Diagnosing supraventricular tachycardia

Your GP may suspect you have supraventricular tachycardia (SVT) from a description of your symptoms.

If so,you may beasked to have anelectrocardiogram (ECG) or be referredto a cardiologist who specialises in heart rhythm disorders andabnormal heart beats (an electrophysiologist).

An ECG is a test that records the heart's rhythm and electrical activity. It's a painless procedure that's usually carried outin hospital or in your GP surgery, and takes about five minutes to complete.

Small stickers (electrodes) are stuck to your arms, legs and chest and connected via wires to an ECG machine. Every time your heart beats, it produces tiny electrical signals. An ECG machine traces these signals onto paper.

During an episode of SVT,your heart ratewill usuallybe between 140 and 250 beats per minute (bpm), compared toa normal heartbeat of 60-100bpm.

If the test is carried out while you're having an episode of SVT, the ECG will record your abnormal heart rate. This will confirm SVTand rule out other conditions.

However, itmay be difficult tocapture an episode,soyour doctor may ask you to wear a small, portable ECG monitor to record your heart rate, either continuously over 24or 48 hours, or from when you switch it on at thestart of an episode.Some monitors can be worn for a week or longer.

Further tests

Further tests may be carried out once SVT has been confirmed. These will help to determine the exact location of the problem in heart.

For example, you may be asked to take part in an electrophysiology study carried out under sedation, where soft, flexible wires are passed up a vein in your legand into your heart. The wires measure the electrical signals in your heart and allow doctors tolocate the problem.