Which lead is most commonly used to assess the electrical axis of the heart?

Lead I is considered the most commonly used lead to assess the electrical axis of the heart because it provides a clear representation of the heart’s electrical activity in the horizontal plane. By evaluating Lead I, clinicians can determine the direction of the electrical impulses as they move through the heart, specifically in relation to the left and right sides.

In a standard 12-lead EKG, Lead I measures the voltage potential between the right arm (negative electrode) and the left arm (positive electrode), offering insight into the axial orientation of the heart. The significance of using Lead I is rooted in its ability to discern leftward or rightward deviations of the heart's axis, which is crucial for diagnosing various cardiac conditions, such as left or right axis deviation caused by structural heart changes or hypertrophy.

In addition to its utility in axis determination, the readings from Lead I can be easily interpreted alongside those from other leads to obtain a comprehensive view of the heart's electrical behavior throughout the cardiac cycle. This makes it a fundamental component of EKG analysis.