Endothelial Dysfunction in Microvascular Angina

To the Editor: Egashira et al. (June 10 issue)¹ described blunted coronary vasodilation in response to acetylcholine infusion in a group of patients with angina pectoris, positive exercise tests, angiographically normal coronary arteries, no coronary-artery spasm, and myocardial lactate production after the administration of intracoronary papaverine. The implications of these results are unclear for other, similar patients in whom the lactate response to papaverine is unknown. What fraction of the patients with angina and normal coronary angiograms had myocardial lactate production after receiving intracoronary papaverine? It seems likely that a number of patients who had no lactate production might have…