S. V. T.

Tachycardia means a rapid heart rate of more than 100 beats per minute. Supraventricular means the problem starts in the upper part of your heart, above your ventricles (the lower chambers of your heart). If you have SVT, your heart may beat at a rate of about 140 to 250 beats per minute.

SVT episodes usually don't last long and go away on their own without any treatment. They often happen in young, healthy people. You will usually get fewer episodes of SVT as you get older, but you may find that the symptoms get worse. How long an episode lasts can vary from a few seconds or minutes, to several hours.

Supraventricular tachycardia (SVT) doesn't always cause symptoms but you’re more likely to have symptoms if you already have heart disease.
Symptoms you may get during an episode of SVT include:
being aware of your heart suddenly beating faster (heart palpitations)
feeling dizzy
feeling short of breath
chest pain
fainting 
These symptoms may be caused by problems other than SVT.
You may need to have a test called an ECG. An ECG records the electrical activity in your heart to see how well it's working. 
ECHO - This test uses ultrasound to provide a clear image of your heart muscles and valves and can show how well your heart is working. 
you can take antiarrhythmic medicines by doctor.
These include beta-blockers, calcium-channel blockers and antiarrhythmic medicines. You can also take them to prevent further SVT episodes.