Abstract 16245: Manifest Atrial Fibrillation Develops Without a Preceding Increase in AF Burden: The IMPACT Substudy on the Natural History of Atrial Fibrillation
Atrial fibrillation (AF) is generally considered to be a progressive syndrome evolving from manifest paroxysmal episodes that ultimately become persistent. It is also believed that the development of AF is preceded by an increasing burden of atrial high rate events (AHRE). We studied the natural history of AF development in patients with implantable defibrillators from their first AHRE to their first true manifest AF that we defined as an episode of 24 hours or longer. To this date, the IMPACT trial has enrolled 2,105 patients undergoing implantation of a dual chamber ICD (64%) or biventricular CRT-D (36%) device with Home Monitoring technology. Development of manifest AF was studied in 909 patients with ≥ 90% transmission rates. The AHRE burden was defined as the mean percentage of AHRE duration over a 24 hour period from enrollment to the onset of manifest AF. AHRE was defined as any atrial episode with at least 36 out of 48 beats over 200 bpm. The results show that manifest AF developed 1) in 41 patients (4.5%) over a follow-up period of 22.1±11.3 months; 2) 7.6±8.3 months following initiation of home monitoring; and 3) with no preceding AHRE episodes in 34% of patients. In an additional 12% of patients, the first AHRE episode occurred within the 24 hours before the development of manifest AF. Additionally, 76% of patients had less than 20 episodes over the time period between enrollment and the development of manifest AF. Also, in 76% of patients who developed manifest AF, the mean AHRE duration was less than 10 mins, and only 22% had a mean AHRE duration greater than 60 mins. All patients (100%) had an overall AHRE burden of <10% prior to the onset of manifest AF, and 95% of patients had an overall AHRE burden of <5%. In conclusion, in almost half of the patients, manifest AF occured as the first manifestation of the arrhythmia or developed within 24 hours of the first AHRE episode. The development of manifest AF is usually not preceded by an increase in AHRE burden. Hence AHRE burden neither correlates with nor predicts the development of manifest AF. These results support the clinical utility of routine, vigilant, daily home monitoring for early detection of manifest AF in the majority of patients with implanted defibrillators.
- © 2012 by American Heart Association, Inc.