What is Supraventricular Tachycardia?
Supraventricular tachycardia, also sometimes referred to as paroxysmal supraventricular tachycardia is a rapid rhythm of the heart originating in the atria, the upper chambers of the heart. The heart rate during SVT is rapid, typically occurring at rates 120-220 beats per minute. Compared with ventricular tachycardia, originating in the ventricles, the lower chambers of the heart, SVT is not typically a potentially deadly rhythm disturbance. Rather, patients with SVT may complain of a variety of symptoms.
Possible symptoms include:
- Palpitations (pounding in the chest)
- Loss of consciousness (passing out)
- Chest pain
- Shortness of breath
Episodes of SVT often occur suddenly and may last for minutes to hours. In some cases, the SVT episode may last until up until treated.
Example of Supraventricular Tachycardia EKG
There are many varieties of SVT. The varieties of SVT are distinguished by where the origin of the SVT occurs in the atria and whether they are characterized by an electrical loop within the heart. Some of the more common varieties include:
- AV nodal reentrant tachycardia
- AV reentrant tachycardia
- Atrial tachycardia
- Atrial flutter
AV nodal reentrant tachycardia is the most common form of SVT and is caused by an abnormal electrical loop occurring within the AV node. (Picture) Approximately 25% of people are born with the potential to develop AV nodal reentrant tachycardia but only some will have an episode in their lifetime.
AV reentrant tachycardia is caused by an abnormal electrical loop utilizing a “bypass tract”. A bypass tract is an extra heart muscle fiber a person is born with. In some people with a bypass tract, there is evidence of this on a routine EKG. When a person has an abnormal routine EKG and episodes of SVT, it is known as Wolf-Parkinson-White syndrome. In others, their routine EKG is normal but there still may be a bypass tract which can lead to episodes of SVT.
Example of "bypass tract"
Atrial tachycardia is a more uncommon form of SVT due to an area of atrial muscle firing rapidly. In atrial tachycardia, there is no abnormal electrical loop. Example of atrial tachycardia
Atrial flutter is due to an abnormal electrical loop occurring in the right atrium of the heart. Similar to atrial fibrillation, people with atrial flutter have an increased risk of stroke as a result of blood clots that can form in the heart due to the sluggish flow of blood.
Example of atrial flutter and flutter waves