Incidence of Heart Failure among Diabetic Patients with Ischemic Heart Disease: A Cohort Study

Background: In population studies of heart failure (HF), diabetes mellitus (DM) has been shown to be an independent risk factor. However, the evidence evaluating it as an independent risk factor in incident HF in patients with ischemic heart disease (IHD) is scarce. Our study aimed to assess the incidence of HF in diabetic IHD patients compared to non-diabetic IHD patients in Ethiopia. Methods: A retrospective cohort study was conducted among 306 patients with IHD followed-up at Tikur Anbessa Specialized Hospital in Addis Ababa, Ethiopia. The IHD patients who did not have HF at baseline were followed for 24 months beginning from November 30, 2015. We assessed the incidence of HF in patients with diabetic IHD versus the non-diabetic IHD. Cox proportional hazards models were used to assess the association between diabetic IHD and HF after controlling for important covariates. Hypertension was examined as a possible effect modifier as well. Results: The mean age was 56.8 years, 69% were male, and 31% were diabetic. During the 24 months follow-up period, 196 (64.1%) had incident HF. On multivariate Cox regression, DM was significantly associated with incident HF [Hazard Ratio = 2.04, 95% confidence interval (CI): 1.32-3.14, p = 0.001]. Furthermore, when the patients were stratified by hypertension (HTN) status, DM was associated with worse prognosis, and the strongest association was in those with co-existing DM and HTN [HR = 2.57,95% CI =1.66-3.98, p<0.0001], followed by the presence of DM without HTN [HR 2.27, 95% CI = 1.38-3.71, p=0.001] (compared to those with neither). Conclusion: DM is the strongest predictor of incident HF, compared to other traditional risk factors, in Ethiopian patients with IHD. Those with both DM and HTN are at the highest risk. Key Words: Ischemic heart disease; Heart failure; Incidence; Diabetes Mellitus; Retrospective cohort study