Abstract 16670: Insulin Resistance is Associated With Impaired Cardiac Sympathetic Innervation in Patients Affected by Heart Failure
Background: Insulin resistance (IR) affects prognosis in patients with heart failure (HF), but pathophysiological mechanisms remain unclear. Since hyperinsulinemia enhances sympathetic drive, it can be hypothesized that IR is associated with impaired cardiac sympathetic innervation in HF patients. Yet, this hypothesis has never been investigated.
Methods: One-hundred seventeen patients (85% males; age 66.5±9.6 yrs) with severe-to-moderate HF (ejection fraction 30.7±7.3%), underwent in the same day iodine-123 metaiodobenzylguanidine (123I-MIBG) myocardial scintigraphy to assess cardiac sympathetic innervation and blood sampling for insulin and fasting glucose measurement. To assess insulin sensitivity Homeostasis Model of Assessment-Insulin Resistance (HOMA-IR) index was calculated using the formula [fasting Glucose (mmol/L) x fasting Insulin (mU/L) / 22.5] (normal values <2.5). From MIBG scintigraphy the early and late heart-to-mediastinum (H/M) ratios were calculated.
Results: Seventy-eight (66.7%) patients showed IR and 39 (33.3%) were non-IR. Early (1.63±0.19 vs 1.80±0.22; p<0.001) and late H/M ratio (1.47±0.19 vs 1.61±0.28; p=0.007) were significantly reduced in IR compared to non-IR patients. Patients were further divided into 3 groups: with type 2 diabetes mellitus (DM; n=54), without DM with IR (non-DM/IR; n=35) and without DM and IR (non-DM/non-IR; n=28). Early and late H/M were lowest in DM (early H/M 1.63±0.22; late H/M 1.46±0.20), intermediate in non-DM/IR (early H/M 1.68±0.17; late H/M 1.53±0.20) and highest non-DM/non-IR patients (early H/M 1.82±0.20; late H/M 1.61±0.28) (p=0.01 by ANOVA test). Early and late H/M, however, did not differ between DM and non-DM/IR patients. In the whole population early and late H/M ratio showed a significant inverse correlation with fasting insulinemia and HOMA-IR.
Conclusions: Cardiac sympathetic innervation is impaired in patients with IR and HF and correlates with HOMA-IR and insulinemia. These findings contribute to explain the unfavorable prognostic impact of IR in patients with HF and provide new insights into mechanisms of adverse prognosis in patients with DM and HF.
- © 2013 by American Heart Association, Inc.