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Continuous cardiac monitoring detects substantial rates of subclinical AF after stroke

Reuters Health - 01/06/2021 - Subclinical atrial fibrillation is often present after ischemic stroke and continuous cardiac monitoring is helpful in detecting it, according to findings from two randomized controlled trials.

The Stroke of Known Cause and Underlying Atrial Fibrillation (Stroke-AF) trial compared subclinical AF detection over 12 months with an insertable cardiac monitor (ICM) versus usual care in 492 patients with ischemic stroke due to either large- or small-vessel disease.

Over 12 months, subclinical AF was detected in 12.1% of patients in the ICM group versus 1.8% of patients in the usual care group (P<0.001), report Dr. Richard Bernstein of Feinberg School of Medicine at Northwestern University, in Chicago, and colleagues.

Most subclinical AF events occurred after 30 days and lasted for 88 minutes on average. Anticoagulant therapy was prescribed for 67% of patients in the ICM group found to have subclinical AF.

The researchers say further research is needed to understand whether identifying subclinical AF in these patients is of clinical importance.

The Post-Embolic Rhythm Detection with Implantable vs External Monitoring (PER DIEM) trial, published along with Stroke-AF in JAMA this week, enrolled 300 patients within six months of non-AF-related ischemic stroke (66% cryptogenic).

Half were randomly allocated to 12 months of implantable loop recorder cardiac monitoring and half to 30 days of conventional external loop recorder monitoring.

"Among patients with recent ischemic stroke and no prior evidence of AF, prolonged continuous electrocardiographic monitoring with an implantable loop recorder over 12 months resulted in a significant increase in newly detected AF compared with a conventional 30-day external loop recorder strategy," report Dr. Brian Buck of the University of Alberta, in Edmonton, Canada, and colleagues.

Subclinical AF was detected in 15.3% of patients in the 12-month implantable-monitor group versus 4.7% of those in the 30-day external monitor group (P=0.003). Subclinical AF detection led to transition to anticoagulation therapy in all patients with subclinical AF, regardless of randomization group.

"Further research is needed to compare clinical outcomes associated with these monitoring strategies and relative cost-effectiveness," Dr. Buck and colleagues conclude.

The authors of an accompanying JAMA editorial note that in both trials, the number of patients needed to monitor with an ICM to detect one patient with subclinical AF at one year is roughly 10, "which is suggestive of an effective intervention for disease detection. However, evidence is lacking for the final link between subclinical AF detection after ischemic stroke and improved clinical outcomes."

Dr. David Tirschwell and Dr. Nazem Akoum of the University of Washington, in Seattle, say based on the findings of the Stroke-AF and the PER DIEM trials, combined with other evidence, "it seems that (1) there is a substantial amount of subclinical AF detectable after non-AF-related ischemic stroke, and not just among patients with cryptogenic stroke or embolic stroke of undetermined source ESUS, (2) the longer patients are monitored, the more subclinical AF will be detected, and (3) the more subclinical AF detected, the greater the risk of stroke."

"What remains missing is an evidence-based threshold based on the frequency and duration of subclinical AF for initiating anticoagulation therapy," they write.

Drs. Tirschwell and Akoum also note that studies have used various definitions of subclinical AF and a variety of detection devices with varied accuracies of subclinical AF detection, "suggesting that consensus standards are needed."

"As the population ages and the incidence of AF-related stroke (including subclinical AF) increases, it will be ever more important to ensure a strong evidence base for selecting the best anti-thrombotic treatment," they add.

Medtronic supported the STROKE-AF trial. Funding for the PER DIEM study was provided by Alberta Innovates Health Solutions Collaborative Research and Innovations Opportunities and a grant from the Partnership for Research and Innovation in the HealthSystem, government of Alberta. Unrestricted in-kind support (implantable loop recorder devices and the electrocardiographic core laboratory) was provided by Medtronic Canada.

SOURCE: https://bit.ly/3fFoLzv , https://bit.ly/2SNNOHS and https://bit.ly/34z0HIi JAMA, online June 1, 2021.

By Reuters Staff

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