Myocardial blood flow fall may underlie hypoglycemia related CV mortality risk
MedWire News: Hypoglycemia appears to decrease myocardial blood flow reserve (MBFR), which may explain the association between low blood glucose and increased cardiovascular (CV) mortality, report UK researchers.
Previous studies have shown that insulin causes a marked increase in MBF and MBFR during euglycemia in both healthy humans and patients with diabetes, they explain.
However, the mechanisms by which hypoglycemia affects the cardiovascular system are unclear.
To investigate, Kim Greaves (Bournemouth University, UK) and team used a one-step hyperinsulinemic clamp technique to induce hypoglycemia among 28 people with Type 1 diabetes and 19 healthy individuals.
For 60 minutes, insulin was infused at a rate that maintained hyperinsulinemic euglycemia (HE). It was then reduced by 20% to induce hyperinsulinemic hypoglycemia (HH) for a further 60 minutes.
The researchers performed myocardial contrast echocardiography (MCE) to measure MBF and quantify MBFR at baseline and during HE and HH.
As reported in the journal Circulation, the authors found that in healthy controls there was a marked increase in peak MBF and MBFR during HE and a decline in peak MBF and MBFR during HH.
MBFR increased by 0.57 U (22%) above baseline during HE and decreased by 0.36 U (14%) below baseline during HH.
Although at baseline, MBFR was lower in patients with diabetes than in healthy patients by 0.37 U (14%), the changes in MBFR during HE and HH in diabetes patients were similar to those observed among those without diabetes.
Further analysis also revealed that the presence of microvascular complications in the patients with DM was associated with a reduction in MBFR of 0.52 U.
"The overall effect of hypoglycemia during HH is to suppress peak MBF, thereby mitigating the vasodilatory action of hyperinsulinemia that occurs during physiological glucose concentrations," write Greaves and team.
"We speculate from our results that alterations in MBFR may explain the association between hypoglycemia and increased CV mortality in susceptible individuals," concludes the team.
MedWire (www.medwire-news.md) is an independent clinical news service provided by Current Medicine Group, a trading division of Springer Healthcare Limited. © Springer Healthcare Ltd; 2010