Which endpoint confirms successful ablation for typical flutter?

Which endpoint confirms successful ablation for typical flutter?

• A. Bidirectional block along the CTI
• B. Decrease in heart rate
• C. Prolonged PR interval
• D. No tachycardia reinduction

Answer: (A)

In typical atrial flutter, the reentrant circuit travels around the tricuspid annulus and uses the cavotricuspid isthmus as the critical pathway. Ablation aims to transect that circuit by creating a line of block across the CTI, so the flutter loop can no longer propagate through the isthmus. The definitive endpoint is bidirectional block along the CTI—meaning conduction cannot cross the ablation line in either direction. When this block is present, pacing from either atrial side does not conduct across the CTI to the other side, and the activation pattern changes to reflect a nonreentrant atrial conduction path. You may see evidence on mapping as separated or double potentials along the line, indicating a continuous, nonconductive barrier. Other endpoints like a decrease in heart rate or a prolonged PR interval aren’t specific to eliminating the flutter circuit. While not being able to reinduce flutter after ablation can be reassuring, it’s not as definitive as proving that the CTI is truly nonconductive in both directions, since reinduction can be affected by factors outside the ablation itself.

In typical atrial flutter, the reentrant circuit travels around the tricuspid annulus and uses the cavotricuspid isthmus as the critical pathway. Ablation aims to transect that circuit by creating a line of block across the CTI, so the flutter loop can no longer propagate through the isthmus. The definitive endpoint is bidirectional block along the CTI—meaning conduction cannot cross the ablation line in either direction. When this block is present, pacing from either atrial side does not conduct across the CTI to the other side, and the activation pattern changes to reflect a nonreentrant atrial conduction path. You may see evidence on mapping as separated or double potentials along the line, indicating a continuous, nonconductive barrier.

Other endpoints like a decrease in heart rate or a prolonged PR interval aren’t specific to eliminating the flutter circuit. While not being able to reinduce flutter after ablation can be reassuring, it’s not as definitive as proving that the CTI is truly nonconductive in both directions, since reinduction can be affected by factors outside the ablation itself.