Dysrhythmia

Dysrhythmia (dis-RITH-mee-uh), or arrhythmia (a-RITH-mee-uh), is a change in the regular beat of the heart. The heart may seem to skip a beat, beat irregularly, or beat very rapidly or very slowly.

Dysrhythmia is any variation in the regular beat of the heart. Dysrhythmia occurs when the electrical impulses that control heartbeat do not work properly. This causes the heart to beat too slowly, too rapidly, or erratically. When the heart does not beat properly, it has trouble pumping blood effectively. When this occurs, the body's organs may be damaged or shut down. Sometimes dysrhythmia is minor, such as Annie's palpitation * . The heart naturally speeds up with emotion or exercise and slows down during sleep. Other times, dysrhythmia is more serious and life threatening such as when it is caused by heart disease.

The human heart is a muscular pump divided into four chambers: two atria located on the top and two ventricles located on the bottom. It is also an amazing piece of electrical machinery that, when healthy, keeps these chambers beating in an organized manner.

Normally, the SA node fires electrical impulses that trigger a heartbeat. In a normal adult, the heart beats about 60 to 100 times per minute. The atria contract about one-fifth of a second before the ventricles, allowing them to empty their blood into the ventricles before the ventricles contract. Dysrhythmia is an abnormal heartrate. It can occur when the SA node fires incorrectly in an abnormal rate or rhythm. It can also occur when the normal conduction pathway for the electrical impulse to the AV node and ventricles is interrupted. In some cases, cells in other parts of the heart fire an electrical impulse to trigger a heartbeat, which interrupts the heart's normal rhythm and beat. Some dysrhythmias are temporary and do not significantly affect the overall heart rate. Other dysrhythmias last longer and cause the heart rate to be too slow, too fast, or erratic.

External and internal forces can cause dysrhythmia. External factors include exhaustion, overexertion, emotional stress (such as when Annie delivered her campaign speech), cigarette smoking, alcohol consumption, and ingesting stimulants * , such as caffeine, decongestants, and cocaine. Internal factors include heart defects present at birth, thyroid problems, inflammatory diseases, and problems in the autonomic nervous system * , which carries nerve impulses from the brain and spinal cord to the heart. The most important factor that contributes to serious dysrhythmias, however, is heart disease, including coronary artery disease, abnormal heart valves, and congenital heart disease.

The more common dysrhythmias are as follows:

Dysrhythmias are extremely common, especially in older people. The American Heart Association estimates that millions of people experience dysrhythmia each year. Most cases are harmless. Some, however, are very serious and should be treated by a doctor.

Dysrhythmias are not contagious. Instead, they are more likely to occur in people who have certain risk factors. People who have heart or heart valve disease, an inflamed heart muscle or lining, or recent heart surgery are more likely to experience dysrhythmia. It is also more common in people with high blood pressure, diabetes, or chronic lung disease. Men are slightly more likely than women to experience dysrhythmias. Age is also a risk factor, with older people more likely to develop a dysrhythmia than younger people. Other risk factors include thyroid disorders, excessive alcohol consumption, smoking cigarettes, and consuming stimulants such as caffeine.

Symptoms of dysrhythmias can vary. Some people have no symptoms, whereas others experience fatigue, lightheadedness, dizziness, palpitations, fainting, shortness of breath, chest pain, and, in some cases, sudden collapse, cardiac arrest, and death. Although many dysrhythmias are harmless, a doctor should check them because they can signal heart disease or other conditions that need treatment.

Like fingerprints found at a crime scene, electrocardiogram * (EKG) tracings are important pieces of physical evidence that track irregularities in a heartbeat. Sometimes an abnormal heartbeat does not show up during a visit to the doctor. In that case, the patient wears a 24-hour Holter EKG monitor to track the heartbeat. A stress test, during which patients walk on a treadmill while being monitored, can help physicians see the effect of exercise on the heart.

Some people need treatment for their abnormal heart rhythms. Slow heartbeats can be controlled with the implantation of a battery-powered pacemaker that sends small electrical charges through an electrode placed next to the wall of the heart. In some cases, doctors prescribe medication to control and steady the heart's beating. Other treatments include implanting a cardioverter/defibrillator, which is a sophisticated device that senses an abnormal rhythm and delivers one or more lifesaving jolts of energy to shock the heart back to normal rhythm, can replace a defective natural pacemaker or a blocked pathway. In other cases, a catheter ablation, which is a surgical technique that uses a tiny device at the end of a catheter (a flexible tube) inserted into the heart to burn away the part of the heart causing the abnormal rhythm can be inserted in the patient.

Over the long term, managing risk factors can reduce dysrhythmia and keep the heart functioning correctly. Patients should follow steps to reduce high blood pressure and control cholesterol levels. Maintaining a healthy weight and eating a heart-healthy diet can also decrease risk. It is also recommended that people avoid smoking tobacco; eat a balanced, low-fat diet; and exercise regularly to keep the heart healthy.

See also Heart Disease: Overview • Heart Murmur

* palpitation is the sensation of a rapid or irregular heartbeat.

* stimulants (STIM-yoo-lunts) are a type of drug that produces a temporary feeling of alertness, energy, and euphoria.

* autonomic nervous system is a branch of the peripheral nervous system that controls various involuntary body activities, such as body temperature, metabolism, heart rate, blood pressure, breathing, and digestion. The autonomic nervous system has two parts—the sympathetic branch and the parasympathetic branch.

* electrocardiogram (e-lektro- KAR-dee-o-gram) is a test that records and displays the electrical activity of the heart. Also called an EKG.