Histopathologic evaluation of coronary artery thrombi obtained by directional coronary atherectomy in patients with restenosis-induced unstable angina pectoris

The pathogenesis of unstable angina pectoris (UAP) following percutaneous t ransluminal coronary angioplasty (PTCA) or directional coronary atherectomy (DCA) has not been adequately investigated, so the present study aimed to determine whether thrombi are present in restenotic lesions. The study grou p comprised 14 patients (16 arterial branches) with angina pectoris in whom either PTCA or DCA was performed and who had developed UAP associated with restenosis, and who then underwent DCA of the restenosed lesion (R-UAP gro up). The control groups comprised individuals with UAP undergoing DCA with no prior history of PTCA or DCA (P-UAP group; n = 29, 29 branches), patient s with acute myocardial infarction (AMI group; n = 34, 34 branches), and pa tients with stable angina pectoris (SAP group; n = 31, 33 branches). The pr esence of thrombi was determined by light microscopy of histologic specimen s. Thrombus was present in only 1 of the 16 (6.3%) branches in the R-UAP gr oup, 21 of the 29 (72.4%) branches in the P-UAP group, and in 25 of the 34 (73.5%) in the AMI group. In the SAP group, it was detected in only 2 of th e 33 (7.1%) branches. The incidence of thrombus was significantly lower in the R-UAP group than in the P-UAP group. In conclusion, the role of thrombu s is limited in causing post-interventional UAP at restenosed sites.