Tachycardia detection performance of implantable loop recorders: results from a large real-life patient cohort and patients with induced ventricular arrhythmias

Implantable loop recorders (ILRs) are valuable for diagnosing arrhythmias. We evaluated tachycardia detection performance of the Medtronic Reveal ILR with FullView Software. The rate of occurrence of tachycardia detection [supraventricular tachycardia, ventricular tachycardia (VT), and ventricular fibrillation (VF)] and the percentage of appropriately detected tachycardias were determined from all 2190 ILR patients that transmitted to CareLink over a 4-month period (total follow-up 135.6 patient-years). All 1909 tachycardia episodes were reviewed. Episodes with actual heart rate above the programmed tachycardia detection rate were classified as appropriate. Sensitivity to detect true ventricular arrhythmias was assessed in another group of 215 patients undergoing implantable cardioverter defibrillator (ICD) implant testing. Skin electrodes represented ILR electrodes. Induced VF (404 episodes) and VT (93 episodes) were processed by an emulation of FullView Software. Generalized estimation equation analysis adjusted for multiple episodes per patient. In the CareLink cohort, 68.7 (63.9 adjusted) of detected episodes had tachycardia above the detection rate. Of 1642 episodes detected in the VT zone (12.1 episodes/patient-year), 78.8 (79.0 adjusted) had tachycardia above the detection rate. Of 267 episodes detected in the fast VT zone (1.9 episodes/patient-year), 6.7 (9.4 adjusted) had tachycardia above the detection rate. Twelve true VT/VF episodes were observed in 10 patients. In the ICD patient cohort, 95.9 (96.5 adjusted) of induced VT/VF segments were correctly detected at nominal rate cutoffs. When VT detection was set to 130 b.p.m. (to include the slowest VT), 99.0 (99.3 adjusted) were correctly detected. The majority (63.9) of detected tachycardias contained true tachycardia. Sensitivity to detect induced VT/VF was 99.3.