49 The use of CT coronary angiography following exercise stress testing in a low risk population presenting to a chest pain service

Abstract

Background Exercise Stress Testing (EST) is commonly used as a non-invasive diagnostic investigation to detect obstructive Coronary Artery Disease (CAD) in low risk chest pain populations, in addition to assessing functional capacity of patients with known CAD. Computerised Tomography Coronary Angiograms (CTCAs) are indicated for continuing symptoms despite a negative EST. Purpose To look at the overall rate of obstructive Coronary Artery disease in patients referred to the Chest Pain Service, to look at the current use of EST as a preliminary investigation, and to compare results of patients’ ESTs with any subsequent CTCAs. Method We used the hospital’s chest pain registry, which contains data on all patients referred through the Chest Pain Service, and selected all patients presenting initially between 1/1/12 and 31/7/14. Patients were classified initially by the GRACE risk tool. We obtained EST results from the electronic patient record, and CTCA results from the Hospital’s Radiology System. Results 1211 patients were referred to the Chest Pain Service for Investigation of Chest Pain over 31 months (Data available on 1200); 1101 Low Risk (91.8%), 93 Intermediate Risk 93 (7.8%), and 6 High Risk (0.5%). 27 patients were referred twice during the study period. 1038 patients were referred for EST; 686 (66.1%) of the ESTs were negative, 177 (17.1%) were inconclusive, 172 (16.6%) were positive, and 3 not specified. The 132 patients who, after EST, were referred for CTCA, had a higher risk of having Obstructive CAD if they were referred after a negative EST (23.8%), than compared with an inconclusive (11.2%) or positive (19.6%) EST. Despite 86.5% of Chest Pain service patients being referred for EST as an initial investigation; 36.9% of these underwent subsequent Coronary Imaging (132 CTCAs and 251 Coronary Angiograms). 17.4% of the overall Chest Pain Service population had obstructive Coronary Artery disease. Conclusion A higher clinical suspicion is required to refer for CTCA (or Invasive Coronary Angiography) after a negative EST, than for an inconclusive or positive EST. Our data showed that the clinical suspicion carries more weight than EST result, with higher rates of Obstructive CAD for CTCAs after negative ESTs, then compared with Inconclusive or Positive results. The decision to proceed with CTCA despite a normal EST can be justified on clinical features.