New research has discovered that irregular heart rhythms were detected in close to 1 in 5 individuals who had survived an ischaemic stroke caused by atherosclerosis.
These individuals were continuously monitored for three years with an insertable cardiac device.
Lead study author, Lee Schwamm, says: “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.”
Schwamm explains that individuals who have survived an ischaemic strokes that were caused by atherosclerosis (or hardening) of the brain arteries, and not by a blood clot travelling from the heart to the brain, will not typically receive continuous cardiac monitoring after discharge.
The danger of this, is that unrecognised irregular heart rhythms may increase the risk of another stroke caused by a blood clot formed in the heart that travels to the brain.
Earlier this year, as part of Stroke Prevention Day, the Stroke Association had a campaign focused on the ‘silent condition’ atrial fibrillation which urged people to get checked for the condition.
Atrial fibrillation (AF) is the most common type of irregular heart rhythm, which research conducted by the Stroke Association revealed that an estimated half a million individuals are living with undiagnosed AF.
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, multi centre study examined whether the incidence of AF would continue to increase over the full three years of follow up after the first stroke.
It included 492 participants who had an ischaemic stroke caused by a clot that formed in a diseased artery, instead of one originating in the heart, and who had no diagnosis of AF.
The patients had an average age of 67 years, with 62 per cent of participants being male, participants also 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 the standard medical treatment, including no continuous heart monitoring and follow-up care every six months for three years.
After researchers compared the rates of AF detection between both groups, the following discoveries were made:
- 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.
On the study’s findings, Schwamm says: “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.
“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.”
AF symptoms include heart palpitations, dizziness, fatigue, chest pain and shortness of breath, however, many do not notice the symptoms.
The survey conducted by the Stroke Association for Stroke Prevention Day, found that 73 per cent of participants did not know AF is a major cause of stroke.
Schwamm says: “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.”
