Wolff-Parkinson-White Syndrome (Arrhythmia)

Arrhythmia An arrhythmia (ah-RITH-me-ah) is a problem with the speed or rhythm of the heartbeat. During an arrhythmia, the heart can beat too fast, too slow, or with an irregular rhythm. A heartbeat that is too fast is called tachycardia. A heartbeat that is too slow is called bradycardia.Most arrhythmias are harmless, but some can be serious or even life threatening. When the heart rate is too slow, too fast, or irregular, the heart may not be able to pump enough blood to the body. Lack of blood flow can damage the brain, heart, and other organs.

Understanding the Heart’s Electrical System The heart has an internal electrical system that controls the speed and rhythm of the heartbeat. With each heartbeat, an electrical signal spreads from the top of the heart to the bottom. As it travels, the electrical signal causes the heart to contract and pump blood. The process repeats with each new heartbeat.

Each electrical signal begins in a group of cells called the sinus node, or sinoatrial (SA) node. The SA node is located in the right atrium (AY-tree-um), which is the upper right chamber of the heart. In a healthy adult heart at rest, the SA node fires off an electrical signal to begin a new heartbeat 60 to 100 times a minute.

From the SA node, the electrical signal travels through special pathways to the right and left atria. This causes the atria to contract and pump blood into the heart’s two lower chambers, the ventricles (VEN-trih-kuls). The electrical signal then moves down to a group of cells called the atrioventricular (AV) node, located between the atria and the ventricles. Here, the signal slows down just a little, allowing the ventricles time to finish filling with blood. The electrical signal then leaves the AV node and travels along a pathway called the bundle of His. This pathway divides into a right bundle branch and a left bundle branch. The signal goes down these branches to the ventricles, causing them to contract and pump blood out to the lungs and the rest of the body. The ventricles then relax, and the heartbeat process starts all over again in the SA node.

A problem with any part of this process can cause an arrhythmia. For example, in atrial fibrillation, a common type of arrhythmia, electrical signals travel through the atria in a fast and disorganized way. This causes the atria to quiver instead of contract.

Overview There are many different types of arrhythmia. Most arrhythmias are harmless but some are not. The outlook for a person with an arrhythmia depends on the type and severity of the arrhythmia. Even serious arrhythmias can often be successfully treated. Most people with arrhythmias are able to live normal, healthy lives.

How the Heart Works The heart is a muscle about the size of your fist. The heart works like a pump and beats about 100,000 times a day.

A healthy adult heart generally beats 60 to 100 times a minute, but it can beat faster or slower at times. For example, physical activity, strong emotion, certain medicines, fever, or infection can make the heart beat faster. A person’s heart rate generally slows down during sleep. Some very fit athletes always have heart rates below 60 beats a minute because their hearts work so well.

The heart has two sides, separated by an inner wall called the septum. The right side of the heart pumps blood to the lungs to pick up oxygen. Then, oxygen-rich blood returns from the lungs to the left side of the heart, and the left side pumps it to the body.

The heart has four chambers and four valves and is connected to various blood vessels. Veins are the blood vessels that carry blood from the body to the heart. Arteries are the vessels that carry blood away from the heart to the body.


Heart Chambers The heart has four chambers or “rooms”—two on the left side of the heart and two on the right.

• The atria are the two upper chambers that collect blood as it comes into the heart.
• The ventricles are the two lower chambers that pump blood out of the heart to the lungs or other parts of the body.

Heart Valves Four valves control the flow of blood from the atria to the ventricles and from the ventricles into the two large arteries connected to the heart.

• The tricuspid (tri-CUSS-pid) valve is in the right side of the heart, between the right atrium and the right ventricle.
• The pulmonary (PULL-mun-ary) valve is in the right side of the heart, between the right ventricle and the entrance to the pulmonary artery that carries blood to the lungs.
• The mitral (MI-tral) valve is in the left side of the heart, between the left atrium and the left ventricle.
• The aortic (ay-OR-tik) valve is in the left side of the heart, between the left ventricle and the entrance to the aorta, the artery that carries blood to the body.

