Impact of Diabetes Mellitus on Mortality and Hospitalization in Patients With Mild-to-Moderate Cardiomyopathy

Objectives: This study examined the independent predictors of all-cause mortality, all hospitalizations, and cardiac hospitalizations in patients with mild-to-moderate cardiomyopathy (left ventricular ejection fractions [LVEFs] of 36% to 50%).

Background: Patients with severe cardiomyopathy have high rates of death. Implantable cardioverter-defibrillators (ICDs) improve survival in this setting. It is not known whether the same applies to patients with mild-to-moderate cardiomyopathy.

Methods: All patients with cardiomyopathy of any etiology seen at our institution between 2011 and 2017 were included. Baseline characteristics and outcomes were compared between patients with mild-to-moderate cardiomyopathy and severe cardiomyopathy (LVEF ≤35%).

Results: Of the 18,003 patients with cardiomyopathy, 5,966 (33%) had a LVEF between 36% and 50%. Over a median follow-up of 3.35 years, 8,037 patients (45%) died and 11,056 (61%) were hospitalized for cardiac reasons. Independent predictors of all-cause mortality included older age (p < 0.001) and a history of diabetes mellitus (DM) (p = 0.005) or heart failure (p = 0.043). A higher baseline hemoglobin was protective (hazard ratio [HR]: 0.79; 95% confidence interval [CI]: 0.71 to 0.89; p < 0.001). Importantly, patients with a history of DM and mild-to-moderate cardiomyopathy had worse survival than those with severe cardiomyopathy and no DM (HR: 1.10; 95% CI: 1.02 to 1.19; p = 0.010).

Conclusions: A history of DM predicts mortality in patients with cardiomyopathy and is associated with worse outcome than the actual severity of cardiomyopathy. Patients with mild-to-moderate cardiomyopathy and DM may therefore benefit from the same life-saving therapies (e.g., ICDs) that are indicated for patients with severe cardiomyopathy. This finding needs to be verified in a prospective, randomized setting.