Geographical differences in thromboembolic and bleeding risks in patients with non-valvular atrial fibrillation: An ancillary analysis from the SPORTIF trials

BACKGROUND: Atrial fibrillation (AF) is associated with an increased risk of stroke, and the use of oral anticoagulation reduces stroke and all-cause mortality. Geographical differences may exist in AF risk factors, risk stratification and treatment strategies.

METHODS: A post-hoc subgroup analysis derived from randomized controlled trials, the SPORTIF III and V trials, studying differences between European and North American warfarin-assigned non-valvular AF patients.

RESULTS: Of 3359 patients 41.6% (n=1397) were enrolled in Europe and 1962 (58.4%) from North America. CHA2DS2-VASc (p=0.002) and HAS-BLED (p<0.001) scores were higher in North Americans. Good anticoagulation control was more common in North American patients than Europeans. 1-Kaplan-Meier estimate curves show that North Americans had a lower risk of stroke/systemic embolic event (SEE) (p=0.012), but higher risk of myocardial infarction(MI) (p=0.007) and major bleeding (p<0.001), compared to Europeans. Cox multivariate analysis confirmed a lower stroke/SEE risk (p=0.008) and higher MI (p=0.014) and major bleeding risks (p<0.001) in North Americans.

CONCLUSIONS: Compared to European AF patients, North Americans had better anticoagulation control and higher thromboembolic and bleeding risk profiles. At follow-up, North American patients had lower stroke/SEE risk but higher MI and major bleeding risks compared to Europeans. Further studies are needed to understand these differences and the discordance between risk profile and lower stroke/SEE rates in North American compared to European patients.