Stroke risk and treatment in patients with atrial fibrillation and low CHA2DS2-VASC scores: Findings from the ORBIT-AF I and II registries

Background—Current American College of Cardiology/American Heart Association guidelines suggest that for patients with atrial fibrillation who are at low risk for stroke (CHA₂DS₂VASc=1) (or women with CHA₂DS₂VASc=2) a variety of treatment strategies may be considered. However, in clinical practice, patterns of treatment in these “low-risk” patients are not well described. The objective of this analysis is to define thromboembolic event rates and to describe treatment patterns in patients with low-risk CHA₂DS₂VASc scores. Methods and Results—We compared characteristics, treatment strategies, and outcomes among patients with a CHA₂DS₂VASc=0, CHA₂DS₂VASc=1, females with a CHA₂DS₂VASc=2, and CHA₂DS₂VASc ≥2 in ORBIT-AF (Outcomes Registry for Better Informed Treatment of Atrial Fibrillation) I & II. Compared with CHA₂DS₂VASc≥2 patients (84.2%), those with a CHA₂DS₂VASc=0 (60.3%), 1 (69.9%), and females with a CHA₂DS₂VASc score=2 (72.4%) were significantly less often treated with oral anticoagulation (P<0.0001). Stroke rates were low overall and ranged from 0 per 100 patient-years in those with CHA₂DS₂VASc=0, 0.8 (95% confidence interval [CI] [0.5–1.2]) in those with CHA₂DS₂VASc=1, 0.8 (95% CI [0.4–1.6]) in females with a CHA₂DS₂VASc score=2, and 1.7 (95% CI [1.6–1.9]) in CHA₂DS₂VASc ≥2. All-cause mortality (per 100 patient-years) was highest in females with a CHA₂DS₂VASc score=2 (1.4) (95% CI [0.8–2.3]), compared with patients with a CHA₂DS₂VASc=0 (0.2) (95% CI [0.1–1.0]), and CHA₂DS₂VASc=1 (1.0) (95% CI [0.7–1.4]), but lower than patients with a CHA₂DS₂VASc ≥2 (5.7) (95% CI [5.4–6.0]). Conclusion—The majority of CHA₂DS₂VASc=0-1 patients are treated with oral anticoagulation. In addition, the absolute risks of death and stroke/transient ischemic attack were low among both male and females CHA₂DS₂VASc=0-1 as well as among females with a CHA₂DS₂VASc score=2.