What lead is primarily examined to assess the depth of LBB placement?

When assessing the depth of left bundle branch (LBB) placement during conduction system pacing, V1 is the primary lead that is examined. The reason for this focus on V1 is that it provides significant information regarding the electrical activity of the heart, particularly in relation to the left bundle branch.

In patients with successful LBB pacing, you would expect to see a specific pattern in the V1 lead, typically characterized by a narrower QRS complex and changes in the morphology that indicate effective pacing at the left bundle. The appearance of a typical R wave pattern in V1 can suggest that the pacing has indeed successfully captured the left bundle branch, facilitating normal conduction through the heart's ventricles.

This assessment is crucial for evaluating the success of the pacing and ensuring proper lead placement, as well as for monitoring the potential impact on cardiac function. The other leads, while they can provide helpful information, do not offer the same level of specificity for evaluating LBB pacing depth as V1 does.