What is the midclavicular line?

• A. The line that runs down the middle of the clavicle
• B. The line that runs down the middle of the sternum
• C. The line along the midaxillary region
• D. The line that runs along the spine

Answer: (B)

The midclavicular line is a vertical reference line that runs from the midpoint of the clavicle downward along the chest on each side. It’s a practical landmark used to describe locations on the chest and for placing certain ECG leads (for example, placements along the left midclavicular line). It does not pass through the sternum—that would be the midsternal (or midsternal) line. The other lines described—one running through the armpit and another along the spine—are the midaxillary line and the posterior median (spinal) line, respectively.