Valves are like doors that open and close. They open to allow blood to flow through to the next chamber or to one of the arteries, and then they shut to keep blood from flowing backward.

When the heart’s valves open and close, they make a “lub-DUB” sound that a doctor can hear using a stethoscope.

• The first sound—the “lub”—is made by the mitral and tricuspid valves closing at the beginning of systole (SIS-toe-lee). Systole is when the ventricles contract, or squeeze, and pump blood out of the heart.
• The second sound—the “DUB”—is made by the aortic and pulmonary valves closing at beginning of diastole (di-AS-toe-lee). Diastole is when the ventricles relax and fill with blood pumped into them by the atria.

Arteries

The arteries are major blood vessels connected to your heart.

• The pulmonary artery carries blood pumped from the right side of the heart to the lungs to pick up a fresh supply of oxygen.
• The aorta is the main artery that carries oxygen-rich blood pumped from the left side of the heart out to the body.
• The coronary arteries are the other important arteries attached to the heart. They carry oxygen-rich blood from the aorta to the heart muscle, which must have its own blood supply to function.

Veins

The veins are also major blood vessels connected to your heart.The pulmonary veins carry oxygen-rich blood from the lungs to the left side of the heart so it can be pumped out to the body.The vena cava is a large vein that carries oxygen-poor blood from the body back to the heart.

Types of Arrhythmia There are four main types of arrhythmia: premature (extra) beats, supraventricular arrhythmias, ventricular arrhythmias, and bradyarrhythmias.

Premature (Extra) Beats Premature beats are the most common type of arrhythmia. They are harmless most of the time and often don’t cause any symptoms. When symptoms do occur, they usually feel like a fluttering in the chest or a sensation of a skipped beat. Most of the time, premature beats need no treatment, especially in healthy people.

Premature beats that occur in the atria are called premature atrial contractions, or PACs. Premature beats that occur in the ventricles are called premature ventricular contractions, or PVCs.

In most cases, premature beats occur naturally, not due to any heart disease. But certain heart diseases can cause premature beats. They also can happen because of stress, too much exercise, or too much caffeine or nicotine.

Supraventricular Arrhythmias Supraventricular arrhythmias are tachycardias (fast heart rates) that start in the atria or the atrioventricular node (cells located between the atria and the ventricles). Types of supraventricular arrhythmias include atrial fibrillation (AF), atrial flutter, paroxysmal supraventricular tachycardia (PSVT), and Wolff-Parkinson-White (WPW) syndrome.

Atrial Fibrillation AF is the most common type of serious arrhythmia. It’s a very fast and irregular contraction of the atria. AF occurs when the heart’s electrical signal begins in a different part of the atrium than the sinoatrial (SA) node or when the signal is conducted abnormally. When this happens, the electrical signal doesn’t travel through the normal pathways in the atria, but instead may spread throughout the atria in a fast and disorganized manner. This causes the walls of the atria to quiver very fast (fibrillate) instead of beating normally. As a result, the atria aren’t able to pump blood into the ventricles the way they should.

In AF, electrical signals can travel through the atria at a rate of more than 300 per minute. Some of these abnormal electrical signals can travel to the ventricles, causing them to beat too fast and with an irregular rhythm. AF is not usually life threatening, although it can be dangerous when it causes the ventricles to beat very fast.

The two most serious complications of chronic (long-term) AF are stroke and heart failure. Stroke can happen when a blood clot travels to an artery in the brain, blocking off blood flow. In AF, blood clots can form in the atria because some of the blood “pools” in the fibrillating atria instead of flowing into the ventricles. If a piece of a blood clot in the left atrium breaks off, it can travel to the brain, causing a stroke. People with AF are often treated with blood-thinning medicines to reduce the chances of developing blood clots.

Heart failure is when the heart can’t pump enough blood to meet the needs of the body. AF can cause heart failure when the ventricles beat too fast and don’t have enough time to fill with blood to pump out to the body. Heart failure causes tiredness, leg swelling, and shortness of breath.

