Supraventricular Tachycardia (SVT)

Supraventricular Tachycardia (SVT)
Including, Atrioventricular Nodal Re-entry Tachycardia (AVNRT), Atrioventricular Re-entry Tachycardia (AVRT), Atrial Tachycardia (AT) 

What is SVT?

Supraventricular tachycardia (SVT) is a fast heart rhythm that starts in the top heart chambers (atria) and travels to the bottom chambers (ventricles) often through extra connections in the circuitry of the heart.  The path the electrical signal takes defines the type of SVT.  The electrical “bridge” between the top and bottom of the heart is called the atrioventricular node (AV node).  There are three common types of SVT.  AVNRT, which is the most common, is an abnormal extra electrical circuit around the AV node.  AVRT occurs when the SVT travels to the ventricles through a different electrical pathway (accessory pathway) that bypasses the AV node altogether. Atrial tachycardia is the least common type of SVT.  This occurs when an abnormal cell in the top chambers wants to beat on its own.  This SVT then travels through the AV node and into the ventricles.      

 Why do people get SVT?

SVT commonly occurs in healthy people with healthy hearts.  It also can occur due to heart disease, heart failure, lung disease, drug and alcohol abuse, or thyroid disease.  While excessive caffeine, other stimulants, alcohol, dehydration, and thyroid disturbances can all cause someone to have more SVT than they would otherwise, most people with SVT will still have some amount of SVT even if they avoid their triggers.   

Is it Dangerous?

SVT is not typically dangerous.  In rare cases, AVRT (or an accessory pathway) can be dangerous.  When there is concern that AVRT could be dangerous testing is done to check risk.  Safety is always our top priority.   

Signs & Symptoms of SVT

Palpitations, racing heart, shortness of breath, lightheadedness, dizziness, fatigue, chest discomfort.  Fainting is possible, but rare.  Symptoms can be very brief, but can also last for hours.    

What should I do if I’m experiencing an SVT episode?

Certain types of SVT, such as AVNRT, may stop with vagal maneuvers (see below).  Your cardiology provider will tell you if trying vagal maneuvers is appropriate for your SVT.  In some cases, your doctor may tell you to take a pill at the onset of SVT.  Oftentimes, there is nothing to do at the onset of SVT, and you simply need to ride through the storm.  You can try relaxation exercises, such as mindfulness meditation or deep breathing.  Take note of how long your symptoms last, how you feel during your episode(s), and identifiable triggers, and whether you are experiencing a change in symptom frequency, duration, or severity.  If your episodes are short (lasting a few minutes or less) and not becoming longer, more frequent, or associated with more severe symptoms than usual, you can just mention it at your next appointment.   

Symptoms of SVT you should call your provider about:

Lightheadedness, dizziness, shortness of breath, palpitations, mild chest discomfort, symptoms that feel worse than usual, or you start feeling worse.   

 Symptoms of SVT to go to the ER for: 

Vagal Maneuvers

Vagal maneuvers can sometimes stop your SVT. Vagal maneuvers stimulate the parasympathetic nervous system which can block an extra electrical circuit in the AV node through which the electricity is traveling fast in a circle.  Because stimulating the parasympathetic nervous system only blocks this extra electrical circuit, vagal maneuvers will only stop SVTs that are AV nodal re-entrant, such as typical AVNRT.  Your cardiology provider will tell you if you have an SVT that can be stopped with vagal maneuvers.  Here are some vagal maneuvers to try:  

How is it Diagnosed? 

How is it Treated? 

If the SVT is lasting a long time and is very fast, it can cause the blood pressure to get too low, in which case a cardioversion may be necessary to stop the SVT.  Since SVT is rarely dangerous, treatment is directed by a person’s symptoms.  For infrequent SVT, trigger avoidance plus or minus vagal maneuvers may be all that is needed to control symptoms.  For those that remain bothered by their symptoms, medications may be used to reduce SVT episode frequency and symptom severity.  

Commonly Used Medications: 

Catheter Ablation is an invasive procedure that does a better job of eliminating SVT than medications.