Silent myocardial infarction (SMI) occurred among a small proportion of patients without high cardiovascular disease risk. However, incorporating SMI into features of atherosclerotic cardiovascular disease (ASCVD) risk did not improve classification, according to results from a study published in the Journal of Electrocardiology.

The Multi-Ethnic Study of Atherosclerosis (MESA) was a prospective cohort design assessment of 2946 individuals without cardiovascular disease enrolled between 2000 and 2002. Study participants were assessed to have intermediate ASCVD risk and underwent electrocardiography. Risk was reassessed at 10 years.

Participants were aged a mean of 63.1±7.6 years; 53.9% were women; and were 36% White, 33% Black, 19% Hispanic, and 11% Asian. At baseline, 2.2% had SMI. Stratified by SMI, those with SMI had elevated diastolic blood pressure (mean, 76.5±10.5 vs 72.9±10.1 mmHg; P =.004).


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At a combined 40,732 person-year (py) follow-up, ASCVD events occurred among 15.0% of participants without SMI and 24.2% with SMI at baseline (18.6 events per 1000 py). Survival free of ASCVD was significantly lower among patients with SMI (P =.02).

In a fully corrected model, SMI associated with all-cause mortality (hazard ratio [HR], 1.73; 95% CI, 1.14-2.64; P =.01), cardiovascular mortality (HR, 2.54; 95% CI, 1.17-5.51; P =.002), ASCVD (HR, 1.68; 95% CI, 1.02-2.77; P =.04), and coronary heart disease (HR, 1.81; 95% CI, 1.03-3.17; P =.03). Baseline SMI was not associated with congestive heart failure (HR, 1.28; 95% CI, 0.52-3.15; P =.59) or stroke (HR, 1.01; 95% CI, 0.32-3.20; P =.99).

Adding SMI to a model that predicted ASCVD increased the area under the receiving operator characteristic curve (AUC) from 0.5812 to 0.5874 (P =.22). The inclusion of SMI in the model had no net reclassification improvement for intermediate to high risk for ASCVD (0.0161; 95% CI, 0.002-0.034; P =.08).

No interaction was observed with ethnicity (P =.16).

This study was limited by its small sample size of patients with SMI. The rate of SMI varied between 0.1% among the general population and 16% among patients with diabetes, indicating SMI may be an important predictor among subsets of patients; however, this study did not have sufficient power to test for this.

These data indicated that patients with SMI were at increased risk for mortality and ASCVD but that SMI was not a significant disease risk feature.

Reference

Singleton MJ, German CA, Soliman EZ, et al. The utility of silent myocardial infarction on electrocardiogram as an ASCVD risk enhancer for primary prevention: the multi-ethnic study of atherosclerosis. J Electrocardiol. 2021;65:105-109. doi:10.1016/j.jelectrocard.2021.01.018