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Progression of Subclinical AF and Risk of HF
Study Questions:
What is the relationship between progression from shorter to longer subclinical atrial fibrillation (SCAF) episodes and heart failure (HF) hospitalizations?
Methods:
The study cohort was comprised of 2,580 subjects enrolled in ASSERT (Asymptomatic Atrial Fibrillation and Stroke Evaluation in Pacemaker Patients and the Atrial Fibrillation Reduction Atrial Pacing Trial), and these subjects were ≥65 years, had a history of hypertension, no prior clinical AF, and an implanted pacemaker or defibrillator. The study authors evaluated the predictors of SCAF progression, defined as the development of at least one episode of SCAF >24 hours in duration or clinical AF in patients previously monitored for 1-4 year in which they only experienced SCAF between 6 minutes and 24 hours, as well as the relationship between SCAF progression and HF hospitalization. The study authors examined patients whose longest SCAF episode during the first year after enrollment was >6 minutes, but ≤24 hours (n = 415). Using time-dependent Cox models, they evaluated the relationship between subsequent development of SCAF >24 hours or clinical AF and HF hospitalization.
Results:
In the first year from enrollment, 415 patients (mean age 76.7 ± 6.6 years) had SCAF lasting between 6 minutes and 24 hours. Over a mean follow-up of 2 years, 65 patients (15.7%) progressed to having SCAF episodes >24 hours or clinical AF (incidence 8.8%/year). Among the patients who progressed, 60 patients developed SCAF >24 hours, 25 patients developed clinical AF, and 20 patients developed both. Compared to patients who did not progress, patients with SCAF progression had greater median longest SCAF episode duration within the first year of enrollment (6.7 [IQR 2.5-13.4] vs. 2.0 [IQR 0.6-5.0] hours, p < 0.001). Older age, greater body mass index (BMI), and longer SCAF duration within the first year were independent predictors of SCAF progression. Every 10-year increase in age was associated with a 1.6-fold increase in the risk of SCAF progression (hazard ratio [HR], 1.59; 95% confidence interval [CI], 1.05-2.39; p = 0.028). BMI was also an independent predictor of SCAF progression, with each 10 kg/m2 increase being associated with an HR of 1.83 (95% CI, 1.14-2.94; p = 0.013). Each 1-hour increase in the duration of the longest SCAF episode within the first year of enrollment was independently associated with a 13% increase in the risk of SCAF progression (HR, 1.13; 95% CI, 1.09-1.17; p < 0.001).
The rate of HF hospitalization among patients with SCAF progression was 8.9%/year compared to 2.5%/year for those without progression. After multivariable adjustment, SCAF progression was independently associated with HF hospitalization (HR, 4.58; 95% CI, 1.64-12.8; p = 0.004). Similar results were observed if patients with prior history of HF were excluded (HR, 7.06; 95% CI, 1.82-27.3; p = 0.005), or if SCAF progression was defined as development of SCAF >24 hours alone (HR, 3.68; 95% CI, 1.27-10.7; p = 0.016).
Conclusions:
The study authors concluded that in patients with a pacemaker or defibrillator, SCAF progression was strongly associated with HF hospitalization.
Perspective:
This is an important study because it supports a growing body of literature that even SCAF contributes to worsening HF. These findings suggest that management of AF should focus not only on stroke prevention, but also prevention of HF.
Keywords: Arrhythmias, Cardiac, Atrial Fibrillation, Body Mass Index, Defibrillators, Geriatrics, Heart Failure, Hypertension, Pacemaker, Artificial, Risk, Secondary Prevention, Stroke
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