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DALLAS -- Long-term monitoring improved the detection of atrial fibrillation (Afib) after a large artery or small vessel stroke, a randomized trial showed.

Among survivors of strokes attributed to small vessel occlusion or large artery atherosclerosis in the STROKE AF trial, Afib was detected in 21.7% of those who underwent insertable cardiac monitoring (ICM) versus 2.4% of those who received standard care over 3 years (HR 10.0, 95% CI 4.0-25.2, P<0.001), reported Lee Schwamm, MD, of Massachusetts General Hospital in Boston, during the American Stroke Association's International Stroke Conference.

While there were similar rates of recurrent stroke between the study groups (17.0% vs 14.1%, respectively; HR 1.10, 95% CI 0.67-1.78, P=0.71), Schwamm said this clinical event analysis was underpowered and explained that only three out of the 34 patients with recurrent stroke in the ICM arm had Afib detected prior to the recurrent stroke, and only one of those three was on oral anticoagulant therapy at the time of recurrent stroke.

"There were similar recurrent stroke rates in both arms by the end of the study, but these were rarely in patients with Afib and this population has a substantial risk factor burden for recurrent atherosclerotic stroke," he said.

Schwamm pointed out that suspicion of Afib based on patient symptom self-report is unreliable: 88% of Afib episodes recorded via ICM were asymptomatic.

"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," Schwamm said in a press release.

This report of STROKE AF extends findings from 12 months, when Afib detection was 12.1% with ICM versus 1.8% with usual care (HR 7.7, 95% CI 2.7-21.9) in a patient population not typically considered for Afib detection and management. The trial was underpowered for clinical endpoints at that time.

Three years into the study, the burden of Afib detected by ICM was clinically relevant, Schwamm said, as over two-thirds of people with Afib detected by ICM had at least one episode lasting more than 1 hour. "This degree of Afib would be considered a sufficient indication by many physicians to treat with anticoagulation for secondary prevention of cardioembolic stroke," he noted.

Insertable cardiac monitors are used frequently in clinical practice to identify post-stroke Afib in patients with cryptogenic stroke. This is based on the that found that long-term ICM detected significantly more occult Afib at 12 months following cryptogenic stroke.

STROKE AF is important for expanding well beyond CRYSTAL-AF to include patients with known vascular disease that could explain the cause of stroke, commented Andrea Russo, MD, of Cooper Medical School of Rowan University in Camden, New Jersey, who was not involved with the trial.

"Even this group demonstrated the benefit of prolonged monitoring with an implantable loop recorder in increasing the yield of detection of Afib during follow-up compared with usual care. These patients had risk factors for Afib (which are similar to risk factors for [stroke]) and Afib was more likely to be detected with the implantable monitor, which could be a future risk for recurrent stroke. This highlights the importance of prolonged monitoring for Afib," she told MedPage Today.

Nevertheless, long-term monitoring for the detection of Afib is currently not recommended for survivors of stroke due to presumed small vessel occlusion or large artery atherosclerosis and is not frequently performed, according to Schwamm.

"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 Afib -- for some of those 25% of patients with recurrent strokes," he said.

"What we need to sort out is what additional risk does Afib add, and can the use of anticoagulation reduce that risk, especially for the type of major and disabling strokes that are often associated with Afib," he added.

STROKE AF had been conducted at 33 U.S. centers from 2016 to 2019 and included nearly 500 patients ages 60 and older (or 50-59 with an additional stroke risk factor) with ischemic stroke attributed to large- or small-vessel disease, who had no prior Afib diagnosis and no contraindication to long-term oral anticoagulation.

Patients were randomized to Reveal LINQ loop recorder monitoring or usual arrhythmia detection within 10 days of the index stroke.

The overall cohort averaged 67 years, and 62% were men. Over half of patients were tobacco smokers, and the median CHA2DS2-VASc score was 5.0. There were no significant differences between groups at baseline.

For this predefined secondary analysis, trial participants with 36-month follow-up totaled 148 in the ICM arm and 146 in the control arm.

The subgroup of patients with congestive heart failure, left atrial enlargement, a body mass index >30, and a QRS >120 ms had a whopping 30% Afib detection rate over the 3 years -- suggestive of a potential high-yield population for ICM.

The STROKE AF trial was conducted open-label but had a clinical events committee to adjudicate irregular heart rhythms lasting more than 30 seconds. Schwamm noted that the Reveal LINQ only captures Afib episodes lasting at least 2 minutes.

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