Implantable cardioverter defibrillators in diabetics: efficacy and safety in patients at risk of sudden cardiac death

Abstract

Diabetes mellitus is a major risk factor for arrhythmogenesis and is associated with a two-fold increase in all-cause mortality and a four-fold increase in cardiovascular mortality including sudden cardiac death when compared with nondiabetics. Implantable cardioverter defibrillators (ICD) have been shown to effectively reduce arrhythmic death and all-cause mortality in patients with severe myocardial dysfunction. With a high competing risk of nonarrhythmic cardiac and noncardiac death, survival benefit of ICD in patients with diabetes mellitus could be reduced, but the subanalysis of diabetic patients in randomized clinical trials provides reassurance regarding a similar beneficial survival effect of ICD and cardiac resynchronization therapy in diabetics, as observed in the overall population with advanced heart disease. In this article, the authors highlight some of the clinical issues related to diabetes, summarize the data on the efficacy of ICD in diabetics when compared with nondiabetics and discuss concerns related to ICD implantation in patients with diabetes.

Keywords:

• clinical trials
• diabetes mellitus
• ICD
• infection
• shocks
• sudden death
• survival

Financial & competing interests disclosure

A Jahangir was supported, in part, by National Heart, Lung, and Blood Institute grants (R01 HL 101240) and (R01 HL089542). The authors have no other relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript apart from those disclosed. The authors gratefully acknowledge Susan Nord and Jennifer Pfaff of Aurora Cardiovascular Services for the editorial preparation of the manuscript and Brian J Miller and Brian Schurrer of Aurora Sinai Medical Center for help with the figures.

Key issues

• The prevalence of diabetes mellitus is increasing with the increasing epidemic of obesity and metabolic syndrome.

• Diabetes mellitus is a major public health concern because of its impact on morbidity, mortality and contribution to rising healthcare costs.

• Both direct and indirect effects of diabetes on myocardial structure and function contribute to increased risk for cardiac arrhythmias including life-threatening ventricular arrhythmias and sudden cardiac death.

• Both hyperglycemia and hypoglycemia due to inadequate diabetes control can contribute to prolongation of cardiac repolarization, and increased heterogeneity of myocardial refractoriness and electrical conduction that predispose to triggered activity- or re-entry-mediated arrhythmias.

• Although diabetes has been identified as an independent risk factor associated with poor outcomes, subanalysis of randomized controlled trials (RCT) provides some reassurance regarding the efficacy of ICD in improving overall survival in patients with advanced heart disease.

• Observational studies in patients with heart failure indicate a reduced clinical and echocardiographic response to cardiac resynchronization therapy in those with diabetes mellitus; however, post hoc analysis of the RCTs indicates maintenance of the beneficial effect.

• Both appropriate and inappropriate therapy are associated with increased all-cause mortality in diabetics; however, the impact of diabetes on such therapies is not entirely clear and requires further research.

• Traditionally, diabetes has been associated with increased risk of infection; however, its role in increasing the risk of cardiac implantable device infection is not entirely clear.

• Additional research into mechanisms underlying cardiac electrophysiological alterations in diabetics may identify new targets for the prevention of cardiac arrhythmias, and better risk stratification strategies may improve selection of patients who benefit most from ICD implantation thus improving its cost effectiveness.

Notes