Impairment of coronary microvascular dilation in response to cold presser-induced sympathetic stimulation in type 2 diabetic patients with abnormal stress thallium imaging

Coronary microcirculation dysfunction may be associated with myocardial per fusion defects on thallium imaging in diabetic patients without coronary ar tery stenosis. Microvascular coronary adaptation to increased myocardial ox ygen demand in response to sympathetic stimulation evoked by the cold press er test was examined in 22 type 2 diabetic patients with thallium imaging d efects and in 15 control subjects. Both the diabetic patients and control s ubjects had angiographically normal coronary arteries and no other risk fac tors. Despite a similar increase in the rate-pressure product in the two gr oups (22.6 +/- 12.4% in diabetic patients and 31.8 +/- 8.2% in control subj ects, NS), coronary blood flow increase in the left anterior descending art ery (mean flow velocity measured by intracoronary Doppler multiplied by the cross-sectional area measured by digital angiography) was significantly lo wer in diabetic patients than in control subjects (14.7 +/- 19.8 vs. 75.5 /- 13.5%, respectively; P = 0.0001). Tn addition, when there was a positive correlation between the two parameters in control subjects (r = 0.651, P < 0.01), there was no relationship in diabetic patients (r = 0.054). In conc lusion, vasodilation of the coronary microcirculation in response to sympat hetic stimulation evoked by the cold presser test is impaired in type 2 dia betic patients without epicardial artery lesions. This microvascular impair ment during sympathetic stimulation may explain exercise-induced myocardial perfusion abnormalities observed in these patients and may impair microcir culatory coronary vasodilation during current life stress episodes such as exercise, mental stress, or cold exposition.