Severity of coronary artery calcification by electron beam computed tomography predicts silent myocardial ischemia

Background-Detection of subclinical coronary artery disease (CAD) before th r development of life-threatening cardiac complications has great potential clinical relevance. Electron beam computed tomography (EBCT) is currently the only noninvasive test that can detect CAD in ail stages of its developm ent and thus has the potential to be an excellent screening technique for i dentifying asymptomatic subjects with underlying myocardial ischemia. Methods and Results-Over 2.5 years, we prospectively studied 3895 generally asymptomatic subjects with EBCT, 411 of whom had stress myocardial perfusi on tomography (SPECT) within a close (median, 17 days) time period. SPECT a nd exercise treadmill results were compared with the coronary artery calciu m score (CACS) as assessed by EBCT. The total CACS identified a population at high risk for having myocardial ischemia by SPECT although only a minori ty of subjects (22%) with an abnormal EBCT had an abnormal SPECT. No subjec t with CACS <10 had an abnormal SPECT compared with 2.6% of these with scor es from 11 to 100, 11.3% of these with scores from 101 to 399, and 46% of t hose with scores greater than or equal to 400 (P<0.0001). CACS predicted an abnormal SPECT regardless of subject age or sex. Conclusions-CACS identifies a high-risk group of asymptomatic subjects who have clinically important silent myocardial ischemia. Our results support t he role of EBCT as the initial screening tool for identifying individuals a t various stages of CAD development for whom therapeutic decision making ma y differ considerably.