Acute Hyperglycemia Does Not Affect the Reactivity of Coronary Microcirculation in Humans

Objective: There is some evidence that acute hyperglycemia (H) may cause vascular dysfunction in normal subjects. This study investigates whether acute, short-term H affects coronary vasodilatory function in healthy subjects. Design: Diastolic peak flow velocity in the left anterior descending coronary artery was measured at rest and after dipyridamole (0.56 mg/kg over 4 min) using transthoracic color Doppler echocardiography in 13 healthy men. Coronary flow reserve (CFR) was defined as the ratio of dipyridamole-induced coronary peak diastolic to resting peak diastolic flow velocity. CFR was measured both in euglycemia (E) and after 3 h H (∼14 mmol/liter) by a variable infusion of glucose and octreotide (0.4 mg/h) to prevent increase in insulin concentration. Results: Fasting plasma glucose increased to 14.3 ± 0.33 mmol/liter during the study and maintained variability within less than 10%. Plasma insulin remained nearly stable during H. Resting diastolic flow velocity was 18.5 ± 0.6 cm/sec in E and increased to 20.0 ± 0.7 cm/sec during H (P < 0.005). Dipyridamole infusion produced a marked increase in coronary flow velocity, which reached values of 50.8 ± 2.9 cm/sec in E and 51.8 ± 2.1 cm/sec in H (P = not significant). CFR was 2.78 ± 0.16 in E and 2.59 ± 0.12 in H (P = not significant). Conclusion: Our study indicates that short-term hyperglycemia does not affect the vasodilatory response of coronary microcirculation in healthy subjects.