Digital implantable loop recorders in the investigation of syncope in children: benefits and limitations.

BACKGROUND: Conventional diagnostic methods for detecting arrhythmogenic causes of syncope in children are poor. Digital implantable loop recorders are of proven value in adults.

OBJECTIVES: The purpose of this study was to evaluate digital implantable loop recorders in the investigation of syncope in children.

METHODS: We reviewed the clinical and technical records of 18 consecutive patients (6 female and 12 male; age
RESULTS: Median age at implantation was 11.3 years (range 4.6-16.5 years). Median duration of the device in situ was 18 months (range 5-36 months). Median time to diagnosis was 6 months (range 1 day to 17 months). Two patients had a congenital heart defect. Ten children (56%) had an event, 9 (50%) of whom had diagnostic information; 5 (28%) had profound bradycardia or asystole; 2 (11%) had polymorphic ventricular tachycardia (VT); and 1 child had supraventricular tachycardia. One patient died, but the automatically activated recording was recorded over again after death. One child had sinus rhythm during syncope. One child with polymorphic VT had no auto-activation on two occasions, and the third activation was triggered by asystole after VT terminated. Sixteen patients (89%) had false-positive activations as a result of either artifact or sinus tachycardia.

CONCLUSION: The digital implantable loop recorder is a useful diagnostic modality in children with unexplained syncope. However, the automatic detection algorithm is imperfect, missing genuine polymorphic VT and frequently interpreting muscle tremors as VT. Because of continuous overwriting by automatic detection, genuine arrhythmias may be over-recorded by artifact.