Tachycardia is the medical term for a heart rate over 100 beats per minute. There are many heart rhythm disorders (arrhythmias) that can cause tachycardia.

Types of tachycardia

There are many different types of tachycardia. They’re grouped according to the part of the heart responsible for the fast heart rate and cause of the abnormally fast heartbeat. Common types of tachycardia include:

• Atrial fibrillation. Atrial fibrillation is a rapid heart rate caused by chaotic, irregular electrical impulses in the upper chambers of the heart (atria). These signals result in rapid, uncoordinated, weak contractions of the atria.Atrial fibrillation may be temporary, but some episodes won’t end unless treated. Atrial fibrillation is the most common type of tachycardia.
• Atrial flutter. In atrial flutter, the heart’s atria beat very fast but at a regular rate. The fast rate results in weak contractions of the atria. Atrial flutter is caused by irregular circuitry within the atria.Episodes of atrial flutter may go away themselves or may require treatment. People who have atrial flutter also often have atrial fibrillation at other times.
• Supraventricular tachycardia (SVT). Supraventricular tachycardia is an abnormally fast heartbeat that starts somewhere above the lower chambers of the heart (ventricles). It’s caused by abnormal circuitry in the heart that is usually present at birth and creates a loop of overlapping signals.

• Ventricular tachycardia. Ventricular tachycardia is a rapid heart rate that starts with abnormal electrical signals in the lower chambers of the heart (ventricles). The rapid heart rate doesn’t allow the ventricles to fill and contract efficiently to pump enough blood to the body.Ventricular tachycardia episodes may be brief and last only a couple of seconds without causing harm. But episodes lasting more than a few seconds can become a life-threatening medical emergency.
• Ventricular fibrillation. Ventricular fibrillation occurs when rapid, chaotic electrical impulses cause the lower heart chambers (ventricles) to quiver instead of pumping necessary blood to the body. This can be deadly if the heart isn’t restored to a normal rhythm within minutes with an electric shock to the heart (defibrillation).Ventricular fibrillation may occur during or after a heart attack. Most people who have ventricular fibrillation have an underlying heart disease or have experienced serious trauma, such as being struck by lightning.