Abstract 13196: The Utility of Silent Myocardial Infarction on Electrocardiogram as an ASCVD Risk Enhancer for Primary Prevention: The Multi-Ethnic Study of Atherosclerosis

Abstract

Introduction: The 2018 AHA/ACC cholesterol guidelines introduced a new list of markers called “risk enhancers” that, if present, confer an increased risk of atherosclerotic cardiovascular disease (ASCVD). Notably absent is silent myocardial infarction (SMI) on electrocardiogram (ECG), even though SMI has been shown to be associated with future ASCVD. Hypothesis: Adding SMI to the pooled cohort equation (PCE) will improve risk discrimination and classification in those with intermediate ASCVD risk (5 - 20% 10-year risk). Methods: SMI was defined as a major Q-wave abnormality or minor Q/QS waves in the setting of major ST-T abnormalities in the absence of history of clinical cardiovascular disease. Incident ASCVD events included myocardial infarction, coronary heart disease death, and fatal and non-fatal stroke. Results: Among 2,278 intermediate-risk MESA participants, 48 (2.1%) had SMI at baseline. Over 32,150 person-years (median 15.8), incident ASCVD events occurred in 297/2,230 (13%) of those without SMI and 13/48 (27%) of those with SMI. In a Cox proportional hazards model that was adjusted for calculated 10-year ASCVD risk based on the PCE, SMI was associated with increased risk of ASCVD (HR 2.22, 95% CI 1.27 - 3.87, p = 0.005). Adding SMI to the PCE did not improve discrimination, with areas under the receiver operating characteristic curves for models without and with SMI of 0.5812 and 0.5874, respectively (p-value for difference 0.22; Figure 1a). The net reclassification improvement for adding SMI as a risk enhancer to reclassify participants from intermediate-risk to high-risk was 0.0242 (95% CI 0.0011 - 0.0472, p = 0.04; Figure 1b). Conclusions: Our findings suggest that the prevalence of SMI is 2.1% among those without known clinical cardiovascular disease considered intermediate-risk by the pooled cohort equation. In our analysis, SMI only modestly improved classification of risk, suggesting that it may not be very useful as an ASCVD risk enhancer.