Diagnostic yield is dependent on monitoring duration. Insights from a full-disclosure mobile cardiac telemetry system

Background: Despite the advancement of electrocardiogram (ECG) monitoring methods, the most important factor influencing diagnostic yield (DY) may still be monitoring duration. Ambulatory ECG monitoring, typically with 24–48 hours duration, is widely used but may result in underdiagnosis of rare arrhythmias. Aims: This study aimed to examine the relationship between the DY and monitoring duration in a large patient cohort and investigate sex and age differences in the presentation of arrhythmias. Methods: The study population consisted of 25 151 patients (57.8% women; median [interquartile range, IQR], 71 [64–78] years), who were examined with mobile cardiac telemetry during 2017 in the United States, using the PocketECG^TM that continuously transmits a signal on a beat-to-beat basis. We investigated the occurrence of atrial fibrillation at a burden of both ≤1% (atrial fibrillation [AF], ≤1%) and ≤10% (AF ≤10%), premature ventricular contractions (PVC; >10 000 per 24 hours), non-sustained ventricular tachycardias (nsVT), sustained ventricular tachycardias (VT ≥30 seconds), atrioventricular blocks (AVB), pauses of >3 seconds duration, and bradycardia (heart rate <40 beats per minute for ≥60 seconds). Results: The median (IQR) recording duration was 15.4, 8.2–28.2) days. The DY increased gradually with monitoring duration for all types of investigated arrhythmias. Compared to DY after up to 30 days of monitoring, a standard 24 hours monitoring resulted in DY for males/females of 20%/18% for AF ≤1%, 29%/28% for AF ≤10%, 45%/40% for PVCs, 17%/11% for nsVT, 17%/11% for VT ≥30 seconds, 49%/42 for AVB, 27%/20% for pauses, 36%/29% for bradycardia. Conclusion: A substantial number of patients suffering from arrhythmias may remain undiagnosed due to insufficient ECG monitoring time.