Insulin-treated type 2 diabetes is associated with a decreased survival in heart failure patients after cardiac resynchronization therapy

Background: Cardiac resynchronization therapy (CRT) improves cardiac performance and survival in patients with congestive heart failure. Recent observations suggest that diabetes is associated with a worse outcome in these patients. The aim of the study was to investigate the effect of diabetes and insulin treatment on outcome after CRT. Methods: Diabetic status and insulin treatment were assessed in 447 patients who underwent CRT (males 80.8%, mean age 65.7 ± 9.7 years, ejection fraction 29.9 ± 6.11%). Patients were stratified in three groups according to the presence or absence of diabetes and insulin treatment. Results: Nondiabetic patients were 366 (79.6%), noninsulin‐treated diabetic patients 62 (13.9%), insulin‐treated diabetic patients 29 (6.5%). The estimated death rate was 5.15 per 100 patients‐year in the nondiabetic group, 8.63 in noninsulin‐treated diabetics (HR 1.59, P = 0.240), and 15.84 in insulin‐treated diabetics (HR 3.05, P = 0.004). Cardiac mortality accounted for 81% of deaths in nondiabetic patients and for 56% of deaths in diabetic patients. Diabetic patients tended to have a worse recovery of left ventricular ejection fraction over time (P = 0.057) and of the distance at 6‐minute walking test (6MWT) (P = 0.018). Conclusions: Insulin‐treated diabetes is associated with a worse functional recovery and a higher mortality in patients with advanced heart failure after CRT. While cardiac death accounts for the majority of deaths in nondiabetic patients, a relevant proportion of the mortality in diabetic patients seem to result from noncardiac causes.