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Jumat, 21 Desember 2012

Wolff-Parkinson-White (WPW) syndrome

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Wolff-Parkinson-White (WPW) syndrome

Definition:
Wolff-Parkinson-White syndrome, or WPW syndrome, is the presence of an extra, abnormal electrical pathway in the heart that leads to periods of a very fast heartbeat (tachycardia).
The extra electrical pathway of Wolff-Parkinson-White syndrome is present at birth. People of all ages, including infants, can experience the symptoms related to Wolff-Parkinson-White syndrome.

Episodes of a fast heartbeat often first occur when people are in their teens or early 20s.
In most cases, the episodes of fast heartbeats aren't life-threatening, but serious heart problems can occur. Treatments for Wolff-Parkinson-White syndrome can stop or prevent episodes of fast heartbeats. A catheter-based procedure, known as ablation, can permanently correct the heart rhythm problems.

Symptoms:
Wolff-Parkinson-White syndrome symptoms are the result of a fast heart rate. Common signs and symptoms include:
  • Sensation of rapid, fluttering or pounding heartbeats (palpitations)
  • Dizziness
  • Lightheadedness
  • Fainting
  • Tiring easily during exercise
  • Anxiety
Symptoms most often appear for the first time in people in their teens or 20s. An episode of a very fast heartbeat can begin suddenly and last for a few seconds or several hours. Episodes often happen during exercise.
Symptoms in more-serious cases
If a person with Wolff-Parkinson-White syndrome also has a very rapid heart rate, more-serious symptoms can develop, including:
  • Chest pain
  • Chest tightness
  • Difficulty breathing
  • Sudden death
Symptoms in infants
Symptoms in infants with Wolff-Parkinson-White syndrome may include:
  • Shortness of breath
  • Not alert or active
  • Poor eating
  • Fast heartbeats visible on the chest
No symptoms
A person may have an extra electrical pathway in the heart but experience no fast heartbeat and no symptoms. This condition, called Wolff-Parkinson-White pattern, is discovered only by chance when a person is undergoing a heart exam for other reasons. Wolff-Parkinson-White pattern is harmless in many people.

When to see a doctor
A number of conditions can cause irregular heartbeats (arrhythmia). It's important to get a prompt, accurate diagnosis and appropriate care. See your doctor if you or your child experiences any symptoms associated with Wolff-Parkinson-White syndrome.
Call 911 or your local emergency number if you experience any of the following symptoms for more than a few minutes:
  • Rapid or irregular heartbeat
  • Difficulty breathing
  • Chest pain
Also call 911 if you are with a person who faints.

Causes:
The extra electrical pathway of Wolff-Parkinson-White syndrome is present at birth. An abnormal gene (gene mutation) is the cause of a small percentage of cases of the disorder. Wolf-Parkinson-White syndrome is associated with some forms of congenital heart disease, such as Ebstein's anomaly. Otherwise, little is known about why this extra pathway develops.

Normal heart electrical system
Your heart is made up of four chambers — two upper chambers (atria) and two lower chambers (ventricles). The rhythm of your heart is normally controlled by a natural pacemaker — the sinus node — located in the right atrium. The sinus node produces electrical impulses that initiate each heartbeat.
From the sinus node, electrical impulses travel across the atria, causing the atria muscles to contract and pump blood into the ventricles. The electrical impulses then arrive at a cluster of cells called the atrioventricular node (AV node) — usually the only pathway for signals to travel from the atria to the ventricles.

The AV node slows down the electrical signal before sending it to the ventricles. This slight delay allows the ventricles to fill with blood. When electrical impulses reach the muscles of the ventricles, they contract, causing them to pump blood either to the lungs or to the rest of the body.

Abnormal electrical system related to Wolff-Parkinson-White syndrome
In Wolff-Parkinson-White syndrome, an extra electrical pathway connects the atria and ventricles. This means that an electrical signal can bypass the AV node. When electrical impulses use this detour through the heart, the ventricles are activated too early — a condition known as preexcitation.

