CORRELATION BETWEEN CLINICAL AND MORPHOLOGIC FINDINGS IN UNSTABLE ANGINA

This study was undertaken to verify the hypothesis that the discrepant findings in published reports on the prevalence of thrombus in unstab le angina depend on the inclusion of different clinical subsets in the various studies. We therefore correlated the clinical characteristics of patients included under the label of unstable angina with the morp hologic features assessed by coronary angiography and intravascular ul trasound, and with histopathologic findings of atherectomy specimens. Fifty-eight patients with unstable angina (class B of the Braunwald cl assification) undergoing coronary arteriography followed by either cor onary angioplasty (n = 20) or directional coronary atherectomy (n = 38 ) were studied. Fifteen patients were in class IB and 43 were in class II to IIIB. Among these 43 patients with angina at rest, 28 had ST-se gment elevation during pain, and 15 had ST-segment depression, and 26 developed the negative T waves on the baseline electrocardiogram (ECG) as a result of prolonged or repeated episodes of resting chest pain. Intravascular ultrasound examination culprit lesion was performed in 4 3 patients before the interventional procedure, and histopathologic an alysis of atherectomy specimens was performed in 38 patients. Complex lesion morphology by angiography was observed in 31 patients (53%) wit hout any significant relation to various clinical subsets. Patients in Braunwald class IB had more calcific plaques than patients in class I I to IIIB (p<0.001). Among patients with angina at rest, those with ne gative T waves on the baseline ECG, as well as those with transient ST elevation during pain, had a significantly higher incidence of noncal cific lesions (p = 0.001 for both). Analysis of atherectomy specimens revealed acute coronary lesions (thrombus and/or intraplaque hemorrhag e) in 18 patients (47%). The incidence of acute coronary lesions was s ignificantly higher in patients with than without negative T waves on the baseline ECG (p = 0.005), ana increased further when negative T wa ves were combined with ST elevation during pain (p = 0.001). Multivari ate analysis revealed that the presence orf negative T waves on the ba seline ECG was the only explanatory variable related to the presence o f acute coronary lesions by histology (p = 0.03). Patient subsets incl uded in the broad spectrum of unstable angina have different morpholog ic features and incidence of acute coronary lesions by histology. Thes e data provide an explanation for the discrepant findings in published reports on the relevance of thrombus formation in the pathogenesis of unstable angina.