Atrial Fibrillation

1. What is Atrial Fibrillation (AF)?

Atrial Fibrillation or AF involves an abnormality in the heart rhythm wherein the heart’s two atria (the upper chambers) beat irregularly, creating chaotic electrical heart signals, placing the two lower ventricles (the lower chambers) out of coordination as well. As the upper chambers or atria control the normal (sinus) heart rhythm, the body’s pulse becomes irregular.

AF is the most common heart rhythm abnormality, with increasing prevalence with older age affecting 4-5% of the population over 70. Young people may also develop AF with certain triggers.

Frequent episodes of rapid irregular heart rates can increase one’s risk of heart-related complications such as heart failure and stroke. Imagine that your heart is continuously a high heart rate akin to running a slow marathon, 24 hours a day! This is what AF could do, with sustained periods of high rates in excess of 110 beats per minute – it’s no wonder that the heart tires and starts to weaken without rest, and this is what then leads to heart failure.

AF increases your risk of stroke by between 4 and 5-fold, and it is important to seek urgent treatment to prevent a stroke, and other complications.

Single lead electrocardiogram (ECG) showing irregularly irregular heart rates, which characterises Atrial Fibrillation (AF)

Types of Atrial Fibrillation:

• Paroxysmal: This is AF which occurs intermittently. Symptoms may come and go, only lasting for a few minutes to hours before stopping spontaneously.
• Persistent: Your heart rhythm doesn’t go back to normal on its own that’s why an electrical shock is used to restore it.
• Long-standing persistent: With its definition as persistent, it is continuous and may last longer than a year.
• Permanent: With this type of AF, your abnormal heart rhythm cannot be restored and the focus of treatment will be to keep your heart rate under good control with medications.

2. Causes Of Atrial Fibrillation

Because AF produces an irregular and fast heart rhythm, your pulse rate in AF may typically range from 100 to 175 beats per minute. (Our normal heart rate is 60 to 100 beats per minute.)

Here are some causes of Atrial fibrillation:

• Abnormal heart valves
• Coronary Artery Disease (CAD)
• Congenital heart defects
• Heart attack (Myocardial Infarction)
• History of previous heart surgery
• Increased or high blood pressure
• Improper functioning of the heart’s pacemaker (or Sick Sinus Syndrome)
• Lung disease
• Metabolic imbalance such as an overactive thyroid gland
• Use of stimulants such as alcohol, caffeine, tobacco and certain medications
• Sleep apnoea (pauses in breathing while asleep)
• Stress due to illnesses such as pneumonia or surgery
• Viral infection

3. The role of the autonomic nervous system in AF

Nearly all arrhythmias, including AF, are triggered by the autonomic nervous system. This is the intrinsic (subconscious) nervous system that governs day-to-day bodily functions that we are unaware of, such as control of heart rate, blood pressure, temperature, peristalsis (gut movement), etc.

The fright or flight response, is one such strong manifestation of the autonomic nervous system and allows you to run for your life (or fight for it) in a threatening situation.

The opposite of this is called the “rest and digest” response – which is where for example after a meal, you get into a deeply relaxed state to allow digestion and recovery/rest of bodily functions.

The relevance of the autonomic nervous system is that some (up to 60%) of individuals may well experience AF which is triggered by autonomic states. For example, when AF occurs with exercise, infection or caffeine-ingestion, then these are clear “fright or flight” triggers for AF. Less commonly know about is the vagally-mediated AF triggers – which is when AF is triggered by:

1. A large meal
2. Dizzy/bubbly drinks
3. During sleep at night
4. Several hours after exertion (i.e. whilst recovering from a heavy workout).

In these instances, AF is said to be vagally-mediated (or vagal AF).

4. Signs and Symptoms of Atrial Fibrillation

With AF, you may experience:

• Chest pain
• Heart palpitations, which is an odd sensation of irregular heartbeats, with weak and strong beats, which may feel like a flip-flopping, racing, and uncomfortable sensation in the chest
• Dizziness
• Fatigue or weakness
• Lightheadedness
• Inability to exercise
• Shortness of breath

5. Diagnostic Investigations of AF

To diagnose AF, your doctor may assess your symptoms, conduct a review of your medical history and a thorough physical exam for signs on AF and complications such as heart failure. Your specialist may order tests to accurately diagnose AF including:

