Conference Coverage

STROKE AF at 3 years: High AFib rate after atherosclerotic stroke


 

FROM ISC 2023

In the STROKE AF study, among patients who had a stroke presumably caused by atherosclerosis, the rate of atrial fibrillation (AFib) was almost 22% at 3 years, as detected by continuous monitoring.

The 3-year results from the study were presented by Lee H. Schwamm, MD, of Massachusetts General Hospital, Boston, at the International Stroke Conference presented by the American Stroke Association, a division of the American Heart Association.

Dr. Schwamm said the high rate of AFib detection in this study suggests that continuous monitoring for AFib should be considered for a larger population of stroke patients, rather than just those with cryptogenic stroke.

“We found a much higher rate of AF[ib] than we expected in this population of patients who have had an atherosclerotic stroke,” Dr. Schwamm said in an interview.

“These AF[ib] occurrences were found by a device, so they are known as ‘device-documented AF[ib].’ The patient is not generally aware of symptoms, but 67% of the AF[ib] episodes lasted for more than 1 hour, showing that this is not trivial AF[ib]. This is meaningful AF[ib],” he said.

Dr. Schwamm said the major question is whether these cases of AFib that are detected with a device warrant treatment with anticoagulation. He noted that, in this study, clinicians decided to provide anticoagulation to 70%-80% of patients in whom AFib was detected.

“If we think it deserves treatment, then we have to look for it. And if we care about finding AF[ib], we have no choice but to monitor continuously,” he said.

“If this data doesn’t convince you that AF[ib] is present in this population, I don’t think any data will. Because it is consistent, it accumulates over time and looks remarkably similar to a set of data that we have all become very comfortable with – the CRYSTAL-AF study in patients with cryptogenic stroke,” he stated.

Dr. Schwamm noted that the STROKE AF trial was not based on the cause of the index stroke; rather, it was asking whether there are risk factors that could contribute to the 25% stroke recurrence rate in this population that are not covered in current guidelines.

“I’m really trying to move away from the anchor that I was trained in, which is to figure out the cause of the last stroke to help decide how to prevent the next stroke, towards more of a probabilistic model – of what is all the information I have at my disposal and how do I act on it to prevent the next stroke? We have to start thinking differently about building models for future stroke risk and determining therapy based on that,” he commented.

Changing practice

ISC 2023 program chair Tudor Jovin, MD, Cooper Neurological Institute, Cherry Hill, N.J., and moderator of the session at which the results were presented, discussed the STROKE AF results in a highlights presentation.

“To me as clinician, these results are even more relevant than those at 12 months,” Dr. Jovin said. “The lesson I took is that AF[ib] is even more prevalent than we thought. The burden of AF[ib] is significant in these patients, and it doesn’t seem to be limited to a particular time. These are very thought-provoking results which are going to change clinical practice. I think the threshold for long-term monitoring will be lower.”

Comoderator Lauren Sansing, MD, Yale University, New Haven, Conn., added: “This study shows that the longer we monitor, the more patients with AF[ib] we are likely to pick up. And because in two-thirds of patients with AF[ib], it lasted longer than 1 hour, I do believe this was clinically relevant AF[ib]. The question now is, do we monitor everyone? I think it puts the burden on us to search for AF[ib] in our patients.”

In his presentation, Dr. Schwamm explained that, on the basis of the CRYSTAL-AF study, insertable cardiac monitoring devices are frequently used to identify poststroke AFib in patients with cryptogenic stroke. In the device-monitored arm of that study, AFib was detected in 12.4% of patients over 12 months versus 2.0% in the control arm.

“However, we don’t know how often AF[ib] is detected in other presumed stroke types – largely those due to atherosclerosis,” he said.

He pointed out that, at present, long-term monitoring post stroke for the detection of AFib is not currently recommended for patients with ischemic stroke, owing to presumed small-vessel occlusion or large-artery atherosclerosis.

“In these patients, we are not suspecting AF[ib] because we believe the cause of the stroke was not embolic. But we wanted to investigate what the AF[ib] risk is in these patients, who often have multiple stroke risk factors,” he said.

The trial enrolled 496 patients at 33 centers in the United States. Eligible patients were aged 60 years or older or aged 50-59 years with at least one additional stroke risk factor and had an index stroke that was attributed to large-artery or small-vessel disease. Patients were randomly assigned either to continuous monitoring with the Reveal LINQ device (Medtronic) or to the control arm following site-specific standard of care for AFib detection.

Dr. Schwamm noted that usual care for these patients normally involves monitoring for just a few days while in hospital, but this picks up less than 5% of AFib occurrences.

Baseline characteristics of patients in the STROKE AF study showed that the enrolled population was at high risk for stroke, with a CHADSVASC score of 5. But the index strokes were generally small; the median National Institutes of Health Stroke Scale score was 2.

Results at 12 months, reported 2 years ago, showed a 12.5% incidence of AFib with continuous monitoring versus 1.8% with standard of care (hazard ratio, 7.7; P < .001), rates similar to that found in the CRYSTAL-AF study.

By 3 years, the rate of detected AFib had risen to 21.7% in the continuous monitoring arm versus 2.4% in the control arm (HR, 10.0; P < .001).

“At 12 months, we were seven times more likely to detect AF[ib] with continuous monitoring in these patients, and by 3 years, it was 10 times more likely that AF would be detected with continuous monitoring. I think we’ve settled the question of the best way to find AF[ib] in these patients – it is with an inserted device,” Dr. Schwamm said.

“We have also shown that this is not a transient rise in AFib after the stroke which then diminishes over the next few years. It is a continuous and progressive detection of AF[ib].”

Dr. Schwamm pointed out that 88% of the recorded AFib episodes were asymptomatic. “So relying on patients self-reporting symptoms when deciding who to monitor is unreliable and not a sensible strategy.”

The median time to the first adjudicated AFib episode at 12-month follow-up was 99 days; at the 3-year follow-up, it was 284 days.

“This shows that 30 days of monitoring with an external patch is not sufficient to exclude the presence of AF[ib]. And this really argues for a strategy of immediate insertion of cardiac monitor placement if your goal is to look for AF[ib],” Dr. Schwamm commented.

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