Abstract 14139: Differential Benefit of Non-Invasive Cardiac Stress Testing by HEART Score Risk Stratification

Introduction: AHA guidelines recommend non-invasive cardiac testing (NIT) within 72 hours after an emergency department (ED) evaluation for suspected acute coronary syndrome (ACS), after acute myocardial infarction (AMI) has been excluded. However, the effectiveness of this strategy to reduce the risk of future AMI or death, in low-risk patients is contested. Hypothesis: We hypothesized that in patients with low risk based on history, electrocardiogram, age, risk factors and troponin (HEART) based scoring, early NIT may not be beneficial compared to higher risk. Methods: We compared the effectiveness of early NIT vs. no early testing, in a retrospective cohort of adult (age ≥18) members of the Kaiser Permanente Southern California health system from 05/2016-12/2020. We included all adults presenting at EDs with suspected ACS and who had data to compute HEART score. We stratified the cohort into low risk (score 0-3); intermediate risk (score 4-6) and high-risk (score ≥7) based on HEART score. Within each group, confounder adjusted instrumental variables models were used to evaluate the marginal effect of early NIT, and the number needed to treat (NNT) was calculated as the inverse of the absolute composite risk reduction in death/AMI within 30 days of ED discharge. Results: The cohort included 174,936 patients [61% Low risk (mean age 53; female 58%; early NIT 5%), 36% intermediate risk (mean age 71; female 72%; early NIT 18%), and 3% high risk (mean age 74, female 45%; early NIT 23%)]. The risk reduction in 30-day death/AMI due to early NIT increased progressively through the intermediate-risk (NNT = 59) and high-risk groups (NNT = 24) (Table 1). Risk reduction in the low-risk group was not statistically significant. Conclusions: HEART score based high risk patients may benefit the most from early NIT. However, the majority of the suspected ACS cohort was classified as low risk and the benefit of early NIT on 30-day death/AMI was uncertain in this low-risk group.