Silent MI may increase stroke risk in older adults

Silent myocardial infarction (MI) or heart attack appears to be associated with an increased risk of stroke in older adults, according to a study presented at ISC 2021.

“We found [that] having a silent heart attack increases stroke risk, suggesting silent heart attacks may need to be recognized as a new risk factor for stroke,” said study author Dr Alexander Merkler from the Department of Neurology at Weill Cornell Medicine in New York, US.

Using data from the Cardiovascular Health Study (CHS), the researchers analysed 4,224 adults (aged ≥65 years) who had no history of stroke at baseline. Electrocardiogram or cardiac magnetic resonance imaging was used to diagnose incident silent or overt MI. [ISC 2021, abstract 58]

At a median follow-up of 9.8 years, 362 and 421 participants had incident silent and overt MI, respectively, and 377 had an incident ischaemic stroke, of which 36.8 percent were nonlacunar stroke and 15.1 percent were lacunar stroke.

After adjusting for age, sex, and vascular risk factors*, patients who experienced a silent MI had a higher risk of developing an ischaemic stroke compared with those without MI (hazard ratio [HR], 1.47).

A higher risk of ischaemic stroke was also observed among those who had an overt MI within 30 days (short term; HR, 80) and at >30 days (long term; HR, 1.60).

“Our research suggests the increased risk for having a stroke in those with silent heart attacks is similar to the risk found in traditional heart attacks [or overt MI]. A silent heart attack may be capable of causing clots in the heart that dislodge and travel to the brain causing a stroke,” said Merkler.

When stroke subtypes were assessed, the researchers found that silent (HR, 2.18) and overt MI (HR, 2.17 [short term] and 2.18 [long term]) were both associated with nonlacunar ischaemic stroke, but not with lacunar stroke (HR, 0.49 and 0.68, respectively).

“Thus, we found that silent MI is associated with incident ischaemic stroke in the CHS. The association seems to be driven by nonlacunar ischaemic stroke,” noted Merkler, who concluded that “silent MI may be a [novel] risk factor for [ischaemic] stroke, specifically for nonlacunar stroke.”

“More research is needed to understand how best to treat patients with silent heart attacks to prevent stroke,” Merkler noted. “It may also be worthwhile to conduct studies aimed at evaluating whether routine cardiac evaluation for silent heart attacks is warranted in order to help stratify the risk of stroke.”

*Body mass index, diabetes, atrial fibrillation, heart failure, blood pressure, use of antihypertensive medications, cholesterol levels, and smoking status