Diabetes and Heart Failure in Patients With Coronary Disease: Separating Markers From Mediators

Patients with type 2 diabetes compared with nondiabetic patients have two- to fivefold higher risk for developing heart failure (1–3) and have poorer outcomes once heart failure is present (4,5). These relationships have been identified in observational studies spanning the clinical spectrum of diabetes, including cohorts comprising patients with newly diagnosed type 2 diabetes (6), patients with or at high-risk for coronary heart disease (7,8), and those suffering acute coronary syndromes (9–11). In the study by van Melle et al. (12) published in this issue of Diabetes Care , the relationship between diabetes and heart failure risk among patients with stable coronary heart disease is again observed. In addition, the observation is made that higher A1C is linearly and independently associated with increased heart failure risk, independent of whether the patient has established diabetes, with the relationships qualitatively and quantitatively similar to prior reports (8,13). Before reviewing these observations in the context of the existing literature, a few comments with regard to the study design, analyses, and interpretations of van Melle et al. are warranted. While the reported observations are consistent with much of the existing literature associating disordered glucose metabolism with incremental heart failure risk, it must be noted that this study identified only 77 incident heart failure events, including 30 among patients with diabetes (15.0%) and 47 in those without diabetes (7.4%). This small number of events limits the statistical power and precision of the analyses and calls for commensurate caution in the interpretation of the significance and magnitude …