About 1 in 5 stroke survivors found to have irregular heart rhythms

Irregular heart rhythms were detected in about 1 in 5 people who survived an ischemic stroke due to atherosclerosis (buildup of fatty substances in the arteries) after being continuously monitored for three years with an insertable cardiac device, according to preliminary late-breaking science presented at the American Stroke Association's International Stroke Conference 2023. The meeting, to be held in person in Dallas and virtually, Feb. 8-10, 2023, is a world premier meeting for researchers and clinicians dedicated to the science of stroke and brain health.

We know that about 25% of ischemic strokes happen in patients who have survived a previous stroke. This drives our quest to understand not just the cause of the most recent stroke, but also their risk for future strokes due to all treatable causes, so we can do our best to prevent the next one."

Lee Schwamm, M.D., FAHA, lead study author, professor of neurology at Harvard Medical School in Boston

Survivors of ischemic strokes that were caused by atherosclerosis (or hardening) of the brain arteries, and not by a blood clot traveling from the heart to the brain, do not typically receive continuous cardiac monitoring after discharge, Schwamm explained. However, unrecognized irregular heart rhythms may increase the risk of another stroke caused by a blood clot formed in the heart that travels to the brain.

Atrial fibrillation, or AF, is the most common type of irregular heart rhythm. This analysis is a 3-year follow up to the Stroke AF study, which monitored heart rhythms in this type of stroke survivor for one year. This follow-up, multicenter study explored whether the incidence of atrial fibrillation would continue to increase over the full three years of follow up after the first stroke. It included 492 participants who had an ischemic stroke caused by a clot that formed in a diseased artery, instead of one originating in the heart, and who had no diagnosis of atrial fibrillation. The patients were older, average age of 67 years, more often male (62%) and had multiple vascular risk factors.

Half of the study participants were randomly assigned to receive an insertable cardiac monitor that recorded the rhythms of the heart 24 hours a day for a full 3 years. The other half received standard medical treatment — i.e., no continuous heart monitoring — and follow-up care every six months for three years. Researchers compared the rates of atrial fibrillation detection between patients in both groups.

The study found:

• The continuous cardiac monitoring device detected atrial fibrillation in more than 20% of the participants during three years after the first stroke. Standard follow-up care detected atrial fibrillation in about 2.5% of participants — representing a 10-fold increased detection rate when using the 24-hour monitoring device.
• Among participants who had atrial fibrillation detected via the insertable cardiac monitor, half experienced an irregular heart rhythm episode of 10 minutes or more, with more than two-thirds of them having an episode lasting greater than one hour. "It's important to note that six minutes of atrial fibrillation significantly increases risk of stroke," Schwamm said.
• No significant difference was seen in the rates of recurrent stroke between the participants who received the insertable cardiac monitor and those who received standard care at the three-year mark (17% versus 14.1%, respectively), although the study was not designed or powered to detect differences in treatments or clinical outcomes.

"We found that the rate of atrial fibrillation continued to increase over the course of the three years, therefore, it's not just a short-lived event and self-resolving related to the initial stroke," Schwamm said. "Fibrillation is common in these patients. Relying on routine monitoring strategies is not sufficient and neither is placing a 30-day continuous monitor on the patient. Even if fibrillation is ruled out in the first 30 days, most of the cases are missed — because, as we found, more than 80% of the episodes are first detected more than 30 days after the stroke."

Symptoms of atrial fibrillation may include heart palpitations, dizziness, fatigue, chest pain and shortness of breath. Still, many people do not notice any symptoms.

"More than 80% of patients in our study didn't have any symptoms of fibrillation, we just captured it on the monitor," Schwamm said. "There is still a lot that we don't yet understand about why people who have had a previous stroke have another one; however, this study contributes important information to one potential cause — namely, unsuspected atrial fibrillation — for some of those 25% of patients with recurrent strokes. These patients are at increased risk of recurrent strokes due to their known vascular risk factors, such as hypertension and elevated cholesterol and blood pressure. What we need to sort out is what additional risk does atrial fibrillation add, and can the use of anticoagulation reduce that risk, especially for the type of major and disabling strokes that are often associated with atrial fibrillation."

Schwamm noted the study's major limitation is that the full clinical significance of atrial fibrillation when detected by a continuous cardiac monitoring device in this population, as compared to when it is detected due to symptoms, is not yet established and needs to be studied in future research specifically designed to answer this important question.