What is PSVT?

What is Paroxysmal Supraventricular Tachycardia?

Paroxysmal supraventricular tachycardia, also called PSVT, is due to an abnormality in the electrical system of the heart. People with this condition have sudden and unexpected episodes of rapid heart rate that start and stop without warning. A normal resting heart rate is between 60 and 100 beats per minute, but heart rates during an episode of PSVT may exceed 150-200 beats per minute.

PSVT episodes can start to occur at any time in a patient’s life time and may occur in otherwise healthy patients.  These episodes may last anywhere from minutes to hours.  Additionally, the frequency and severity of PSVT episodes vary from patient to patient.  While PSVT is not typically life threatening, symptoms can significantly affect some patient’s quality of life due the unexpected nature of episodes.   Since patients are unsure of when they will have an episode, PSVT may limit certain activities such as driving or travel and create significant anxiety and fear of the next episode. The episodes themselves can be debilitating and exhausting, diverting patients focus away from work and family.

The prevalence of PSVT is poorly documented in the literature, but is estimated to be around several cases per thousand persons1. A recent medical claims analysis done by Milestone Pharmaceuticals uncovered that PSVT has been reported in an estimated 1.7 million patients in the US in the last 5 years alone.2

What Causes PSVT?

There are two types of PSVT that account for roughly 90% of cases; both of these are reentrant tachycardias3.  These are tachycardias caused by an accessory or extra pathway that forms a “loop” of electrical impulses. This loop prematurely reactivates the atrial ventricular (AV) node between the upper chambers of the heart and the lower chambers of the heart, causing the heart to beat faster. Most people who have PSVT are born with these accessory pathways at birth, but the tachycardia may not be present until they reach adulthood while some patients do not present until their seventh or eighth decade.4,5,6

AV nodal reentrant tachycardia (AVNRT) is the most common type of PSVT and occurs in 60% of patients with PSVT (with a female gender predominance).  This occurs when there is an accessory or extra pathway in the AV node. This extra pathway allows the electrical impulse to reenter the AV node, causing a circular or re-entrant pathway that results in a very rapid heartbeat.

Atrioventricular reciprocating tachycardia (AVRT) is the second most common form of PSVT.  Normally, the AV node is the only tissue that conducts electrical impulses between the upper and lower chambers of the heart. In AVRT, electrical impulses travel one direction in the normal manner, down the AV node to the lower chambers (ventricles), but they then travel back up to the upper chambers (atria) through an abnormal, accessory pathway located outside the AV node.  AVRT includes Wolff-Parkinson-White (WPW) syndrome. About 10% of PSVT is WPW, which is not treated with the same types of drugs as most PSVT.

References

  1. http://emedicine.medscape.com/article/160215-overview#a6
  2. Number of estimated patients with PSVT code: 427.0 , “supraventricular Tachycharia” in Symphony data base from 2009-2013
  3. http://www.aafp.org/afp/2010/1015/p942.html
  4. https://en.wikipedia.org/wiki/Atrioventricular_reentrant_tachycardia
  5. https://stanfordhealthcare.org/medical-conditions/blood-heart-circulation/supraventricular-tachycardia/types/atrioventricular-reciprocating-tachycardia-avrt.html
  6. https://www.bostoncardiovascular.org/handler.cfm?event=practice,template&cpid=50214