Myocardial blood flow is increased by insulin

Lautamäki R et al. (2006) Insulin improves myocardial blood flow in patients with type 2 diabetes and coronary artery disease. Diabetes 55: 511–516

Coronary artery disease is the leading cause of death for patients with type 2 diabetes. Insulin has been shown to improve endothelial function, decrease ischemia, and stimulate blood flow, yet the effect of insulin on myocardial blood flow has not been studied in diabetic patients with coronary artery disease. A new Finnish study has investigated whether exogenous insulin increases myocardial blood flow in regions of compromised myocardial perfusion in this population, and also compared flow rates in ischemic versus nonischemic regions.

Ischemic regions were identified using single-photon emission CT, perfusion imaging, coronary angiography, and echocardiography. Following insulin infusion, myocardial blood flow was measured at rest and during adenosine-induced hyperemia in 43 patients, using PET and [¹⁵O]-labeled H₂O. At rest, insulin infusion improved myocardial blood flow by 13% in ischemic regions and by 22% in nonischemic regions (P = 0.043 and P = 0.003, respectively). During hyperemia, it improved blood flow by 20% in ischemic regions and by 18% in nonischemic regions (P = 0.018 and P = 0.045, respectively). The researchers found that blood flow was lower in ischemic regions in both conditions (overall P <0.001).

Previous studies have found that metabolic control of myocardial blood flow is reduced during adenosine stimulation, but that endothelial and neurogenic control is maintained. These results complement previous findings that insulin improves endothelial function in healthy subjects. The authors suggest that insulin infusion might result in a higher ischemic threshold.