Atrial Fibrillation – Causes, Symptoms, Diagnosis, Prognosis and Latest Treatment

If you have heart beat that is quicker than 60-80 beats per minute at rest or 90-115 beats per minutes during exercise, you might have fast and irregular heart beat or arrhythmia.    There are different kinds of arrhythmia but atrial fibrillation (AF) is the most common type 

Causes

AF occurs when more than one cardiac cell in the upper chamber (atrial) of your heart are beating.  This usually occurs in patients who have pre-existing cardiovascular diseases (secondary AF) such as coronary artery disease, cardiac surgery, hypertension, myocardial infarction, valve disorders (e.g. mitral valve disease) and congestive heart failure.  The changes in cardiac structure associated with these diseases have damaged the conduction pathway of the cardiac muscle, making AF more prone to happen.

There are, however, some instances where there is no evidence of underlying disease and AF occurs spontaneously.  These are termed “lone AF” and happened in approximately 20% of AF patients. 

Symptoms

Beside a quicker heart rate, patients with AF also experience palpitations, chest pain, dyspnea, fatigue or light-headedness.

Diagnosis and Prognosis

The only way to find out whether you have AF is by conducting an ECG test.  Patients who have arrhythmia will find their P wave absence and their R-R interval shorten in their ECG.

The good news about AF is that it is not life-threatening, but patients with long-term AF occurrence can lead to stroke and heart failure.  In fact, patients with AF have a double risk of death, a 5-fold increase in stroke and a 3-fold increase in heart failure compared with those who do not have AF.

Treatment

Depending on your clinical situation (whether you have hypertension, diabetes or stroke or heart failure), your doctor might prescribe warfarin (Coumadin) or aspirin to prevent stroke and prescribe anti-arrhythmic drugs to slow down your heart rate and convert your heart into rhythm again.  In certain situations where pharmacological therapy fails to convert the heart into rhythm, ablation might be considered.

Anticoagulant

When taking warfarin (Coumadin), it is important to keep your INR is between 2.0 and 3.0.  An INR that is lower than 2 indicated that you are not protected from stroke while an INR of greater than 3 means that you might have an increased chance of bleeding.

Anti-arrhythmic agents

There are 2 methods to treat your AF: lower your heart rate (rate-control) or convert your heart into regular rhythm (rhythm-control).

Theoretically, rhythm-control drugs should be superior to the rate-control drugs.  However, the presence of some nasty side-effects associated with the rhythm control drugs prevents these drugs to demonstrate superior mortality benefit. 

As a result, the usage of one method over the other is subject to physicians’ discretion.  In general, younger patients with symptomatic AF will be given rhythm control drugs while older patients with minimal symptoms will be given rate control drugs.

A) Rhythm control drugs

Even though rhythm control drugs possess the ability to convert your heart into rhythm, it can also slow down your heart rate.

1) Amiodarone (Codarone) – Amiodarone is one of the oldest and most powerful antiarrhythmic drugs.  It is used mostly in patients with heart failure and with coronary heart diseases.  Its use, however, has been limited by its organ related side-effects such as hyper/hypothyroidism, pulmonary fibrosis and liver toxicity.

2) Sotalol (Betapace) – Sotalol belongs to the same class of drug as amiodarone.  It is less efficacious than amiodarone and is used in AF patients with coronary heart disease.  Since sotalol is very effective in reducing the heart rate, patients taking sotalol will often experience fatigue.

 3) Flecainide (Tamboco) and Propafenone (Rythmol) – Flecainide and propafenone are used in AF patients without any other cardiovascular heart diseases.  If used in AF patients with cardiovascular disease, it might also cause arrhythmia.  

 4) Dronedarone (Multaq) – Dronedarone is the latest addition to the rhythm control drugs.  It is less efficacious than amiodarone in preventing AF recurrences, but has a more favourable safety profile.  It is also the first and the only drug to demonstrate a reduction in cardiovascular mortality.  The most common side-effects associated with dronedarone are diarrhea, nausea and vomiting.

B) Rate control drugs

Rate control drugs can slow down your heart rate, but can not convert your heart into rhythm.  Most of these drugs have fewer side-effects than the rhythm control drugs.

In certain situation, physicians might prescribe a combination of beta-blockers and digoxin or calcium channel blockers and digoxin for you to control your heart rate

1)      Beta-blockers (metoprolol (Lopressor), propranolol (Inderal)) – B-blockers are the most effective drugs for slowing heart rate.  The effectiveness of these drugs to slow down the heart rate, however, might also make you tired.  If you always experience fatigue, you might need to inform your doctor and your doctor might install a pace-maker to prevent your heart from beating too slow.

2)      Calcium Channel Blockers (verapamil(Isoptin) and diltiazem(Tiazac)) – Calcium channel blockers are effective agents to slow down your heart rate with minimal adverse effects.

3)      Digoxin (Lanoxin) – digoxin is more effective at controlling heart rate during exercise than b-blockers or calcium channel blockers.  However, due to its narrow therapeutic range between efficacy and toxicity, digoxin is seldom used in AF patients.  It is used mainly in patients with heart failure.

Radiofrequency Ablation

Radiofrequency ablation involves inserting a catheter with an electrode at its tip into the heart and then using radiofrequency energy to destroy abnormal cardiac cells that stimulate AF.

Even thought ablation has a high initial success rate of 90%, it is not a cure.  More than 50% of the patients will have AF recur after 6 years.  Also, ablation is associated with some rare, but serious adverse side-effects (vascular access complications (1%), stroke and transient ischaemic attack (1%) and proarrhythmia (10-20%)).

If you have AF or other arrhythmia, it is important to get treated earlier.  The longer you wait, the more difficult it is to convert your heart back to rhythm again.  Your heart might have undergone extensive anatomical and electrophysiological that prevent it to respond to any anti-arrhythmic agents or surgical procedures.

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