Which block is considered more crucial during AF ablation?

In the context of atrial fibrillation (AF) ablation, the exit block is considered crucial because it ensures that reentrant circuits within the atria are effectively interrupted. This type of block prevents impulses generated within the atrium from exiting into the rest of the heart, thereby stopping the arrhythmia from continuing.

When an exit block is successfully established, it indicates that the electrical signals originating from the pulmonary veins or other areas are unable to propagate into the surrounding atrial tissue. This effectively isolates these areas, preventing them from contributing to AF, which is characterized by disorganized electrical activity.

While entrance block, which prevents impulses from entering a particular region of the heart, is also important, the primary goal of AF ablation is to create a situation where the arrhythmia cannot sustain itself. Therefore, achieving exit block is a critical step in ensuring long-term success in the management of atrial fibrillation during ablation procedures.