Young Dae Kim, et al. Fig. 1. Flow chart of patient selection and grouping. EC, extracranial; IC, intracranial. the EC and IC cerebral arteries. The degree of stenosis was measured using the North American Symptomatic Carotid Endarterectomy Trial18 or Warfarin vs. Aspirin for Sympto- matic intracranial disease method.19 When multiple stenotic lesions were present in one artery, data of the most severe degree was used. The stenotic lesions were divided into EC, IC, or combined EC and IC atherosclerosis, and were also classified as mild (< 50%) or severe (≥ 50% or occluded). The number of atherosclerotic lesions was the sum of the number of stenotic lesions in the predetermined portion at each side; the common carotid artery, extracranial internal carotid artery (ICA), intracranial ICA, branch arteries of the ICA, anterior cerebral artery, middle cerebral artery, extracranial vertebral artery, intracranial vertebral artery, basilar artery, posterior inferior cerebellar artery, anterior inferior cerebellar artery, superior cerebellar artery, and posterior cerebral artery. Statistical analysis Statistical analysis were performed using the Windows SPSS package (version 15.0) (SPSS Inc, Chicago, IL, USA). The independent sample t-test, the Pearson chi- square test, or ANOVA test was used to compare means and proportions. The temporal changes of atherosclerosis were compared by the Mantel-Haenszel test. Multivariate logistic analysis was used to compute odds ratios of vas- cular risk factors. The correlation between the number of lesions and other factors was determined by Spearman’s rank test. Predicted changes in the number of lesions were analyzed by a Poisson regression analysis. RESULTS Demographic characteristics of the study group Enrolled for the final analysis were 1,955 patients with a mean age of 63.7 ± 10.9 years (range, 24-93), 1,230 (62.9%) of which were men. These demographic data were not different from those of the entire 2,977 patients registered during the study period in that the mean age of the 2,977 patients was 63.7 ± 11.8 years (range 6-95) and men comprised 62.1% (1,850 patients). During the eight-year study period, there was an increas- ing tendency in performing angiographic studies, either MRA or DSA, from 83.4% in 1999 to 94.1% in 2007 among the entire 2,977 patients. In 1,957 patients, the proportion of angiographic study with MRA increased from 53.9% in 1999 to 66.2% in 2007. Frequency and distribution of atherosclerosis Among 1,955 patients, 1,517 patients (77.6%) were found to have atherosclerosis in one or more arteries of the EC or IC artery. Isolated EC atherosclerosis was found in 239 (12.2%), isolated IC atherosclerosis in 516 (26.4%), and combined EC and IC atherosclerosis in 762 (39.0%) patients. Among the arteries involved, the MCA was most com- mon (44.2%), followed by the extracranial ICA (37.4%), and the extracranial vertebral artery (27.0%). The same pattern of distribution was noted among cases with severe atherosclerosis (Table 1). However, in a subgroup having had DSA performed, involvement of the extracranial ICA was most common (52.3%) (Table 1). Temporal changes in the presence and burden of atherosclerosis After excluding patients with PCSE The prevalence of atherosclerosis in 1,955 ischemic stroke patients during the past eight-year period was compared annually using the Mantel-Haenszel test. There was a significant increase in atherosclerosis in this study popula- tion (p < 0.001) (Table 2). An increasing tendency of athero- sclerosis was also observed in the analysis of the DSA subgroup findings (p = 0.010). These increases appear to be ascribable to the increased frequency of combined EC and IC atherosclerosis (p < 0.001) (Fig. 2A). Likewise, the pro- portion of severe atherosclerosis showed a similar increasing trend (p = 0.043), although it did not reach statistical signi- ficance in the analysis using the DSA findings (p = 0.075). 320 Yonsei Med J http://www.eymj.org Volume 51 Number 3 May 2010