Coronary artery calcification as a marker for coronary artery disease.

Coronary artery disease (CAD) remains the leading cause of mortality in the United States. Many individuals who experience myocardial infarction have no warning symptoms. Noninvasive methods to identify individuals with CAD are often insensitive, especially for the detection of early disease. Known risk factors account for only half of the incidence of myocardial infarction; further elucidation of risk factors is hampered by the present inability to detect CAD in asymptomatic patients. Since calcium is often present in early atherosclerotic lesions, it is a potent marker of early as well as advanced CAD. This research evaluated the use of coronary artery calcium detected by electron-beam computed tomographic scanning (EBCT) as a marker to noninvasively identify the presence and quantify the severity of atherosclerosis in a sample of 160 individuals 20-59 years of age with indications for coronary angiography. The following questions were addressed: (1) Is scoring of calcium by EBCT repeatable across observers? (2) What definition of calcium presence and what measure of calcium quantity maximize agreement between EBCT and angiography? (3) Is calcium an accurate marker for CAD? What factors affect accuracy? (4) What risk factors predict CAD? What risk factors predict calcium? Does knowing quantity of calcium aid the prediction of disease? (5) Does knowing quantity of calcium aid the determination of clinical disease status? The findings indicated that scoring of coronary artery calcium by EBCT is highly repeatable, that presence of calcium is an accurate marker for the presence of CAD, and that quantity of calcium is a better indicator of severity of CAD than all risk factors combined. Therefore, EBCT exams for coronary artery calcification could be useful in several areas. First, EBCT could have an important impact on the public health if used as a screening test for CAD, as the procedure is quick, painless, safe, and reasonably affordable. Second, quantitative EBCT exams could be used clinically to indicate the probable severity of CAD to assist physicians in determining whether further diagnostic procedures should be performed. Third, EBCT provides a method for epidemiologists researching CAD to accurately classify asymptomatic individuals as diseased or nondiseased, and to identify and separate risk factors associated with initiation and progression of atherosclerosis.PhDEpidemiologic ScienceUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/103618/1/9332100.pdfDescription of 9332100.pdf : Restricted to UM users only