What Is Non-Sustained Ventricular Tachycardia (NSVT)?

Ventricular tachycardia is an abnormally fast heartbeat caused by irregular electrical impulses that originate in the lower chambers of the heart (the ventricles). Ventricular tachycardia that stops by itself within 30 seconds is called non-sustained ventricular tachycardia (NSVT).

Any ventricular tachycardia is considered a potentially dangerous cardiac arrhythmia. However, because NSVT does not persist, it is substantially less dangerous than a sustained ventricular tachycardia (SVT) and may turn out to be completely benign.

Still, NSVT can cause potentially worrisome symptoms and may indicate an increased cardiac risk.

NSVT Symptoms

NSVT is defined as an episode of ventricular tachycardia that:

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

Most often, this either does not cause any symptoms at all or it causes palpitations. Occasionally, however, NSVT can produce lightheadedness, dizziness, or, more rarely, syncope (loss of consciousness).

Because NSVT often does not produce alarming symptoms, it is typically discovered incidentally while recording an electrocardiogram (ECG) or during some other form of cardiac monitoring.

Causes

NSVT may be caused by a previously unknown underlying heart disease.

It may also stem from an electrical instability that may become worse, leading to even more dangerous arrhythmias such as ventricular fibrillation.

Structural Heart Disease

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

• Coronary artery disease (CAD)
• Heart failure due to dilated cardiomyopathy

NSVT is also seen with:

• Hypertrophic cardiomyopathy
• Heart valve disease (especially aortic stenosis and mitral regurgitation)

Most of these conditions can be ruled out with an echocardiogram. A stress thallium test may also be useful if you have risk factors for CAD.

Electrical Instability

Sometimes, NSVT is caused by cardiac conditions that are not associated with structural heart disease (that is, heart disease that does not alter the anatomy of the heart).

The most common of these conditions is repetitive monomorphic ventricular tachycardia (RMVT). This is a congenital disorder involving the heart's electrical system that does not produce structural changes that are detectable with an echocardiogram.

Disorders like this that produce NSVT are usually diagnosed when a doctor notices particular characteristics of the arrhythmia on an ECG.

Diagnosis

Ambulatory ECGs may be used to evaluate whether or not your symptoms correlate with NSVT or another cardiac arrhythmia.

The monitor is worn for a fixed period of time up to 24 hours to continuously record your heart rhythm. A cardiologist then analyzes the recording for any arrhythmias that may accompany your symptoms.

In most cases, NSVT is significant as an indicator that underlying heart disease may be present. If a heart disease is subsequently discovered, treatment should be directed toward that.

If no underlying heart disease is found, in general, NSVT does not measurably increase the risk of cardiac arrest. From a strictly medical standpoint, it is often the case that no treatment is necessary.

Treatment

NVST 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 (an abnormally thick heart muscle).

With that being said, 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 defibrillator may be recommended in certain patients.

Having NSVT does not change the prognosis of valvular heart disease, including mitral valve prolapse. In these conditions, it generally should not be a factor in making treatment decisions.

Young people with a lot of NSVT and no structural heart disease may be referred to a cardiac electrophysiologist (a heart rhythm specialist) to be evaluated for RMVT and other conditions that can produce this arrhythmia.

These kinds of arrhythmias can sometimes be treated with ablation therapy.

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Medications

If drug therapy is used, beta blockers, calcium channel blockers, or amiodarone may be chosen. The decision depends on the circumstances around the NSVT, such as the presence of symptoms and overall cardiovascular health.

Medications like flecainide and sotalol are not generally recommended to treat NSVT, especially if the NSVT happens as a result of a heart attack. However, in certain highly symptomatic cases and under the care of an electrophysiologist, these and other antiarrhythmic drugs may be used.

However, antiarrythmic drugs are not always effective in treating symptoms of NSVT. In these cases, ablation therapy may be used and is successful at controlling symptoms around 80% of the time.

A Word From Verywell

The bottom line is that NSVT is important because it can be a clue to an underlying cardiac problem that needs to be evaluated and treated.

This means that anyone who is found to have NSVT needs to have at least a baseline cardiac assessment to look for potential underlying causes.