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Atrial Fibrillation and Moderate Risks for Stroke

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Atrial fibrillation (AFib) is a highly prevailing arrhythmia with an increased risk of stroke. Read this article to learn more about it.

Medically reviewed by

Dr. Muhammad Zohaib Siddiq

Published At March 27, 2023
Reviewed AtMarch 27, 2023

Introduction:

AFib is estimated to affect nearly one percent of the US population and 33 million people worldwide. AFib prevalence increases with age. Hence its rising prevalence corresponds to a rise in the elderly population and the raised prevalence of risk factors, such as hypertension, diabetes, obesity, and alcohol consumption. AFib is a leading preventable reason for ischemic stroke for which earlier detection and treatment are vital. However, the risk of stroke varies broadly, ranging from 1 % to 15 % annually, and is also greatly dependent on other coexisting risk factors. Strokes due to AFib are very common and are associated with very poor outcomes that are 70 % to 80 % of people die or become disabled).

What Is Atrial Fibrillation?

AF comprises an irregular heartbeat that begins froheart's m the upper chambers ( heart. AF is the most common type of heart arrhythmia. In the case of AFib, normal beating in the atria is irregular, and blood does not flow as it should from the atria to the ventricles (lower chambers of the heart). AFib may occur in brief episodes or be a permanent condition. Thus uncoordinated atrial and ventricle rhythms may lead to too fast or irregular heartbeats.

What Is a Stroke?

A stroke is a serious life-threatening state that occurs when the blood supply to the brain is interrupted or decreased, preventing the supply of oxygen and nutrients to the brain tissues of the affected part, ultimately leading to brain tissue death in minutes. A stroke happens when a blood vessel supplying the brain ruptures, leading to bleeding or a blockage in the brain's blood vessels.

How Does AFib Cause Stroke?

In the case of AFib, the resulting fast contractions of the atria are weaker than regular contractions. This results in a slow blood flow in the atrium leading to blood pooling, which in turn becomes sluggish. This consequently forms blood clots. If this clot travels to the brain's blood vessels from the heart, it may create a block in that particular blood vessel and interrupt or cut the blood supply to the affected part of the brain resulting in a stroke.

What Are the Risk Factors for Stroke in the Case of AFib?

  • Age: Increasing age is a potent independent risk factor for stroke in individuals with AFib. Growing old age is a consistent risk factor for stroke, with a 1.5 - fold risk increment per decade.

  • Sex: A study has found an association between the female sex and the risk of stroke in AFib. Women with AFib and no other stroke risk factors had a nonsignificantly higher risk of stroke than men.

  • Prior Stroke: A previous stroke is the most substantial risk factor for subsequent stroke in individuals with AFib. Some reports established that it increased the risk of stroke by 2.5 - fold.

  • Hypertension: A history of hypertension and blood pressure of more than 160 mmHg is a consistent independent risk factor for stroke resulting in a two-fold increased risk of stroke.

  • Diabetes Mellitus: It is also a significant independent risk factor of stroke in individuals with AFib, resulting in a 1.7 - fold increased risk of stroke.

  • Heart Failure: Clinical heart failure is generally considered a risk factor for stroke in AFib individuals, and although some reports support this, the overall evidence is not as confirmatory.

  • Vascular Disease: Vascular diseases such as myocardial infarction and peripheral arterial disease are independent predictors of stroke in individuals with AFib.

  • Others: Chronic kidney disease, C-reactive protein level of more than 50 mg/l, estrogen hormone replacement therapy, high-density lipoprotein, and total cholesterol level in the blood.

How to Calculate the Risk of Stroke in Individuals With AFib?

The risk of stroke in individuals with AFib can be stratified using validated prediction scores like CHADS2, which is the most widely used. Scores for each condition and the method to calculate them are given below;

Condition and Its Points:

Congestive heart failure - 1 point.

Hypertension - 1 point.

Age more than 75 years - 1 point.

Diabetes mellitus - 1 point.

Previous stroke or transient ischemic attack - 2 points.

Stroke Risk According to CHADS2:

The risk categories for stroke and CHADS2 Score are as below;

Low risk - 0 points.

Medium risk - 1 to 2 points.

High risk - 3 to 6 points.

How to Prevent Stroke in Individuals with AFib?

Proper risk assessment and early initiation of suitable preventive therapy significantly reduce AFib-related strokes and their associated mortality.

A. Pharmacological Management:

  • Antiplatelet Therapy: It is most commonly indicated with Aspirin or Clopidogrel in the case of low-risk individuals with AFib.

  • Anticoagulation Therapy: Multiple clinical trials confirm the superior therapeutic effect of Warfarin over antiplatelets. Therefore, in individuals having intermediate and high stroke risk, anticoagulation using Warfarin, Dabigatran, or other newer oral anticoagulants such as Dabigatran, Rivaroxaban, and Apixaban is the preferred treatment for stroke prevention. However, anticoagulant therapy is contraindicated in individuals with mechanical heart valves and moderate or severe mitral stenosis (narrowing of the mitral valve between the two left heart chambers), and advanced kidney failure.

B. Nonpharmacologic Options:

This approach is used in case of limitations of pharmacological therapy, such as left atrial appendage (LAA) occlusion. This is a surgically placed device in which the polyester fabric covers the distal 50 % of the depth, and it prevents thrombi (blood clots) from flowing out of the left atrium by the anchors on the bottom the device.

What Are the Limitations and Drawbacks of Pharmacological Therapy?

  • Inconvenience with daily medication administration.

  • Cost of medications.

  • The need for frequent blood tests.

  • Dietary restrictions in individuals taking Warfarin.

  • The increased risk of bleeding complications.

  • Difficulty in managing anticoagulants in the cases of elective or nonelective invasive or surgical procedures or trauma.

Conclusion:

AFib is a very common heart arrhythmia with significant cardiovascular morbidity and mortality. In addition, AFib is associated with the risk of blood clot events, particularly occlusion of brain blood vessels with this blood clot is its most serious complication, which results in stroke. Careful risk categorization and estimation of the risk of stroke using a validated scoring system such as CHADS2 can help to recognize the high-risk individua

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Dr. Muhammad Zohaib Siddiq
Dr. Muhammad Zohaib Siddiq

Cardiology

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