What is atrial fibrillation?
Atrial fibrillation (AF) is a common heart rhythm disorder that produces an irregular heartbeat. It is detrimental to heart function and causes considerable suffering for many individuals. It often occurs in older individuals and those with existing heart conditions, but can also affect young and otherwise healthy individuals.
Episodes of AF may last for minutes, hours, or even days before the heart corrects itself and normal heart rhythm is restored. Doctors call this “paroxysmal AF”. In some, the heart may stay in AF for a week or longer, and this is termed “persistent AF”.
How does AF occur?
AF refers to the presence of chaotic electrical activity in the heart’s upper chambers, the atria. This disorganized activity originates from the left atrium. Most often, it is triggered by flurries of electrical “sparks” from the four pulmonary veins, which drain blood from the lungs into the left atrium.
During AF, the chaotic electrical activity in the upper chambers results in these chambers quivering instead of pumping normally. The lower chambers receive rapid irregular signals from above, resulting in these chambers pumping to an abnormal irregular rhythm.
The longer the heart remains in AF, the more established it becomes. Addressing AF early in its course provides the best chance of restoring and maintaining normal rhythm in the long run.
Why do I have AF?
In many individuals who develop AF, the cause is unknown, and the heart is otherwise sound. In some individuals, AF can develop due to other conditions such as high blood pressure, prior heart attack, heart failure, leaky heart valves, alcohol excess, obesity, and sleep apnoea. There may be a familial tendency to have AF.
What are the possible consequences of AF?
- AF symptoms. The heart becomes inefficient at pumping blood around the body. This produces breathlessness, dizziness, and fatigue, often accompanied by palpitations. These are the key symptoms of AF, and are not in themselves life threatening.
- Stroke. During AF, blood flow in the heart’s upper chambers slows down, and can stagnate in the “nooks and crannies” of the left atrium. In some individuals, this may result in blood clot formation. If released into circulation, such blood clots may lodge in the brain causing stroke.
- Heart failure. AF causes the heart’s lower chambers to pump rapidly and irregularly. Left unchecked, these muscular chambers can weaken and distend, resulting in heart failure. It is important to prevent this either by slowing down the irregular heart rate with medications, or correcting the heart rhythm altogether so that normal electrical function resumes.
What tests do I need if I have AF?
You may require the following initial tests:
- Blood tests – To determine if there is an underlying condition that has provoked your arrhythmia, such as thyroid or electrolyte disturbances and to check the condition of your liver and kidneys.
- ECG – To evaluate your heart rhythm.
- Holter monitor – To evaluate your heart rhythm over a 24 h period. If you are in normal rhythm, this may reveal episodes of AF that correspond with your symptoms, or which you may be unaware of. However, if you are AF, this assesses whether your heart rate is too rapid, or is well-controlled with medications.
- Echocardiogram – To evaluate the structure and function of your beating heart. Left atrial size is an important indicator of how established AF has become. Left ventricular size and function provide an idea of whether there is an element of heart failure accompanying your AF. Your “ejection fraction” is a key measure of the strength of your heart.
What treatments are available for AF?
- Lifestyle changes and reduction of cardiac risk factors. Lifestyle factors have a major impact on the risk of AF. Obesity, low fitness level, poor diet, alcohol consumption, and smoking all increase the risk of AF. Keeping a healthy lifestyle reduces the chance of recurrent AF, and this means weight loss if you are overweight, daily exercise, a balanced diet, alcohol in moderation or not at all, and smoking cessation. If you have high blood pressure, heart failure, or diabetes, then optimal management of these conditions further lowers your risk of recurrent AF. Conversely, your AF will invariably worsen if these factors are not addressed.
- Blood thinners. In some individuals, AF promotes blood clot formation. Depending on a number of factors, you may benefit from a blood thinner (anticoagulant) to prevent blood clot formation and stroke. This may be warfarin, or one of the new generation of blood thinners: Pradaxa, Xarelto, or Eliquis.
- Antiarrhythmics. Antiarrhythmics medications include sotalol, flecainide, and amiodarone. These medications are used to prevent AF from occurring by suppressing pulmonary vein triggers and stabilizing the electrical properties of the atrial muscle tissue. In some individuals, these are highly effective at controlling symptoms. In others, they may be partially effective or ineffective, and may produce unwanted side effects.
- Rate-controlling medications. The most commonly used rate-controlling medications include atenolol, metoprolol, diltizem, verapamil, and digoxin. These do not prevent AF from occurring, but control the heart rate during AF by preventing overstimulation of the AV node. They are often used in combination with antiarrhythmic medications.
- Direct current reversion (DCR). When the heart remains in AF it can be reverted back to normal rhythm with an “electric shock” to the chest under a brief general anaesthetic. While usually successful, the shock does not prevent the heart from returning to AF in the future. Thus, most patients will also require medications and/or catheter ablation to help maintain the heart in normal rhythm.
- AF ablation. Catheter ablation for AF is a minimally invasive technique that is used to treat AF. This approach has also been used for decades in the curative treatment of many other heart rhythm disorders. It is particularly effective when combined with lifestyle changes. It is most effective early in the course of AF, and is normally performed under general anaesthesia.
- Pacemaker implantation followed by AV node ablation. AV node ablation involves cauterizing the main electrical connection between the upper and lower chambers of the heart. This does not cure AF but prevents AF in the upper chambers from overstimulating the lower chambers. As a result, the heart relies on a pacemaker to generate the electrical signals that regulate the heart beat. This approach is very effective at reducing symptoms.
Which treatments are right for me?
Three major treatment goals
- Stroke prevention.
- Heart failure prevention.
- AF symptom control.
The most important consideration is stroke prevention. In fact, the only treatment shown to save lives in AF is the use of blood thinners to prevent stroke. Several options are available that are generally equally effective. These differ in safety (in particular, availability of an antidote), convenience (once vs twice daily dosing), and use in individuals with advanced kidney disease.
In preventing heart failure and controlling AF symptoms, the next major consideration is whether to attempt to keep the heart in normal rhythm, or to accept episodic or continuous AF. This is a sometimes controversial issue that requires an individualized approach. A combination of medications, DCR, and/or catheter ablation may be appropriate for you, depending on your circumstances.