Stroke & bleeding risk assessment in AF

what are the two types of ischaemic stroke

• thrombotic → clot forms in brain

• embolic → clot forms elsewhere and travels to the brain to cause a blockage 

a stroke with AF is called a cardio-embolic stroke 

what is the link between AF and strokes

irregular heartbeat of AF → chambers of heart don’t empty fully when heart contracts → pooling of blood in chambers of heart → clot, which can leave heart and reach blood vessel in brain → cardio embolic stroke (type of ischaemic stroke)

• AF is a leading cause of ischaemic strokes

• Stroke is often the first presentation of AF

• AF is associated with more severe strokes and ‘longer’ TIAs

what are risk factors for embolic stroke

atrial fibrillation is a potent, independent risk factor but actual risk is dependent on other risk factors such as 

• age 

• gender 

• co-morbidities 

what is the prevalence of AF

3% in adults 

• prevalence increases with age and with co-morbidities

what are the most effective pharmacological intervention to prevent the risk of stroke in patients with AF

anticoagulation

• vitamin K antagonists like warfarin 

• DOACs

(antiplatelets are no longer recommended)

why is the risk with anticoagulant therapy 

• anticoagulants are high risk drugs that increase the risk of major bleeds

• we needs to balance the benefits against the increased risk of bleeding using 

  • CHA₂DS₂-Vasc stroke risk score

  • ORBIT bleeding risk score

what is the CHA₂DS₂-Vasc score 

a risk assessment tool that estimates the likelihood that any given with with AF will suffer stroke in the next 12 months 

• used to support clinical decision-making, regarding suitability for anticoagulant therapy 

• each letter of the acronym represents an independent risk factor, which contribute 1 or 2 points to the final score 

• higher score → greater risk of the patient suffering a stroke 

calculating CHA₂DS₂-Vasc score: what are the different risk factors 

CHA₂DS₂-Vasc score: example patient

what are the clinical effects of the CHA₂DS₂-Vasc score

• the score correlates to an estimated risk of having a stroke over the following 12 months 

  • higher score → the greater the risk of having a stroke + the greater the benefit of anticoagulation 

• NICE have recommendations to prevent stroke 

  • don’t offer stroke prevention to people under 65 with AF and no risk factors under than their gender

  • consider anticoagulation for men (but not women) with a score of 1

  • offer anticoagulation to people with a score of 2 or above 

  • regardless of their score, take account of the patient’s bleeding risk 

how do you explain stroke risk to patients

• regardless of the CHA₂DS₂-Vasc score, it is the patient’s decision whether they accept or reject anticoagulation 

• we have the responsibility to explain the risk, in order to support patients to make informed decisions 

what is the ORBIT score

a risk assessment tool that estimates the likelihood that a patient with AF, who is on oral anticoagulation, will suffer a major bleed in the coming 12 months

• used to support clinical decision-making, regarding suitability for anticoagulant therapy 

• each letter of the acronym represents a risk factor, or factors that contribute to the final score 

• higher score → greater risk of suffering a major bleed 

• some risk factors are modifiable 

calculating ORBIT score: what are the different risk factors 

what are the limitations of the ORBIT score

• there are many bleeding risk factors that are not considered in the ORBIT score, but are part of other risk assessment tools such as HAS-BLED

  • hypertension

  • liver disease

  • ischaemic stroke history

  • Labile INRs (unstable, fluctuating International Normalized Ratio in patients taking anticoagulant medications, typically warfarin.)

  • medications other than antiplatelets e.g. SSRIs, NSAIDs

  • alcohol intake (>8 units/week)

• need to fully investigate modifiable risk factors anyway, regardless of the tool used

ORBIT SCORE score: example patient

what are the clinical effects of the ORBIT score 

• the score correlates to an estimated risk of the patient suffering a major bleed in the next 12 months

  • higher risk → greater risk of having a major bleed: low (0-2) = 2.4%, medium (3) = 4.7%, high (>4) = 8.1%

  • some risk factors are modifiable

• NICE have recommendations for assessing bleeding risk and modification/monitoring of risk factors

  • unlike CHA₂DS₂-Vasc score, there are no definite threshold over which treatment should not be offered

  • for many people, the benefits of anticoagulation outweighs the risks

  • don’t withhold anticoagulation solely due to age or falls risk