Atrioventricular Reentrant Tachycardia (AVRT)

Overview

Atrioventricular reentrant tachycardia (AVRT) is a rapid heartbeat condition that develops as a result of an extra electrical pathway between the upper and lower chambers of the heart. This condition is usually associated with Wolff-Parkinson-White (WPW) syndrome. The extra electrical pathway causes electrical signals to form a loop and the heart suddenly begins to beat very rapidly.

Normally, electrical signals between the upper chambers of the heart (atria) and the lower chambers (ventricles) pass through a single pathway called the AV node. In AVRT, however, there is an extra side pathway that has been present since birth. The electrical signal travels down the normal pathway and back up the side pathway, forming a loop. This loop can raise the heart rate to 150-250 beats per minute.

An AVRT episode (palpitation attack) usually begins suddenly and stops suddenly. In some people it occurs a few times in life, while in others it recurs frequently. In most cases it is not dangerous but it is bothersome. With permanent treatment methods, episodes can be completely prevented.

Symptoms

The symptoms of AVRT vary depending on how high the heart rate rises and how long the episode lasts.

The most common symptoms are:

• Suddenly starting heart palpitations. This is the most noticeable symptom. The heart suddenly begins to beat very rapidly and regularly. The person clearly feels their heart racing in the chest.
• Pulse sensation in the neck. During a rapid heartbeat, a pulse can be felt in the neck vessels. This is due to simultaneous atrial and ventricular contractions.
• Dizziness. When the heart beats very fast, blood pressure can drop and the brain may not receive enough blood. This creates dizziness and a feeling of lightheadedness.
• Shortness of breath. Breathing can become difficult during a rapid heartbeat.
• Chest discomfort. A feeling of pressure, tightness, or discomfort in the chest may be felt.
• Weakness and fatigue. When the heart beats rapidly, the body becomes tired.
• Feeling of anxiety and panic. Suddenly starting palpitations can create worry.
• Fainting. Rarely seen but fainting can occur if the heart rate is very high or blood pressure is very low.

Symptoms usually last anywhere from a few seconds to a few hours. The episode may stop on its own or may need to be terminated with certain maneuvers or medications.

When to See a Doctor

See a doctor in the following situations:

• If you regularly experience episodes of heart palpitations that start and stop suddenly, see a cardiologist.
• If chest pain, severe shortness of breath, or fainting develops during a palpitation episode, call emergency services immediately.
• If you have experienced such an episode for the first time, evaluation is important.
• If you notice sudden palpitation episodes in your child, see a pediatric cardiologist.

Causes

AVRT is due to the presence of an extra electrical pathway that forms during the development of the heart. This side pathway has been present since birth and is a hereditary condition.

Why this extra pathway forms in some people is not fully understood. In most cases, similar conditions are not seen in the family. Rarely, however, there can be familial inheritance.

Factors that can trigger AVRT episodes include physical activity, stress, caffeine, alcohol, inadequate sleep, and certain medications. Often, however, episodes can begin without any obvious trigger.

Complications

AVRT does not lead to serious complications in most people. In some cases, however, problems can develop.

• Heart failure. Long-lasting and frequently recurring rapid heartbeat can rarely weaken the heart muscle. This can occur particularly if episodes last for hours and recur frequently.
• Fainting and injury. There is a risk of fainting during an episode. Injury from falling can occur during fainting.
• Transition to atrial fibrillation. AVRT can rarely convert to atrial fibrillation. In the presence of WPW syndrome, atrial fibrillation can be dangerous because the extra electrical pathway can conduct very rapid signals to the ventricles.
• Decline in quality of life. Frequent episodes can negatively affect daily life, work performance, and psychological state.

Diagnosis

AVRT is diagnosed with an electrocardiogram (ECG) and sometimes advanced tests.

The diagnostic process typically includes:

• Electrocardiogram (ECG). An ECG taken during an episode confirms the diagnosis. The ECG shows narrow or wide QRS complexes with a rapid regular rhythm. An ECG taken when there is no episode is examined for the presence of WPW findings.
• Holter monitor. This is a portable ECG device worn for twenty-four hours or longer. It is used to capture episodes during daily life when episodes are infrequent.
• Event recorder. This is a small device worn for weeks or months. When you feel palpitations, you activate the device and the heart rhythm at that moment is recorded.
• Electrophysiology study. This is an advanced test performed via cardiac catheterization. Electrodes are placed inside the heart to map the electrical pathways. The exact location of the extra electrical pathway is determined and AVRT is deliberately triggered for evaluation. This test is used for both diagnostic and treatment purposes.
• Echocardiography. This images the structure and function of the heart. It is performed to investigate any accompanying heart abnormalities and to assess heart function.

