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Atrial Fibrillation and Anticoagulation

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Version Jan 2023

Atrial fibrillation anticoagulation risk assessment

CHA2DS2VaSc score: assess stroke risk in those with AF. CCF history (+1), hypertension (+1), age: 65-74 (+1), >75 (+2), diabetes mellitus (+1), stroke/ TIA or thromboembolism (+2), sex: female (+1), vascular disease or CAD, MI, PAD, or aortic plaque (+1). Adjusted annual stroke risk by score: (0) 0%, (1) 1.3%, (2) 2.2%, (3) 3.3%, (4) 4.0%, (5) 6.7%, (6) 9.8%, (7) 9.6%, (8) 6.7%, (9) 15.2%. Recommend anticoagulate if score >0 or 1. Discuss with patient.
HAS -BLED score: assess bleeding risk. Hypertension (SBP >160 mmHg) (+1), abnormal renal (+1) and/or liver function (+1), stroke in past (+1), bleeding (+1), labile INR (+1), elderly age >65 (+1), drugs (+1) or alcohol abuse (+1). A score of 3 or more indicates increased 1 year bleed risk on anticoagulation sufficient to justify caution or more regular review. Risk is for intracranial bleed, bleed requiring hospitalisation or a haemoglobin drop >2 g/L or that needs transfusion.

CHADS2VASC Score

For patients with non-valvular AF and a CHA2DS2-VASc score of 0, it is reasonable to omit antithrombotic therapy. For patients with non-valvular AF with prior stroke, transient ischaemic attack (TIA), or a CHA2DS2-VASc score of 2 or greater, oral anticoagulants are recommended.
However one has to balance this with bleeding risk which can be quantified to some extent by the HAS-BLED criteria shown below. Interestingly the risks of bleeding often are similar to those of risks of ischaemic cardioembolic stroke e.g. stroke, blood pressure and age. It is a delicate balance but most of us would favour anticoagulation and managing any risks of bleeding as and when they happen. Expert and multidisciplinary decisions may be needed involving patients and those important to them in many instances.
The risk of major haemorrhage attributable to anticoagulation therapy is typically between 0.5% and 1.0% per year. When the risks of ischaemic stroke exceed this then anticoagulation is recommended. The optimal intensity of anticoagulation appears to be an INR of 2.0 to 3.0. However, we are now seeing new drugs that are likely to replace warfarin. The holy grail of AF anticoagulation management is to find a drug more effective, but less harmful than warfarin that is cheap too.

CHADS2VASC Score	Yearly risk of stroke without warfarin (or equivalent)	Management
0	0%	Regard as truly low risk so that no antithrombotic therapy is preferred
1	1.3%	Warfarin or DOAC. may consider as low risk if only risk is female, under 65 and lone AF
2	2.2%	Warfarin or DOAC
3	3.2%	Warfarin or DOAC
4	4.0%	Warfarin or DOAC
5	6.7%	Warfarin or DOAC
6	9.8%	Warfarin or DOAC
7	9.6%	Warfarin or DOAC
8	6.7%	Warfarin or DOAC
9	15.2%	Warfarin or DOAC

HAS-BLED score for bleeding risk on oral anticoagulation in atrial fibrillation

A HAS-BLED score of 3 or more indicates increased one year bleed risk on anticoagulation (of 3.7 Bleeds per 100 patient-years) sufficient to justify caution or more regular review.
Increased risk of intracranial bleed, bleed requiring hospitalisation or a haemoglobin drop > 2g/L or that needs transfusion [Pisters R et al. 2010]
Warfarin anticoagulation titrated to an INR of 2.0-3.0 is recommended for the average patient with a CHA2DS2-Vasc score =2 unless contraindicated (e.g., history of frequent falls, clinically significant bleeding, inability to obtain regular INR). Either Warfarin or Aspirin can be used for the average patient with a CHA2DS2-VASc score of 1 depending on physician discretion and patient preference. Aspirin 75-325 mg daily or no treatment may be reasonable depending on patient preference for the average patient with a CHA2DS2-VASc score of 0.

Feature	Score
Hypertension (SBP > 160 mmHg)	+1
Abnormal renal (Dialysis, Creat > 200umol/l) /liver function (> 2x bilirubin or x3 ALT/AST/ALP)	+1/+1
Stroke	+1
Bleeding (any bleeding hx or anaemia)	+1
Labile INRs (time in therapeutic range <60%)	+1
Elderly Age > 65	+1
Drugs (anti-platelets, NSAIDs) or Alcohol	+1/+1

Anticoagulants

Drug	Mechanism	Dosing advice	Antidote if active bleeding
Warfarin x mg OD	Vitamin K antagonist	Give sufficient to get INR 2-3 or 2.5-3.5 for high risk patients. Many interactions and dietary advice which require close monitoring	Vitamin K and Octaplex/Beriplex
Dabigatran 150 mg BD	Thrombin inhibitor	Avoid if avoid if creatinine clearance < 30 mL/minute. Reduce dose to 110 mg BD in those over 80 or if creatinine clearance 30-50 mL/minute or on Verapamil	Praxbind
Apixaban 5 mg BD	Factor Xa Inhibitor	reduce dose to 2.5 mg BD if creatinine clearance 15-29 mL/minute, or if serum-creatinine = 133 micromol/litre and age = 80 years or body-weight = 60kg. Avoid if creatinine clearance less than 15 mL/minute	Octaplex/Beriplex
Rivaroxaban 20 mg OD	Factor Xa Inhibitor	If creatinine clearance 15-49 mL/minute reduce dose to 15 mg OD. Avoid if creatinine clearance < 15 mL/minute	Octaplex/Beriplex
Edoxaban 60 mg OD	Factor Xa Inhibitor	Reduce dose to 30 mg OD in moderate to severe renal impairment; avoid in end stage renal disease or in dialysis. Reduce dose to 30 mg OD in patients weighing = 60 kg	Octaplex/Beriplex

PLEASE NOTE LEGAL ADVICE: The contents are under continuing development and improvements and may contain errors of omission or fact. The official launch will be at the end of 2018. Feedback vital and always welcome at drokane at gmail.com. This is not to be used for the assessment, diagnosis or management of patients. It should not be regarded as medical advice. It is only for educational purposes. Please adhere to your local protocols. If you are unwell please seek healthcare advice from your doctor. This does not replace senior or specialist advice. If you do not accept this then please do not use the website. If you need medical advice, please consult a doctor or other appropriate medical professional. If you are a medical professional and you need advice then speak to your senior or colleagues.

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