Where is V3 placed?

• A. Midway between V2 and V4
• B. Right sternal border, fourth intercostal space
• C. Left midaxillary line, fifth intercostal space
• D. Midclavicular line, fifth intercostal space

Answer: (A)

V3 sits where the heart’s electrical activity is transitioning between the positions of V2 and V4. Specifically, V2 is placed at the left sternal border in the fourth intercostal space, and V4 is at the left midclavicular line in the fifth intercostal space. Placing V3 midway between V2 and V4 gives an anterior chest view that neatly links those two points, helping to map the electrical activity across the heart’s front surface.

The other placements correspond to different leads: right sternal border in the fourth intercostal space is V1; left midaxillary line in the fifth intercostal space is V6; and left midclavicular line in the fifth intercostal space is V4.