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When your heart skips a beat

If you’re like many people, you’ve experienced heart palpitations—the feeling that your heart is pounding, beating too quickly or skipping beats.

Most often, palpitations are harmless. But because palpitations may signal a problem with your heart’s electrical system, you should discuss them with your healthcare provider.

The irregular heartbeats caused by electrical malfunctions within the heart are called arrhythmias. Here are the three main categories of arrhythmias:

Bradycardia. In bradycardia, the heart beats less frequently than normal, either because it beats slowly (less than 50 times per minute) or because it pauses between beats. Symptoms of a slow heartbeat include fatigue, shortness of breath and light-headedness. If the heart is pausing between beats, blackouts (called syncope) may occur.

Bradycardia can originate in three sites: the autonomic nervous system (the nerves that control heartbeat speed); the sinus node (called the heart’s spark plug because it kicks off each beat with an electrical signal); and the conduction system (the circuit that sends electrical signals throughout the heart muscle). A pacemaker is usually implanted to treat bradycardia.

Tachycardia. This condition is marked by a very rapid heartbeat. Symptoms include palpitations, shortness of breath, angina, light-headedness and syncope. The most dangerous form of tachycardia is ventricular fibrillation (VF), which can cause cardiac arrest or sudden cardiac death. Usually, VF occurs in people who have other major heart problems. People who go into VF have no effective heartbeat, so blood stops circulating. Without immediate treatment, a person who goes into VF will die. Treatment may include external defibrillation or cardiopulmonary resuscitation.

Treatment for less severe forms of tachycardia include antiarrhythmic medications and/or external cardioversion (also called defibrillation). In external cardioversion, an electrical shock is administered to the heart through the chest wall. In some cases, an internal cardioverter-defibrillator is implanted in the abdomen. This device senses when the heart is beating too fast and automatically administers a shock to restore normal rhythm. Some patients may benefit from the elimination (ablation) of the electrical pathway causing the tachycardia. Today, most ablation is done using a catheter (thin tube) to administer the radiofrequency energy that heats up and destroys the malfunctioning areas. Some patients who have undergone ablation need a pacemaker.

Irregularly spaced heartbeats. There are several types. The most common type is extrasystoles (extra beats), which, although usually harmless, may cause palpitations. Atrial fibrillation is another common arrhythmia. It produces a heartbeat that is both irregular and fast, which the patient experiences as a fluttering sensation. Treatment for irregularly spaced heartbeats may include antiarrhythmic medications and/or external defibrillation.