Bidirectional block confirmation is specifically important for which ablation procedure?

Bidirectional block confirmation is specifically important for which ablation procedure?

• A. Unidirectional block procedures
• B. CTI ablation
• C. Ventricular outflow tract ablation
• D. Atrioventricular nodal modification

Answer: (B)

The key idea is that preventing reentry in a macroreentrant atrial flutter requires a line of block that stops conduction in both directions across the ablation path. In CTI ablation, you create a linear lesion across the cavotricuspid isthmus to interrupt the flutter circuit. If the line is only blocked in one direction, impulses can still cross the isthmus in the opposite direction and the reentrant circuit can continue. Therefore, confirming bidirectional block across the CTI line ensures that the circuit cannot re-enter from either side, making the ablation durable. This focus on bidirectional block is most relevant to CTI ablation because the procedure’s goal is a complete linear blockade to collapse the typical atrial flutter circuit. Other procedures involve different targets—ventricular outflow tract ablations aim at focal triggers rather than a cross-line block, and AV nodal modification aims to alter conduction properties rather than create a complete bidirectional barrier.

The key idea is that preventing reentry in a macroreentrant atrial flutter requires a line of block that stops conduction in both directions across the ablation path. In CTI ablation, you create a linear lesion across the cavotricuspid isthmus to interrupt the flutter circuit. If the line is only blocked in one direction, impulses can still cross the isthmus in the opposite direction and the reentrant circuit can continue. Therefore, confirming bidirectional block across the CTI line ensures that the circuit cannot re-enter from either side, making the ablation durable.

This focus on bidirectional block is most relevant to CTI ablation because the procedure’s goal is a complete linear blockade to collapse the typical atrial flutter circuit. Other procedures involve different targets—ventricular outflow tract ablations aim at focal triggers rather than a cross-line block, and AV nodal modification aims to alter conduction properties rather than create a complete bidirectional barrier.