Atrial fibrillation and Stroke

 

Atrial fibrillation (AFib) is an irregular heart rhythm often associated with conditions such as high blood pressure (hypertension), coronary artery disease (CAD), and heart failure. More people over 70 develop AFib. As we grow older, stroke risks associated with high blood pressure, coronary artery disease and heart failure become progressively lower. The risk of stroke associated with AFib, however, continues to rise as we age.

 

AFib is known to increase the risk of stroke in the following situations:

  • Rheumatic heart disease with moderate to severe mitral valve narrowing (stenosis)

  • Hypertrophic cardiomyopathy

  • Mechanical valve.

In individuals over 70, AFib seems more likely to occur without these conditions. When that happens, it’s called non-valvular AFib. The Framingham study indicated that AFib has a significant impact on the risk of stroke that is separate from other cardiac problems.[1] The 10- year risk for stroke due to non-valvular AFib rises from 1.5% for those who are 50-59 years to 23.5% for those who are 80-89 years. The risk of stroke is as much as 5 times higher when AFib is present. 

 

Stroke risk associated with AFib is managed by the use of anticoagulant or antiplatelet drugs.[2] Your doctor may further define your risk of stroke due to AFib and the appropriate treatments using a measure called the CHA2DS2-VASc score.[3] This score takes into account a variety of risk factors in addition to age and sex. Patients with low scores (i.e. 0-1) are likely to be managed with Aspirin or Clopidogrel. Individuals with elevated CHA2DS2-VASc scores (i.e. >=2 in men; >=3 in women) are likely to be prescribed an oral anticoagulation medicine.[4]  Warfarin (coumadin) has been the main anticoagulant therapy used in the prevention of stroke, but it carries a high risk of bleeding. Recently, a group of novel oral anticoagulants (NOACs) have been shown to have similar benefits and better safety than Warfarin.[5] Even better, these medications do not require regular blood tests to monitor the therapeutic range as are needed for Warfarin.

 

Individuals who cannot tolerate anticoagulation medications may be helped by surgical ablation of the left atrial appendage (LAA).[6]  The durability of LAA occlusion and the long-term risk of stroke is still unknown.

 

[1] Wolf PA, Abbott RD, Kannel WB, Atrial fibrillation as an independent risk factor for stroke:  The Framingham Study.  Stroke 1991;22:983-988.

[2] Hart RG, Pearce LA, Aguilar MI. Meta-analysis: antithrombotic therapy to prevent stroke in patients who have nonvalvular atrial fibrillation.  Ann Intern Med. 2007;146:857-67.

[3] Philippart R, Brunet-Bernard A, Clementy N, et al. CHA2DS2-VASc score for predicting stroke and thromboembolism in patients with AFib and biological valve prosthesis.  J Am Coll Cardiol. 2016;67:343-4.

[4] January CT, et al. 2019 Focused Update on Atrial Fibrillation. Circulation 2019 (www.ahajournals.org/doi/suppl/10.1161/CIR.0000000000000665)

[5] Ahmad Y, Lip GYH, Apostolakis S. New oral anticoagulants for stroke prevention in atrial fibrillation: impact of gender, heart failure, diabetes mellitus and paroxysmal atrial fibrillation.  Expert Rev Cardiovas Ther. 2012;10:1471-80.

[6] Melduni RM, SchAFibf HV, Lee H-C, et al. Impact of left atrial appendage closure during cardiac surgery on the occurrence of early postoperative atrial fibrillation, stroke, and mortality: A propensity score-matched analysis of 10633 patients.  Circulation 2017;135:366-78.

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