Paroxysmal Supraventricular Tachycardia (PSVT)

Picture of the interior of the heart and chambers of the heart.

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.

The PSVT can cause the atrium to beat more quickly than it should normally (AFib).

In paroxysmal supraventricular tachycardia (PSVT), abnormal conduction of that electricity causes the atrium, and secondarily the ventricles, to beat very rapidly. It is referred to as paroxysmal because the rapid rate can occur sporadically and without warning and may also stop on its own. The rapid heartbeat may last a few seconds or many hours. Often the PSVT resolves before the patient reaches a health care professional.

In many patients with PSVT, there is a “wiring” problem in the AV node and instead of having just one pathway for electricity to travel to the ventricle, there are two. This allows electricity to circle back and cause the atrium to beat more quickly than it should normally. PSVT is one of many electrical abnormalities that cause the atrium to beat too quickly. These abnormalities were once lumped together and called paroxysmal atrial tachycardia or PAT but, as more has been learned about the electrical wiring of the heart, the terminology has been updated to better reflect the specific abnormal rhythm.

Some examples include

• atrial tachycardia,
• multifocal atrial tachycardia,
• atrial fibrillation,
• atrial flutter, and
• Wolff-Parkinson-White (WPW) syndrome.

As well, there are numerous abnormalities in the AV node that cause rapid heartbeats and palpitations. PSVT and other electrical abnormalities located in the atrium or AV node should not be confused with ventricular tachycardia, which arises from the ventricle and is potentially life-threatening.

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.

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.

For infrequent events, an implantable device (LINQ) can be placed just under the skin, and can scan for a month looking for rare rhythm changes.

There is a stepwise approach to treating the rapid heartbeat of PSVT.

Vasovagal maneuvers stimulate the vagus nerve and can slow the heart rate. Some options include holding one's breath and bearing down as if to have a bowel movement or splashing cold water on the face. A care professional might cautiously massage the carotid artery in the neck, but in older patients, there is a risk of stroke and this procedure is usually reserved for younger patients.

Depending upon the heart rhythm, medications can be injected intravenously to reset the AV node or to decrease heart muscle excitability. Adenosine is a short-acting medication that is commonly used as a first-line drug to treat PSVT. Other treatment options for other atrial tachycardias include calcium channel blockers, beta blockers, digoxin, and amiodarone.

If the PSVT does not convert with intravenous medication or if the patient has low blood pressure or complains of chest pain or shortness of breath, cardioversion may be required. This means that an electrical shock is given that resets the heart's electrical system to beat with a regular rate and rhythm.

PSVT can result because of underlying medical conditions or because of foods and medications that are ingested. Caffeine, alcohol, and over-the-counter (OTC) cold medications that contain pseudoephedrine can stimulate and irritate the heart's electrical conduction system and precipitate an episode of PSVT. Decreasing or avoiding use of these chemicals completely may prevent PSVT. Electrolytes abnormalities can cause heart electrical irritability. Abnormal thyroid levels can also precipitate abnormal heart rhythms.

Medications can be used to minimize the recurrence of PSVT, including calcium channel blockers, beta blockers, or other antiarrhythmic medications.

If PSVT continues to recur, an electrophysiologic study (EPS) can be done by a cardiologist and the electrical system of the heart can be mapped. If abnormal tracts or short circuits are found, they can be ablated or destroyed with high frequency radio waves and hopefully, prevent future episodes of PSVT. This is often a highly effective modality for patients with recurrent episodes who don't wish to have to take long-term medication.