What is typically assessed during the pace in the atrium to identify an entrance block?

In the context of atrial fibrillation and its assessment, identifying an entrance block often involves evaluating the conduction signals in relation to the pulmonary veins. The pulmonary veins are significant because they are commonly associated with the initiation of atrial fibrillation due to ectopic foci within them. By assessing the signal to the adjacent pulmonary veins, healthcare providers can determine if there is effective conduction from the atrial tissue into the veins and vice versa. This assessment is crucial for understanding the electrical activity in the atrium and for determining the effectiveness of treatments such as catheter ablation, which aims to isolate these veins to prevent the triggering of atrial fibrillation.

In this context, signal conduction to the atrial walls, signal duration in the left atrium, and duration of fibrillation episodes do not specifically address the mechanism of entrance block as it relates to the pulmonary veins, making them less relevant for this particular assessment.