Type of Atrial Fibrillation and Clinical Outcomes
What is the impact of atrial fibrillation (AF) type (nonparoxysmal [NPAF] vs. paroxysmal [PAF]) on thromboembolism, bleeding, and mortality?
PubMed was searched for randomized controlled trials, cohort studies, and case series reporting prospectively collected clinical outcomes stratified by AF type. The authors extracted the incidence of thromboembolism, mortality, and bleeding.
AF clinical outcome data were extracted from 12 studies containing 99,996 patients. The unadjusted risk ratio (RR) for thromboembolism in NPAF vs. PAF was 1.355. In the study subset off oral anticoagulation, unadjusted RR was 1.689. The overall multivariable adjusted hazard ratio (HR) for thromboembolism was 1.384. The overall unadjusted RR for all-cause mortality was 1.462. Multivariable adjusted HR for all-cause mortality was 1.217 (all had significant p values). Rates of bleeding were similar.
The authors concluded that NPAF is associated with a highly significant increase in thromboembolism and death.
Current guidelines recommend the use of oral anticoagulants for the prevention of thromboembolism irrespective of the type of AF. The guidelines focus on comorbidities, which affect the risk of stroke and thromboembolism. Until recently, it has been very difficult, if not impossible, to know how often and how much AF an individual patient experiences, and analysis of AF duration and outcomes was not done in a longitudinal fashion (i.e., patients labeled as rare paroxysmal may have progressed to frequent or persistent AF during the course of the studies). Our ability to accurately assess the amount of time patients spend in AF has changed overnight with the implantable loop monitors with AF monitoring capabilities. These should be a great tool for prospective studies assessing the risks associated with AF of various durations. The mechanisms by which NPAF patients in this meta-analysis experienced increased mortality are unknown, but include worsened heart failure or perhaps a higher burden of comorbidities. AF may not just be a cause of stroke, but also a marker of greater procoagulant propensity.
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