Abstract 58: Silent Myocardial Infarction and Subsequent Ischemic Stroke in the Cardiovascular Health Study

Abstract

Background: Whether silent myocardial infarction (MI) is a risk factor for ischemic stroke remains uncertain. Hypothesis: Silent MI is associated with incident ischemic stroke. Methods: The Cardiovascular Health Study prospectively enrolled community-dwelling individuals ≥65 years of age with follow-up through June 30, 2015. For this study, we included participants from the first study cohort (enrolled in 1989-1990) without prevalent stroke or baseline electrocardiographic (ECG) evidence of MI. Our exposures were silent and clinically apparent MI. Silent MI was defined as new evidence of Q-wave MI, without clinical symptoms of MI, on ECGs performed during annual study visits from 1989-1999. Clinically apparent (overt) MI was adjudicated on the basis of information about chest pain, ECG changes, and cardiac enzymes. The primary outcome was incident ischemic stroke. Secondary outcomes were ischemic stroke subtypes: non-lacunar, lacunar, and other/unknown. Cox proportional hazards analysis was used to model the association between time-varying MI status (silent, overt, or no MI) and stroke after adjustment for baseline demographics and vascular risk factors. Due to a violation of the proportional hazards assumption, the association between overt MI and stroke was modeled separately for short-term (within 30 days) and long-term (beyond 30 days) risk. Results: Among 4,224 participants included in this analysis, 362 (8.6%) had an incident silent MI, 421 (10.0%) an incident overt MI, and 377 (8.9%) an incident ischemic stroke during a median follow-up of 9.8 years. After adjustment for demographics and comorbidities, silent MI was independently associated with subsequent ischemic stroke (HR, 1.47; 95% CI, 1.01-2.16). Overt MI was associated with ischemic stroke both in the short term (HR, 80; 95% CI, 53-119) and long term (HR, 1.60; 95% CI, 1.04-2.44). In secondary analyses, the association between silent MI and stroke was limited to non-lacunar ischemic stroke (HR 2.18; 95% CI, 1.24-3.83). Conclusions: In a community-based sample, we found an association between silent MI and ischemic stroke, specifically non-lacunar stroke. These findings suggest that silent MI may be a novel risk factor for ischemic stroke.