Calculating Thromboembolic Risk (For Anticoagulation in AF)

 

ASSESS NEED FOR ANTICOAGULATION

Recommend using European Society Guidelines For Management  of Atrial Fibrillation to establish thomboembolic  and bleeding risks in  making decisions regarding anticoagulation. These are summarised as follows:

Thromboembolic risk:

Use of CHA₂DS_2-VASc  Score to assess risk allocating points  as follows:

                            

RISK FACTOR	SCORE*
Congestive heart failure/EF </= 40%	1
Hypertension	1
Age =/> 75 years	2
Diabetes Mellitus	1
Stroke/TIA/thromboembolism	2
Vascular disease (MI, peripheral artery disease, aortic plaque)	1
Age 65-74	1
Sex category ( i.e female)	1
MAXIMUM	9

 
 

Adjusted stroke rate per year according ESC*

CHA2DS2VASc Score	Adjusted stroke rate (%/year)
0	0.78
1	2.01
2	3.71
3	5.92
4	9.27
5	15.26
6	19.74
7	21.5
8	22.38

 
 
 

In the absence of contraindication :

CHA2DS2VASc Score	Recommeded antithrombotic therapy
>/=2	Oral anticoagulant (OAC)*
1	Either aspirin or OAC* Preferred:  OAC*
0	Either no antithrombotic therapy or aspirin Preferred: no antithrombotic therapy

 

*OAC= Warfarin or new oral anticoagulant; dabigatran/rivaroxaban can be considered  as per Peninsula Prescribing Group recommendations.

Decisions regarding thromboprophylaxis will obviously  need to take into account the  patient’s individual risk of bleeding complications.

The HAS-BLED Scoring system below can be used  to identify/reduce ongoing bleeding risks.

Those with score=/> 3 require more careful supervision/ monitoring

RISK FACTOR	SCORE
Hypertension (systolic BP>160mmHg)	1
Abnormal liver/renal function (chirrosis or bilirubin 2xULN, other LFTsx3 ULN/ Creatinine >200umol/L	1 point each =  max  2
Stroke	1
Bleeding (previous bleeding or tendency to eg. diathesis)	1
Labile INRs (high/unstable or <60% in therapeutic range)	1
Elderly (age>65years)	1
Drugs or alcohol (concomitant use of antiplatelets/NSAIDs etc)	1 point each = max 2
MAXIMUM	9

 

Risk of falls has not been included but can  be taken into consideration. Bear in mind that there is some evidence to suggest that to exceed benefits from anticoagulation patients at high risk of thromboembolic complications would have to be falling many times per year.
 

Antiplatelets are a poor substitute for OAC in reducing risk of stroke in AF and should only be considered if there are specific contraindictions to OAC or the patient refuses OAC.

Aspirin / Clopidogrel combination may be the most efficacious but the bleeding risk for this and even aspirin monotherapy in high risk patients eg the elderly, should be considered to be similar to the use of OAC.

Concomitant use of Oral anticoagulants and antiplatelets is not generally recommended without advice from specialist.  

The GP is usually best placed to make a decision regarding anticoagulation, given better  knowledge of the patient’s  individual circumstances, past history and medications. 

Patients should be involved in the discussion regarding choice of anticoagulation

Remember to reassess thromboprohylaxis requirements  if relevant medical conditions develop or patient reaches 65/75 years.

 

Further Information