OBJECTIVES: To estimate the prevalence of non-calcified coronary artery disease (CAD) in patients with suspected stable angina and a zero coronary artery calcium (CAC) score, and to assess the prognostic significance of a zero CAC in these symptomatic patients.

METHODS: In this prospective cohort study, consecutive patients with stable chest pain underwent CAC scoring +/- CT coronary angiography (CTCA) as part of routine clinical care at a single tertiary centre over 7 years. MACE was defined as cardiac death, non-fatal myocardial infarction and/or non-elective revascularisation.

RESULTS: A total of 915 of 1753 (52.2%) patients (mean age 56.8 ± 12.0 years; 46.2% male) had a zero CAC score. Of the 751 (82.1%) patients with a zero CAC in whom CTCA was performed, 674 (89.7%) had normal coronary arteries, 63 (8.4%) had non-calcified coronary artery disease (CAD) with <50% stenosis and 14 (1.9%) had ≥50% stenosis in at least one coronary artery. The negative predictive value of a zero CAC for excluding a ≥50% CTCA stenosis was 98.1%. Over a median follow-up period of 2.2 years (range 1.0-7.0 years), the absolute annualized rates of MACE were: zero CAC 1.9 per 1,000 person-years and non-zero CAC 7.4 per 1,000 person-years (hazard ratio 3.8, p=0.009). However, after adjusting for age, gender and cardiovascular risk factors using a multivariable Cox proportional hazards model, there was no statistically significant difference in the risk of MACE between the two patient cohorts (p=0.19). After adjusting for age, gender and cardiovascular risk factors, the hazard ratio for all-cause mortality among the zero CAC cohort versus non-zero CAC was 2.1 (p=0.27).

CONCLUSION: A zero CAC score in patients undergoing CT scanning for suspected stable angina has a high negative predictive value for the exclusion of obstructive CAD and is associated with a good medium-term prognosis.