The most common cause of a narrow complex tachycardia is AVNRT or atrioventricular reentrant tachycardia.

The term “SVT” can be confusion at times. In general, this term is used to describe a narrow complex tachycardia not including atrial fibrillation/flutter. The term SVT frequently refers to AVNRT, however technically it means any tachycardic rhythm that originates from above the ventricles (above the AV node). This would include:

1. Sinus tachycardia
2. Atrial tachycardia
3. Atrial fibrillation
4. Atrial flutter
5. AV nodal reentrant tachycardia (AVNRT)
6. AV reentrant tachycardia (AVRT)
7. Other less common SVTs