Subclinical Atrial Fibrillation in Older Patients
How common is subclinical atrial fibrillation (SCAF) in patients 65 years of age or older with no history of atrial fibrillation (AF)?
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.
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.
SCAF is common in patients ≥65 years old who have cardiovascular or AF risk factors, but the clinical significance of the SCAF is unclear.
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.
< Back to Listings