Rhythm control in atrial fibrillation: endpoints for device-based trials.

Newer generations of pacemakers and implantable cardioverter defibrillators have enhanced diagnostic features that permit detection and storage of information about the frequency, duration, time of onset, and rate characteristics of multiple consecutive episodes of atrial tachycardia and atrial fibrillation (AF). Parameters available in implantable devices that might serve as outcome measures to assess the impact of pharmacologic and nonpharmacologic therapies for prevention of AF include time to first recurrence of AF, intervals between successive episodes of AF, AF frequency, AF duration, AF burden (amount/unit time), and episodes of symptomatic AF. Each parameter has advantages and limitations. The characteristics/temporal patterns of AF may determine the ideal study outcome measure to address a specific hypothesis. Clinical studies of therapies for prevention of AF need to be directed to populations with the arrhythmia substrate that will be targeted by the therapy. Device-based metrics are suitable to assess the impact of pacing or pharmacologic therapies for prevention of AF. However, it is important to establish that suppression of AF is associated with an improvement in some clinical outcome. Relevant outcomes might include improvement in symptoms, quality of life, or functional capacity; reduction in hospitalization for cardiovascular causes, stroke death, or overall mortality; or a composite of some of these parameters.