AVRT (atrioventricular re-entrant tachycardia): symptoms, tests and treatment

The NHS explains that supraventricular tachycardia (SVT) happens when the electrical system that controls your heart rhythm is not working properly, so the heart suddenly beats much faster, then can slow down abruptly. A normal resting heart rate is 60 to 100 beats a minute; with SVT it goes above 100.

AVRT is one mechanism behind SVT. In normal hearts, the electrical signal passes from the upper chambers (atria) to the lower chambers (ventricles) through one route. In some people there is a second, extra route. The British Heart Foundation describes this extra pathway as one that can send additional electrical signals between the upper and lower chambers and creates a loop; signals travel round the loop and the heart beats very fast. A fast rhythm that uses the extra pathway as part of that loop is what clinicians call AVRT.

The NHS and BHF pages read for this guide describe the extra pathway under the heading of Wolff-Parkinson-White (WPW) syndrome rather than using the abbreviation AVRT. That is why this page draws on those sources: they describe the same underlying wiring difference and the same fast-heartbeat episodes.

The BHF makes a useful distinction. Some people have the extra electrical connection but never have a fast heartbeat. That is called a WPW pattern, seen on an ECG, rather than WPW syndrome. People with WPW syndrome are those who also get episodes of tachycardia. The NHS says that sometimes the condition is found when you have tests for another reason, in people with no symptoms.

The BHF says WPW syndrome affects between 1 and 3 people out of 1,000, is sometimes found to run in families, and is more common in men than in women. The NHS also says it is more common in men and in people with other heart conditions.

So a person can have an extra pathway for life without trouble, while another person has repeated episodes that need treatment. Which group someone falls into is decided by symptoms, the ECG and, if needed, more detailed heart rhythm testing.

The NHS says the main symptom of WPW syndrome is suddenly getting a very fast heartbeat, which can last from a few seconds to several hours and usually stops by itself. How often it happens varies, from every day to a few times a year or less. You may feel a fluttering in the chest or a pounding, racing heartbeat, dizziness or faintness, shortness of breath, or chest pain or discomfort.

The BHF adds that episodes can be triggered by strenuous exercise, stress, caffeine or alcohol, and that symptoms can include feeling anxious and sweating. In babies and small children, the BHF says WPW may show up as not feeding well, being restless or unsettled, a blue or grey tint to the skin, lips or nails, or fast or difficult breathing, and it advises booking a GP appointment if you see these signs.

The NHS says symptoms usually start in adults aged between 30 and 50 but can happen at any age, while its SVT page says SVT often starts for the first time in children and young adults, with many people having first symptoms between 25 and 40.

• Call 999 or go to A&E, as the NHS advises, if a fast heartbeat keeps happening or is getting worse, does not go back to normal after a few minutes, or comes with dizziness, sickness, faintness, breathlessness or chest pain.

• The BHF also lists pain in the chest, neck, jaw, arms or back for more than 15 minutes, or fainting without being able to be woken, as reasons to call 999.

• Do not drive yourself to A&E; the NHS says to ask someone to drive you or call 999 for an ambulance.

• See a GP if you keep getting a fast or noticeable heartbeat, so it can be recorded and checked.

The NHS says a GP who thinks you may have a heart problem such as WPW syndrome will refer you to a cardiologist. It is usually diagnosed with an electrocardiogram (ECG), where sensors on the chest record the heart, ideally while you have symptoms.

Other tests the NHS lists are an exercise ECG on a treadmill or exercise bike, wearing a small heart monitor for 24 hours or longer, an ultrasound of the heart (echocardiogram), and an electrophysiological (EP) study, which uses thin tubes (catheters) passed through a vein to the heart to look at how it works in more detail. The BHF also mentions an adenosine test, in which a small amount of medicine is injected into a vein to let doctors see extra pathways.

The BHF notes two typical routes to diagnosis: a WPW pattern seen on an ECG during or after an episode needing medical attention, or during routine investigation of palpitations.

Treatment depends on symptoms and on whether the cardiologist thinks you are at high risk of serious problems. The NHS says you might not need any treatment if you have no symptoms or mild symptoms that happen rarely, and the BHF says someone with a WPW pattern who has never had a fast heartbeat probably will not need treatment, and for some young people it gets better as they grow up.

To stop an episode, the NHS says doctors may teach vagal manoeuvres such as coughing, breathing techniques or putting very cold water on the face. If those do not work, an injection of medicine into a vein or electrical cardioversion, a procedure using electricity to reset the rhythm, may be needed. The BHF describes further manoeuvres such as the Valsalva manoeuvre and says your doctor will show you which are right for you.

To prevent episodes, the NHS says the main treatment is cardiac ablation, a procedure to burn or freeze a small section of the heart, which usually works well. Medicines to block the extra signals or control heart rate may be offered, and the NHS and BHF advise avoiding triggers such as alcohol, caffeine and intense exercise. The NHS SVT page says catheter ablation permanently cures the problem in most people.

The BHF says WPW syndrome is not usually serious but that people with it can sometimes also have atrial fibrillation. This can increase the risk of a very fast heartbeat that can become life-threatening if not treated, although the BHF stresses this is rare. People in high-risk jobs, such as pilots or professional athletes, and people at risk of a life-threatening rhythm may be offered treatment to lower the risk.

The NHS says that if doctors think you are at risk, you will be offered treatment to prevent a life-threatening rhythm. Even if you do not need treatment, the BHF says it is important to keep to your appointments so that your specialist can check how your heart is working.

Many people with episodes find that learning a vagal manoeuvre, noting triggers and having a plan for when an episode does not settle give them confidence. The BHF says that if you have been diagnosed and have an episode, you should first try the techniques you have been taught or take any medicines you have been given.

In the UK, assessment usually runs through the GP and an NHS cardiology or arrhythmia service, including ablation. Some people choose a private cardiology appointment for ECG monitoring or an opinion. If so, it helps to bring copies of ECG tracings and letters so that the NHS and private teams work from the same information.