had an 18-fold increased risk of cardiovascular mortality, and this increased risk was comparable to individuals with ICM. While more research is needed, these results suggest that MRI findings may represent a promising means to risk-stratify patients with NICM.

Clinical Topics: Arrhythmias and Clinical EP, Heart Failure and Cardiomyopathies, Noninvasive Imaging, Implantable Devices, Acute Heart Failure, Magnetic Resonance Imaging

Keywords: Heart Diseases, Minority Groups, Risk, Myocardial Ischemia, Follow-Up Studies, Cardiology, Cardiomyopathies, Heart Failure, Heart Ventricles, Fibrosis, Magnetic Resonance Imaging, Cardiac Resynchronization Therapy


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