AF and other supraventricular arrhythmias can occur for no apparent reason. Most of the time, however, they are caused by an underlying condition that damages the heart muscle and its ability to conduct electrical impulses. These conditions include high blood pressure (hypertension), coronary artery disease, heart failure, or rheumatic heart disease.

Other conditions also can lead to AF, including overactive thyroid gland (too much thyroid hormone produced) and heavy alcohol use. AF also becomes more common as people get older.

Atrial Flutter

Atrial flutter is similar to atrial fibrillation, but instead of the electrical signals spreading through the atria in a fast and irregular rhythm, they travel in a fast and regular rhythm. Atrial flutter is much less common than atrial fibrillation, but has similar symptoms and complications.

Paroxysmal Supraventricular Tachycardia

PSVT is a very fast heart rate that begins and ends suddenly. PSVT occurs due to problems with the electrical connection between the atria and the ventricles. In PSVT, electrical signals that begin in the atria and travel to the ventricles can reenter the atria, causing extra heartbeats. This type of arrhythmia is not usually dangerous and tends to occur in young people. It can happen during vigorous exercise.

A special type of PSVT is called Wolff-Parkinson-White syndrome. WPW syndrome is a condition in which the heart’s electrical signals travel along an extra pathway from the atria to the ventricles. This extra pathway disrupts the timing of the heart’s electrical signals and can cause the ventricles to beat very fast. This type of arrhythmia can be life threatening.

Ventricular Arrhythmias

These are arrhythmias that start in the ventricles. They can be very dangerous and usually need immediate medical attention. Ventricular arrhythmias include ventricular tachycardia and ventricular fibrillation (v-fib). Coronary artery disease, heart attack, weakened heart muscle, and other problems can cause ventricular arrhythmias.

Ventricular Tachycardia

Ventricular tachycardia is a fast, regular beating of the ventricles that may last for only a few seconds or for much longer. A few beats of ventricular tachycardia often don’t cause problems, but ventricular tachycardia episodes that last for more than just a few seconds can be dangerous. Ventricular tachycardia can turn into other, more dangerous arrhythmias, such as v-fib.

Ventricular Fibrillation

V-fib occurs when disorganized electrical signals make the ventricles quiver instead of pump normally. Without the ventricles pumping blood out to the body, a person will lose consciousness within seconds and will die within minutes if not treated. To prevent death, the condition must be treated immediately with defibrillation, an electric shock to the heart. V-fib may happen during or after a heart attack, or in a heart that is already weak because of another condition. Health experts think that most of the sudden cardiac deaths that occur every year (about 335,000) are due to v-fib.

Torsades de pointes (torsades) is a specific form of v-fib with a unique pattern on anEKG (electrocardiogram). Certain medicines and imbalanced amounts of potassium, calcium, or magnesium in the bloodstream can cause this condition. People with a particular finding on an EKG test, called prolonged QT interval, are at increased risk of developing torsades. People with prolonged QT interval need to be careful about taking certain antibiotics, heart medicines, and over-the-counter medicines.

Bradyarrhythmias

Bradyarrhythmias are arrhythmias in which the heart rate is slower than normal. If the heart rate is too slow, not enough blood reaches the brain, and the person can lose consciousness. In adults, a heart rate slower than 60 beats per minute is considered a bradyarrhythmia. Some people normally have slow heart rates, especially people who are very physically fit. For them, a heartbeat slower than 60 beats per minute is not dangerous and doesn’t cause symptoms. But in other people, bradyarrhythmia can be due to a serious disease or other condition.

Bradyarrhythmias can be caused by heart attack, conditions that harm or change the heart’s electrical system (such as underactive thyroid gland or aging), an imbalance of chemicals or other substances (such as potassium) in the blood, or even some medicines (such as beta blockers).

Bradyarrhythmias also can happen as a result of severe bundle branch block. Bundle branch block is a condition in which the electrical signal traveling down either or both of the bundle branches is delayed or blocked. When this happens, the ventricles don’t contract at exactly the same time, as they should, and the heart has to work harder to pump blood to the body. The cause of bundle branch block is often an existing heart condition.

