Paroxysmal Supraventricular Tachycardia (PSVT)

What is paroxysmal supraventricular tachycardia (PSVT)?

Normally, an electrical signal is generated in special pacemaker cells in the upper chamber (atrium) of the heart. This impulse causes the atrium to beat in a coordinated fashion and push blood into the ventricles (the lower heart chambers). The electrical signal continues to a junction box between the atrium and ventricle (the AV node), where there is a slight delay. This allows the atrium to contract and send blood to the ventricle. The signal continues throughout the ventricles and causing them to beat and push blood to the body.

In paroxysmal supraventricular tachycardia (PSVT), abnormal conduction of that electricity causes the atrium, and secondarily the ventricles, to beat very rapidly. It is paroxysmal, because the rapid rate can occur sporadically and without warning. It may last a few seconds or many hours. Often the PSVT resolves before the patient reaches a healthcare provider. The abnormal conduction pathways may occur anywhere in the atrium or around the AV node.

PSVT was once also called paroxysmal atrial tachycardia or PAT. As more has been learned about the electrical wiring of the heart, terminology has changed, and the term PAT is more often reserved for a specific type of circular electrical conduction pattern occurring in the true atrial tissue, and not the AV node.

Regardless of the terminology, the rhythm disturbance occurs in the AV node, or in the atrium above, and should not be confused with ventricular tachycardia, which arises from the ventricle and is life-threatening.

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

PSVT often presents with the complaints of palpitations described as a rapid heart rate often felt in the throat and may be associated with:

• lightheadedness,
• weakness,
• shortness of breath, and
• chest pressure.

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 care provider may suggest a test known as a Holter monitor. This is a small device worn for 24 or 48 hours that records every heart beat and may give a clue as to the underlying cause of the palpitations. If this fails to give direction, a 30-day event monitor may be considered. Again, a small monitor is worn, but with this device the patient triggers the recording when the palpitations begin.

How is paroxysmal supraventricular tachycardia (PSVT) treated?

Treatment for PSVT is directed at resetting the electrical conduction of the heart. Maneuvers to stimulate the vagus nerve and slow the heart may be the first line treatment. These include straining as if to have a bowel movement or putting cold water on the face. Otherwise, intravenous medications, like adenosine, can be used to convert the heart to a normal rate and rhythm. Less commonly, electrical cardioversion can be used to shock the heart into a normal electrical pattern when other treatments have failed.

How can paroxysmal supraventricular tachycardia (PSVT) be prevented?

There are several measures that may help prevent PVST. Caffeine, alcohol, over-the-counter cold medications that contain pseudoephedrine, and smoking are all associated with recurrences. Medications, such as beta blockers, calcium channel blockers, or primary anti-arrhythmia drugs, can be used to control heart rhythm. An electrophysiology study, a procedure similar to a heart catheterization but focusing on the electrical system instead of the blood vessels, can identify abnormal electrical pathways. Radio frequency ablation can often be used to destroy short circuits to prevent recurrence of PSVT. The aggressiveness of preventive measures depends on the frequency and severity of the PSVT episodes.