Paroxysmal Supraventricular Tachycardia Explained

The heart is a two-stage electrical pump. A coordinated electrical signal is required for the heart muscle cells to contract in a coordinated way and generate a heartbeat. Normally, an electrical signal is generated in special pacemaker cells found in the sinoatrial (SA) node located in the right atrium or upper chamber of the heart.

This impulse spreads to the whole atrial muscle causing it to contract and push blood into the ventricle or the lower chamber of the heart.

The electrical signal continues to a junction box between the atrium and ventricle (the AV node), where there is a slight delay that allows the ventricle to fill before it contracts and pumps blood to the body.

The signal continues throughout the ventricles and causes them to beat and push blood to the body.

What Are the Risk Factors for Paroxysmal Supraventricular Tachycardia?

PSVT is more common in children and younger adults than in older adults. You increase your risk of experiencing PSVT by ingesting caffeine, alcohol, and illegal drugs, and by smoking.

There are also certain medications and conditions that can cause PSVT. The heart medication digitalis can lead to episodes of PSVT when taken in large doses.

Wolff-Parkinson-White syndrome is the most common cause of PSVT in children and infants. Someone with this disorder has an extra electrical pathway, or circuit, in the heart that leads to a rapid heartbeat.

In a normal heart, the sinus node directs electrical signals through one specific pathway, which regulates the frequency of your heartbeats.

An extra pathway, as is present in patients with Wolff-Parkinson-White syndrome, causes the fast heartbeat of PSVT.

What are the symptoms of paroxysmal supraventricular tachycardia (PSVT)?

One of the most common symptom of PSVT is heart palpitations, often described as a “rapid heartbeat.” There can also be a fullness in the throat that is associated with the rapid heartbeat.

Other symptoms include the following:

  • Lightheadedness,
  • Weakness and fatigue
  • Shortness of breath
  • Chest pressure
  • Syncope (passing out)

The symptoms of PSVT usually occur while the heart is beating quickly, but the fatigue can persist after the heartbeat returns to normal.

By its nature, PSVT is intermittent and its onset cannot be predicted. As well, once the heart starts to beat quickly, there is no way of predicting if and when it will return to normal rhythm on its own.

Some patients are unaware that their heart is beating quickly and PSVT is found only when the patient presents for care and is found to have a rapid heartbeat.

How is paroxysmal supraventricular tachycardia (PSVT) diagnosed?

The diagnosis of PSVT is based upon interpretation of the heart rate monitor and electrocardiogram.

Sometimes the diagnosis is difficult because the rapid heart rate resolves before the patient presents for medical care.

In these cases, where there is a recurrent pattern of palpitations, the healthcare professional may suggest monitoring the patient’s heart rate and rhythm as an outpatient.

A Holter monitor is a small device that can be worn for 24 or 48 hours that records every heartbeat and may give a clue as to the underlying cause of the palpitations. A 30-day event monitor may also be considered, which gives a longer window to detect the rhythm.

Again, a small monitor is worn, but with this device the patient triggers the recording when the palpitations begin. In some cases, specialized electrophysiology tests may be necessary to monitor the heart and try to reproduce abnormal rhythms.

Treatment

Episodes of paroxysmal supraventricular tachycardia often can be stopped by one of several maneuvers that stimulate the vagus nerve and thus decrease the heart rate.

These maneuvers are usually conducted or supervised by a doctor, but people who repeatedly experience the arrhythmia often learn to do the maneuvers themselves.

Maneuvers include straining as if having a difficult bowel movement, rubbing the neck just below the angle of the jaw (which stimulates a sensitive area on the carotid artery called the carotid sinus), and plunging the face into a bowl of ice-cold water.

These maneuvers are most effective when they are used shortly after the arrhythmia starts.

If these maneuvers are not effective, if the arrhythmia causes severe symptoms, or if the episode lasts more than 20 minutes, people are advised to seek medical intervention to stop the episode.

Doctors can usually stop an episode promptly by giving an intravenous injection of a drug, usually adenosine or verapamil.

Rarely, drugs are ineffective, and cardioversion (delivery of an electrical shock to the heart) may be necessary.

Prevention is more difficult than treatment. When episodes are frequent or bothersome, doctors usually recommend radiofrequency ablation.

For this procedure, energy that has a specific frequency is delivered through an electrode catheter inserted in the heart.

This energy destroys the tissue in which paroxysmal supraventricular tachycardia originates. If radiofrequency ablation is not an option, almost any antiarrhythmic drug may be effective.

Drugs commonly used include beta-blockers, digoxin, diltiazem, verapamil, propafenone, and flecainide.

What Is the Outlook for Paroxysmal Supraventricular Tachycardia?

In most cases, the outlook for PSVT is very good. As long as your doctor can rule out any underlying heart conditions, PSVT is not life threatening.

If you do have other heart conditions, your outlook depends on what they are and which treatments are available.

Unfortunately, having PSVT raises your risk for experiencing heart failure in the future.

Source & More Info: Healthline, Medicine Net and Merck Manuals

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