Lead I in a 12 lead EKG measures the electrical activity between which two limbs?

Lead I in a 12 lead EKG measures the electrical activity between which two limbs?

• A. The right arm and left foot
• B. The left arm and left foot
• C. The right arm and left arm
• D. The right foot and left foot

Answer: (C)

Lead I in a 12-lead EKG specifically measures the electrical activity of the heart in the frontal plane by recording the voltage difference between the right arm and the left arm. This bipolar lead captures the electrical impulses traveling from the right arm electrode toward the left arm electrode, providing valuable insight into the heart's electrical activity from a left-right orientation.

Understanding this is essential for interpreting EKGs, as lead placements determine the vector of electrical activity being assessed. The orientation of Lead I allows clinicians to analyze how the heart is functioning, identify conditions like left or right axis deviation, and aid in diagnosing arrhythmias or other cardiac abnormalities effectively.