An irregularly fast or erratic heartbeat that affects the heart's upper chambers.

Supraventricular tachycardia, also called SVT, is a type of irregular heartbeat, called an arrhythmia. During SVT, the heart beats about 150 to 220 times a minute. Heart failure, heart disease, thyroid disease and some medicines might cause SVT. Other causes include too much caffeine or alcohol, smoking, and drug misuse.

The main symptom is a very fast heartbeat. The fast heartbeat may come and go suddenly. Other symptoms may include a fluttering or pounding feeling in the chest, shortness of breath, dizziness, sweating, and fainting or near fainting. Some people don't have symptoms.

Most people with supraventricular tachycardia don't need treatment. For others, lifestyle changes, medicines and heart procedures may be needed.