Temporal Relationship between Subclinical Atrial Fibrillation and Embolic Events
Background—Among patients with implantable pacemakers and defibrillators, sub-clinical atrial fibrillation (SCAF) is associated with an increased risk of stroke; however, there is limited understanding of their temporal relationship.
Methods and Results—The ASSERT trial enrolled 2580 pacemaker and defibrillator patients ≥ 65 years old, with a history of hypertension, but without a history of atrial fibrillation. Pacemakers and ICDs precisely logged the time and duration of all episodes of SCAF and recorded electrograms which were adjudicated by experts. We examined the temporal relationship between SCAF > 6 minutes in duration and stroke or systemic embolism. Of 51 patients who experienced stroke or systemic embolism during follow-up; 26 (51%) had SCAF. In 18 patients (35%) SCAF was detected prior to stroke or systemic embolism. However, only 4 patients (8%) had SCAF detected within 30 days prior and only one of these 4 patients was experiencing SCAF at the time of their stroke. In the 14 patients with SCAF detected more than 30 days prior to stroke or systemic embolism, the most recent episode occurred at a median interval of 339 days (P25-P75: 211-619) earlier. Eight patients (16%) had SCAF detected only after their stroke, despite continuous monitoring for median duration of 228 (P25-P75: 202-719) days prior to their event.
Conclusions—Although SCAF is associated with an increased risk of stroke and embolism, very few patients had SCAF in the month prior to their event.
Clinical Trial Registration—http://www.clinicaltrials.gov. Identifier: NCT00256152.
- Received November 29, 2013.
- Revision received February 11, 2014.
- Accepted March 4, 2014.