Limited coronary flow reserve after dipyridamole in patients with ergonovine-induced coronary vasoconstriction.

Patients with anginal chest pain despite angiographically normal coronary arteries and left ventricles may have abnormalities of coronary flow reserve. Twenty-five patients were found to have limited flow reserve during rapid atrial pacing after administration of 0.15 to 0.30 mg iv ergonovine, associated with precipitation of chest pain and hemodynamic and metabolic evidence of myocardial ischemia. No significant narrowing occurred in epicardial coronary artery luminal diameter. An additional 15 patients had no chest pain during pacing; because they developed significantly higher great cardiac vein flow and lower coronary resistance they were considered to have normal vasodilator reserve. After administration of dipyridamole (0.5 to 0.75 mg/kg iv), the lowest absolute levels to which coronary resistance fell (0.79 +/- 0.23 vs 0.47 +/- 0.12 mm Hg X min/ml; p less than .001) and the maximal absolute levels to which great cardiac vein flow rose (134 +/- 34 vs 202 +/- 45 ml/min; p less than .001) were impaired in the 25 patients with ergonovine-induced flow limitation compared with the 15 patients without flow limitation after ergonovine. In addition, 18 of the 25 patients with limited flow reserve after dipyridamole experienced chest pain despite an increase in coronary flow. In these patients, dipyridamole-induced increased flow across small prearteriolar coronary arteries, which were narrowed because of abnormal tonus or sensitivity to vasoconstrictor stimuli, could have resulted in a transmural redistribution of blood flow away from the subendocardium, precipitating subendocardial ischemia. These studies suggest that patients with anginal chest pain despite normal epicardial coronary arteries may have exaggerated coronary responses to vasoconstrictor stimuli, which can result in myocardial ischemia during stress, as well as attenuated responses to coronary vasodilator stimuli.