Silent myocardial infarction (MI) is associated with the subsequent occurrence of incident ischemic stroke in older patients, according to research published in Neurology.
In this prospectively conducted cohort study, researchers enrolled 5888 patients in the Cardiovascular Health Study between 1989 and 1993. Patients were eligible irrespective of whether they were diagnosed with any heart disease. In total, 5888 participants were recruited (Cohort 1: 5201; Cohort 2: 687). Only Cohort 1 data were included in primary analyses, though both Cohort 1 and 2 participants were included in sensitivity analyses.
Follow-up (median, 9.8 years) included annual appointments and semiannual phone calls. Researchers collected data on cardiovascular events and history of hospitalizations; this information was evaluated by adjudication committees.
Incident ischemic stroke was designated as the primary outcome and organized into 4 categories: lacunar stroke, stroke caused by atherosclerosis of a large artery, cardioembolic stroke, and stroke due to other/unknown reasons. These were determined by the adjudication committees yielding a kappa reliability statistic value of 0.77.
In total, 4224 participants were included in the primary analysis. The incidence of overt MI was 10% (n=421), silent MI was 8.6% (n=362), and ischemic stroke was 8.9% (n=377). Of the 10% of patients who experienced overt MI, 0.5% (n=23) experienced a silent MI prior. Of the 8.9% of patients reported to have had a stroke, 15.1% (n=57) were classified as lacunar, 36.1% (n=136) were nonlacunar, and 48.8% (n=184) were of other/unknown classification.
Overall, there was a significant association between MI with a silent manifestation and the occurrence of subsequent ischemic stroke (hazard ratio [HR], 1.51; 95% CI, 1.03-2.21). After adjustments for demographics and risk factors, secondary analyses showed a significant association between silent MI and nonlacunar-type stroke (HR, 2.40; 95% CI, 1.36-4.22) but not with other/unknown ischemic strokes (HR, 1.29; 95% CI, 0.73-2.31). Sensitivity analyses were consistent with these findings.
A significant association also remained between overt MI and both incident and nonlacunar ischemic stroke in short terms (HR, 80; 95% CI, 53-119 and HR, 210; 95% CI, 127-348, respectively) and long terms (HR, 1.60; 95% CI, 1.04-2.44 and HR, 2.21; 95% CI, 1.16-4.22, respectively).
A potential limitation of this study is that Cohort 2 was excluded from primary analysis since data were available from Cohort 1 for a longer period of time. However, because Cohort 1 was composed of mostly White participants and the majority of Cohort 2 was composed of Black participants, additional research would help reaffirm the generalizability of this study to a diverse population.
The study authors concluded that “the association between silent MI and incident ischemic stroke is consistent with the hypothesis that silent MI may lead to thrombus formation and subsequent cardiac embolism, as also seen in overt MI.” Ultimately, “although the MI is silent or unrecognized, it should not be considered benign, but rather a covert risk factor for many adverse outcomes.”
Disclosure: Several study authors declared affiliations with pharmaceutical companies. Please see the original reference for a full list of authors’ disclosures.
Merkler AE, Bartz TM, Kamel H, et al. Silent myocardial infarction and subsequent ischemic stroke in the Cardiovascular Health Study. Neurology. Published online May 24, 2021. doi:10.1212/WNL.0000000000012249