Which of the following describes the formula for Coronary Perfusion Pressure (CPP)?

• A. Aortic Systolic minus Right Atrial Systolic
• B. Mean Arterial minus Right Atrial Diastolic
• C. Aortic Diastolic minus Right Atrial Diastolic
• D. Right Atrial Diastolic minus Aortic Diastolic

Answer: (C)

CPP is the pressure gradient that drives blood into the coronary arteries, and it matters most during diastole when the heart muscle relaxes and coronary vessels fill. It is calculated as the aortic pressure during diastole minus the pressure in the right atrium. That makes the description “aortic diastolic minus right atrial pressure” the correct one.

Using systolic values would not reflect diastolic coronary flow, since coronaries receive flow mainly when the heart is relaxed. Averaging to mean arterial pressure is a rough approximation and not the standard diastolic-driven definition. Reversing the order would imply a negative gradient, which doesn’t describe the true driving pressure for coronary perfusion.