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 PocketECGTM 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.

The importance of the longest R-R interval on 24-hour electrocardiography for mortality prediction in patients with atrial fibrillation.

BACKGROUND: Heart rate control in atrial fibrillation (AF) is typically assessed by 24­hour electrocardiography (ECG). There are scarce data on the use of 24­hour ECG parameters to predict mortality in patients with AF. AIMS: We aimed to identify 24­hour ECG parameters that predict mortality in patients with AF. METHODS: We enrolled 280 ambulatory patients (mean [SD] age, 72 [8.7] years; 57.9% men) with permanent or persistent AF. Data on mortality and pacemaker or defibrillator implantation during follow­up were collected. Predictors of mortality were assessed using the Cox proportional hazards model and C statistic. RESULTS: Compared with survivors, 78 patients (28%) who died were older, more often had comorbidities, left bundle branch block (LBBB), reduced left ventricular ejection fraction, lower maximum heart rate, higher number of ventricular extrasystoles, and the longest R­R interval below 2 seconds. Univariate analysis showed higher mortality in patients with the longest R­R intervals below 2 seconds compared with those with R­R intervals of 2 seconds or longer (P <0.001). Independent mortality predictors in the regression model included older age, renal failure, history of coronary intervention, chronic obstructive pulmonary disease, LBBB, and a high number (≥770) or absence of R­R intervals of at least 2 seconds. The area under the curve for mortality prediction increased after including ECG parameters (0.748; 95% CI, 0.686-0.81; vs 0.688; 95% CI, 0.618-0.758; P = 0.02). CONCLUSIONS: A high number of R­R intervals longer than 2 seconds or their absence on 24­hour ECG may predict mortality in patients with AF.