• Blood tests. To help rule out abnormal blood count, thyroid problems, and heart failure.
• Chest X-ray. Your doctor may order a chest X-ray to diagnose conditions other than atrial fibrillation that may explain your signs and symptoms.
• Echocardiogram. This test is noninvasive and uses ultrasound waves to produce a moving video image of your heart and its underlying structures in motion. Another form of echo is a transesophageal echocardiography, wherein your doctor may insert a tube with a transducer down your esophagus to exclude blood clots in your heart, which is typically done prior to a cardioversion or ablation procedure.
• Electrocardiogram (ECG). This is important as it is the primary diagnosing tool for AF.
• Event recorder. This is a portable ECG device that monitors your heart activity for a week or two depending on your doctor’s advice. You will be asked to activate it when you feel a fast heart rate.
• Holter monitor. This is another portable ECG device worn on a shoulder strap or belt, where it monitors your heart’s activity for between 24 and 72 hours. This aims to provide your doctor with a continued monitoring of your heart rhythm at the time of your symptoms. You will be asked to press a button, so an ECG strip will be printed during an episode of AF.
• Treadmill Stress Test. Also known as exercise testing, stress testing involves running tests on your heart while you’re running on a treadmill.
• Sleep apnoea screening. This is a wrist device that can be fitted easily which you can wear overnight. This screening test will be able to accurately diagnose sleep apnoea, which is a significant emerging risk factor for AF.

Dr. Boon Lim will be able to provide all these state-of-the-art diagnostic tests in modern comfortable surroundings. Please contact us to arrange this.

6. Atrial Fibrillation Treatment

Your treatment for atrial fibrillation will depend on a lot of factors and this includes the symptoms you experience, how long have you’ve had it and the underlying cause or triggers of AF.

The primary treatment goals are:

A. To decrease your risk of stroke
B. To reset your heart rate and rhythm

A. Decreasing stroke risk

Experiencing AF and undergoing treatments for AF may put you at risk for developing blood clots in your heart. If these blood clots become dislodged from the heart, and pumped into the blood vessels in the brain, you may suffer with a stroke. Your risk of stroke is determined by risk factors such as:
Congestive Heart Failure
Hypertension
Age (>65yo)
Diabetes
Stroke, or previous transient ischaemic attack (TIA or mini-strokes which fully resolve)
Vascular Disease (such as previous heart attack, peripheral vascular disease)
Sex (Female above 65yo)
These risk factors may be summarized as the CHA2DS2VASc, and your doctors will ask you all these questions above when assessing whether you should be started on anti-coagulant drugs.

Preventing blood clots by using anticoagulants

Your doctor may prescribe anticoagulants or blood-thinning medications. They are:

• Warfarin (Coumadin) is the oldest drug to avoid blood clots. Regular blood monitoring to check levels (INR – International Normalised Ratio) is advised to keep the levels well-controlled.
• Apixaban (Eliquis), Dabigatran (Pradaxa), Rivaroxaban (Xarelto), and Edoxaban (Lixiana) are termed Direct Oral Anticoagulants (DOAC) and are agents which have been introduced to replace warfarin as good alternatives. The immediate advantage of these are that they can be prescribed without the need for continuous lifelong monitoring, although they have similar effectiveness, and bleeding risks as warfarin. This means that your doctors may offer you these agents as a useful alternative to warfarin.

Aspirin, which is an antiplatelet drug, is no longer routinely recommended to prevent strokes in AF as a sole agent.

It may have a role, in combination with an anticoagulant drug, in patients who have had a past history of heart attacks or coronary artery stenting, but please be guided by your cardiologist on this. Other antiplatelet drugs include clopidogrel and ticragrelor.

Always check with your cardiologist before stopping any of these antiplatelet drugs.

B. Resetting your heart’s rate and rhythm

This is done through Cardioversion, a method used to reset to normal your heart rate and regular (sinus) rhythm.

A cardioversion may be offered depending on how long you’ve had AF and the underlying cause.

Cardioversion Methods:

Cardioversion using drugs

Depending on your likelihood of restoring normal rhythm, your doctor may prescribe a trial of drugs to cardiovert you. These are termed anti-arrhythmic drugs, and include agents such as amiodarone, flecainide, sotalol and propafenone. Your doctor will usually give you a trial of these drugs for at least 3 months to see if you are likely to cardiovert at home (termed spontaneous cardioversion), without need for a shock.

However, these drugs may fail to cardiovert you, in which case, the next step would be to arrange an electrical cardioversion.

Electrical cardioversion

This procedure is usually performed under a short general aneasthetic. Once asleep, an electrical shock is delivered to your heart through patches placed on your chest.

The shock stops your heart’s beat momentarily before normal rhythm (termed sinus rhythm) starts again.

