As Detection Improves, Is Any AF Problematic? The Short Answer is No (ACCEL)

  • RATE is a prospective, outcome-oriented registry designed to document the prevalence of atrial tachycardias and AF with associated clinical data, in a large group of patients with implanted cardiac rhythm management devices.
  • These devices are highly effective at detecting asymptomatic arrhythmias, but what is the clinical significance of subclinical events?
  • The RATE data suggest that asymptomatic "short" episodes of AF are common but not associated with any greater risk of adverse events than patients without arrhythmias; "long" asymptomatic episodes, however, are associated with increased risk.
  • Atrial fibrillation (AF) is often asymptomatic. In patients with implanted pacemakers and defibrillators, accurate documentation of asymptomatic episodes provides the opportunity to better understand AF burden and its clinical consequences. The Registry of Atrial Tachycardia and Atrial Fibrillation Episodes (RATE) is designed to follow at least 5,000 patients with pacemakers, defibrillators, and resynchronization devices for 2 years.1

    More accurate detection of asymptomatic episodes of AF raises important issues in clinical decision making:

    • What is the appropriate reaction of the clinician and patient to the discovery at a routine office visit of asymptomatic AF?
    • Should the trigger be pulled for anticoagulant therapy?
    • There are widely disseminated anticoagulation guidelines for balancing risk of stroke in patients with AF and the risks of anticoagulation. But how much AF burden needs to be present to invoke the guidelines?
    • Permanent or persistent AF seems clear, but what about a single long episode with no further episodes in a patient who has an implanted device to detect even asymptomatic recurrences? What about more frequent episodes that only last a few seconds or minutes?

    Investigators hypothesized that atrial tachycardia (AT)/AF episodes in the RATE population would be associated with pre-specified adverse events, including progression from asymptomatic to symptomatic or sustained AF, hospitalizations for AT/AF, HF, stroke, and death. Besides telling a lot about such events, data accumulated in RATE were designed to allow quantitative characterization of atrial tachyarrhythmias, including atrial rates, duration, frequency of occurrence, and time of day.

    As a registry, it also would allow analyses of clinical associations with atrial tachyarrhythmias, as well as proposed measures of arrhythmia burden in the device population, including relationships with symptoms, quality of life, outcomes, and treatments (both pharmacologic and device based) the patients receive.

    RATE Registry

    A total of 5,379 patients were enrolled, including 3,141 with pacemakers and 2,238 with implantable cardioverter-defibrillators (ICDs), and median follow-up was 23.6 months. Data collected included 2,232 hospitalizations and 11 in-hospital deaths. A total of 20,153 ECGs were adjudicated, with another 350 electrocardiograms not adjudicated for patients who died out of the hospital.

    In data presented at AHA.12, Steven Swiryn, MD, said AT/AF was documented in half of the device population at 2 years. Short episodes were defined as those that began and ended within one ECG tracing; long episodes were those lasting more than one tracing. Patients with only short AT/AF episodes were not at greater risk of adverse events than those without AT/AF. However, long episodes of AT/AF were associated with adverse clinical events, including a higher rate of any adverse event in both the pacemaker and ICD groups as well as a greater risk of hospitalization for clinical AT/AF in the ICD group.

    For ICD patients, a number of long AT/AF episodes greater than the median was associated with greater risk of any adverse events and AF hospitalizations.

    In an analysis of RATE data presented at the May 2013 Heart Rhythm Society meeting, subclinical arrhythmias were common; only short AT/AF episodes were documented in 12% of patients.


    1. RATE Steering Committee; RATE Investigators. Am Heart J. 2009;157:983-7.

    To listen to an interview with Steven Swiryn, MD, about detecting atrial tachycardia and atrial fibrillation, visit  The interview was conducted by Albert L. Waldo, MD.

    Keywords: Registries, Stroke, Follow-Up Studies, Decision Making, Quality of Life, Documentation, Atrial Fibrillation, Pacemaker, Artificial, Electrocardiography, Hospitalization, Defibrillators, Implantable

    < Back to Listings