Which lead would you place to assess the left lateral wall of the heart?

The correct lead to assess the left lateral wall of the heart is Lead V5. This lead is positioned over the left side of the chest, specifically in the mid-axillary line at the fifth intercostal space. It provides clear views of the electrical activity from the left lateral wall, which includes areas supplied by the left circumflex artery.

Lead V6, while also assessing the left lateral wall, primarily provides information from a more posterior perspective than V5, making V5 superior for direct lateral wall assessment. Lead V4 is more anterior and focuses on the anterior aspects of the heart, particularly the left ventricle's anterior wall. Lead V3 is primarily oriented towards the anterior wall but does not capture the lateral wall well. Therefore, V5 is the most appropriate choice for evaluating the left lateral wall of the heart.