Subclinical Atrial Fibrillation in Older Patients

Study Questions:

How common is subclinical atrial fibrillation (SCAF) in patients 65 years of age or older with no history of atrial fibrillation (AF)?

Methods:

In this multicenter study, a subcutaneous electrocardiographic monitor was implanted in 256 patients ≥65 years old (mean 76 years) who had ≥2 risk factors for stroke, sleep apnea, or body mass index >30 kg/m2 and also had either left atrial enlargement (volume ≥58 ml or diameter ≥4.4 cm) or serum N-terminal pro–B-type natriuretic peptide ≥290 pg/ml. The patients were monitored for SCAF lasting ≥5 minutes over a mean follow-up of 16.3 months.

Results:

The incidence of SCAF at 1 year was 31%. The mean duration of the longest episode was 62 minutes and the median weekly burden in patients with SCAF was 3.4 minutes. The annual incidence of SCAF lasting ≥6 hours was 7.1%, with an annual incidence of 2.7% for episodes lasting ≥24 hours. Clinically apparent AF occurred at a rate of 7.9%/year. The independent predictors of SCAF were age, left atrial size, and a lower systolic blood pressure. There was no association between SCAF and a history of stroke. None of the four patients who had a stroke during follow-up had SCAF.

Conclusions:

SCAF is common in patients ≥65 years old who have cardiovascular or AF risk factors, but the clinical significance of the SCAF is unclear.

Perspective:

An important finding of this study is that SCAF was not more common among the patients with a prior stroke. A subcutaneous monitor often is implanted in patients with cryptogenic stroke to see whether AF could have been the cause of the stroke. Given how frequently SCAF is detected with long-term monitoring, however, it cannot be assumed that AF is causal in patients with a cryptogenic stroke. A determination of whether anticoagulation is useful in patients with SCAF awaits completion of ongoing clinical trials.


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