Arrhythmias in Children

Normally, a child’s heart beats between 70 and 100 times a minute. A newborn’s heart beats about 140 times a minute. A baby or child’s heart can beat faster or slower than normal for many reasons. As is true for adults, when children are active, their hearts will beat faster. When they are sleeping, their heart will beats slower. Their heart rates can speed up and slow down as they breathe in and out. All of these changes are normal.

Some children are born with heart defects that cause arrhythmias. In other children, arrhythmias can develop later in childhood. Doctors do the same kinds of tests in children and adults to diagnose arrhythmias.

Treatments for children with arrhythmias include medicines, electric shock (defibrillation), surgically implanted devices that control the heartbeat, and other procedures that fix distorted electrical signals in the heart.

What Causes an Arrhythmia?

An arrhythmia can occur when the electrical signals that control the heartbeat are delayed or blocked. This can happen when the special nerve cells that produce the electrical signal don't work properly or when the electrical signal doesn't travel normally through the heart. An arrhythmia also can occur when another part of the heart starts to produce electrical signals, adding to the signals from the special nerve cells and disrupting the normal heartbeat.

Stress, smoking, heavy alcohol use, heavy exercise, use of certain drugs (such as cocaine or amphetamines), use of certain prescription or over-the-counter medicines, and too much caffeine or nicotine can lead to arrhythmia in some people.

A heart attack or an underlying condition that damages the heart's electrical system also can cause an arrhythmia. These conditions include high blood pressure(hypertension), coronary artery disease, heart failure, overactive or underactive thyroid gland (too much or too little thyroid hormone produced), and rheumatic heart disease.

For some arrhythmias, such as Wolff-Parkinson-White syndrome, the underlying heart defect that causes the arrhythmia is present at birth (congenital). Sometimes, the cause of an arrhythmia can't be found.

What Are the Signs and Symptoms of Arrhythmias?

Many arrhythmias cause no signs or symptoms. When signs or symptoms are present, the most common ones are:

• Palpitations (a feeling that your heart has skipped a beat or is beating too hard)
  
• A slow heartbeat
  
• An irregular heartbeat
  
• Feeling of pauses between heartbeats

More serious signs and symptoms include:

• Anxiety
  
• Weakness
  
• Dizziness and light-headedness
  
• Fainting or nearly fainting
  
• Sweating
  
• Shortness of breath
• Chest pain

How Are Arrhythmias Treated?

Common arrhythmia treatments include medicines, medical procedures, and surgery. Treatment is needed when an arrhythmia causes serious symptoms, such as dizziness, chest pain, or fainting, or when it increases your chances of developing complications, such as heart failure, stroke, or sudden cardiac death.

Medicines

Medicines can be used to speed up a heart that's beating too slow, or slow down a heart that's beating too fast. They also can be used to convert an abnormal heart rhythm to a normal steady rhythm. Medicines can be used to control an underlying medical condition, such as heart disease or a thyroid condition, that might be causing an arrhythmia. Medicines used to convert an abnormal rhythm are called antiarrhythmics.

Some of the medicines used to slow a fast heart rate are beta blockers (such as metoprolol and atenolol), calcium channel blockers (such as diltiazem and verapamil), and digoxin (digitalis). These medicines are often used to slow the heart rate in people with atrial fibrillation.

Some of the medicines used to restore an abnormal heartbeat to a normal rhythm are amiodarone, sotalol, flecainide, propafenone, dofetilide, ibutilide, quinidine, procainamide, and disopyramide. These medicines often have side effects. Some of the side effects can make an arrhythmia worse or even cause a different kind of arrhythmia.

People with atrial fibrillation and some other arrhythmias are often treated with blood-thinning medicines (anticoagulants) to reduce the chances of developing blood clots. Aspirin, warfarin (Coumadin®), and heparin are commonly used blood thinners.

