Atrial Fibrillation

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Atrial fibrillation (also called AF) is one of the most common type of irregular heart beats seen in clinical practice. It can occur due to a number of reasons, and can last for variable periods of time. Treatment options are many, and here we discuss this condition in detail.

What is atrial fibrillation?

Before reading this article, we urge you to take a quick look at the article on normal electrical conduction of the heart by clicking here.

In atrial fibrillation, the heart beats at a rate that is a lot higher than the normal heart rate. It also beats in an irregular fashion. The strength with which the heart contracts is also variable.

We have already learned that the heart beat originates from electrical activity generated in the sinoatrial node.

In atrial fibrillation, electrical activity is generated from multiple points within the muscle of the atrium. These multiple generators take over the heart, and suppress the sinoatrial node.

Due to these multiple impulses, the atrium start to beat at a very rapid rate of up to 350 – 400 beats per minute.

However, only a few of these beats pass down to the ventricle. The ventricles contract at a rate of 150-180 beats per minute, and in an irregular fashion. This can be felt as an irregular pulse in your wrist.

What causes atrial fibrillation?

Atrial fibrillation often occurs in older individuals, with the highest incidence seen in patients over 80 years of age. There are no specific statistics on how common the condition is in India.

There are a  number of different causes of AF.

  1. High blood pressure (hypertension) is recognised as the most common cause of AF.
  2. Ischemic heart disease
  3. Heart valve disease such as mitral stenosis and mitral regurgitation. These conditions can cause enlargement of the left atrium.
  4. Overactive thyroid gland
  5. High alcohol intake – Binge drinking in large amounts can cause atrial fibrillation. This condition is sometimes called ‘holiday heart syndrome’.
  6. Associated illnesses include pneumonia, urinary infections (in elderly), blood clots in the lung (called pulmonary embolism) and cancer.
  7. High intake of caffeine (coffee) and caffeinated drinks (like energy drinks and cola)

Around 10% of patients who have AF do not have an identifiable cause. This type of AF is called ‘lone AF’.

 Types of AF

There are 3 types of atrial fibrillation that have been described.

1. Paroxymsal AF

In this type of AF, symptoms start suddenly and last for less than 7 days.

2. Persistent AF

Here, atrial fibrillation lasts for more than 7 days. However, it can be changed back to a normal rhythm with medical treatment or shock therapy.

3. Permanent AF

Atrial fibrillation that has lasted for a long period of time (months to years) is called permanent atrial fibrillation. Patients would have tried many treatments without success, and the heart continues to beat in an irregular fashion.

Symptoms of atrial fibrillation

Patients with atrial fibrillation may experience the following symptoms –

  1. Palpitations or a feeling of the heart beating hard in the chest
  2. Chest pain
  3. Breathing difficulty – You may notice that you are out of breath at rest or when exerting yourself, which is not normal for you.
  4. Dizziness – This is because the blood pressure may drop due to inefficient contraction of the heart. This reduces the amount of blood reaching the brain, causing dizziness.

While the above are the common symptoms, a large number of patients do not develop any specific symptoms and may be completely unaware that they have this condition.

Diagnosis and tests

An electrocardiogram is the best test to diagnose atrial fibrillation. It can provide information on how fast the heart is beating.

AF

Atrial Fibrillation. Notice the irregular interval between the spikes.

However, in patients who have short lived episodes of atrial fibrillation (paroxysmal atrial fibrillation), a holter recording may be needed to pick up the irregular rhythm.

Other tests that can help include –

  1. Echocardiogram – This provides information on the structure and function of the heart muscle. It can also indicate any problems with the heart valves.
  2. Blood tests – The thyroid function test can help determine if it is overactive.

Complications of AF

One of the most dreaded complications of AF is the development of stroke. As the atrium is not contracting sufficiently, the blood does not completely empty out into the ventricle. The blood that remains behind can form clots, and these clots can migrate to the brain causing a stroke.

Other complications include –

  • Development of heart failure
  • Angina in patients who have underlying coronary artery disease

Treatment of atrial fibrillation

The aim of treatment in atrial fibrillation is either to control the heart rate (called ‘rate control’) or to convert the rhythm back to normal (rhythm control).

Rate control  is usually pursued if you have permanent AF. It can be achieved with the help of medications such as –

  • Beta blockers
  • Digoxin
  • Calcium channel blockers

These medicines are started at a small dose, and are increased over a period of time depending on the response. The aim is to bring the heart rate down to around 70 to 80 beats per minute. Various combinations of treatments may be needed, and these are different for different patients.

Rhythm control is pursued if you have paroxysmal or persistent atrial fibrillation. It can be achieved through 3 ways –

  • Medical therapy with drugs like amiodarone (called chemical cardioversion)
  • Shock therapy (called electrical cardioversion)
  • Catheter ablation

Rhythm control however is only offered if –

  • There is no complicated heart disease
  • The likelihood of AF returning is low on clinical assessment
  • If you are under the age of 65 years
  • If AF only developed recently
  • If the AF is causing additional problems with the heart such as heart failure

Rhythm control and cardioversion are not options in permanent AF.

Shock therapy is a useful way to treat AF. We have discussed this further here.

Catheter ablation is a specific technique where a wire is inserted into the heart through blood vessels in the leg. The wire is used to locate the different electrical generators and burns them, thus inactivating them. You can read more about the procedure here.

Anticoagulation treatment

Anticoagulation treatment is the administration of medication that thins the blood i.e. blood thinners.

Patients with AF are at a high risk of developing blood clots within the heart. These clots can migrate up to the brain and cause a stroke.

If you take blood thinners such as Warfarin or Acetrom, the risk of having a stroke is reduced dramatically. The decision to offer blood thinners depends on the risk of the patient developing a stroke, and this is usually calculated using a validated scoring system by your doctor (called the CHA2DS2VASc scoring system).

In the recent years, newer blood thinning agents have emerged including Dabigatran, Rivoroxaban and Apixaban. They are only used in some parts of India, and Warfarin or Acetrom are still preferred currently.

Patients taking blood thinners will require constant monitoring through the means of blood tests.

Prognosis

The prognosis of atrial fibrillation is generally very good. However, this can vary depending on the severity of the underlying heart conditions. As long as patients have good rate control and have the right dose of blood thinners, the long term outcomes are very good.

If you feel your heart racing or beating irregularly, make sure you visit your physician or cardiologist today for further management.

 

 

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