Disease of the month: Atrial Fibrillation

Atrial fibrillation (AF) is a type of heart rhythm disorder called an 'arrhythmia' and occurs when there is a fault in the electrical activity in the heart muscle, causing the heart to beat irregularly and in an uncoordinated way.

The regulation and coordinated pumping action of the heart is provided by a network of electrical connections, which deliver electrical signals to the heart muscle.

Inside the right atrium is the body's natural 'pacemaker', called the sinus node, and this generates regular electrical impulses in order for the heart to contract regularly.

The sinus node controls the rate at which the heart beats and can change the heart rate depending on the requirements of the body. For example, during exercise the body needs more blood that contains oxygen and the sinus node responds to this demand by generating faster electrical signals, which increases the heart rate.

After completion of the exercise and during rest, the sinus node slows down. The normal heart rhythm produced by a healthy sinus node is called 'sinus rhythm'.

In people with AF the 'normal' regular electrical signal from the pacemaker (sinus node) is no longer working properly. Instead of just the sinus node firing, other parts of the atria begin to send electrical signals. These signals however are not as regular or as co-ordinated as the signals from the sinus node and this leads to the atria (top chambers of the heart) not contracting properly and the ventricles (bottom chambers of the heart) beating irregularly.

Depending on how many electrical impulses reach the ventricles, the heart beat could be slow or fast, but it tends to be very fast in AF.

For example, in a person without AF at rest, the normal sinus node generates approximately 60 to 90 beats per minute. In a person with AF the atria generate about 600 impulses per minute, but usually only 80 to 120 of them will reach the ventricles and will make it contract.

Atrial fibrillation may be defined in various ways, depending on the degree to which it affects you:

 Paroxysmal atrial fibrillation - this comes and goes and usually stops within 48 hours without any treatment.
 Persistent atrial fibrillation - this lasts for longer than seven days (or less when it is treated).
 Longstanding persistent atrial fibrillation - this means you have had continuous atrial fibrillation for a year or longer.
 Permanent atrial fibrillation - atrial fibrillation is present all the time and no more attempts to restore normal heart rhythm will be made.
How common is Atrial fibrillation?

AF is the most common sustained cardiac arrhythmia, and estimates suggest its prevalence is increasing.

The actual prevalence is approximately 1% of the population and increases with age from approximately 0.7% in people aged between 55-59 years to 18% in those older than 85 years. AF is more common in males than in females.

What causes AF?

There are many factors that can increase the risk of developing AF, but no single universal factor. AF is more common in patients with certain health problems and is often associated with heart problems such as heart attacks, heart failure or disease of the heart valves. AF is also common in patients with abnormal functioning of their thyroid gland, those who have diabetes and/or those with high blood pressure (even if controlled by medication), and in patients with some lung illnesses, such as pneumonia, lung cancer, and pulmonary embolism.

It is also common in people who have obstructive sleep apnoea, whose breathing is interrupted during sleep. Excessive alcohol intake and illegal drug use have also been linked to an increased risk of AF.

However, in some people there is no obvious reason for the development of AF. These people are described as having 'lone AF' or AF with no underlying heart disease.

How serious is AF?

AF can cause significant discomfort (particularly if the sufferer has lots of symptoms) and this may reduce the ability to exercise and complete daily activities which may affect the quality of life.

Alternatively, in certain instances AF may not affect day-to-day life. AF itself does not pose a direct and immediate risk of death and many patients live with the arrhythmia for decades. However, AF can lead to serious complications.

The most common and serious complication of AF is stroke. People with AF have a five times greater chance of having a stroke compared to someone of the same age and sex who does not have AF.

Why does AF increase the risk of stroke?

Patients with AF have uncoordinated electrical activity in the top chambers of the heart, resulting in them not contracting properly. Due to this irregularity in the beating of the heart, the flow of blood is affected.

This can cause blood cells to stick together and increases the risk of a blood clot forming in the heart. In people with AF, the most common place for these blood clots to travel to is the brain and this can result in a stroke.

The bigger the clot is and the larger the blocked artery is, the more devastating the consequences of the stroke can be. If very small clots are dislodged from the main clot in the heart, a mini-stroke (TIA) could occur which is less severe than a stroke.

It is rare for patients with AF to develop symptoms from blockages in other arteries, for example a blockage in the arteries in the heart, resulting in a heart attack.

This is because the brain is affected much more by the loss of its blood supply caused by a blood clot and the brain produces symptoms when smaller blood vessels are blocked. In addition, there is a large flow of blood to the brain so clots emerging from the heart are more likely to be directed to the brain than elsewhere.

Treatment

Treatment varies from person to person and depends on the type of AF, the symptoms, age of the sufferer and whether or not there is an underlying cause for the AF. If a cause can be found treatment for this may often be sufficient.

If no underlying cause can be found, the treatment options are the following:

 Medicines to reduce the risk of a stroke - for example Warfarin
 Medicines to control atrial fibrillation - this will depend on the type of AF and includes anti-arrhythmic and beta blocker medication
 Cardioversion - this is where the heart is given a controlled electric shock to try to restore a normal rhythm
 Catheter ablation-a procedure that very carefully destroys the diseased area of the heart and interrupts abnormal electrical circuits. It's an option if medication has not been effective or tolerated.
Catheters (thin, soft wires) are guided through one of the veins into the heart, where they record electrical activity. When the source of the abnormality is found, an energy source (such as high-frequency radiowaves that generate heat) is transmitted through one of the catheters to destroy the tissue.
 Having a pacemaker fitted - this is often used in older people where medicines are not affective or unsuitable. Its purpose is to regulate and control the heart beat.

Underwriting considerations

The underwriter will need to know when the AF was diagnosed, the type of AF and whether or not there is any underlying cause.

Results of all investigations will need to be provided along with details of treatment and its effectiveness.

Terms will vary depending on the medical records provided and the age of the life to be insured.

Fergus Bescoby is underwriting development manager at VitalityLife