Electron Beam Computed Tomography Detects Coronary Artery Disease in Fit Asymptomatic Middle-Aged Individuals
Electron Beam Computed Tomography (EBCT) is used to detect coronary artery calcification (CAC), a marker of atherosclerosis. The EBCT was used to determine the presence of CAC in a population of very fit individuals. EBCT determined the calcification scores in 436 asymptomatic individuals (400 males 36 females, mean age 43.5±3.2 yrs, range 33 to 56 yrs). All underwent extensive cardiovascular and fitness evaluations including medical, fitness and nutritional histories; lipid profiles, fasting blood sugars, homocysteine, and lipoprotein(a) levels. Individuals underwent a physical examination, resting electrocardiogram, measurements of strength and flexibility, a maximal symptom-limited treadmill test, and a direct measurement of maximal oxygen consumption. CAC was detected by EBCT scan (3 mm thick, ECG-triggered, axial images) and quantified using the Agatston scoring technique. EBCT scores ranged from 0 to 2112 and were classified into standard categories - insignificant atherosclerosis: calcium <10 (n=364 83.3%); mild atherosclerosis: calcium 10-99 (n=31 13.5%); moderate atherosclerosis: calcium 100-399 (n=7 1.6%); and marked atherosclerosis: calcium >399 (n=7 1.6%). CAC was more likely in individuals who had an elevated LDL-Chol level (p≤.001) and CHOL/HDL ratio (p≤.001), but there was wide variance. Factors that had little or no correlation included fitness parameters as determined by strength measurements, aerobic capacity or bodyfat determination. Individuals with family history of early CAD had tendency for the development of CAC but again there was wide variation in the severity of the calcium score. Of the four individuals who had CAC scores over 1000, two subsequently sustained a myocardial infarction despite previous normal maximal exercise treadmill tests. In this group exercise thallium studies were not predictive for future events. It is difficult to detect CAD in fit, asymptomatic middle-aged individuals. EBCT is helpful in defining a high risk CAD group that is not readily determined by standard risk factors.