Significant Coronary Artery Disease in Patients with a Negative Calcium Scan and Suspicious Ischemic Heart Disease in a Racially Diverse Patient Population

Background: Although coronary calcium assessment has been demonstrated to be strongly associated with significant coronary artery disease (CAD) and future cardiac events, it is still not clear whether zero calcium on CT scan can exclude significant CAD and eliminate the need for further multi-detector computed tomography (MDCT) coronary angiography (CCTA). The purpose of this study is to test the hypothesis that zero coronary calcium on MDCT does not exclude significant CAD and CCTA is required to exclude CAD in diverse populations who have a zero calcium score. Methods: We studied 737 consecutive patients, 383 females and 354 males (average age 57.4 +/12.9 years), referred to CCTA from June 1, 2005 to January 31, 2007 for clinically suspicious CAD. All patients underwent 16-slice MDCT (n=287) or 64-slice MDCT (n=450) calcium score scan prior to CCTA. We analyzed atherosclerotic plaques and degree of coronary artery stenosis on CCTA, and coronary calcium score calculated on MDCT calcium scan. Significant CAD was defined by >50% coronary artery diameter stenosis. Results: Significant CAD was found in 211 of 737(29.6%) patients. Of these patients, 186(88.2%) patients had a positive calcium score and 25 (11.8%) patients had a zero calcium score. Significant CAD in patients with zero calcium score was found more often in younger (p<0.01) and female patients (p<0.05). There is no significant racial difference (p=NS) in patients with significant CAD without a positive calcium score. Conclusion: Absence of coronary calcium deposit does not exclude the presence of significant CAD with non-calcified plaque. Therefore, a calcium score of zero on MDCT calcium scan does not preclude the need for MDCT coronary angiography in patients with clinically suspicious CAD.