During cryo ablation for AVNRT, what is typically observed?

• A. Immediate AV block
• B. Ablate during NSR only
• C. No effect during tachycardia
• D. Ablate during tachycardia and watch for slow then termination

Answer: (D)

In cryoablation for AVNRT, the key idea is to test and confirm the slow pathway contribution while the tachycardia is running, using a reversible, cryomapping approach. You apply the cold energy during the tachycardia and look for a change in the arrhythmia. The typical observation is that conduction through the slow pathway slows and the tachycardia eventually terminates. If the effect is favorable, you can proceed to create a permanent lesion; if not, you can rewarm and move to a different site. This approach reduces the risk of permanent AV block because you’re able to observe the tachycardia response before committing to a full lesion. Immediate AV block is not the expected initial finding, and ablation during NSR alone typically won’t reveal the critical slow-pathway involvement. The hallmark is slow conduction followed by termination during tachycardia.