Can We Rely Onmachines? Device-detected Atrial High Rates Correspond Well With Atrial Arrhythmias in Cardiac Resynchronization Recipients

Ewa Jędrzejczyk-Patej; Radosław Lenarczyk; Michał Mazurek; Agnieszka Liberska; Katarzyna Przybylska-Siedlecka; Tomasz Podolecki; Jacek Kowalczyk; Adam Sokal; Anna Leopold-Jadczyk; Oskar Kowalski; Zbigniew Kalarus


Europace. 2016;18(3):436-444. 

In This Article

Abstract and Introduction


Aims The aim of the study was to verify in what proportion of patients, device-detected atrial high rate (AHR) episodes are indeed atrial arrhythmias (AAs). We investigated also the reasons for inappropriate arrhythmia classification and assessed if patients with misdiagnosed arrhythmias have distinct characteristics that would help to identify them.

Methods and results The study population consisted of 304 consecutive patients implanted with cardiac resynchronization therapy defibrillators (CRT-Ds) and subsequently monitored via remote monitoring for a median follow-up (FU) of 30.5 months. Intracardiac electrograms of every recorded AHR episode were assessed and classified (AA vs. no AA) by two experienced cardiologists. During FU, 14 386 episodes of AHR were recorded and classified in 176 (57.9%) patients. In 89.2% of them, these episodes were true AA (94% atrial fibrillation, 62% de novo). The reasons for AHR misdiagnosis were atrial far-field signals (89.5%) and noise (10.5%). The mean per cent of day spent in AHR (54.9 vs. 5.86%; P < 0.001) and the occurrence of periods with low CRT pacing (82.8 vs. 55%; P = 0.003) were significantly higher in AA subjects than in those with misdiagnosed AHR. Episode duration of properly detected AHRs was longer than that of misdiagnosed AHRs. Higher per cent of time spent in AHR was an independent marker of appropriate arrhythmia detection [adjusted hazard ratio (HR) 1.04; P = 0.023].

Conclusion Nearly two-thirds of CRT-D patients had AHR episodes within 2.5 years after implantation. Almost 90% of AHRs were indeed AA. Misdetections were caused by far-field sensing or noise. A two-step diagnostic algorithm (>9% of time spent in AHRs and episode duration >36 s) allowed for proper detection of AA with a high hit-rate and specificity.


Atrial fibrillation (AF) is the most common arrhythmia in patients with heart failure (HF) and is associated with an increased risk of mortality in those subjects.[1–3] Recent technological advances have made it possible to track even short arrhythmic episodes using specific algorithms implemented into modern cardiac implantable devices. Consequently, it has become clear that AF occurrence is much higher than it was previously thought to be, and that assessment, based on standard electrocardiograms (ECGs) or Holter monitoring only, tends to underestimate the occurrence thereof. Some studies showed that short, asymptomatic AF as many episodes occur in as many as 5–49.5% of patients.[4–7] As many episodes of arrhythmia are asymptomatic and as recent data show that even short periods in arrhythmia can have serious consequences, monitoring of asymptomatic AF is of constantly growing interest.[8,9] Currently used devices recognize arrhythmias on the basis of specific algorithms, which may be unreliable, leading to arrhythmia misdiagnosis. Moreover, intracardiac electrograms (EGMs) are often lacking, making the verification impossible. Because both missed AF (leading, for example, to delay in institution of anticoagulation) and overestimated occurrence of arrhythmia (with unnecessary anticoagulation) can have serious consequences, it seems crucial to explore the relation between device-detected atrial high rate (AHR) episodes and the real incidence of AF.

The aim of this study was to verify in what proportion of patients device-detected AHRs are indeed atrial arrhythmias (AAs). We aimed also to investigate the reasons for inappropriate arrhythmia classification and to assess if patients with misdiagnosed arrhythmias have distinct characteristics.