What is the acute endpoint of pulmonary vein isolation?

• A. Complete circumferential ablation around each PV.
• B. Demonstration of entrance and exit block or durable isolation of all mapped PVs.
• C. Absence of any PV potentials alone defines success.
• D. Only entrance block needs to be demonstrated.

Answer: (B)

The main idea is that the goal of pulmonary vein isolation is to completely disconnect the pulmonary veins from the left atrium so triggers cannot travel either way. The acute endpoint is bidirectional block of the veins: there is no conduction from the left atrium into the veins (entrance block) and no conduction from the veins back into the left atrium (exit block). This is typically demonstrated for all mapped veins, either by showing both entrance and exit block or by confirming that the veins are durably isolated at the end of the procedure.

Why this is the best answer: showing bidirectional block ensures that there is no pathway for arrhythmogenic impulses to enter the PVs or to originate from the PVs and propagate into the left atrium. Merely eliminating PV potentials can be misleading due to far-field signals or temporary suppression; completing both directions of block confirms true isolation. If only one direction is checked, a residual conduction path could allow reconnection or recurrence. If the endpoint focused only on circumferential ablation, that describes the technique, not the measuring criterion for success. And focusing on entrance block alone ignores the possibility of conduction from the PVs to the LA.

In practice, you test by pacing from the left atrium to look for PV potentials (entrance block) and by pacing from the PVs to see if the left atrium is activated (exit block); achieving both across all mapped veins, or ensuring durable isolation of them, meets the acute endpoint.