Subclinical Atrial Fibrillation and the Risk of Stroke

Jan 11, 2012
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Authors:
Healey JS, Connolly SJ, Gold MR, at al.
Citation:
N Engl J Med 2012;366:120-129.
Summary By:
Fred Morady, MD, FACC

Study Questions:

Do asymptomatic episodes of atrial tachyarrhythmia (AT) detected by a pacemaker or implanted cardioverter-defibrillator (ICD) increase the risk of stroke?

Methods:

The subjects of this study were 2,580 patients who underwent implantation of a pacemaker or ICD. The selection criteria were age ≥65 years (mean age 76 years), hypertension, and no history of atrial fibrillation (AF). A subclinical AT was defined as an asymptomatic atrial high-rate event >190 bpm lasting >6 minutes. Patients in whom ATs were noted at 3 months of follow-up were randomly assigned to receive or to not receive continuous atrial overdrive pacing. The primary outcome was ischemic stroke or systemic embolism.

Results:

Subclinical ATs (median of two/patient, mean rate 480 bpm) were noted in 10.1% of patients at 3 months of follow-up. During the entire follow-up, subclinical ATs were noted in 34.6% of patients and clinical AF occurred in 15.7% of patients. During a mean of 2.5 years of follow-up, the annual risk of stroke/embolism was significantly higher in patients with than without a subclinical AT detected at 3 months (1.7% vs. 0.7%, hazard ratio [HR], 2.5). During follow-up, AT episodes >6 minutes, >6 hours, and >24 hours in duration were associated with a similar degree of increased risk of stroke/embolism (HRs 1.8, 2.0, and 2.0, respectively). Continuous atrial overdrive pacing did not prevent ATs.

Conclusions:

The authors concluded that asymptomatic AF detected by cardiac devices is associated with an increased risk of stroke/embolism.

Perspective:

Because only AT episodes longer than 6 minutes were included in the analysis, the minimum duration of subclinical ATs associated with thromboembolic complications is unclear. Whether anticoagulation has a net benefit in patients with subclinical ATs also remains to be determined.

Keywords: Risk, Stroke, Defibrillators, Follow-Up Studies, Heart Atria, Tachycardia, Thromboembolism, Blood Coagulation, Cardiology, Pacemaker, Artificial, Hypertension


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