WPW Syndrome

WPW syndrome

The heart works by following a sequence of electrical signals that cause the heart chambers to contract in a certain order. Normally, the atrioventricular node acts like a junction box and controls the electrical impulses that pass between the upper and lower chambers of the heart (the atria and ventricles).

In Wolff-Parkinson-White (WPW) syndrome, the normal electrical activity of the heart is disrupted. There is a risk of developing a tachycardia (a fast heart rate) from time to time and other arrhythmias (heart rhythm disturbances). This sometimes causes serious problems. Radiofrequency ablation (destruction) of the accessory pathway is the common treatment. Medication is an alternative option.

What is the function of heart?

 Heart is a muscular organ in the body whose main function is to pump blood through the blood vessels too various parts of the body. It has two sides- the right side that receives deoxygenated blood from the body and sends this blood for oxygenation to the lungs, and the left side of heart, which receives oxygenated blood from the lungs and pumps this blood to the other parts of the body. The right side of the heart is composed of two chambers, i.e., right atrium, right ventricle, and they are separated by atrioventricular valve (tricuspid valve). The left side of the heart is composed of left atrium and left ventricle, separated by another atrioventricular valve (mitral valve).

What do you understand by electrical activity of the heart?

The hearts pumping action works well if the electrical signals that cause the muscles in each chamber to contract in a certain order. If this order is broken or changed then heart may not pump that well. The sequence of each heartbeat is as follows:

The sinoatrial node (SA node) in the right atrium is like a tiny in-built timer. It fires off an electrical impulse at regular intervals (about 60-80 per minute when you are resting and faster when you exercise). Each impulse spreads across both atria, which causes them to contract. This pumps blood through one-way valves into the ventricles.

The electrical impulse then gets to the atrioventricular (AV) node at the lower right atrium. The AV node acts like a junction box between the atria and ventricles. It can limit the number of electrical impulses that conduct from the atria to the ventricles and it also slows down the electrical impulse slightly. Most of the tissue between the atria and ventricles does not conduct the impulse. However, a thin band of conducting fibres called the atrioventricular bundle (AV bundle) acts like wires and carries the impulse from the AV node to the ventricles.

The AV bundle splits into two - a right and left branch. These then split into many tiny fibers (the Purkinje system), which carry the electrical impulse throughout the ventricles. The ventricles contract and pump blood through one-way valves into large arteries.

What do you understand by Wolff-Parkinson-White syndrome?

In thissyndrome, an accessory pathway (an extra connection) is present between the atria and ventricles. This means that as well as electrical impulses passing normally between the atria and the ventricles at the AV node, electrical impulses can also pass abnormally along the accessory pathway.

This accessory pathway is essentially a strand of extra heart muscle tissue passing between the atria and the ventricles. It is a congenital problem which means that it is present from birth. As the electrical impulse that passes along the accessory pathway can arrive at the ventricles more quickly than normal. There is not the usual impulse delay that occurs at the AV node and no limiting of the electrical impulses that pass through. This can cause the heart rate to speed up. The accessory pathway can also sometimes transmit electrical impulses backwards from the ventricles to the atria.

So, in WPW syndrome, the normal electrical activity of the heart is disrupted. There is a risk of developing a tachycardia (a fast heart rate) from time to time and other arrhythmias (heart rhythm disturbances). This can sometimes cause serious problems.

Because the muscle of the ventricles can contract early, WPW syndrome is known as a pre-excitation syndrome. It can lead to what is called a supraventricular tachycardia because the abnormal electrical impulse starts in the atria (the accessory pathway starts here). Tachycardia is a heart rate over 100 beats per minute. Supra means above and because the atria are above the ventricles, the tachycardia is supraventricular.

The common arrhythmia that occurs in WPW syndrome is a paroxysmal (intermittent) supraventricular tachycardia (PSVT). Other arrhythmias that can also occur include atrial fibrillation, atrial flutter and atrioventricular re-entrant tachycardia (AVRT). Rarely, another arrhythmia called ventricular fibrillation can develop.

What is the incidence of Wolff-Parkinson-White syndrome?

WPW syndrome probably affects somewhere between 1-3 in 1,000 people. It is more common in men. There does seem to be some genetic basis, as WPW syndrome can run in families. However, most cases of WPW syndrome occur in people with no known family history.

What is the presentation of Wolff-Parkinson-White syndrome?

People come with episodes of rapid heart rate (tachycardia). In some people, the rapid heart rate only ever occurs once or twice. In others, it can occur a few times per week. Many people may not be aware that they have WPW syndrome because their symptoms are mild or infrequent. If symptoms are present, some people first notice them during childhood. In others, they may not be obvious until middle age.

Symptoms can also vary from person to person. They can include palpitations (a sensation of feeling, or being aware of, your heartbeat) and mild dizziness or light-headedness. Chest pain or chest tightness can also sometimes occur.

In some people, symptoms can be more severe. For example, an episode of a very rapid heart rate (up to about 250 beats per minute) can occur. If your heart is beating this quickly, your blood pressure can drop because your heartbeats become less effective and this can lead to collapse (blackout). If your heart is beating very fast, this can also lead to a build-up of fluid in your lungs and shortness of breath. In extreme cases, your heart can stop beating altogether (a cardiac arrest). However, this is rare.

How do you diagnose Wolff-Parkinson-White syndrome?

It is generally diagnosed by doing an electrocardiogram (ECG). There are classic seen on an ECG are signs of the pre-excitation of their ventricles due to the accessory pathway. One such ECG change is known as a delta wave.Occasionally, WPW syndrome may be picked up on a routine ECG recording done for another reason such as a medical check-up. Sometimes an ambulatory ECG may be suggested. This is an ECG recording device that you wear usually over a 24-hour period. It can monitor your heart whilst you are going about your normal activities.

Special tests called electrophysiology studies may be carried out in some people. They can help to find the precise area in the heart where the accessory pathway is located.

How do you treat Wolff-Parkinson-White syndrome?

Most people with WPW syndrome are referred to a cardiologist (heart specialist).  No treatment is required if patient has no symptoms and there is low risk of complications. Treatment of choice is radiofrequency ablation. Other treatments include:

  • Radiofrequency ablation is usually the first treatment that is offered to those who have symptoms. It may even be considered in some people with no symptoms.

A thin tube called a catheter is inserted into an artery near your groin through a small cut in your skin. The tube is passed from here up to your heart. When the tip of the tube reaches the small area in your heart that causes the fast heart rate (the accessory pathway), this area is destroyed using a type of energy called radiofrequency. When carried out, radiofrequency ablation can have very good results and can cure the condition in the majority of people.

  • Medication to prevent episodes of rapid heart rate can be given , For example, for people who don't wish to have radiofrequency ablation, or in those where this has failed. Medicines may also be given in an emergency situation to slow down your heart rate, interrupt the accessory pathway and restore a normal heart rhythm. In the rare case that you are unwell with very low blood pressure, you may need treatment with oxygen and a shock to your heart using a defibrillator to restore a normal heart rhythm.
  • Traditional heart surgery used to be done more commonly in the past for WPW syndrome it has now been replaced by radiofrequency ablation in most cases.

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