Arrhythmias Are More Common Than People Think

Monday, September 20, 2004

Each day, the heart pumps about 2,000 gallons of blood through the body. The pumping action is regulated by the heart’s electrical system, which is powered by a natural pacemaker in the heart’s upper right chamber. The more active a person is, the faster the heart pumps. This electrical signal is distributed to the entire heart muscle via an intricate network of nerve fibers, much like the wiring in a house.

Any disturbance in the normal beating pattern of the heart is called an arrhythmia. Arrhythmias—disorders of the heart’s electrical system—are quite common, especially as people age. They can occur in people who have an otherwise healthy heart as well as in people with known heart disease.

Some arrhythmias are harmless, requiring only simple lifestyle changes—or no treatment at all. Other arrhythmias are more serious, and can lead to fainting, collapse, dizziness, stroke, or cardiac arrest. In fact, most deaths from cardiac arrest are caused by an arrhythmia and not a sudden blockage of the artery, as is commonly believed. Most of the cardiac arrests that lead to sudden death occur when the electrical impulses in the heart become rapid or chaotic or both. This irregular heart rhythm causes the heart to beat ineffectively. A small number of cardiac arrests are caused by severe slowing of the heart.

The two main categories of arrhythmia are:

  • Tachycardia—too fast a heartbeat (more than 100 beats per minute)
  • Bradycardia—too slow a heartbeat (fewer than 60 beats per minute)

Both types can occur in surges or as persistent conditions.

Signs and Symptoms
Symptoms of arrhythmias vary from person to person, and depend largely on the type of arrhythmia. Some people have no symptoms at all. Symptoms may include:

  • Palpitations (rapid, skipping, or pounding heartbeat)
  • Dizziness or fainting
  • Unexplained falls, particularly in elderly people
  • Angina (chest pain, pressure, or discomfort)
  • Shortness of breath or fatigue
  • In severe cases, cardiac arrest and death

People tend to downplay certain symptoms, especially if they occur only now and then. If you’ve experienced any of these symptoms, it’s important to see your doctor to determine if you have an arrhythmia or other heart-related problem.

Heart Attack Survivors at Risk
A heart attack caused by a blockage in the artery can damage the heart muscle, reducing the heart’s ability to pump. While many heart attack survivors strive to get more exercise; control their stress, blood pressure, and cholesterol, and eat a healthier diet, few are aware of the importance of knowing their “heart pump number.” This is a number you can measure just like blood pressure and cholesterol. The heart pump number, which indicates the heart’s ability to pump blood (the ejection fraction), normally runs at 50-60 percent.

The lower the heart pump number, due to damage to the muscle, the greater the risk for an arrhythmia. Your doctor can get important information from this number that can be lifesaving for you if it is lower than 40 percent.

Studies have shown an improved survival among high-risk patients with an ejection fraction less than 40 percent with the preventive use of an implanted defibrillator (see below). It’s important to ask your doctor to check your heart pump function and risk for future cardiac arrest.

Causes of Arrhythmia
An arrhythmia may be related to a heart condition (e.g., damage from a heart attack or scarring of the heart muscle from inflammation) or to other factors such as caffeine, stress, or medication. Many forms of heart disease can cause arrhythmia, such as severe coronary heart disease, congenital heart defects, congestive heart failure, heart muscle disease, heart valve disorders, high blood pressure, and other diseases.

Other factors that may increase the risk of developing an arrhythmia include age, thyroid problems, diabetes, overuse of alcohol, and illicit drug use. Rarely, exercise can provoke an arrhythmia in those who are susceptible. Usually, however, there is no clear trigger.

Testing and Diagnosis
The longer an arrhythmia lasts without detection or treatment, the greater the chances of potential permanent damage and additional heart dysfunction.

Several tests can performed to diagnosis and guide the treatment of an arrhythmia. Some tests are done by a cardiologist, and others are done by an electrophysiologist. Tests may include:

  • An electrocardiogram (EKG) records the heart’s electrical activity.
  • A stress test monitors heart rate and rhythm during walking or running.
  • A Holter monitoring digitally records and analyzes the heartbeat over 24 hours.
  • An event monitor is a small recorder that “captures” an arrhythmia that occurs once every few weeks.

Sometimes the heart’s electrical system may need to be checked with an electrophysiology (EP) study. This test, performed by an electrophysiologist, is similar to a cardiac catheterization. One or more electrode catheters are moved through the blood vessels into the heart under X-ray guidance. The catheters are placed at various points in the heart to record the transmission of electrical signals. The “electrical map” produced by the catheter readings charts the location, direction, and speed of signals through the wiring of the heart.

During this study, the heart can be stimulated to beat rapidly or irregularly to duplicate or identify the cause of symptoms. The test is done under sedation and is generally painless.

If an arrhythmia is diagnosed, in some cases no treatment is needed except, perhaps, for lifestyle changes and reassurance. When treatment is needed, it may include medication, a catheter ablation, and/or surgery to implant a pacemaker or defibrillator. These devices regulate the heart when it beats too slowly or rapidly.

  • Ablation is a catheter procedure used to destroy very small, selected parts of the heart that are causing tachycardia (rapid heartbeat). As a result, the heart’s normal, regular rhythm is restored. The ablation procedure is generally combined with an EP study.

  • A pacemaker is an electronic device that is implanted in the chest during a surgical procedure. Pacemakers correct an abnormally slow heartbeat by sending electrical impulses to one or more chambers of the heart to make the heart contract in a more regular rhythm. A pacemaker provides a “floor” for the heart rate so it doesn’t go below a certain level.

  • An implantable cardioverter defibrillator (ICD) is a device that is implanted in the chest to monitor for and correct episodes of an arrhythmia. If the heartbeat gets too fast, the ICD will stimulate the heart to restore a normal rhythm. In cases where the heartbeat is so rapid that the person may die, the ICD may give a life-saving electric shock (defibrillation) when needed to “reset” the heartbeat. A defibrillator provides a “ceiling” for the heart rate so it doesn’t get too fast. All defibrillators have a built-in pacemaker.

Some people also may need medications, and in some cases, open-heart surgery may be necessary to correct valve disease or coronary artery disease that cause arrhythmias.

Electrophysiology deals with the electrical wiring of the heart. An electrophysiologist is a cardiologist with special training in the heart's electrical system. Because cardiovascular disease and arrhythmias are usually linked, an electrophysiologist works with a cardiologist to diagnose and treat heart disease.

Dr. Sanjay Deshpande is an electrophysiologist on staff at Columbia St. Mary’s. For more information on arrhythmias, call 414-962-7500.


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