Which statement about coronary perfusion pressure changes is correct?

• A. CPP increases if LVEDP increases with constant aortic diastolic pressure.
• B. CPP decreases if aortic diastolic pressure decreases with constant LVEDP.
• C. CPP is determined by systolic pressures only.
• D. CPP is the sum of aortic diastolic pressure and LVEDP.

Answer: (C)

Coronary perfusion pressure is the pressure gradient that drives blood into the heart muscle, and for the left coronary circulation it is determined by the aortic pressure during diastole minus the left ventricular end-diastolic pressure. This diastolic gradient matters because the heart is best perfused when the aorta is providing pressure during diastole and the myocardium is not compressing its vessels as during systole. If LVEDP rises while the diastolic aortic pressure stays the same, the gradient narrows and CPP falls. Similarly, if the aortic diastolic pressure falls with LVEDP constant, CPP falls as well. The idea that CPP is the sum of aortic diastolic pressure and LVEDP is incorrect—the driving force is a difference, not a sum. And CPP is not determined by systolic pressures alone, since systole tends to impede coronary flow and diastolic pressure is what primarily sets the perfusion gradient. In short, CPP ≈ aortic diastolic pressure minus LVEDP.