Supraventricular tachycardia

Also called SVT, Palpitations, Fast heart rate

A heart suddenly racing at 150 to 250 beats a minute, then stopping just as abruptly. Frightening, usually harmless, and curable by a single procedure.

What it is

Episodes of a very fast heart rate arising above the ventricles, typically 150 to 250 beats per minute. They start and stop abruptly, which is the feature that distinguishes them from anxiety-driven palpitations that build and fade.

It is common, often begins in young adulthood, and in most people the heart is otherwise structurally normal. It is not the same as atrial fibrillation, which is irregular; SVT is fast and regular.

The most useful thing to know is that it is curable. Catheter ablation, a day-case procedure, cures the great majority permanently, and many people spend years having episodes without ever being told this is an option.

Vagal manoeuvres stop many episodes without any medication. The modified Valsalva, blowing hard against a closed airway then lying flat with the legs raised, is substantially more effective than the standard version and is worth learning properly.

Wolff-Parkinson-White syndrome is a related condition with an extra electrical pathway, visible on a resting ECG, which carries a small risk of dangerous rhythms and generally warrants ablation.

Signs you might notice

A sudden onset of a rapid, regular, pounding heartbeat, often described as switching on.

Chest discomfort or tightness, breathlessness, dizziness, sweating, and anxiety.

Sometimes needing to pass urine after an episode.

Episodes lasting seconds to hours, ending as abruptly as they began.

999: chest pain, fainting or collapse, severe breathlessness, or an episode that will not stop.

Any palpitations with fainting, or palpitations during exercise, need proper assessment rather than reassurance.

Getting an ECG during an episode is what secures the diagnosis, which is why going to A and E while it is happening is genuinely useful rather than a waste of time.

How it can affect day-to-day life

The anxiety it generates is often worse than the arrhythmia itself, and people frequently have their symptoms attributed to panic attacks for years. Both can be true, and the way to tell them apart is a tracing.

Caffeine, alcohol, stimulants, decongestants, poor sleep and dehydration all provoke episodes in many people.

Learning the vagal manoeuvres transforms the experience: the person moves from being at the mercy of it to having something to do.

Wearable devices and phone ECGs are now good enough to capture episodes and are worth using to get a recording.

Driving rules apply where episodes cause or could cause incapacity; ask rather than assume.

Supporting someone well

Get an ECG during an episode. Go to A and E while it is happening, or use a validated phone ECG device.

Learn the modified Valsalva properly: blow hard into a syringe or against a closed nose and mouth for 15 seconds, then lie flat and have the legs raised for 15 seconds.

Do not use eyeball pressure, and only use carotid massage if a clinician has taught it.

Ask about catheter ablation. It is curative for most people and is frequently not offered.

Reduce the provokers: caffeine, alcohol, energy drinks, decongestants, and short sleep.

Keep a diary of episodes: what, how long, what preceded it.

Ask for a resting ECG to look for Wolff-Parkinson-White.

Call 999 for chest pain, fainting or an episode that will not stop.

Where to get help

A GP practice for referral to cardiology; A and E during an episode to capture the tracing.

An electrophysiology service for ablation.

Arrhythmia Alliance run a helpline and are the specialist charity.

British Heart Foundation on 0808 802 1234.