Supraventricular Tachycardia (SVT) Overview

Supraventricular tachycardia, or SVT, is a family of cardiac arrhythmias that cause an inappropriately rapid heart rate. SVTs originate in the atria (the upper chambers of the heart). An older name for SVT, which you still may occasionally hear, is paroxysmal atrial tachycardia (PAT).

Symptoms

Typically, SVT occurs in discrete episodes, which most often begins very suddenly and stop equally suddenly. So the symptoms of SVT tend to appear out of nowhere and to disappear just as quickly. The duration of these episodes can be from a few seconds to several hours.

During an episode of SVT, the heart rate is at least 100 beats per minute but is usually closer to 150 beats per minute. In some people, the heart rate can become substantially faster than that, in some cases over 200 beats per minute.

In addition, a person can experience lightheadedness and dizziness, passing out, weakness, fatigue or dyspnea (shortness of breath). This means that SVT can be pretty annoying, and if it occurs often enough, SVT can even become very disruptive to your life. Fortunately, SVT is only rarely life-threatening.

Causes

SVT occurs due to a problem with the electrical connections in the heart. Usually, the electricy of the heart flows along a set pathway in a specific order.

Sometimes, the heart may form an extra connection which can suddenly disrupt the normal electrical patterns within the heart, temporarily establish new electrical patterns, and produce the arrhythmia.

Certain medical problems can cause or worsen a rapid heart rate, like anemia or hyperthyroidism. The SVT caused by such medical disorders is usually different from the more typical SVT, in that it tends to be more persistent. Adequate treatment usually requires aggressively treating the underlying medical problem.

Types

SVT is actually a family of related arrhythmias, and within this family, there are many types. The symptoms of all these types of SVT are the same. While the range of therapeutic options is also the same, the "optimal" therapy can vary, depending on the type.

So if you have SVT, you may want to ask your doctor about the specific type you have, so you can learn more about it.

Treatment

Acute episodes of SVT almost always stop spontaneously. However, many people have learned to stop their episodes by doing something to increase the tone of the vagus nerve. The easiest way to increase your vagal tone is to perform a Valsalva maneuver. A less pleasant method is to initiate the diving reflex by immersing your face in ice water for a few seconds.

You may also want to consider more chronic therapy aimed at preventing recurrent SVT. It is important to keep in mind that SVT is only rarely dangerous (but "merely" symptom-producing). This means there are many options for chronic therapy.

For instance, many people who have only very occasional and time-limited episodes of SVT opt for no specific treatment at all; they simply deal with their episodes as they occur.

In the large majority of cases, SVT can be cured once and for all by an ablation procedure. Most SVTs are caused by extra electrical pathways, and usually, those extra pathways can be accurately localized by electrical mapping during an electrophysiology study and then treated by destroying the abnormal tissue. Once the extra pathway is gone, the SVT should never come back.

Antiarrhythmic drugs can also be used to attempt to prevent SVT. But since these drugs are often only partially effective, and many of them have the potential to cause significant adverse effects, most doctors are reluctant to prescribe chronic antiarrhythmic drug therapy to treat SVT, which again is a benign arrhythmia that may occur only infrequently. In some people, however, a single dose of an antiarrhythmic drug, taken at the onset of SVT, can help terminate the episode more quickly.

A Word From Verywell

SVT, while rarely life-threatening, can cause significant symptoms and can become quite disruptive to a normal life. Fortunately, almost all varieties of SVT can be successfully treated and prevented.

If you have SVT, your best bet is to talk to a cardiac electrophysiologist (a cardiologist who specializes in heart rhythm problems), who can review with you the pros and cons of all the treatment options available for your specific type of SVT.