Supraventricular Tachycardia (SVT): A Patient Guide

The Saint Francis Heart and Vascular Institute

Supraventricular tachycardia or “SVT” is a sudden, fast heart rate (by definition, more than 100 beats per minute) lasting several minutes to hours. It may sometimes also be referred to as an arrhythmia or simply abnormal, fast heart rhythm. Because it is a malfunction of electrical signals, SVT can also manifest as sudden slowing down of the heart rate.

Sudden changes in heart rate that aren’t related to physical exertion can be very scary and confusing. Luckily, SVT is treatable and manageable once diagnosed.

I’m Dr. Andrew Hinojos with the Saint Francis Heart and Vascular Institute, and in this article I’ll outline everything you need to know about recognizing, treating and managing SVT for yourself or your loved ones.

How is SVT diagnosed?

While feeling a rapid and sustained heartbeat may suggest SVT, the only true way to diagnose it is to record the heart rhythm. This can be done with an electrocardiogram (EKG) or a heart monitor worn for an extended period.

Are there different types of SVT?

Yes, SVT is a generic term and typically it can be further classified as:

Atrioventricular nodal re-entrant tachycardia (AVNRT): This is a re-entrant tachycardia involving 2 functionally distinct pathways, generally referred to as “fast” and “slow” pathways. This is the most common type of SVT.
Atrioventricular re-entrant tachycardia (AVRT): This is a re-entrant tachycardia that involves a connection between the upper chamber (atrium) and lower chamber (ventricles) called an accessory pathway. This may also be referred to as Wolf-Parkinson-White or WPW.
Atrial tachycardia (AT): This is an arrhythmia originating from a localized site in the upper chambers of the heart.

Although other arrhythmias may be classified as SVT, AVNRT, AVRT, and AT are considered the most common types. Atrial fibrillation and/or atrial flutter may sometimes be classified as SVT: Atrial fibrillation (AF) is where the upper chambers of the heart (atria) beat rapidly and in an uncoordinated manner (fibrillation). This uncoordinated, rapid beating affects the flow of blood through the heart, causing an irregular pulse.

What symptoms are associated with SVT?

The main symptom of SVT is a very fast heartbeat that may last for minutes to hours. The fast heartbeat may come and go suddenly. Some people do not experience any symptoms with SVT.

Symptoms may include:

Pounding or fluttering feelings in the chest (palpitations)
Pounding feeling in the neck
Chest pain
Passing out or fainting
Lightheadedness or dizziness
Shortness of breath
Sweating
Weakness or extreme tiredness

What are the risks associated with SVT?

In most patients, the risks are the symptoms associated with episodes of SVT—i.e. a fall injury from dizziness or passing out.

Typically, but not always, SVT is recurrent and progressive. Patients may become more symptomatic and with longer episodes that can become more difficult to treat.

Patients with WPW (Wolf-Parkinson-White) may have an increased risk of sudden cardiac death if it is a pathway that conducts rapidly. If you have WPW, your provider will discuss this risk and if additional testing is needed.

What are ways of stopping an episode of SVT?

Vagal maneuvers: These are techniques designed to stimulate the vagus nerve, which slows down the electrical signals in your heart to abruptly stop the episode of SVT. There are many different types of maneuvers, but all are designed to have the same effect. An example is to close your mouth and exhale hard through your nose while straining as if you’re on the toilet. Other maneuvers involve blowing through a straw, blowing up a balloon, or ice-cold water on the face.
Medications: An injection of a medicine, such as adenosine, can be given in the hospital if vagal maneuvers are ineffective. It can block the abnormal electrical signals in your heart.
Cardioversion: This is a type of electrical shock provided in the hospital. This resets the heart back into normal rhythm.

How do I prevent future episodes of SVT?

In general, management of SVT typically involves medications and/or electrophysiology (EP) study and catheter ablation. Your provider will review your symptoms and make recommendations specifically for you.

What is an EP Study and Catheter Ablation?

An EP study is done to find out why your heart isn’t beating in a regular way. Although EKGs and heart monitors are accurate, they don’t provide all the information into the specific type of SVT.

An EP study will analyze the electrical activity in your heart (called cardiac mapping) and can help find where the arrhythmia is coming from, thus defining what type of SVT you’re experiencing. The procedure is minimally invasive—an electrophysiologist (cardiologist who specializes in diagnosing arrhythmias) will insert flexible wires (catheters) into the heart via a blood vessel in the groin.

From there, they’ll use a 3D cardiac mapping system to locate the abnormal heart tissue. If the type and location of the abnormal heart rhythm is found and treatment is decided, cardiac ablation may be done during the EP study.

Cardiac ablation is a way to fix an abnormal heart rhythm—during the EP study a special ablation catheter will be inserted. The tip of the catheter is very small and delivers energy (hot, cold, or electrical) to the abnormal tissue causing the arrhythmia, destroying it.

What are the outcomes for catheter ablation?

Compared to other options, catheter ablation can be very successful with an estimation of 97% cure rates for AVNRT, the most common type of SVT.

There is a low chance of recurrence of 1.3-4% over a patient’s lifetime. Typically, catheter ablation is the treatment of choice.

What can I do to help prevent future episodes of SVT?

Lifestyle changes may be effective if episodes are directly triggered to specific activities. For example, if episodes are triggered by excessive alcohol or caffeine intake, avoiding these may help.

Saint Francis Heart and Vascular Institute:

Saint Francis Hearth and Vascular Institute Arrhythmia Clinic is the leading provider of comprehensive arrhythmia care for patients in Tulsa and the greater Tulsa area.

Our team of specialists use state-of-the-art equipment to help you control your arrhythmia. Our staff includes medical assistants, nurses, advanced practitioners, and electrophysiologists who specialize in treating heart rhythm issues.