Abnormal rhythm or fast heartbeat in patients with WPW:
Two major types of rhythm disturbances can be related to the presence of the extra electrical pathway:
  • Looped electrical impulses. The problem with a fast heartbeat usually occurs in Wolff-Parkinson-White syndrome because electrical impulses travel down either the normal or the extra pathway and up the other one, creating a complete electrical loop of signals. This condition, called AV reentrant tachycardia, sends impulses to the ventricles at a very rapid rate. The ventricles, as a result, pump very quickly, causing symptoms.
  • Disorganized electrical impulses. If electrical impulses don't begin correctly in the right atrium, they may travel across the atria in a disorganized way, causing them to beat very quickly and out of step with each other. This condition is called atrial fibrillation. These disorganized signals also increase the pumping rate of the ventricles to some extent. If there's an extra electrical pathway, as with Wolff-Parkinson-White syndrome, the ventricles can beat even faster. The ventricles don't have time to fill up with blood and don't pump enough blood to the body. This less common condition can be life-threatening.
Complications:
Wolff-Parkinson-White syndrome doesn't cause significant problems for many people, but complications can occur, and it's not always possible to know your risk of serious heart-related events. If the disorder is left untreated, and particularly if you have other heart conditions, you could experience the following:
  • Sudden death
  • Chaotic electrical signals through the ventricles and very rapid beating of the ventricles (ventricular fibrillation)
  • Low blood pressure (hypotension)
  • Inability of the heart to pump enough blood (heart failure)
  • Frequent fainting spells
Treatments and drugs:
 The treatment goals for Wolff-Parkinson-White syndrome are to slow a fast heart rate when it occurs and prevent future episodes.

Stopping a fast heart rate
A fast heartbeat may correct itself, and you may be able to slow your heart rate using simple physical movements. However, you may need medication or other medical treatment to slow down your heartbeat. Ways to slow your heartbeat include:
  • Vagal maneuvers. Your doctor will ask you to perform an action called a vagal maneuver during an episode of a fast heartbeat. Vagal maneuvers affect the vagus nerve, which helps regulate your heartbeat. The maneuvers include coughing, bearing down as if you are having a bowel movement, and putting an ice pack on your face.
  • Medications. If vagal maneuvers don't stop the fast heartbeat, you may need an injection of an anti-arrhythmic medication, such as adenosine, to restore a normal heart rate. An injection of this drug is administered at a hospital. Your doctor may also prescribe a pill version of an anti-arrhythmic drug, such as flecainide (Tambocor) or propafenone (Rythmol, Rythmol SR), to take if you have an episode of a fast heartbeat that doesn't respond to vagal maneuvers.
  • Cardioversion. In this procedure, a shock is delivered to your heart through paddles or patches on your chest. The current affects the electrical impulses in your heart and restores a normal rhythm. It's typically used when maneuvers and medications aren't effective.
Preventing episodes of a fast heart rate
With the following treatments, it's possible to correct or manage problems related to Wolff-Parkinson-White syndrome in the majority of cases.
  • Radiofrequency catheter ablation. This procedure is the most common treatment for Wolff-Parkinson-White syndrome. In this procedure, catheters are threaded through the blood vessels to your heart. Electrodes at the catheter tips are heated to damage (ablate) the extra electrical pathway and prevent it from sending electrical signals. This procedure is highly effective, and complications — which can include heart injury or infection — are uncommon.
  • Medications. Anti-arrhythmic medications such as flecainide or propafenone may prevent a fast heart rate when taken regularly. Medications are usually given to people who can't undergo radiofrequency catheter ablation for some reason or don't want to have the procedure.
  • Surgery. The success rate for surgical destruction (ablation) of the extra pathway using open-heart surgery is almost 100 percent. However, because radiofrequency catheter ablation is almost as effective and less invasive, surgery for Wolff-Parkinson-White syndrome is now rare. It's typically reserved for people who are having heart surgery for other reasons.
If you don't have symptoms
If you have the Wolff-Parkinson-White pathway but don't have any symptoms, you probably won't need treatment. In some people without symptoms, the extra pathway may spontaneously disappear over time.
Your doctor may be able to evaluate your risk of having episodes of a fast heartbeat based on findings from an ECG or electrophysiological testing. If he or she determines that you may be at risk of an event, your doctor may suggest radiofrequency catheter ablation.

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