Antiplatelet Therapy For Atrial Fibrillation

Imagine your heart as the instrument of life’s symphony, orchestrating the rhythmic dance that bears the melody of vitality. What if this harmony is shattered, replaced by chaotic beats, and dissonant rhythm? This unsettling transformation symbolises the crux of atrial fibrillation, a ruthless intruder destroying the natural tempo of the heart. In the dominion of cardiovascular disorders, atrial fibrillation stands as a daunting force, demanding attention and strategic intervention to restore the once-serene orchestration of the human heartbeat. 

What is atrial fibrillation?

Atrial fibrillation is a kind of arrhythmia that disrupts your heartbeat. Any rhythm that is not normal is called “arrhythmia”. There are several types of arrhythmias and atrial fibrillation is one of them. It is usually caused by fast heartbeats (usually around 400 per minute) from the heart's upper chambers, i.e. atria. A normal cardiac rhythm means a regular contraction of the heart at its usual pace. A normal heartbeat rate at rest is about 70 to 80 beats per minute, which increases with exercise. Each contraction pushes blood from the atria (the two upper chambers) to the ventricles (the two lower chambers). The ventricles then contract and push the blood to the lungs or the rest of the body.

In a patient with atrial fibrillation, the disrupted electrical signals make the atria contract irregularly and much faster than normal. The atria then get out of synchronisation with the ventricles. Blood can pool in the atrium ultimately causing the formation of blood clots.

Why do you need to manage atrial fibrillation?

Atrial fibrillation is a complex condition which demands careful management using the following strategies:

• Management with several treatment decisions about optimum prophylaxis of thrombus formation (prevention of clot formation)
• Control of symptoms
• Prevention of progression of atrial fibrillation
• Identification and management of associated cardiovascular risk factors and comorbidity 

Ignoring atrial fibrillation is letting a storm cause chaos in the symphony of your life. Dealing with atrial fibrillation at the right time and with the right drugs helps you to be in control of your health and conduct a harmonious future – one beat at a time. 

Warning signs of atrial fibrillation

According to Rosalie Linver Ungar, author of a book called “In a Heartbeat: The Ups and Downs of Life with Atrial Fib” a lot of patients don’t feel or know atrial fibrillation when it’s happening, so they don’t believe the atrial fibrillation exists. But when it does cause signs and symptoms these may be:

• Palpitations
• Syncope (fainting)
• Fatigue
• Dizziness
• Angina (chest pain)
• Shortness of breath
• Weakness
• As a complication of atrial fibrillation the patient may developblood clots causing angina and stroke
• Heart failure

Role of antiplatelet drugs in atrial fibrillation 

 In patients with atrial fibrillation the drug of choice is anticoagulants like warfarin, however, if there is a low risk of developing stroke or if the patient develops side effects of oral anticoagulants, in that case, antiplatelet drugs are considered.

Several drugs are available as antiplatelet drugs eg, aspirin, clopidogrel, prasugrel, cilostazol, ticagrelor, and dipyridamole, however, when we are considering atrial fibrillation, aspirin, and clopidogrel are most important of these.³

Prevalence risk factors and outcomes

Atrial fibrillation is the most prevalent type of cardiac arrhythmia. Due to the increased average life span and the success in reducing overall cardiovascular (CV) mortality, atrial fibrillation is predicted to become an epidemic in the 21st century.⁴ It is increasingly common in older patients. However, patients with long-standing hypertension, heart failure, coronary artery disease, problems with heart valves, and hyperthyroidism are likely to suffer from this condition. Being obese, a smoker or an alcoholic puts you in the risk category too.

Atrial fibrillation is both a cause and consequence of heart failure. According to several studies, atrial fibrillation is associated with a three-fold increased risk of incident heart failure. Other outcomes of atrial fibrillation are ischemic stroke, transient ischemic attack (TIA), bleeding, and death.

How to manage atrial fibrillation?

