A heart arrhythmia refers to an irregular heartbeat. Under normal circumstances, the sinus node in the right atrium of the heart acts as a natural pacemaker, producing an electrical impulse that stimulates the atria muscles to contract and pump blood into the ventricles. A slight delay allows the ventricles to fill with blood before they contract and pump blood to the lungs and the rest of the body.
A heart arrhythmia occurs when the electrical impulses are not coordinated. This causes the heart to beat too fast, too slow or irregularly.
Some people experience this as a fluttering or racing heart, which is usually harmless. Others experience more severe symptoms that can be life-threatening.
There are different types of heart arrhythmias. Tachycardia refers to a fast heartbeat with a resting rate of over 100 beats per minute, and bradycardia refers to a slow heartbeat with a resting rate of less than 60 beats per minute.
Common types of tachycardia include:
- Atrial fibrillation, caused by irregular electrical impulses. These result in rapid, irregular rhythm.
- Supraventricular tachycardia broadly refers to many forms of arrhythmia originating above the ventricles in the atria or AV node. It may cause sudden episodes of palpitations that begin and end abruptly.
- Ventricular tachycardia is a rapid, regular heart rate that doesn't allow the ventricles to fill and contract efficiently, making it difficult to pump enough blood to the body.
- Ventricular fibrillation occurs when rapid, chaotic electrical impulses cause the ventricles to quiver ineffectively instead of pumping the necessary blood to the body. Most people who experience ventricular fibrillation have an underlying heart disease.
Common types of bradycardia include:
- Sick sinus syndrome occurs when the sinus node that is responsible for setting a regular rhythm fails to send impulses properly. When this happens, your heart may alternate between beating too fast or too slow. It is more common among elderly persons.
- Conduction block refers to a blockage of your heart’s electrical pathway. It can occur in or near the AV node, or along other pathways to each ventricle. This leads to impulses being slowed or blocked.
In addition to tachycardia or bradycardia, you may also experience what is known as premature heartbeat. While it may feel like a skipped heartbeat, it is actually an extra beat. It can occur while you are at rest or be triggered by stress, strenuous activity or stimulants such as caffeine or nicotine. Frequent occurrence of premature beats, especially over several years, may lead to a weak heart.