Abstract 20663: The Effect of Insulin and Insulin-induced Hypoglycemia on Myocardial Blood Flow Reserve in Patients with Complicated Type 1 Diabetes Mellitus
Background and Purpose: Hypoglycemia is a frequent complication of insulin therapy in patients with diabetes mellitus (DM) and is associated with increased cardiovascular mortality. This study assessed the effect of insulin-induced hypoglycemia on myocardial perfusion in Type 1 DM patients with microvascular complications.
Methods: Eight (44.5±4 years) Type 1 DM patients with microvascular disease (two of the following: retinopathy, nephropathy and neuropathy) and normal exercise stress echocardiograms participated. Hyperinsulinemic euglycemia (HE) was maintained for 60 minutes followed by hyperinsulinemic hypoglycemia (HH) for a further 60 minutes. Real-time myocardial contrast echocardiography (MCE) with flash impulse imaging was used to assess the myocardial blood flow (MBF) and myocardial blood flow reserve (MBFR) before and after dipyridamole administration at baseline, HE and HH.
Results: MBFR was 1.72±0.16 at baseline and increased by 17% with insulin during HE to 2.02±0.31 (p=0.018). This was due to an increase in the baseline MBF from 36.6±4.8 dB2.s−1 to peak stress HE 43.7±3.5 dB2.s−1 (p=0.02). During HH, MBFR decreased significantly to 1.57±0.12 (vs. HE, p=0.001). This was due to a lower peak stress HH MBF of 39.8±6.0 dB2.s−1 (p = 0.06). Baseline endothelin-1 levels were 3-fold elevated in comparison to healthy subjects (p<0.0001) but did not change during HE or HH. Following multivariable adjustment, age emerged as the only variable that was independently associated with MBFR in the entire cohort which included 19 healthy volunteers and 28 patients with type 1 DM. Finally, ET-1 levels at 180 minutes (HH) had a weak albeit significant correlation with MBFR at HH for the entire study population (r=−0.291, p=0.04).
Conclusion: This study has shown that insulin-induced hypoglycemia leads to a reduction in MBFR in subjects with complicated Type 1 DM. In the presence of flow limiting coronary disease this may worsen coronary ischemia.
- © 2010 by American Heart Association, Inc.