Coronary artery calcium (CAC) score – a prognostic tool in coronary artery disease?

Introduction: The aim of this study was to evaluate the impact of measurement of coronary artery calcification score (CAC) in patients with suspected coronary artery disease (CAD) and a normal myocardial perfusion scan. Methods: In a prospective study we measured the calcium score of 74 patients (29 m, 45 f, mean age 58.7 (m) and 64.4 (f)) with suspicion of CAD and a normal perfusion scan. In all patients a pharmacological stress myocardial perfusion imaging (MPI) with dipyridamole was performed. Both the myocardial perfusion scintigraphy and calcium scoring were performed on a T6 Symbia gamma camera (Siemens, Knoxville, USA). Attenuation correction was performed using a low dose CT. Results: The mean total CAC score was 182.6±435.7 and ranged from 0 -2309. 21/29 of the male patients (72%) and 17/45 of the female patients (38%) had an Agatston score of > 10. There were 9 cases (5m, 4f) with a calcium score of > 400 and 3 cases (2m, 1f) with a calcium score > 1000. No cardiac event was noted in these patients during a mean follow up time of 10.3 months (range 7-13 months, median 11 months) except one cardiac death of a patient with total Agatston score of 278. Seven patients also underwent angiography because of their clinical symptoms, 4 of which (57%) had an elevated Agatston score. Conclusion: Our study showed that calcium score measurement accompanied with SPECT imaging is feasible in routine myocardial perfusion imaging with SPECT/CT machines. Calcium score measurement in patients with normal stress myocardial perfusion scintigraphy, may be useful in risk stratification of the patients. Further prospective studies with larger patient numbers and longer follow-up time are needed to find out the impact of this advantage by hybrid imaging.