Treatment

The aim of AVRT treatment is to stop episodes, prevent future episodes, and prevent complications.

Treatment approaches include:

• Vagal maneuvers. These are the first interventions that can be applied during an episode. Immersing the face in cold water, the Valsalva maneuver (bearing down while holding the breath), or carotid sinus massage (gentle massage in the neck area) stimulates the vagus nerve and can stop the episode. These methods are simple, safe, and can be effective.
• Emergency medication. If vagal maneuvers do not work, medication is given intravenously. Adenosine is the most commonly used medication and can stop the episode within seconds. Calcium channel blockers such as verapamil or diltiazem can be used as alternatives. Beta blockers can also be effective.
• Electrical cardioversion. If the episode does not stop with medications or the patient is not hemodynamically stable, an electrical shock can be applied. This method terminates the episode quickly.
• Preventive medication. In people who experience frequent episodes, medication can be used regularly to prevent episodes. Beta blockers, calcium channel blockers, or antiarrhythmic medications are used for this purpose. Medication does not permanently solve the condition, however, and may require lifelong use.
• Catheter ablation. This is the most effective method for permanently treating AVRT. A thin catheter is advanced to the heart through a vessel in the groin. Radiofrequency energy or cryoablation at the tip of the catheter destroys the extra electrical pathway. The procedure takes one to two hours and has a success rate above 95 percent. Most people recover completely after the procedure and no longer need medication. An overnight stay in the hospital may be required or discharge can happen the same day.

What to Do in an Emergency

During an AVRT episode you can try the following:

• Perform a vagal maneuver. Bearing down while holding a deep breath is the easiest method. Straining as if you need to use the toilet can be effective. Splashing cold water on your face or immersing your face in a basin of cold water can also be tried.
• Sit or lie down. Remaining standing increases the risk of fainting. Sit or lie down immediately.
• Try to stay calm. Panic can increase the heart rate even further. Try to breathe slowly and deeply.
• Ask for help. If the episode lasts longer than 15-20 minutes, if there is chest pain, or if you are fainting, call emergency services.

Living with AVRT

After catheter ablation, most people recover completely and continue their lives without restrictions. If ablation has not been performed or if medication is being taken, certain points should be kept in mind.

If you have AVRT, pay attention to the following:

• Identify triggers. Learn which factors trigger episodes. Caffeine, alcohol, inadequate sleep, and stress are common triggers. Avoid them if possible.
• Learn vagal maneuvers. Your doctor or nurse can show you effective vagal maneuvers. Learning these techniques allows you to intervene yourself during an episode.
• Have regular follow-up. Do not miss your cardiology appointments. The frequency of episodes and response to treatment should be monitored.
• Use your medications regularly. If you are taking medication, use it regularly as your doctor recommends. Stopping medication can increase the frequency of episodes.
• Consult about exercise. Most people can exercise safely. Before engaging in high-intensity or competitive sports, however, consult your cardiologist.
• Inform those close to you. Tell the people around you that you have AVRT and what they should do during an episode. They can especially help you with vagal maneuvers.
• Be careful about driving. If you experience frequent and unpredictable episodes, be careful when driving. In some countries, frequent episodes can be a barrier to holding a driver's license.

Preparing for Your Appointment

What you can do:

• Note when palpitation episodes started and how often they occur.
• How long did episodes last? Did they resolve on their own or did you go to the emergency room?
• Did you notice any triggering factors?
• Did you try vagal maneuvers? Did they work?
• List all medications and supplements you are taking.
• Mention if there is a family history of heart rhythm disorders.
• Write your questions down in advance.

Questions you can ask your doctor:

• Is the diagnosis of AVRT certain?
• Do I have WPW syndrome?
• What is the most appropriate treatment for me?
• How successful and risky is catheter ablation?
• Will I need to use medication for life?
• Can I exercise?
• I am planning pregnancy — what should I do?
• What should I do during an episode?

Your doctor may ask you:

• When did palpitation episodes begin?
• How long did episodes last?
• How did episodes end?
• Did you notice any triggering factors?
• Did you faint during an episode?
• Is there a family history of heart rhythm disorders?
• What medications are you taking?