Which AVRT form is more common?

Which AVRT form is more common?

• A. Antedromic
• B. Orthodromic
• C. Both Equally Common
• D. Neither Occurs

Answer: (B)

The pattern most often seen in AVRT uses the AV node for the forward (antegrade) conduction and the accessory pathway for the retrograde return. This orthodromic form forms a reentrant circuit where the impulse travels down the AV node into the ventricles and goes back up to the atria via the accessory pathway. It’s the typical pattern because accessory pathways commonly conduct well retrogradely but not as reliably antegradely, while the AV node provides a dependable antegrade route. The result is a tachycardia with a normal-appearing, narrow QRS that uses the normal ventricular activation, making this form far more common. The antidromic (antegrade through the accessory pathway and retrograde through the AV node) form is less frequent and often produces a wide QRS, so it appears less often in clinical practice.

The pattern most often seen in AVRT uses the AV node for the forward (antegrade) conduction and the accessory pathway for the retrograde return. This orthodromic form forms a reentrant circuit where the impulse travels down the AV node into the ventricles and goes back up to the atria via the accessory pathway. It’s the typical pattern because accessory pathways commonly conduct well retrogradely but not as reliably antegradely, while the AV node provides a dependable antegrade route. The result is a tachycardia with a normal-appearing, narrow QRS that uses the normal ventricular activation, making this form far more common. The antidromic (antegrade through the accessory pathway and retrograde through the AV node) form is less frequent and often produces a wide QRS, so it appears less often in clinical practice.