Do cardiac risk factors influence the probability of acute myocardial infarction in emergency department? Analysis from a multicentre prospective observational study in the high sensitivity troponin era
Background:
Cardiac risk factors including hyperlipidaemia, hypertension, diabetes mellitus, tobacco smoking and family history are known to be contributing factors to developing coronary artery disease (CAD) Evidence from a decade ago suggests that risk factors do not affect the probability of an acute myocardial infarction (AMI) in the Emergency Department (ED) population with suspected cardiac chest pain. However, common decision aids including the HEART score and Thrombolysis in Myocardial Infarction (TIMI) risk score still use the presence of at least three risk factors to assign greater risk to patients.
We aimed to determine the diagnostic value of cardiac risk factors in patients presenting to the ED with suspected acute coronary syndromes using data from a large, contemporary, multi-centre study.
Methods:
This is a sub-study of the Bedside Evaluation of Sensitive Troponin (BEST) study, a prospective diagnostic test accuracy study conducted across 14 hospitals in England. The patients were prospectively recruited when presenting to ED with symptoms that the treating clinician suspected may have been caused by an acute coronary syndrome. The presence or absence of cardiac risk factors (hypertension, hyperlipidaemia, diabetes mellitus, smoking, family history of CAD in a first degree relative aged under 65 years) were recorded using a bespoke case report form at the time of initial presentation, and therefore blinded to the patient’s outcome. To emulate how cardiac risk factors are used in clinical practice, we collected the data that were known to emergency physicians at the point of care, including data from patients’ health records and patient-reported cardiac risk factors. All participants underwent cardiac troponin testing on arrival and 3-12 hours later. The primary outcome was a diagnosis of AMI, adjudicated by two independent investigators in accordance with the 3rduniversal definition, without referring to cardiac risk factors. Written consent was obtained from each participant and the study had ethical approval from the Health Research Authority (14/NW/1344).
Results:
There were a total of 1,613 participants (males 62%, mean age 56yrs), with 217 (13.5%) patients excluded due to missing data. Overall, 178 (14.3%) patients had AMI. The prevalence of AMI in patients with zero, 1, 2, 3 and 4-5 cardiac risk factors was 9.8%, 12.2%, 17.1%, 15.4%, 23.1% and 23.8% respectively. The area under the receiver operating characteristic (ROC) curve (AUC) was 0.58.
Conclusion:
This study shows that cardiac risk factors influence the probability of AMI very little in the ED population. An AUC of 0.58 shows that cardiac risk factors have little value as a diagnostic test in this regard.
Funding:
BEST was funded by Research grants from EU-H2020, Abbott Point of Care & RCEM
