ABNORMAL TRANSESOPHAGEAL DOPPLER CORONARY FLOW RESERVE IN PATIENTS WITH DILATED CARDIOMYOPATHY - RELATIONSHIP TO EXERCISE CAPACITY

1. In patients with dilated cardiomyopathy, abnormal myocardial blood flow may contribute to poor myocardial function. 2. The aim of this st udy was to investigate the possible contribution of abnormal myocardia l blood flow to the limitation of exercise capacity in patients with d ilated cardiomyopathy. 3. Coronary flow reserve was assessed in 16 pat ients with dilated cardiomyopathy and 9 matched normal control individ uals, All participants had angiographically normal coronary arteries. At rest and after dipyridamole infusion (0.56 mg/kg intravenously), pe ak systolic and diastolic coronary flow velocities were measured in th e proximal left anterior descending coronary artery using transoesopha geal pulsed Doppler echocardiography, guided by colour flow imaging. C oronary flow reserve was calculated as the ratio of hyperaemic to basa l diastolic and systolic peak coronary flow reserve. 4. Baseline diast olic and systolic coronary flow velocities were significantly higher i n patients (50 +/- 6 and 30 +/- 4 cm/s respectively) compared with con trol individuals (37 +/- 3 and 20 +/- 1 cm/s respectively) (mean +/- S .E.M.) (P < 0.05). Diastolic and systolic peak coronary flow reserve w ere significantly lower in patients (1.60 +/- 0.14 and 1.40 +/- 0.09 r espectively) compared with control individuals (2.89 +/- 0.15 and 2.17 +/- 0.17 respectively) (P < 0.001), Although peak VO2, and exercise t ime were significantly lower in patients compared with control individ uals, coronary flow reserve did not correlate to exercise capacity in patients with dilated cardiomyopathy. 5. These results confirm the abn ormalities of coronary flow reserve previously observed in patients wi th dilated cardiomyopathy, but suggest that such abnormalities do not contribute to the limitation of exercise capacity in these patients.