Silent Myocardial Infarction and Long-Term Risk of Heart Failure: The ARIC Study

Abstract

Background: Although silent myocardial infarction (SMI) accounts for about one-half of the total number of myocardial infarctions (MIs), the risk of heart failure (HF) among patients with SMI is not well established.

Objectives: The purpose of this study was to examine the association of SMI and clinically manifested myocardial infarction (CMI) with HF, as compared with patients with no MI.

Methods: This analysis included 9,243 participants from the ARIC (Atherosclerosis Risk In Communities) study who were free of cardiovascular disease at baseline (ARIC visit 1: 1987 to 1989). SMI was defined as electrocardiographic evidence of MI without CMI after the baseline until ARIC visit 4 (1996 to 1998). HF events were ascertained starting from ARIC visit 4 until 2010 in individuals free of HF before that visit.

Results: Between ARIC visits 1 and 4, 305 SMIs and 331 CMIs occurred. After ARIC visit 4 and during a median follow-up of 13.0 years, 976 HF events occurred. The incidence rate of HF was higher in both CMI and SMI participants than in those without MI (incidence rates per 1,000 person-years were 30.4, 16.2, and 7.8, respectively; p < 0.001). In a model adjusted for demographics and HF risk factors, both SMI (hazard ratio [HR]: 1.35; 95% confidence interval [CI]: 1.02 to 1.78) and CMI (HR: 2.85; 95% CI: 2.31 to 3.51) were associated with increased risk of HF compared with no MI. These associations were consistent in subgroups of participants stratified by several HF risk predictors. However, the risk of HF associated with SMI was stronger in those younger than the median age (53 years) (HR: 1.66; 95% CI: 1.00 to 2.75 vs. HR: 1.19; 95% CI: 0.85 to 1.66, respectively; overall interaction p by MI type <0.001).

Conclusions: SMI is associated with an increased risk of HF. Future research is needed to examine the cost effectiveness of screening for SMI as part of HF risk assessment, and to identify preventive therapies to improve the risk of HF among patients with SMI.

Keywords: electrocardiogram; heart failure; silent myocardial infarction.

Figure 1. Associations between Type of Myocardial Infarction and Incident Heart Failure in Subgroups

HR=hazard ratio; CI=confidence interval; MI= myocardial infarction. Models adjusted for age, sex, race, plus body mass index, smoking status, heart rate, systolic blood pressure, blood pressure lowering medications, and diabetes mellitus (subgroup used in stratification is not included in the model).

Central Illustration. Risk of HF Associated with Different Patterns of MI

Cumulative Incidence of Heart Failure Stratified by Myocardial Infarction Status. MI= Myocardial Infraction; HF= Heart Failure.