294 Assessment of the Diagnostic Utility of Non-Invasive Cardiac Imaging Modalities in Accurately Excluding Obstructive Coronary Artery Disease in Low to Intermediate Risk Patients. A Calcium Score of Zero is Predictive of a Negative Myocardial Perfusion Study and Thus can be Utilized in the Absence of an MPS for Exclusion of Obstructive Coronary Artery Disease

Abstract

Myocardial perfusion scan (MPS) is an established non-invasive diagnostic tool for assessing reversible ischaemia in low-to- intermediate-risk chest pain patients. The diagnostic utility of Coronary Artery Calcium Score {CACS} in isolation is less established in this cohort at excluding obstructive coronary artery disease. In comparison to MPS; CACS is less costly; more time efficient and utilizes smaller doses of ionizing radiation. In this tertiary single-centred retrospective analysis we assessed the utility of a CACS of 0 in the prediction of a negative MPS; and ultimately the exclusion of obstructive coronary artery disease. 137 consecutive patients of whom underwent simultaneous CACs and MPS with low to intermediate risk chest pain were included in the study. The criteria for adjunctive CACs assessment included patients aged between 45- 75years; with no prior history of ischaemic heart disease. 137 patients underwent paired MPS and CACs; 37 of the 137 patients {27%} had a CACS of zero; all of whom had a paired negative MPS. 100 patients {73%} had a CACs of >1; with 9 positive MPS results showing demonstrable reversible perfusion defects. The mean age of patients was 62 years; with 53% Male and 47% Female. Further stratification incorporating cardiac risk factors included diabetes mellitus, smoking history, hypertension and hypercholesteraemia with 80% having greater than one risk factor. CACS of 0 predicts a negative MPS {p=0.113; Fisher`s exact test}. Coronary artery calcium score of zero is suggestive of a negative myocardial perfusion study; although not statistically significant. Further studies are recommended with the aim of applying coronary artery calcium scoring as a diagnostic non-invasive screening tool in patients with low to intermediate risk chest pain.