Myocardial ischemia is frequently associated with left ventricular outflow obstruction. To assess coronary flow impairment in obstructive hypertrophic cardiomyopathy (HC), 10 patients with echo-Doppler-detected obstructive HC and normal coronary arteries underwent transesophageal echo-Doppler examination of both coronary flow velocity (CFV) at rest, recorded in the proximal left anterior descending coronary artery, and coronary flow reserve (CFR) evaluated by means of dipyridamole infusion response. Ten normal patients were similarly studied and served as a control group. Two relevant alterations in coronary flow dynamics were detected in patients with HC: (1) a significantly increased diastolic/systolic CFV ratio, and (2) a significantly reduced dipyridamole/baseline CFV ratio. Compared with normal subjects, the CFV pattern showed a significantly greater diastolic and a significantly lower systolic component at rest (in some patients it was reversed). Diastolic/systolic CFV ratio was significantly higher in patients with HC at baseline (3.1 +/- 1 vs 1.6 +/- 0.5; p < 0.01) and increased further after dipyridamole infusion (4.9 +/- 2 vs 2.2 +/- 0.7; p < 0.01). In addition, CFR was impaired in patients with HC (1.8 +/- 0.3 vs 3.1 +/- 0.5; p < 0.01). Furthermore, a significant correlation between CFR and intraventricular pressure gradient was found. Thus, transesophageal echo-Doppler examination is a useful tool for evaluating CFV dynamics and CFR as demonstrated in patients with obstructive HC.