How is mean arterial pressure calculated?

• A. MAP ≈ systolic pressure + diastolic pressure divided by 2.
• B. MAP ≈ diastolic pressure + 1/3 pulse pressure.
• C. MAP equals systolic pressure.
• D. MAP equals diastolic pressure.

Answer: (B)

Mean arterial pressure represents the average pressure in the arteries over one heartbeat, and it’s what drives blood flow to the organs. A practical way to estimate it is diastolic pressure plus one third of the pulse pressure (where pulse pressure is systolic minus diastolic). This matches the idea that the arterial pressure spends more time in diastole, so the average is closer to diastolic with a modest contribution from the systolic rise. Equivalently, you can think of it as (2/3) times diastolic plus (1/3) times systolic. For example, with a systolic of 120 and diastolic of 80, MAP ≈ 80 + 1/3(40) ≈ 93.3 mm Hg. The simple average of systolic and diastolic (systolic plus diastolic divided by 2) overestimates MAP in typical conditions because it gives more weight to the systolic peak than the time spent in diastole. And MAP equals either systolic alone or diastolic alone—that would ignore the true pressure variation across the cardiac cycle.