'Silent' heart attacks may increase risk of stroke

Silent heart attacks appear to increase stroke risk in adults 65 and older, according to preliminary research to be presented at the American Stroke Association International Stroke Conference 2021.

A silent heart attack, also known as a silent myocardial infarction, has no, minimal or unrecognized symptoms. An electrocardiogram (ECG) or some form of imaging of the heart like an echocardiogram or a cardiac magnetic resonance imaging (MRI) is needed for diagnosis.

"Long-term risk of death can be as high after a silent heart attack as it is with a recognized heart attack, and it turns out silent heart attacks are more frequent than traditional chest-crushing heart attacks in older adults," said study author Alexander E. Merkler, M.D., assistant professor of neurology at Weill Cornell Medicine in New York City. "We found having a silent heart attack increases stroke risk, suggesting silent heart attacks may need to be recognized as a new risk factor for stroke."

Merkler and colleagues analyzed health information on more than 4,200 adults who participated in the Cardiovascular Health Study. Participants were 65 years old or older at the start of the study and were enrolled from 1989-1990. Participants had annual study visits from 1989-1999 at multiple centers across the U.S. Researchers evaluated participants' stroke risk for an average of 10 years, with follow-up through June 30, 2015.

Researchers found:

• Participants who had evidence of a silent heart attack had a 47% increased risk of developing a stroke, compared to adults who did not have a silent heart attack. Participants who had classic symptoms for a heart attack had an 80-fold increased risk of stroke within one month after their heart attack, compared to participants who were heart attack-free. After the high-risk, one-month period, participants with classic symptoms for a heart attack had a 60% increased risk of having a stroke.

"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. A silent heart attack may be capable of causing clots in the heart that dislodge and travel to the brain causing a stroke," Merkler said.

The research indicates patients with evidence of a silent heart attack found on an ECG should be considered as having an increased risk of 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."

A major limitation of the study is that the majority of study participants were white. The results might not be applicable to younger adults or adults of other races or ethnic groups.