Differential coronary calcification on electron-beam CT between syndrome Xand coronary artery disease in patients with chronic stable angina pectoris

Study objectives: The differential diagnosis of syndrome X and coronary art ery disease (CAD) in patients with evidence of myocardial ischemia may be d ifficult. The possible difference in coronary calcium detected by electron- beam CT (EBCT) between syndrome X and CAD is rarely evaluated, especially i n aged patients with chronic, stable angina. Design and settings: Prospective, controlled study at a tertiary referral m edical center. Patients and measurements: Forty patients with syndrome X (85% male) and 53 patients with CAD (89% male) were enrolled. Ten control subjects (90% male ) with negative exercise treadmill test results and normal coronary angiogr aphic findings served as control subjects. EBCT determined the coronary cal cium scores (CCSs), and standard cardiovascular risk factors of all study s ubjects were analyzed. Results: The 93 study patients had CCSs that ranged from 0 to 1,857. Corona ry calcification was seen in 2 of the 10 control subjects (20%),21 of the 4 0 syndrome X patients (52.5%), and 51 of the 53 CAD patients (96.2%) [p<0.0 1.]. The CCS (median [range]) was significantly lower in syndrome X patient s than in CAD patients: 1 (0 to 117) vs 202 (0 to 1,857) [p<0.001]. Receive r operating characteristic curve analyses also demonstrated that coronary c alcification differentiated syndrome X from CAD (area under curve, 0.891; 9 5% confidence interval, 0.806 to 0.947). Of the CAD patients whose CCSs wer e <117 and overlapped with CCSs of syndrome X multivariate analyses determi ned CCS >5 (odds ratio, 13.1; 95% confidence interval, 2.86 to 59.7), hyper tension (odds ratio, 6.4; 95% confidence interval, 1.5 to 27.4), and hyperc holesterolemia (odds ratio, 6.7; 95% confidence interval, 1.5 to 30.5) to b e independent discriminators to differentiate CAD from syndrome X. Patients with CAD had more frequent hypertension than patients with syndrome X. Conclusions: The coronary calcium detected noninvasively by EBCT was differ ent, though with some overlapping, between patients Kith syndrome X and CAD . In addition to standard cardiovascular risk factors, CCS determined by EB CT (especially >117 or = 0) could differentiate between syndrome X and CAD in patients with chronic, stable angina with evidence of myocardial ischemi a. Larger trials would be useful to validate CCS on EBCT as a predictor of clinical outcome in these patients.