Blood thinners may not be as effective in preventing strokes in patients with short arrhythmias as previously thought

Implantable devices and wearables like smart-watches enable continuous or near-continuous monitoring of cardiac rhythm. This leads to detection of short arrhythmias in many people, especially elderly persons with cardiovascular conditions. These arrhythmias, called atrial high rate episodes (AHRE), look like atrial fibrillation (AF). It is well established that blood thinners (anticoagulants) provide effective stroke prevention in patients with AF. Therefore, patients with AHRE are often treated with blood thinners as well.

Dr. Tobias Toennis, University Medical Center Hamburg-Eppendorf (UKE), Hamburg, Germany, is the lead author of an update published in the journal Europace. He explained, "Implanted pacemakers, defibrillators, or cardiac monitors can continuously capture and quantify atrial arrhythmias. Patients with such devices are a suitable population to study the role of infrequent atrial arrhythmias for outcomes in elderly people. AHRE occur in 10%–30 % of elderly patients without atrial fibrillation. We reviewed a number of previous AHRE studies and summarized the current knowledge on stroke risk."

It remains unclear whether anticoagulants can prevent strokes in patients with AHRE. This lack of knowledge is reflected in the current guidelines worldwide. Oral anticoagulants are not routinely recommended in patients with AHRE, but decisions on anticoagulation can be individualized based on clinical risk assessment.

The reviewed trials indicate AHRE are associated with an increased thromboembolic risk, even though it is lower than that of clinical AF. The thromboembolic risk appears to be influenced by the duration and frequency of AHRE episodes and by the number and severity of comorbidities. Recently published trials suggest that blood thinners prevent fewer strokes in patients with AHRE than previously thought.

NOAH—AFNET 6 (2), a controlled clinical trial conducted by the German Atrial Fibrillation Network (AFNET), evaluates the efficacy and safety of blood thinners in patients with AHRE. NOAH—AFNET 6 compares treatment with Edoxaban, a non-vitamin K antagonist oral anticoagulant (NOAC), to current therapy (antiplatelet therapy or no antithrombotic therapy) in patients with AHRE aged 65 years or more with at least two stroke risk factors. The trial can be expected to report soon.

The principal investigator of NOAH—AFNET 6, Prof. Kirchhof, UKE, summarized, "NOAH—AFNET 6 will provide much-needed information on the efficacy and safety of oral anticoagulation in patients with AHRE. We hope that these new data will shed some more light on the subject and that further studies will follow."