The investigators propose to augment ongoing case-control studies, HL35333, """"""""Carotid Atherosclerosis Progression Study"""""""" and HL59503, """"""""Vascular Disease, Structure and Function"""""""". HL35333 comprises 280 symptomatic individuals > 45 years equally divided between men and women, 1/2 with and 1/2 without angiographically defined CAD evaluated for risk factors and extracranial carotid intimal-medial thickness (ECIMT, with B-mode ultrasound) at baseline and yearly for 3 years. It has quantified the associations of CAD and CAD risk factors for ECIMT and its progression. HL59503 quantifies flow-mediated brachial artery reactivity (FM-BAR) in this cohort. Literature review suggests that while ECIMT predicts CAD status in clinical samples it does less well in asymptomatic samples; longitudinal data (CLAS study) suggest that progression of ECIMT best predicts incident CAD, and Electron Beam Computed Tomography (EBCT) quantification of Coronary Artery Calcium (CAC) likely has even greater discriminatory power for CAD than ECIMT. However, EBCT has limited accessibility. The investigators' pilot data suggest that a new method of potentially greater accessibility than EBCT, Fast Gated Helical Computed Tomography, FGHCT, accurately quantifies CAC: FGHCT-CAC correlates with EBCT (r = 0.98). CAC scores by FGHCT for 10 patients with and 8 patients without CAD were 1297 +/-1178 and 41 +/-60 respectively (p < 0.01). These data support the aims of this project (1) to evaluate use of FGHCT-CAC for discrimination of CAD, and (2) to quantify progression of CAC over 1.5 years in the symptomatic clinical HL35333/HL59503 cohort with and without CAD. The investigators will also relate FGHCT-CAC to ECIMT, ECIMT progression, and FM-BAR in individuals with defined CAD status. The investigators are among the finalists for a new RFP to evaluate CAC in asymptomatic populations. If the investigators are successful, support of this application would permit comparisons of symptomatic with asymptomatic individuals. The investigators note that this application builds on availability of a well characterized cohort with and without CAD and on strengths with the newly developed FGHCT; they also state that it will directly quantify the relation of CAC and CAC progression to coronary status, ECIMT, FM-BAR, and risk factors. They point out that pilot data support the feasibility and likely informativeness of this study.
