Progression of Device-Detected Subclinical Atrial Fibrillation and the Risk of Heart Failure

Background: Long-term continuous monitoring detects short-lasting, subclinical atrial fibrillation (SCAF) in approximately one-third of older individuals with cardiovascular conditions. The relationship between SCAF, its progression, and the development of heart failure (HF) is unclear.

Objectives: This study examined the relationship between progression from shorter to longer SCAF episodes and HF hospitalization.

Methods: Subjects in ASSERT (Asymptomatic Atrial Fibrillation and Stroke Evaluation in Pacemaker Patients and the Atrial Fibrillation Reduction Atrial Pacing Trial) were ≥65 years old, had history of hypertension, no prior clinical AF, and an implanted pacemaker or defibrillator. We examined patients whose longest SCAF episode during the first year after enrollment was >6 min but ≤24 h (n = 415). Using time-dependent Cox models, we evaluated the relationship between subsequent development of SCAF >24 h or clinical AF and HF hospitalization.

Results: Over a mean follow-up of 2 years, 65 patients (15.7%) progressed to having SCAF episodes >24 h or clinical AF (incidence 8.8% per year). Older age, greater body mass index, and longer SCAF duration within the first year were independent predictors of SCAF progression. The rate of HF hospitalization among patients with SCAF progression was 8.9% per year compared with 2.5% per year for those without progression. After multivariable adjustment, SCAF progression was independently associated with HF hospitalization (hazard ratio [HR]: 4.58; 95% confidence interval [CI]: 1.64 to 12.80; p = 0.004). Similar results were observed when we excluded patients with prior history of HF (HR: 7.06; 95% CI: 1.82 to 27.30; p = 0.005) or when SCAF progression was defined as development of SCAF >24 h alone (HR: 3.68; 95% CI: 1.27 to 10.70; p = 0.016).

Conclusions: In patients with a pacemaker or defibrillator, SCAF progression was strongly associated with HF hospitalization.