Supraventricular Tachycardia

Atrioventricular nodal reentry tachycardia (AVNRT)

Atrioventricular nodal reentry tachycardia (AVNRT) is the most common type of supraventricular tachycardia. People with AVNRT have episodes of an irregularly fast heartbeat (more than 100 beats per minute) that often start and end suddenly. The episodes are due to an extra pathway — called a reentrant circuit — located in or near the AV node that causes the heart to beat prematurely.

AVNRT tends to occur more often in young women, but it can affect anyone.

Diagnosis

Tests and procedures used to diagnose AVNRT may include:

• Blood tests to check thyroid function, heart disease or other conditions that may trigger an irregular heartbeat
• Electrocardiogram (ECG) to measure the electrical activity of the heart and measure the timing and duration of each heartbeat
• Holter monitor, which is a portable ECG device designed to record the heart's activity as you perform everyday activities
• Echocardiogram, which uses sound waves to produce images of the heart's size, structure and motion

Your health care provider might also try to trigger an episode with other tests, which may include:

• Stress test, which is typically done on a treadmill or stationary bicycle while the heart activity is monitored
• Electrophysiological study and cardiac mapping, which can reveal the precise location of the irregular heartbeat (arrhythmia)

Treatment

Most people with AVNRT don't need medical treatment. However, if you have prolonged or frequent episodes, your health care provider may recommend:

• Vagal maneuvers. You may be able to stop an episode of atrioventricular nodal reentry tachycardia by using particular maneuvers that include holding your breath and straining, dunking your face in ice water, or coughing.
• Cardioversion. If particular movements, such as coughing or straining, don't work, your health care provider may recommend cardioversion. This treatment can be done using medications or by delivering a shock to your heart through paddles or patches on your chest. The shock affects the electrical signals in your heart and can restore a typical heart rhythm.
• Medications. If you have frequent episodes of AVNRT, your health care provider may prescribe medication to control your heart rate or restore a normal heart rhythm.
• Catheter ablation. In this procedure, a health care provider threads one or more catheters through the blood vessels to the heart. Sensors at the tip of the catheter use heat energy (radiofrequency) or extreme cold (cryoablation) to scar a small area of heart tissue and block the faulty signals that are causing the arrhythmia.

Diagnosis

To diagnose supraventricular tachycardia (SVT), your health care provider will examine you and ask questions about your symptoms and medical history. Blood tests are usually done to check for conditions that can cause similar symptoms, such as thyroid disease.

Tests

Tests that may be done to evaluate the heart and diagnose supraventricular tachycardia (SVT) include:

• Electrocardiogram (ECG or EKG). An ECG records the electrical activity of the heart. An ECG measures the timing and duration of each electrical phase in the heartbeat. It can show how fast or slow the heart is beating.
• Holter monitor. This portable ECG device can be worn for a day or more to record the heart's activity during daily activities.
• Event recorder. This wearable ECG device is used to detect infrequent arrhythmias. You press a button when symptoms occur. An event recorder is typically worn for up to 30 days or until you have an arrhythmia or symptoms.
• Echocardiogram. Sound waves are used to create images of the heart in motion. An echocardiogram can provide details about the heart and heart valves.
• Implantable loop recorder. This device detects irregular heart rhythms and is implanted under the skin in the chest area.

Other tests that may be done include:

• Exercise stress test. Supraventricular tachycardia may be triggered or worsened by stress or exercise. During a stress test, you typically exercise on a treadmill or stationary bicycle while your heart activity is monitored. If you can't exercise and your provider thinks heart disease may be causing your arrhythmia, you may receive a drug during the test to stimulate the heart in a way that's similar to exercise.
• Tilt table test. Your health care provider may recommend this test if you've had fainting spells. Your heart rate and blood pressure are monitored as you lie flat on a table. The table is then tilted as if you were standing up. Your provider observes how your heart and the nervous system that controls it respond to the change in angle.
• Electrophysiological (EP) study. One or more thin, flexible tubes (catheters) are guided through a blood vessel, usually in the groin, to various spots in the heart. Sensors on the tips of the catheters record the heart's electrical patterns. An EP study allows a health care provider to see how electrical signals spread through the heart during each heartbeat.

