What is the most common SVT?

• A. Atrial flutter
• B. Atrial tachycardia
• C. AVRT
• D. AVNRT

Answer: (D)

The most common form of supraventricular tachycardia is AV nodal reentrant tachycardia. It arises from a reentrant circuit within or around the AV node due to dual pathways (a fast and a slow pathway) inside the nodal tissue. This dual-pathway setup is a frequent substrate in many people, making AVNRT the most commonly encountered SVT in clinical practice.

Clinically, AVNRT presents as a sudden onset and termination of a rapid, regular, narrow-complex tachycardia, often with rates around 150–250 beats per minute. The P waves are frequently hidden inside or just after the QRS complex because atrial activation is retrograde. Vagal maneuvers or adenosine can terminate the tachycardia by interrupting the reentrant circuit, and definitive treatment is often catheter ablation of the slow pathway.

Other SVTs involve different mechanisms or substrates—AVRT uses an accessory pathway outside the AV node (e.g., WPW syndrome), atrial tachycardia originates from an ectopic atrial focus, and atrial flutter is an atrial macroreentrant circuit. These are less commonly the source of SVT compared to AVNRT, which is why it is identified as the most common SVT.