Controlling your heart rate:

Your doctor may prescribe medications to control and restore your heart rate to normal. These include the following:

• Digoxin helps control your heart rate at rest, but not during physical activity.
• Beta blockers causes untoward side effects such as hypotension or low blood pressure.
• Calcium channel blockers are not prescribed if you have low blood pressure or heart failure.

If performing cardioversion and prescribing medications such as beta-blockers does not resolve your symptoms during AF, your doctor might recommend more invasive procedures that aim to restore normal rhythm.

These include:

Atrioventricular (AV) node ablation and pacemaker insertion. If all other treatment modalities do not work for you, your doctor might recommend an AV node ablation.

In this type of ablation, through a thin tube, radiofrequency is applied to prevent the atria from sending electrical impulses to the heart’s ventricles. A pacemaker is implanted prior to this procedure to provide electrical impulses to your heart.

Catheter ablation (keyhole surgery through the groin)

HOW IS AF ABLATION PERFORMED

This procedure is recommended if drugs or cardioversion do not successfully restore normal rhythm.

Occasionally, your doctors may offer this procedure to you as a first line (initial) treatment if you wish to avoid drugs. Your heart has “hot spots” (abnormal pacemaker cells acting like discharging triggers) causing the upper atria (upper chambers) to quiver and beat inefficiently.

These “hot spots” are typically located within the pulmonary veins, 4 vessels which drain blood from the lungs back into the heart.

In this procedure, your doctor will insert thin catheters (electrical wires) through tubes in your groin all the way to your blood vessels and heart.

Using electrical navigation (3D mapping systems and X-ray), your doctor will be able to position these catheters precisely to either freeze or cauterise (radiofrequency energy) these “hot spots” to destroy these areas, which will help minimize the chances of AF recurrence.

Surgical ablation (Maze) procedure

This may be recommended by your doctor if you don’t respond to noninvasive treatment or catheter ablation. This is clearly more invasive as it involves open heart surgery and is usually considered if you are undergoing heart surgery for any other reason such as heart valve replacement or coronary artery bypass surgery.

Occasionally, your surgeon will be able to perform keyhole chest surgery through small incisions in your chest wall on then right side, to access the left atrial chamber of the heart to perform surgery in this way.

Success rates of treatment

It is important that you understand that success rates of any treatment depend on many factors, such as the duration of AF, co-existing conditions such as valvular heart disease, and the structure of your heart. Please discuss these success rates with your doctor each time. In general, you can expect that with the paroxysmal (intermittent) form of AF, that success rates will be between 65 and 85%, and for persistent AF, this is usually lower at around 50 to 70%. You will need to be prepared for a repeat ablation, which is often necessary to treat recurrence of AF.

Complications of ablation

Complications from catheter ablation are rare, but include:

1. Groin haematoma (bruising), 4%
2. Pericardial effusion (small collection of fluid around the heart), 2%
3. Pericardial tamponade (due to perforation in the heart), which may necessitate a drain insertion into the chest wall), 1%
4. Phrenic nerve injury (causing diaphragm paralysis), 1%
5. Life-threatening complications (need for open heart surgery, stroke, heart attack, atrio-oesophageal fistula) <0.5%

The Correlation between Atrial Fibrillation (AF) and Obstructive Sleep Apnea (OSA)

Atrial Fibrillation (AF) is the most prevalent arrhythmia worldwide. It shares most of the same risk factors as another prevalent clinical disorder, sleep apnoea.

Obstructive sleep apnea (OSA), is characterized by persistent partial or complete collapse of the upper airway during sleep and is usually associated with excessive sleepiness during daytime.

The major risk factor for OSA include obesity with heavy snoring being a clear sign of risk of sleep apnoea, where you may wake up many times each night (but be unaware of this), to gasp for breath with an abrupt startle before going back to sleep.

Multiple research studies assert that OSA has a role in the initiation and development of atrial fibrillation due to the autonomic “stress” that apnoea places on the heart many times each night.

The presence of OSA complicates the success of medical treatment for AF specifically when doctors prescribe certain medications and initiate cardioversion. Similarly, there is also high recurrence of AF in patients who have undergone Catheter Ablation.

Therefore, aggressive treatment of OSA is an important holistic step in treating AF. This is usually done by reducing weight, maintaining a healthy diet and exercise, and if appropriate, to start continuous positive airways pressure (CPAP) ventilation at night, where a tight-fitting mask if worn at night time to keep the airways open. Effectively treating OSA significantly improves the success rates for AF.

Learn More: Sleep Apnoea & Atrial Fibrillation