Prognostic Meaning of Coronary Microvascular Disease in Type 2 Diabetes Mellitus: A Transthoracic Doppler Echocardiographic Study

Background The prognostic value of Doppler-derived coronary flow velocity reserve (CFVR) of the left anterior descending coronary artery in patients with type 2 diabetes with preserved left ventricular systolic function and without flow-limiting stenoses on angiography remains undetermined. Methods The study sample consisted of 144 patients with type 2 diabetes (82 men; mean age 62 ± 10 years) with chest pain or angina-equivalent symptoms, no histories of coronary artery disease, and echocardiographic ejection fractions ≥ 50%. All patients underwent dipyridamole stress echocardiography with CFVR assessment of the left anterior descending coronary artery by transthoracic Doppler echocardiography and coronary angiography showing normal coronary arteries or nonobstructive coronary artery disease. Results Mean CFVR was 2.44 ± 0.57. On individual patient analysis, 109 patients (76%) had CFVR > 2, and 35 (24%) had CFVR ≤ 2. During a median follow-up period of 29 months (interquartile range, 14–44 months), 17 hard events (five deaths, 12 nonfatal myocardial infarctions) occurred. The annual hard-event rate was 13.9% in subjects with CFVR ≤ 2 and 2.0% in those with CFVR > 2. The annual event rate associated with CFVR ≤ 2 was significantly higher both in patients with left ventricular hypertrophy ( P < .0001) and in those without left ventricular hypertrophy ( P = .048). On Cox analysis, CFVR ≤ 2 (hazard ratio, 11.20; 95% confidence interval, 3.07–40.92), and male sex (hazard ratio, 7.80; 95% confidence interval, 1.74–34.97) were independent prognostic indicators, whereas nonobstructive coronary artery disease was not an independent predictor of outcomes. Conclusions Microvascular dysfunction before the occurrence of coronary artery involvement is a strong and independent predictor of outcomes in patients with type 2 diabetes. Vasodilator stress CFVR is a suitable tool to assess microvascular dysfunction in routine clinical practice.