5Brief Communications Vasoreactivity of the Culprit Lesion in Unstable Angina

involved in the pathogenesis of the acute coronary syndromes, the vasoreactivity of the lesion responsible for unstable angina (culprit lesion) has not been directly investigated. It is also unknown if enhanced vasoreactivity is found downstream to this lesion or extends to uninvolved coronary arteries. Methods and Results We studied seven unstable angina patients whose condition had sufficiently stabilized to allow ergometric bicycle exercise and a cold pressor test to be performed as provocative stimuli during coronary arteriogra-phy. We measured the luminal diameter of the culprit lesion, a normal-appearing distal segment, and the segment of an uninvolved coronary artery using quantitative coronary angi-ography. Seven stable angina patients served as controls. Antianginal medications were tapered and interrupted. The culprit lesion constricted significantly with exercise and th