Temporal Relationship Between Subclinical Atrial Fibrillation and Embolic Events
How often are episodes of subclinical atrial fibrillation (SCAF) detected by a pacemaker or implantable cardioverter-defibrillator (ICD) the direct cause of a stroke or systemic embolism?
This was a post hoc analysis of 51 patients (mean age 77 years) who had a stroke or systemic embolism during a clinical study (ASSERT) designed to investigate the prevalence and clinical significance of SCAF in patients not taking an anticoagulant. The date and duration of all episodes of SCAF were determined by device interrogation.
SCAF occurred before the stroke or embolism in 18 (35%) of the 51 patients and within the 30 days prior to the stroke or embolism in only four patients (8%). In the other 14 patients, the SCAF (median duration 4.2 hours) preceded the stroke/embolism by >30 days (median 339 days). Only one patient had an episode of SCAF lasting >24 hours within 30 days prior to an embolic event. SCAF was detected after the stroke/embolism in 8/51 patients (16%).
The authors concluded that SCAF infrequently can be implicated as the direct cause of a stroke.
The ASSERT trial demonstrated that SCAF is associated with a 2.5-fold increase in the risk of stroke or embolism. However, based on the results of the present analysis, it appears that SCAF is often a marker of increased stroke/embolism risk instead of the direct cause of the stroke/embolism. Possible mediating factors include atrial fibrosis or hypercoagulability. Whether anticoagulation therapy can reduce the risk of stroke/embolism in patients with SCAF as yet is unclear.
Keywords: Stroke, Pacemaker, Artificial, Embolism, Defibrillators, Implantable
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