Extended ECG monitoring with an implantable loop recorder in patients with cryptogenic stroke: time schedule, reasons for explantation and incidental findings (results from the TRACK-AF trial).

Background: Implantable loop recorders (ILR) may be used to detect occult atrial fibrillation (AF) in patients with cryptogenic stroke. At present, there has been no description on the incidental findings of stored episodes in these patients. Furthermore, no standard practice has been established with respect to the duration of continued ECG monitoring in these patients.
Materials and Methods: In the prospective monocentric study (TRACK-AF), a total of 173 patients with cryptogenic stroke received an ILR for detection of AF between November 2010 and December 2014. Before implantation all patients had undergone recommended protocols for detection of stroke causes.
Results: During a mean follow-up of 24.8 ± 11.5 months, atrial tachyarrhythmias were detected in n = 33 pts (19.1%). Diagnosis of AF was made after a mean of 10.7 ± 11.4 months, time to first AF detection ranged between 0.2 and 39.8 months. In 15 patients (8.7%), other incidental findings were stored in the ILR memory. Short episodes of sinus arrest at night not requiring a permanent pacemaker were present in 8 pts (4.6%). DDD-pacemaker implantation due to sinus arrest or symptomatic bradyarrhythmias occurred in 5 patients (2.9%) after a median monitoring period of 23.1 ± 7.4 months. Further incidental findings were atrial flutter and an AV-nodal-reentry tachycardia in one patient, respectively. Both patients underwent successful catheter ablation. So far, ILR were explanted in 111 pts, and 71 ILR were explanted before end of service status of the battery. Main reason for ILR explantation was patients' preference (51%), followed by battery depletion (24%) and diagnosis of AF (15%).
Conclusion: The present study revealed a significant number of ECG findings during continued ECG monitoring for AF in patients with cryptogenic stroke. Apart from AF (17.5% during the first 1.5 years), other clinical relevant arrhythmias requiring, e.g., pacemaker implantations, were observed. With respect to these findings, we recommend to extend ILR monitoring to the end of battery life. However, acceptance of continued ECG monitoring until battery depletion was poor; in 71 patients (64%), the ILR were explanted before the end of battery life.
Trial Registration: Registered at ClinicalTrials.gov: NCT02641678.