Abstract 206: High False Positive Rates of Atrial Fibrillation Detection Among Stroke Patients who Receive Medtronic Implantable Loop Recorders

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Introduction: Atrial fibrillation is a known risk factor for the development of stroke. Implantable loop recorders (ILRs) have specific algorithms to detect occult atrial fibrillation and can be used in patients with cryptogenic stroke. There is limited data on the frequency of false positive atrial fibrillation detected by the Medtronic ILR.

Hypothesis: Medtronic ILRs have a high rate of false positives but despite this are still effective at detecting atrial fibrillation in patients with cryptogenic stroke.

Methods: All stroke patients who underwent ILR placement from Jan 1, 2013 to June 30, 2015 were prospectively collected through an administrative database. Baseline and clinical characteristics were retrospectively obtained. A random sampling of ILR tracings identified as atrial fibrillation by the Medtronic algorithm was adjudicated by a board certified electrophysiologist for accuracy.

Results: Among 52 patients with a history of ischemic stroke or TIA (mean age 68±14 years, 58% male, 83% white), there were 166 rhythm strips identified as atrial fibrillation by the Medtronic algorithm which were adjudicated. Of the 166 strips reviewed, 140 (84%) were incorrectly identified as atrial fibrillation; of those false positives, adjudication identified 57% as premature atrial complexes(PACs), 22% as T wave over-sensing, 10% due to noise, 5.0% due to premature ventricular complexes (PVCs), 2.9% due to under-sensing, and 2.9% due to sinus arrhythmia. Of the 38 (73%) patients who had ILR implantation for cryptogenic stroke, 4 (11%) were identified as having true atrial fibrillation by ILR after adjudication over 413 patient-months of monitoring; mean time to atrial fibrillation detection was 93 days after implantation.

Conclusions: Stroke patients who undergo Medtronic ILR placement have high false positive rates of atrial fibrillation detected with the Medtronic algorithm. When adequately reviewed by a trained cardiologist for accuracy, the Medtronic ILRs remain effective at detecting atrial fibrillation in cryptogenic stroke patients.

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