Should Every Patient With Atrial Fibrillation and a CHA2DS2-VASc Score of 1 Be Anticoagulated? A Systematic Review of 37,030 Patients

Patients with atrial fibrillation (AF) are at risk of thromboembolic events. The CHA2DS2-VASc (congestive heart failure, hypertension, age 65-74, diabetes, female sex and vascular disease, which all count for 1 point, and previous transient ischemic stroke/stroke or age ≥ 75 years, which count for two points) score stratifies this risk and consequently indicates whether anticoagulation is required but leaves room for debate regarding patients with a CHA2DS2-VASc score of 1, irrespective of sex. A score of 1, irrespective of sex, is derived from varying risk factors and may represent different risks. We systematically searched PubMed from inception to July 31, 2017, for studies describing thromboembolic risk per risk factor of the CHA2DS2-VASc score in patients with AF not treated with an anticoagulant. Two independent reviewers selected, appraised, and extracted the data to determine the thromboembolic risk per risk factor. Per study, risk factors were ranked for highest through lowest risk. Five studies were included, comprising 37,030 subjects with a CHA2DS2-VASc score of 1. Numerically, the highest event rates were seen in patients without comorbidities, but aged 65-74 years, while event rates in patients with vascular disease tended to be the lowest. Age 65-74 years is associated with the highest risk, hazard ratios ranging from 1.9 (95% confidence interval, 1.7-2.1) to 3.9 (95% confidence interval, 2.3-6.6), while comorbid cardiovascular conditions are associated with lower, but still considerably increased, risks. The thromboembolic risk differed between the risk factors of the CHA2DS2-VASc score in patients with AF, with age 65-74 years associated with the highest and most consistent risk. However, all show a significantly and clinically relevant increased thromboembolic risk. Besides the differences between risk factors of the CHA2DS2-VASc score, differences within risk factors may also alter stroke risk