High coronary artery calcium score affects clinical outcome despite normal stress myocardial perfusion imaging and normal left ventricular ejection fraction.

BACKGROUND: Normal myocardial perfusion imaging (MPI) indicates a low risk for cardiac death and new ischaemic events. However, the impact of normal MPI combined with a high coronary artery calcium score (CACS) is not clear. The aims of this study were to evaluate the risk of severely elevated CACS and to identify other risk factors in patients with normal MPI.

METHODS: The study included 318 consecutive patients who underwent a Tc-sestamibi MPI protocol along with either the ergometer bicycle test or the pharmacological stress test. Acquisition of CACS was performed immediately before MPI. Patient history and events were retrieved from hospital files. The median follow-up time was 989 days. End points were myocardial infarction, need for revascularization of coronary arteries and/or death.

RESULTS: CACS was less than 400 in 256 patients (81%) and at least 400 in 62 patients with normal MPI. Cox regression analysis showed that CACS was a predictor of cardiovascular events or death [relative risk (RR) 3.4, P=0.008]. Inability to perform the ergometer stress test (RR 5.6, P=0.02) was also included in the model. CACS (RR 4.2, P=0.01) and diabetes (RR 3.7, P=0.03) were the strongest predictors of cardiac events without death.

CONCLUSION: CACS is the single most important predictor of cardiac events and/or death in patients with normal MPI. If possible, CACS could be included when performing MPI to identify patients with an increased risk for cardiac events and/or death.