What Is Non-Sustained Ventricular Tachycardia (NSVT)?

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Non-sustained ventricular tachycardia (NSVT) is an abnormal heart rhythm that starts in the the ventricles, which are the lower chambers of the heart. It occurs as three or more consecutive heartbeats at a rate of more than 100 beats per minute and lasts for less than 30 seconds.

Because it does not persist, NSVT is not considered as dangerous as sustained ventricular tachycardia (SVT), which lasts more than 30 seconds. In fact, while not true for everyone, NSVT may turn out to be completely harmless in some people.

This article reviews the possible symptoms and causes of NSVT, as well as how it is diagnosed. You'll also learn how this type of abnormal heart rhythm, or arrhythmia, is managed, and when you should seek medical attention.

NSVT Symptoms

NSVT is defined as an episode of ventricular tachycardia that:

  • Involves a heart rate of more than 100 beats per minute
  • Persists for at least three heartbeats
  • Lasts less than 30 seconds

Most often, NSVT does not cause any symptoms at all. If it does, palpitations—when one feels a fast or irregular heartbeat—may be the only one. The palpitations may be associated with trouble breathing or chest pain.

Occasionally, NSVT can cause light-headedness and/or dizziness. Rarely, loss of consciousness (syncope) may occur.

non-sustained ventricular tachycardia (NSVT) symptoms
Illustration by JR Bee, Verywell

When to Seek Medical Attention

While NSVT can be harmless, it can also be a marker for the development of sustained ventricular arrhythmias and sudden death.

It's important to see your healthcare provider if you are experiencing:

  • Fleeting chest pain
  • Light-headedness
  • Your heart racing, even if it comes and goes

Call 911 or seek emergency care if you are experiencing:

  • Trouble breathing
  • Chest pain lasting more than a few minutes
  • Chest pain accompanied by other symptoms, like nausea, light-headedness, and/or cold sweats

Causes

NSVT may be caused by a previously unknown structural heart disease—that is, a condition that alters the anatomy of the heart.

It may also stem from an electrical instability within the heart that can eventually lead to even more dangerous arrhythmias, such as ventricular fibrillation. This is when the heart stops beating as it should and begins to quiver instead, causing cardiac arrest.

There are also reversible factors that may contribute to the development of PVCs.

Structural Heart Disease

The kinds of heart disease most commonly associated with NSVT are:

NSVT is also seen with:

Electrical Instability

Sometimes, NSVT is caused by an electrical problem in the heart rather than a structural problem.

The most common of these conditions is repetitive monomorphic ventricular tachycardia (RMVT).

RMVT is a disorder that almost only occurs in young to middle-age patients without structural heart disease.

Common symptoms include palpitations and light-headedness. The episodes of NSVT in this disorder tend to be triggered by emotional stress or exercise.

Reversible Factors

Various reversible factors may trigger NSVT, such as:

  • Electrolyte imbalances (e.g., low potassium or low magnesium levels in the blood)
  • Substance use, including cocaine and methamphetamine use
  • Low oxygen level in the bloodstream (hypoxia)
  • A low number of healthy red blood cells in the bloodstream (anemia)
  • Certain non-heart conditions, like thyroid disease

Diagnosis

Because NSVT does not usually produce alarming symptoms, it is typically discovered during an electrocardiogram (ECG) done for another reason. If a person is having symptoms, NSVT may be diagnosed through an ambulatory ECG monitoring system.

Heart Rhythm Monitoring

Ambulatory ECG systems record the electrical activity of your heart over days, weeks, or even years. This longer monitoring period allows for heart arrhythmias that may come and go, like NSVT, to be detected and recorded.

A cardiologist—a physician who treats heart conditions—analyzes the recordings from the ambulatory ECG system for NSVT or another arrhythmia.

A Holter monitor is one type of ambulatory ECG system. This lightweight and portable monitor is connected by wires to small discs called electrodes that are taped to your chest. The Holter monitor is worn for 24 to 48 hours or longer and records your heart rhythm continuously.

Additional Testing

If NSVT is diagnosed, your healthcare provider will do further testing to determine if any reversible factors are present. For example, in addition to a medical history/physical exam, various blood tests like a basic metabolic panel, complete blood count, or thyroid-stimulating hormone (TSH) may be ordered.

