REN and diabetes mellitus: Several mechanisms have been proposed for the association between diabetes and heart failure including endothelial dysfunction, abnormal calcium handling, myocardial fibrosis, and inappropriate activation of the renin–angiotensin–aldosterone system.9,10 Observational research has shown that diabetes is associated with an increase in left-ventricular (LV) mass11 and impaired diastolic function.12 Over time, these structural and functional changes lead to impaired systolic function and the clinical syndrome of heart failure.13