The impact of atrial fibrillation type on the risk of thromboembolism, mortality, and bleeding: a systematic review and meta-analysis

AIMS: Thromboembolic risk stratification schemes and clinical guidelines for atrial fibrillation (AF) regard risk as independent of classification into paroxysmal (PAF) and non-paroxysmal atrial fibrillation (NPAF). The aim of the current study was to conduct a systematic review evaluating the impact of AF type on thromboembolism, bleeding, and mortality. METHODS AND RESULTS: PubMed was searched through 27 November 2014 for randomized controlled trials, cohort studies, and case series reporting prospectively collected clinical outcomes stratified by AF type. The incidence of thromboembolism, mortality, and bleeding was extracted. Atrial fibrillation 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 (95% CI: 1.169-1.571, P < 0.001). In the study subset off oral anticoagulation, unadjusted RR was 1.689 (95% CI: 1.151-2.480, P = 0.007). The overall multivariable adjusted hazard ratio (HR) for thromboembolism was 1.384 (95% CI: 1.191-1.608, P < 0.001). The overall unadjusted RR for all-cause mortality was 1.462 (95% CI: 1.255-1.703, P < 0.001). Multivariable adjusted HR for all-cause mortality was 1.217 (95% CI: 1.085-1.365, P < 0.001). Rates of bleeding were similar, with unadjusted RR 1.00 (95% CI: 0.919-1.087, P = 0.994) and adjusted HR 1.025 (95% CI: 0.898-1.170, P = 0.715). CONCLUSION: Non-paroxysmal atrial fibrillation is associated with a highly significant increase in thromboembolism and death. These data suggest the need for new therapies to prevent AF progression and further studies to explore the integration of AF type into models of thromboembolic risk.