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.