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Peripheral Artery Disease: causes and consequences

Coronary Artery Disease: causes and consequences

Preventing AF-Related Stroke

This section covers the epidemiology and demographics of AF, and stroke risk assessment

  • AF affected over 6 million people in the EU,1 and approximately 5.3 million people in the US in 20092
  • It is anticipated that these figures will rise to between 14–17 million by the year 2030 in the EU3 with projections in the US reaching 12 million by the year 20504
  • The exact epidemiological profile of AF is incomplete and underestimated, because 10-40% of patients with AF (particularly the elderly) can be asymptomatic (referred to as ‘clinically silent or subclinical AF’)5
  • Prevalence increases from 0.7% in those aged 55–59 years to almost 18% in those >85 years of age6
  • The overall prevalence of AF is predicted to at least double in the next 50 years, as a consequence of the ageing population7
  • In AF, the atria beat irregularly and often rapidly, due to an abnormal, fast electrical rhythm in the upper chambers of the heart
  • During AF the upper chambers do not contract fully and in areas the blood flow can become impaired
  • When blood becomes stagnant, the mechanisms that form a clot are activated and a thrombus can form in the fibrillating atria of the heart
  • Thrombus formation most commonly occurs in the LAA, an extension originating from the main body of the left atrium with reduced contractility and stasis, only 10% form in the right atrial appendage8
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An uncommon right atrial appendage thrombus

  • This thrombus can embolize and travel to the brain, blocking arterial blood flow and causing ischaemic stroke
  • Consequently, patients with AF have an increased risk of stroke9
    • There is a five fold increased risk of stroke in patients with non-valvular AF (i.e. AF in the absence of rheumatic mitral stenosis, a mechanical or bioprosthetic heart valve or mitral valve repair)9
    • Note: For patients with AF caused by valvular disease, the risk of stroke is increased 20-fold9
  • Elderly patients with AF are particularly vulnerable to stroke
    • The prevalence of AF increases with age, and approximately 35% of patients with AF are ≥80 years of age9
  • AF-related strokes are generally more severe and are associated with greater mortality and morbidity than strokes in patients without AF10
  • Stroke in patients with AF results in longer hospital stays and greater healthcare resource use and associated costs than in those without AF11,12

Several risk assessment scoring systems are available to help clinicians estimate the risk of stroke in patients with AF, and guide recommendations for antithrombotic therapy.

  • CHADS2 is a simple, well-validated points-based risk assessment tool widely used to assess individual patient risk for stroke
Stroke risk assessment: CHADS2 score
Classification Risk factor Points
C Congestive heart failure 1
H Hypertenstion 1
A Age ≥75 years 1
D Diabetes mellitus 1
S2 Prior stroke/TIA/thromboembolism 2

Adapted from Gage et al 2001.13

 

CHADS2 score calculator Accessed date: 29/09/2016

CHADS2 risk assessment does not incorporate a number of documented risk factors for stroke.

  • The CHA2DS2-VASc score was developed in an effort to improve the predictive value for stroke risk, especially in low-risk patients14
    • CHA2 DS2 -VASc is now preferred over CHADS2 in the latest European 2016 and American 2014 guidelines3,9
  • CHA2DS2-VASc identifies ‘major’ risk factors, comprising stroke/TIA/thromboembolism and age ≥75 years (2 points each), and ‘clinically relevant non-major’ risk factors, comprising congestive heart failure, hypertension, diabetes mellitus, age 65–74 years, female gender and vascular disease (1 point each)15
Stroke risk assessment: CHA2DS2-VASc score
  Risk factor Points
C Congestive heart failure/left ventricular dysfunction 1
H Hypertension 1
A2 Age ≥75 years 2
D Diabetes mellitus 1
S2 Stroke/TIA/thromboembolism 2
V Vascular disease (prior myocardial infarction, peripheral artery disease, aortic plaque) 1
A Age 65−74 years 1
Sc Sex category (i.e. female gender) 1

Adapted from Lip et al. 2010.15

 

CHA2DS2-VASc score calculator Accessed date: 29/09/2016

  • Score of ≥2
    • In both schemes, patients with a score of ≥2 are considered to be at high risk of stroke and NOAC therapy is recommended by all guidelines3,9
  • Score of 1
    • Patients with a score of 1 are at moderate risk of stroke, unless they are female patients with a CHA2DS2-VASc-score of 1 by virtue of gender alone, in which case they should be classified as low risk3
    • Guidelines vary in their recommendations for antithrombotic therapy for patients with moderate stroke risk
  • Score of 0
    • Patients with a CHA2DS2-VASc score of 0 are at low risk of stroke and do not require antithrombotic therapy3
    • Traditionally, patients with a CHADS2 score of 0 have also been considered to be at low risk of stroke. However, these patients may have a CHA2DS2-VASc score of between 0 and 3 (if they are female, aged 65–75 and have vascular disease)
    • Registry data show that the non-anticoagulated stroke rate in patients with a CHADS2 score of 0 can range from 0.8%/year (CHA2DS2-VASc score=0) to 3.2%/year (CHA2DS2-VASc score=3) after 1 year of follow-up.16 Thus patients with a CHADS2 score of 0 are not necessarily at low risk of stroke, and anticoagulation decisions simply based on a CHADS2 score of ≥1 may leave many patients at an unacceptable risk of stroke

AF management strategies should aim to relieve symptoms (when present), optimize cardiac function, and minimize the risk of stroke. It is important to note that approaches intended to restore normal sinus rhythm do not necessarily reduce the risk of stroke in patients with AF. Therefore, even for patients who have undergone successful cardioversion, lifelong anticoagulation may be appropriate when the risk of stroke or recurrent AF is high.3

Guidelines recommend the use of antithrombotic therapy for stroke prevention in patients with AF based on an individual’s predicted risk of stroke.3,9,17

Guideline recommendations for stroke prevention in patients with AF
Risk category CHADS2 score CHA2DS2-VASc score ESC 20163 AHA/ACC/HRS 20149
High ≥2 ≥2a,b NOACc NOAC
Moderate 1 1d NOAC should be considered based upon an assessment of individual characteristics and patient preferencesdd,e No antithrombotic therapy or treatment with a NOAC or ASA may be considered
Low 0 0 No antithrombotic therapy No antithrombotic therapy

aOne ‘major’ risk factor or ≥2 ‘clinically relevant non-major’ risk factors; bCHA2DS2-VASc score of ≥2 in males and ≥3 in females is considered high risk according to ESC guidelines; cNOACs are recommended in preference to VKA therapy; done ‘clinically relevant non-major’ risk factor; efemale patients who are aged <65 years and have lone AF (but still have a CHA2DS2-VASc score of 1 by virtue of their gender) are low risk and no antithrombotic therapy should be considered

 

ACC, American College of Cardiology; AHA, American Heart Association; ESC, European Society of Cardiology; HRS, Heart Rhythm Society

References

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