Medications are the most helpful form of treatment for the majority of patients, however, cardioversion is also considered in patients depending upon the type and duration of atrial fibrillation. Different drugs are used for the treatment of atrial fibrillation. There are several factors based on which the management and medication of atrial fibrillation are decided. These factors are age, level of atrial fibrillation (depending upon the duration and persistence), severity of symptoms, any other underlying heart condition, and stroke risk. At a young age, with atrial fibrillation alone, there is less chance of developing clots, as compared to old people, especially if they have other comorbid conditions like diabetes, hypertension, and heart failure. Different groups of drugs that are used in atrial fibrillation are

• Anticoagulants eg. warfarin, dabigatran
• Antiplatelet eg. aspirin, clopidogrel⁶
• Drugs controlling abnormal heart rate eg. amiaderone, beta-blockers, and calcium channel blockers
• Digoxin (slows heart rate in atrial fibrillation)

What benefit does antiplatelet drug treatment give in atrial fibrillation?

In patients with atrial fibrillation, the atria fail to function properly and do not pump blood efficiently to the ventricles. This results in the pooling of blood in parts of the atria. If this condition of atrial fibrillation persists the pooling of blood may lead to clot formation, which when dislodged may go to the brain or heart and get impacted in the blood vessels, bringing on the turmoil of stroke or heart attack.⁵ The purpose of giving antiplatelet drugs is not to control arrhythmias but to prevent clot formation and its consequences i.e. stroke. 

In the process of clot formation, platelet aggregation is the first step. Antiplatelet drugs, such as aspirin and clopidogrel, work by inhibiting platelet aggregation.

Aspirin is the most commonly used oral antiplatelet drug. It works by irreversibly inhibiting the cyclooxygenase enzyme (COX) activity in the pathway of prostaglandin synthesis. This prostaglandin is a precursor of thromboxane A2 (TXA2) which in turn is responsible for inducing platelet aggregation and vasoconstriction. 

Differences between aspirin and other antiplatelet agents

Adverse effects of using antiplatelet drugs                                                 

Antiplatelet drugs are effective in atrial fibrillation but these may be associated with certain side effects. Following are a few side effects of antiplatelet drugs

• Bleeding
• Gastrointestinal disturbance
• Allergic reactions
• Haematological effects
• Renal dysfunction
• Tinnitus
• Interaction with other medication

Summary

Atrial fibrillation is a type of arrhythmia that originates from the upper chambers of the heart i.e. atria. The disrupted electrical signals make the heart contract irregularly and faster than normal. Atrial fibrillation may be transient or permanent depending upon the cause, however, it is important to correct this condition either by cardioversion or medication. The medication used is meant to control abnormal heart rate and to prevent clot formation. There are different drugs for this purpose but two important groups of drugs are anticoagulants and antiplatelets. While both antiplatelets and anticoagulants play roles in managing AF, anticoagulants are more effective for stroke prevention in moderate to high-risk patients. The choice between these medications is individualised, taking into account various patient-specific factors and risk assessments. 

FAQs

What is cardioversion?

Cardioversion is a medical procedure in which low voltage and quick shocks are used to treat too fast or irregular heart rate, and restore a normal rhythm. Cardioversion is used by your health provider if you have atrial fibrillation which is troublesome or this is the very first episode of atrial fibrillation. Cardioversion can be achieved through medication as well.

How atrial fibrillation is diagnosed?

Atrial fibrillation can be diagnosed through ECG (electrocardiogram). Your health provider may also suggest blood tests for serum potassium level or thyroid hormone level to determine the cause of atrial fibrillation. An echocardiography may be suggested to assess the function of the heart.

Which antiplatelet drug is better, clopidogrel or aspirin?

In atrial fibrillation, there is an environment that promotes coagulation and platelet aggregation leading to clot formation. Both anticoagulants and antiplatelets can be given. When we specifically talk about antiplatelet, studies show that the addition of clopidogrel to aspirin is preferred over aspirin alone, because of a significantly greater reduction in platelet aggregation than that observed with aspirin alone.⁸