806Implantable loop recorders and short episodes of rapid atrial rate: relevant in the medical work-up of patients with embolic strokes of unknown source

Abstract

BACKGROUND: Embolic strokes of unknown source (ESUS) account for up to 25% of cases, and subclinical asymptomatic atrial fibrillation episodes may be the etiologic factor. Rapid atrial rate (RAR) episodes longer than 6 minutes are found in ESUS patients and are known to have clinical significance, but do shorter RAR episodes mean anything? And what is the appropriate length of time to look for RAR? PURPOSE: To establish the significance of short episodes of RAR (≥2 minutes and <6 minutes) in this group of patients and the length of time needed to detect RAR episodes in more than 50% of patients. METHODS: we performed a unicentric prospective observational study in a tertiarycare center from 2012 to 2015, with patients who were diagnosed with an ESUS after diagnostic work-up with brain CT-scan or MRI scan, supra-aortic and intracranial arteries ultrasound or angio-CT scan, on top of transthoracic echocardiography and 24-hour Holter monitoring didn't find a source of stroke. All of them received an implantable loop recorder (ILR) and were followed via remote monitoring. Rapid atrial rate (RAR) episodes were assessed by two electrocardiography experts, and patients with true AF episodes of ≥ 2 minutes were selected and studied. ILRs were monitored until RAR episodes were found, or battery end-of-life was reached. RESULTS: 244 patients with ESUS received an ILR. Episodes of RAR were found in 124 patients, out of whom 63 had real RAR episodes. 26 (41.3%) patients had a first short episode (SE) (≥2 minutes and <6 minutes) of RAR, and during follow up 15 (57.7%) of these patients developed a long episode (LE) (≥ 6 minutes) of RAR; whereas 33 of the 37 (89.2%) patients that had a first LE of RAR continued having them during follow up (p=0.004). 75% of the patients that had an RAR episode developed it before 10-month follow up, and 95% of them by 28-month follow-up. Only 50% of patients that had a LE of RAR developed it during the first 6 months since implantation of ILR, with more than 95% of them having a LE of RAR by 33-month follow up. CONCLUSIONS: SEs of RAR were predictive of developing LEs of RAR during follow- up. We recommend a follow-up period of ≥ 6 months, preferably ≥ 2 years with ILRs given that almost all of the RAR episodes reported developed in this time frame. (Figure presented).