Treatment

Most people with supraventricular tachycardia (SVT) don't need treatment. However, if you have long or frequent episodes, your health care provider may recommend the following:

• Carotid sinus massage. A health care provider applies gentle pressure on the neck where the carotid artery splits into two branches. During this type of massage, the body releases chemicals that slow the heart rate. Don't attempt to do carotid sinus massage on your own.
• Vagal maneuvers. Simple but specific actions such as coughing, bearing down as if having a bowel movement or putting an ice pack on the face can help slow down the heart rate. Your health care provider may ask you to do these actions during an episode of SVT. These actions affect the vagus nerve, which helps control the heartbeat.
• Medications. If you have frequent episodes of SVT, your health care provider may prescribe medication to control your heart rate or restore a typical heart rhythm. It's very important to take the medication exactly as directed in order to reduce complications.
• Cardioversion. Paddles or patches on the chest are used to electrically shock the heart and help reset the heart rhythm. Cardioversion is typically used when vagal maneuvers and medications don't work.
• Catheter ablation. In this procedure, the doctor inserts thin, flexible tubes called catheters through the veins or arteries, usually in the groin. Sensors on the tip of the catheter use heat or cold energy to create tiny scars in the heart to block irregular electrical signals and restore a typical heartbeat.
• Pacemaker. Rarely, a small, implantable device called a pacemaker is needed to stimulate the heart to beat. The pacemaker is implanted under the skin near the collarbone in a minor surgical procedure. A wire connects the device to the heart.

Lifestyle and home remedies

If you have supraventricular tachycardia, a heart-healthy lifestyle is an important part of your treatment plan.

Heart-healthy lifestyle changes include:

• Eating heart-healthy foods. Eat a healthy diet rich in fruits, vegetables and whole grains. Limit salt and saturated fats.
• Exercising regularly. Exercise daily and increase your physical activity.
• Quitting smoking. If you smoke and can't quit on your own, talk to your health care provider about strategies or programs that can help.
• Maintaining weight. Being overweight increases the risk of developing heart disease. Ask your health care provider what weight is best for you.
• Controlling blood pressure and cholesterol. Make lifestyle changes and take medications as prescribed to correct high blood pressure (hypertension) or high cholesterol.
• Avoiding or limiting alcohol. If you choose to drink alcohol, do so in moderation. For healthy adults, that means up to one drink a day for women of all ages and men older than age 65, and up to two drinks a day for men age 65 and younger.
• Maintaining follow-up care. Take your medications as prescribed. Get regular health checkups. Tell your provider if SVT symptoms worsen.

Alternative medicine

Some types of complementary and alternative therapies may help reduce stress. Stress can trigger supraventricular tachycardia in some people. Stress-relieving techniques include:

• Yoga
• Meditation
• Relaxation techniques

Preparing for your appointment

If you think you may have supraventricular tachycardia, make an appointment with your health care provider. If the condition is found early, treatment may be easier and more effective. You may be referred to a doctor trained in heart conditions (cardiologist).

Appointments can be brief. Because there's often a lot to discuss, it's a good idea to be prepared for your appointment. Here's some information to help you get ready for your appointment, and what to expect from your health care provider.

What you can do

• Be aware of any pre-appointment restrictions. At the time you make the appointment, be sure to ask if there's anything you need to do in advance, such as restrict your diet. You may need to do this if your health care provider orders any blood tests.
• Write down any symptoms you're having, including any that may seem unrelated to irregular heartbeats.
• Write down key personal information, including any family history of heart rhythm disorders (arrhythmias), heart disease, stroke, high blood pressure or diabetes, and any major stresses or recent life changes.
• Make a list of all medications, vitamins or supplements that you're taking. Include those bought without a prescription.
• Take a family member or friend along, if possible. Sometimes it can be difficult to remember all the information provided to you during an appointment. Someone who accompanies you may remember something that you missed or forgot.
• Write down questions to ask your health care provider.

For supraventricular tachycardia, some basic questions to ask your health care provider include:

• What's the most likely cause of my symptoms?
• Are there other possible causes for my symptoms?
• What kinds of tests will I need? Do I need to do anything to prepare for these tests?
• What's the most appropriate treatment?
• Are there any foods or drinks that you recommend I avoid? Is there anything you suggest that I add to my diet?
• What's an appropriate level of physical activity?
• How often should I be screened for heart disease or other complications of supraventricular tachycardia?
• I have other health conditions. How can I best manage these conditions together?
• Is there a generic alternative to the medicine you're prescribing?
• Are there any brochures or other printed material that I can take home with me? What websites do you recommend visiting?

What to expect from your doctor

Your health care provider is likely to ask you many questions. Being ready to answer them may save time to go over anything you want to spend more time on. Your health care provider may ask:

• When did you first begin having symptoms?
• Do you always have symptoms, or do they come and go?
• How severe are your symptoms?
• Does anything seem to improve your symptoms?
• What, if anything, appears to worsen your symptoms?
• Do you have a family history of irregular heart rhythms?