Which of the following leads is primarily used for monitoring the lateral wall of the heart?

The lateral wall of the heart is primarily monitored using Lead V5, which is positioned on the left side of the chest, typically at the fifth intercostal space in the anterior axillary line. This lead's placement allows it to capture electrical activity that reflects the overall function of the lateral aspect of the left ventricle.

Lead V5 is part of the standard 12-lead electrocardiogram (ECG) setup and is specifically oriented to detect changes associated with ischemia or injury in the lateral wall of the heart. It derives its readings mainly from the left circumflex coronary artery territory, which supplies blood to the lateral wall.

In contrast, other leads such as Lead II and Lead III are more reflective of inferior wall activity, while Lead V1 is predominantly associated with monitoring the right ventricle and anterior wall. Therefore, Lead V5 is the most relevant choice for specifically assessing the lateral wall of the heart.