Guidelines recommend initiation of oral anticoagulant (OAC) therapy in atrial fibrillation (AF) patients with a CHA2DS2-VASc score ≥ 2 (males) and ≥ 3 (females) for lowering stroke risk (IA), while OAC in patients with a CHA2DS2-VASc score of 0 is not recommended (IIIB) .
OAC should be considered (IIaB) for AF patients with a CHA2DS2-VASc score of 1 (males) and of 2 (females) , although there is no evidence from randomised controlled trials to guide OAC therapy in these patients. Real clinical practice demonstrates that the occurrence of CHA2DS2-VASc score 1 in AF patients is 8-15% and they may benefit from OAC [2,3].
Current opinion statement on OAC in patients with non-valvular AF with a CHA2DS2-VASc score of 1 of the European Society of Cardiology working group of cardiovascular pharmacotherapy and the European Society of Cardiology Council on Stroke was published recently . Now easily applicable tools for the personalised refinement of the individual thromboembolic risk in these AF patients can help physicians to decide whether to anticoagulate them or not.
Therapeutic decision about OAC should weigh individual benefit of thromboembolic risk reduction against potential harm due to an increase in bleeding risk in this intermediate risk of stroke patients.
Weighing of individual risk factors
AF patients with intermediate risk of stroke are heterogeneous cohort and thus thromboembolic risk stratification of CHA2DS2-VASc scale should be refined and additional criteria should be considered. Data from China demonstrated a different individual risk of stroke/SE depending on the particular risk factor, thus the most prominent risk increase was observed for ‘age 65-74 years’ and ‘Type II diabetes mellitus’ . Current guidelines state, that OAC should be considered in AF patients irrespective of the AF type and patients with atrial flutter and AF should receive OAC in accordance with uniform principles. However, some data revealed that patients with permanent AF are at higher risk of stroke compared to patients with paroxismal AF and the type of atrial arrhythmia may be considered for the refinement of stroke/SE risk in patients with intermediate risk. There is an assumption that other stroke risk factors - congestive heart failure and hypertension are less important for risk prognosis if they are well controlled .
Additional thromboembolic risk factors: obesity, impaired renal function, increased left atrial size and decreased left atrial appendage emptying velocity as well as high level of serum biomarkers concentration (N-terminal pro-B-type natriuretic peptide and high sensitive cardiac Troponin T and I) and the ABC Stroke Risk Score may also help to refine the risk of stroke (Table 1).
Table 1. Values for individual risk stratification 
|Favors oral anticoagulation (in case of low bleeding risk)|
|Age (>65 years)|
|Type II diabetes mellitus|
|Atrial fibrillation (not atrial flutter)|
|Persistant/permanent artial fibrillation|
|Additional factors for thromboembolic risk modification|
|Obesity (body mass index ≥30 kg/m2)|
|Proteinuria (>150 mg/24 h or equivalent)|
|eGFR (<45 ml/min)|
|Nt-proBNP (>1400 ng/l)|
|Positive cardiac troponin T and I|
|Enlarged LA volume (≥73 ml) or diameter (≥4.7 cm)|
|LAA emptying velocity (<20 cm/s)|
|ABC (age/biomarker/clinical history) score|
Values that favour oral anticoagulation and allow individual thromboembolic risk stratification in patients with a AF and a CHA2DS2-VASc score of 1. eGFR, estimated glomerular filtration rate; LA, left atrium; LAA, left atrial appendage; Nt-proBNP, N-terminal pro-B-type natriuretic peptide.
A personalised decision based on comparison risk of stroke and risk of bleeding is crucial in these patients. In case annual bleding risk with HAS-BLED score ≥ 2, the annual risk of bleeding owerweighs the stroke risk, thus OAC should not be considered. If the bleeding risk is low (<2), than individual risk stratification should be performed. Factors favors oral anticoagulation and additional factors for thromboembolic risk modification should be assessed (Table 1). If thromboembolic risk prevails over bleeding risk, than patients preferences are crucial and if patient choses OAC than NOAC are preferrable (Figure 1).
Figure 1. Decision tree for oral anticoagulation in patients with atrial fibrillation and a CHA2DS2-VASc score of 1. NOAC, non-vitamin K antagonist oral anticoagulants; OAC, oral anticoagulation; VKA, vitamin K antagonist .
- Decisions for or against OAC therapy in AF patients with a CHA2DS2-VASc score of 1 should be based on the individual balance between thromboembolic and bleeding risk.
- OAC should not be considered in intermediate thromboembolic risk patients with a HAS-BLED score ≥2.
- In case of low bleeding risk (<2) the individual thromboembolic risk stratification should be performed.
- Age ≥65 years and diabetes mellitus Type II may be the most important isolated risk factors for thromboembolic events.
- Obesity, proteinuria, decreased GFR, enlarged left atrial size and elevated level of high-sensitive Troponin T or I and Nt-proBNP as well as the AF burden are reasonable and easily assessable markers for risk stratification.
- The patients individual preference for, or against initiation OAC therapy should be taken into account in AF patients with a CHA2DS2-VASc score of 1.
- In case the decision of OAC therapy initiation in AF patients has been made, NOACs should be preferred over VKAs.