Atrial fibrillation is a disorder of cardiac muscle contraction caused by the uncoordinated flow of electric impulses.
Uncoordinated impulses result in weaker contractions. Weaker contractions results in incomplete emptying of atria and ventricles. Incomplete emptying leads to stagnant pools of blood. Stagnant pools of blood leads to formation of clots.
The unit Atrial Fibrillation: Where to Start covers the pathophysiology and categorization of atrial fibrillation.
Medical Management of Atrial Fibrillation
The greatest concern in patients with AF is the risk of stroke and pulmonary embolism.
15-20% of all strokes results from AF.
AF pharmacotherapy centers on:
- Risk Reduction: of thrombus formation and stroke
- Treatment: of thrombus and stroke
The course of treatment is dependent on a number of patient specific factors that places them in distinct categories.
Calculating Risk of Stroke in Atrial Fibrillation
There should be an attempt to mitigate any modifiable risk factors for AF throughout all the progressive stages of the disease.
These risk factors are also important because they are what we use to stratify patients for risk of stroke and in turn determine the course of treatment. We do this by using the CHA2DS2 VASc Score.
The CHA2DS2 VASc score is considered the most validated score for risk stratification of stroke in AF.
Most clinical trials for therapies concerning AF use this score to show efficacy making it the generally preferred score.
The score helps to determine the one year risk of thromboembolic event in a non- anticoagulated patient with non valvular AF.
The score provides guidance for which patients will benefit from oral anticoagulation to prevent stroke.
Each risk factor carries a score of 1 except history of stroke, TIA or thromboembolism and age >75 which carries a score of 2.
Congestive Heart Failure: the presence of signs and symptoms of either right or left ventricular failure or both.
Hypertension: A resting blood pressure >140 mm Hg systolic and/or >90 mm Hg diastolic on at least 2 occasions or current antihypertensive pharmacological treatment.
Diabetes: Fasting plasma glucose level ≥7.0 mmol/L (126 mg/dL) or treatment with hypoglycemic agent and/or insulin.
Thromboembolism: peripheral embolism or pulmonary embolism.
Vascular disease: prior MI, peripheral artery disease, or aortic plaque , coronary artery bypass surgery, intermittent claudication.
When To Anticoagulate in Atrial Fibrillation
Anticoagulation is recommended in patients with atrial fibrillation and an estimated annual risk of thromboembolic event > 2%. That risk translates to a CHA2DS2 VASc Score of > 2 in men and > 3 in women.
In patients with AF who are considered to have an intermediate annual risk of stroke i.e. between 1-2%, the use of anticoagulation can be reasonable.
Together, the patient and provider must decide between no treatment and treatment with anticoagulants.
Consideration of patient preferences and individual risk factors is crucial.
There are decision aid programs available to help guide patients with choices for stroke reduction therapy.
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Risk of Bleed with Anticoagulation
The greatest risk assumed with the use of anticoagulation is the risk of major bleed. There must be an assessment of the risk of bleed with treatment versus the risk of stroke or thromboembolic event with no treatment.
Bleeding risk scores are risk stratification tools to help identify patient risk of bleed with anticoagulation.
The 3 most used bleed risk score are: HAS-BLED, HEMORR2HAGES and ATRIA
It is crucial to understand that bleed risk scores cannot be used in isolation to determine whether a patient should receive anticoagulation or not. It is a tool to support this decision.
Bleeding risk scores are very limited in their predictive value for bleed because the assessment uses many of the same risk factors that are used for risk of stroke. This includes factors like age, hypertension, renal disease, and previous stroke.
The 2023 guidelines are very clear: in patients who are categorized as high risk for stroke bleeding risk scores should not be used in isolation to determine eligibility for anticoagulation.
We want to manage the risk of bleed. Which means we need to identify modifiable risks of bleed in high risk patients and minimize them.
This includes interventions such as discontinuing and avoiding the use of other medications that can heighten bleeding risks like antiplatelet therapies and NSAIDs. Management of hypertension and alcohol consumption are other ways to minimize risk of bleed.
Reassessing Risks
AF is a lifelong disease. A patient’s characteristics, risk factors, preferences and lifestyle are likely to change over time.
It is therefore necessary to reassess a patient’s risk for stroke, risk of bleed, compliance and preferences periodically to determine if any changes in therapy are needed. This is usually done at annual medical visits.
Overview of Pharmacotherapy in Atrial Fibrillation
Medical management of AF centers on:
oral anticoagulation rate control rhythm control
Each of these will be tackled individually in separate post.
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The information on this website is intended to be used solely for educational and informational purposes. While the content may be about specific medical and health care issues, it is not a substitute for or replacement of personalized medical advice and is not intended to be used as the sole basis for making individualized medical or health-related decisions.
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