Atrial Fibrillation Burden and Stroke Risk

May 17, 2018
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Authors:
Go AS, Reynolds K, Yang J, et al.
Citation:
Association of Burden of Atrial Fibrillation With Risk of Ischemic Stroke in Adults With Paroxysmal Atrial Fibrillation: The KP-RHYTHM Study. JAMA Cardiol 2018;May 16:[Epub ahead of print].
Summary By:
Fred Morady, MD, FACC

Study Questions:

What is the risk of an arterial thromboembolic event (TE) related to the atrial fibrillation (AF) burden in unanticoagulated patients with paroxysmal AF?

Methods:

In this retrospective cohort study, 1,965 patients (mean age 68.8 years) with paroxysmal AF underwent 2 weeks of continuous ambulatory monitoring while not taking an anticoagulant. Hospitalizations for ischemic stroke or other TEs were noted during follow-up of up to 5 years.

Results:

The median AF burden was 4.4% (interquartile range [IQR], 1.1-17.2%), and the median duration of the longest episode of AF was 171 minutes (IQR, 49-590 minutes). The median CHA2DS2-VASc score was 3 (IQR, 1-4). During follow-up, there were 19 ischemic strokes, eight transient ischemic attacks, and two systemic TEs. The overall incidence of a TE was 1.5%/year. After adjustment for the CHA2DS2-VASc score, the risk of a TE was 215% higher in the third tertile of AF burden than in the first or second tertiles. The duration of the longest episode of AF was not associated with the risk of a TE event.

Conclusions:

Among unanticoagulated patients with paroxysmal AF, the risk of a TE is related to the AF burden, independent of risk factors for stroke.

Perspective:

Intuitively, it is reasonable to believe that the risk of a TE correlates with the number or duration of AF episodes, but there has been no definitive evidence supporting this, and contemporary practice guidelines consistently have based recommendations for anticoagulation solely on risk factors, independent of the AF burden. Given the median CHA2DS2-VASc score of 3 and the lack of anticoagulation, the surprisingly low risk of a TE (1.5%/year) suggests that not all TE events were captured in this retrospective analysis. Furthermore, the study was underpowered to analyze risk in specific subgroups, such as CHA2DS2-VASc score 0-1 or 5-6. Although intriguing, the findings are not robust enough to modify current practice guidelines.

Keywords: Anticoagulants, Arrhythmias, Cardiac, Atrial Fibrillation, Blood Coagulation, Brain Ischemia, Ischemic Attack, Transient, Monitoring, Ambulatory, Primary Prevention, Risk Factors, Stroke, Thromboembolism, Vascular Diseases


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