Medical Procedures Some arrhythmias are treated with a device called a pacemaker. The pacemaker is a small device that's surgically placed under the skin at the collarbone; wires lead from it to the atrium and ventricle(s). The pacemaker sends small electric signals through the wires to control the speed of the heartbeat. Most pacemakers contain a sensor that activates the device only when the heartbeat is abnormal.

Some arrhythmias are treated with a jolt of electricity delivered to the heart. This type of treatment is called cardioversion or defibrillation, depending on which type of arrhythmia is being treated.

Some people who are at risk for ventricular fibrillation are treated with a device called an implantable cardioverter defibrillator (ICD). This device is surgically implanted in the chest and connected to the heart with wires. It continuously monitors the heartbeat. If it senses a dangerous ventricular arrhythmia, it sends an electric shock to the heart to restore a normal heartbeat.

A procedure called radiofrequency ablation is sometimes used to treat certain types of arrhythmias when medicines don't work. In this treatment, a special wire is inserted through a vein in the arm or leg and threaded up to the heart. Radiowave energy is sent through the wire to destroy abnormal tissue in the heart that's interrupting the normal flow of electric signals. Radiofrequency ablation is usually done in the hospital as part of an electrophysiologic study.

Surgery Sometimes, surgery is used to treat arrhythmia. Often this is done when surgery is already being performed for another reason, such as repair of a heart valve. One type of surgery for atrial fibrillation is called "maze" surgery. In this operation, the surgeon makes small cuts or burns in the atria, which prevent the spread of disorganized electrical signals.

Coronary artery bypass surgery may be needed for arrhythmias caused by coronary artery disease. The operation improves blood supply to the heart muscle.

Other Treatments Vagal maneuvers are another arrhythmia treatment. These are simple exercises that sometimes can stop or slow down certain types of supraventricular arrhythmias. They stop the arrhythmia by affecting the vagus nerve, which is one factor that controls the heart rate. Some vagal maneuvers include:

• Gagging
• Holding your breath and bearing down (Valsalva maneuver)
• Immersing your face in ice-cold water
• Coughing
• Putting your fingers on your eyelids and pressing down gently

Vagal maneuvers aren't an appropriate treatment for everyone. Discuss with your doctor whether vagal maneuvers are safe and effective for you to try.

Who Is At Risk for an Arrhythmia? Populations Affected Millions of Americans have arrhythmias. They are very common in older adults. About 2.2 million Americans have atrial fibrillation (a common type of arrhythmia that can cause problems).

Most serious arrhythmias happen in adults older than 60. This is because older adults are more likely to have heart disease and other health problems that can lead to arrhythmias. Older adults also tend to be more sensitive to the side effects of medicines, some of which can cause arrhythmias. Some medicines used to treat arrhythmias can cause arrhythmias as a side effect.

Some types of arrhythmia happen more often in children and young adults. Paroxysmal supraventricular tachycardias (a fast heart rate that begins and ends suddenly), including Wolff-Parkinson-White syndrome, are more common in young people.

Major Risk Factors Arrhythmias are more common in people who have a disease or condition that weakens the heart, such as:

• Heart attack
• Heart failure or cardiomyopathy, which weakens the heart and changes the way electrical signals move around the heart
• Heart tissue that is too thick or stiff or that hasn't formed normally
• Leaking or narrowed heart valves, which make the heart work too hard and can lead to heart failure
• Congenital problems (problems that are present at birth) with the heart's structure or function

Other conditions also can increase the chances of arrhythmia, such as:

• High blood pressure
• Infections that damage the heart muscle or the sac around the heart
• Diabetes, which increases the risk of high blood pressure and coronary artery disease
• Sleep apnea (when breathing becomes shallow or stops during sleep), which can stress the heart because it doesn't get enough oxygen
• Overactive or underactive thyroid gland (too much or too little thyroid hormone in the body)

In addition to certain diseases and conditions, several other risk factors increase a person's chance of having an arrhythmia. Heart surgery, certain drugs (such as cocaine or amphetamines), or an imbalance of chemicals or other substances (such as potassium) in the bloodstream can increase a person's chance of having an arrhythmia.