Original-clinicalComparison of continuous versus intermittent monitoring of atrial arrhythmias
Introduction
Atrial tachycardias (AT) and atrial fibrillation (AF) are the most commonly diagnosed arrhythmias, resulting in significant morbidity and cost to the health care system.1 Furthermore, patients with AT/AF are at an increased risk for stroke and mortality.2 However, numerous studies have indicated that the vast majority of AT/AF episodes are asymptomatic,3, 4, 5 including many episodes of clinically significant duration.6 In patients without implantable devices, intermittent external monitoring is often used to determine the existence of asymptomatic AT/AF, but the ability of these techniques to identify patients with AT/AF has not been quantified. Accurate identification of asymptomatic AT/AF is of primary importance for guiding anticoagulation therapy in patients with clinical risk factors.7
The current guidelines for anticoagulation management8 do not differentiate between patients with symptomatic or asymptomatic AT/AF because asymptomatic (or silent) AT/AF is equally associated with increased stroke risk.9 Furthermore, the guidelines recommend anticoagulation therapy for patients with paroxysmal atrial fibrillation and risk factors irrespective of the arrhythmia duration or burden. In fact, a study showed that the risk of death or stroke was higher in patients with atrial high rate episodes as brief as 5 minutes in duration.10 Therefore, identification of patients with any amount of asymptomatic AT/AF is clinically important. Conversely, accurate long-term identification of patients who are free from any AT/AF also may be clinically important if discontinuation of anticoagulation is desired in order to reduce bleeding complications, when appropriate. Whether it is safe for patients with certain durations or burden of AT/AF not to undergo anticoagulation therapy currently is a topic of study and debate. Although limited clinical data support that lesser amounts of AT/AF may confer a lower stroke risk, one study has shown an increased risk for embolism in patients with device-detected AT/AF episodes lasting longer than 1 day.11 A larger clinical trial presently is underway to further assess the relationship between device-recorded AT/AF burden and stroke risk.12 In addition, changes in AT/AF burden have been shown to correlate with changes in cardiac hospitalization rates,13 suggesting that it may be a surrogate for clinical outcomes when maintenance of sinus rhythm is the therapeutic goal. Therefore, identification of patients with longer-duration episodes of AT/AF and accurate estimates of AT/AF burden may be of clinical importance as more data supporting their relevance become available.
Common methods of atrial arrhythmia monitoring include intermittent 24-hour Holter monitoring, infrequent periods of long-term monitoring (e.g., 7-day or 30-day recordings), and the transient use of event monitors when symptoms are present. Each method presents significant limitations for the diagnosis and quantification of atrial arrhythmias. The ability of Holter monitoring to diagnose and quantify AT/AF is highly dependent on whether or not the day(s) selected for monitoring coincides with a cluster of AT/AF episodes. External recorders now are capable of recording for up to 30 days and have been shown to increase the yield for arrhythmia detection compared with a single 24-hour Holter monitor.14 However, these external devices often are bulky and interfere with showering and other daily activities. In addition, the patch electrodes can cause skin irritation over such prolonged usage. As a result, patient compliance with such systems often is relatively low.5 Data suggest that the vast majority of AT/AF episodes are asymptomatic and that most symptoms attributed to AT/AF actually are not associated with the arrhythmia.3, 5 Therefore, monitoring of AT/AF episodes based on only symptomatic events will adversely affect the reliability of identifying patients with AT/AF. In contrast, chronic monitoring with implantable devices has been demonstrated to have both high sensitivity and specificity for AT/AF detection.15, 16 Although these devices require an invasive implant procedure, patient compliance is generally not an issue, and these devices rarely interfere with normal daily activities.
The objectives of this investigation were to compare intermittent and symptom-based monitoring to continuous monitoring for (1) identification of patients with any AT/AF, (2) identification of patients with long-duration AT/AF (≥21.6 hours of AT/AF [90%] on at least 1 day), and (3) assessment of AT/AF burden. The various methods of noninvasive monitoring that were simulated included intermittent (annual, quarterly, and monthly) 24-hour Holter recordings, annual long-term recordings (7-day and 30-day duration), and symptom-based monitoring.
Section snippets
Study design
Data from 574 pacemaker (AT500, Medtronic, Inc., Minneapolis, MN, USA) patients with a bradycardia pacing indication, at least one symptomatic AT/AF episode in the 3 months prior to implant, and more than 365 days of device follow-up data were analyzed retrospectively.
The AT500 device has an algorithm to detect AT/AF using both rate and pattern information obtained from dual-chamber bipolar electrograms. The detection criteria require >1:1 AV conduction for a minimum of 24 ventricular cycles.
Results
Patient demographics and baseline antiarrhythmic drug use are given in Table 1. Baseline programming of device parameters is given in Table 2.
Key results
The primary findings from this investigation are that commonly used methods of intermittent and symptom-based monitoring are quite inaccurate in identifying patients with any AT/AF or long-duration AT/AF and in assessing AT/AF burden. However, identification of patients with AT/AF and assessment of AT/AF burden improve as the frequency or duration of intermittent monitoring increase and as the patient’s actual AT/AF burden increases.
Identification of patients with AT/AF by intermittent and symptom-based monitoring
Identifying patients with any AT/AF is clinically important
Conclusion
The highly variable recurrence patterns of AT/AF episodes do not lend themselves to accurate monitoring on an intermittent basis. All methods of intermittent monitoring in this analysis identified significantly fewer patients with any or long-duration AT/AF episodes and provided inaccurate assessments of AT/AF burden compared to continuous monitoring with an implantable device. In addition, chronic monitoring with implantable devices eliminates many of the patient compliance or tolerance
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All authors are employees and shareholders of Medtronic, Inc.