[Dysfunction of the coronary microcirculation in type 2 diabetic patients].

A failure of coronary blood flow to increase during cold pressor test has been shown in patients with coronary atherosclerosis and impaired metabolic coronary vasodilatation in response to atrial pacing has been demonstrated in diabetic patients without significant epicardial artery stenoses. This study was designed to evaluate coronary microvascular adaptation to increased myocardial oxygen demand in response to sympathetic stimulation in diabetic patients with angiographically normal coronary arteries. Microvascular coronary adaptation to increased myocardial oxygen demand due to sympathetic stimulation evoked by the cold pressor test has been examined in 22 type 2 diabetic patients and in 15 control subjects with angiographically normal coronary arteries and no other risk factors. Coronary blood flow was calculated by measuring mean flow velocity in left anterior descending coronary artery by intracoronary Doppler and cross sectional area of the artery by digital angiography. Results show that despite a similar increase in rate-pressure product in the 2 groups (+22.6 +/- 12.4% in diabetic patients and +31.8 +/- 8.2% in control subjects, NS), coronary blood flow increase in left anterior descending artery was significantly lower in diabetic patients than in control subjects (+14.7 +/- 19.8% vs +75.5 +/- 13.5%, respectively, p = 0.0001). In addition, when there was a positive correlation between the 2 parameters in control subjects (R = 0.651, p < 0.01), there was no relationship in diabetic patients (R = 0.054). In conclusion, this study demonstrates that vasodilatation of coronary microcirculation in response to sympathetic stimulation evoked by cold pressor test is impaired in type 2 diabetic patients without epicardial artery lesions. This microvascular impairment during sympathetic stimulation may explain exercise-induced myocardial perfusion abnormalities observed in these patients and may impair microcirculatory coronary vasodilatation during current life stress episodes such as exercise, mental stress or cold exposure.