Your healthcare provider will also want to determine if any underlying heart disease is present.

Tests that may be done to check for heart disease include:

If the results from one or more of these tests show that underlying heart disease such as coronary artery disease is present, treatment is directed toward that diagnosis.

If no underlying heart disease is found, patients may be referred to a heart rhythm specialist called a cardiac electrophysiologist to be evaluated for RMVT and other conditions that can produce this arrhythmia.

Recap

NSVT is diagnosed when an abnormal reading is captured during heart rhythm monitoring. Various blood tests and heart-related tests can confirm whether or not heart disease is the cause.

Treatment

The treatment of NSVT depends on the underlying cause of the arrhythmia and whether symptoms are present.

If no symptoms are present and there is no underlying heart disease, no treatment—other than periodic follow-up with a healthcare provider—may be necessary.

NSVT in patients with a healthy heart is usually considered harmless.

Medications

For patients with symptoms from NSVT, beta-blockerscalcium channel blockers, or Pacerone (amiodarone) may be used. Amiodarone is an antiarrhythmic drug—a medicine that works to keep your heart in a regular rhythm.

Tambocor (flecainide) and Betapace (sotalol) are also antiarrhythmic drugs, but they are not generally recommended to treat NSVT. This is especially true if the NSVT happens as a result of a heart attack.

However, these and other antiarrhythmic drugs may be used in certain cases when a patient has severe symptoms and is under the care of an electrophysiologist.

Ablation Therapy

For patients with severe symptoms or those who cannot tolerate or receive no benefit from anti-arrhythmic drugs, ablation therapy may be utilized.

This therapy involves the use of heat or cold energy to destroy the part of the heart that is deemed the source of abnormal electrical signals.

Ablation therapy is successful at treating NSVT around 80% of the time.

Implantable Cardioverter-Defibrillator

NSVT poses an increased risk of cardiac arrest and sudden death if it occurs in tandem with coronary artery disease or heart failure. This is especially true in people with hypertrophic cardiomyopathy.

With these conditions, the risk is related more to the reduced flow of the blood from the left ventricle (called the ejection fraction) than it is to the presence of NSVT itself.

To reduce the risk, an implantable cardioverter-defibrillator (ICD) may be recommended in certain patients.

An ICD is a battery-operated device placed underneath the skin on your chest. It monitors the rhythm of your heart and delivers mild electrical currents or shocks if the rhythm becomes abnormal.

Recap

NSVT treatment depends on the cause and if symptoms are present. Potential options include medication that controls your heartbeat, a procedure that destroys the abnormal electrical part of the heart, and an implantable device that helps normalize the heart's rhythm.

Prevention

NSVT cannot be directly prevented, but some heart conditions that cause it can be.

To optimize your heart health, it's important to do the following:

It's also important to see your healthcare provider for regular check-ups. These appointments are, among other things, to monitor you for high blood pressure, high cholesterol, and type 2 diabetes, all of which can contribute to the development of heart disease.

Summary

Ventricular tachycardia is an abnormally fast heartbeat caused by irregular electrical impulses that originate in the heart's lower chambers. Non-sustained ventricular tachycardia is a type that stops by itself within 30 seconds.

NSVT may arise in healthy people or in those with significant heart disease. Diagnosis involves the use of heart rhythm test or monitoring system. Other tests may be ordered to help figure out the cause of the ventricular tachycardia.

Treatment may not be necessary if there are no symptoms. But some with NSVT will need to address any underlying heart disease and/or alleviate serious symptoms. NSVT is often harmless, but can develop into a more dangerous ventricular arrhythmia and cause sudden death.

A Word From Verywell

While being diagnosed with NSVT may understandably cause you anxiety, keep in mind that this arrhythmia is common and may occur in healthy people. In other words, while it could be a sign of heart disease, it isn't always.

If you or a loved one is diagnosed with NSVT, be sure to see a cardiologist for a careful and detailed heart assessment. You can then move forward with a uniquely tailored treatment plan based on the presence or absence of symptoms or any heart problem.

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