Technical Features

The tachogram and EGM show a sinus rhythm (at around 90-100 bpm) with a sudden acceleration on the atrial level. The atrial cycles suddenly have a short cycle length (406-438 ms) and occur during the WARAD (Window of Atrial Rate Acceleration Detection, explained here) which is why they are have different markers (Ar). When multiple atrial events occur within the WARAD, the device suspects an atrial arrhythmia and may perform a mode switch (explained here).

Clinical Relevance

As is the same for nonsustained ventricular arrhythmias, the clinical relevance of atrial arrhythmias is not completely understood. But as atrial fibrillation (AF) is the most common arrhythmia and because AF is associated with risk of developing stroke and heart failure, there has been a lot of research performed on this topic. Most literature agrees that the occurrence of nonsustained atrial arrhythmia should not result in commencing anticoagulation as most studies use 6 minutes of atrial arrhythmia as a cut-off. And even then, the largest studies show no decrease in stroke risk when anticoagulating implanted patients based on such episodes; using a cut-off of 6 minutes or even one hour. There is no evidence that treating patients with medical therapy (e.g. betablockers or calcium antagonists) or invasive therapy (ablation) prevents the occurrence of longer episodes of atrial arrhythmia. The clinical relevance of these short episodes are mostly to correlate with clinical symptoms, if present. Patients implanted with a pacemaker commonly feel palpitations and the parallel registration of atrial runs may very well relieve the patient.

Lead surveillance

Similar to “ventricular runs” episodes, these episodes can also show the first signs of atrial lead dysfunction, where the fast atrial events are not caused by atrial arrhythmia, but rather oversensing of noise artifacts.