Which chamber has the lowest normal pressure among those listed?

• A. RA
• B. RV
• C. PA
• D. LV

Answer: (A)

The pressures in the heart chambers vary with their roles in circulation, and the right-sided chambers operate at the lowest pressures. The right atrium acts as a reservoir that collects systemic venous return with a filling pressure of roughly 2–6 mmHg. In contrast, the right ventricle must generate enough pressure to push blood into the low-resistance pulmonary circulation, and the left heart must generate much higher pressures to propel blood systemically (left ventricle systolic ~90–140 mmHg; diastolic ~4–12 mmHg). The pulmonary artery carries blood after it leaves the right ventricle, with mean pressures around 9–18 mmHg, still higher than the typical right atrial pressure. Therefore, among the listed chambers, the right atrium has the lowest normal pressure.