Which of the following most directly determines coronary perfusion pressure for LV perfusion?

• A. LV preload.
• B. Heart rate.
• C. The difference between aortic diastolic pressure and LVEDP.
• D. LV end-diastolic pressure.

Answer: (C)

The main idea is that left-ventricular coronary perfusion pressure is driven by the pressure gradient across the coronary circulation during diastole. This gradient is essentially the difference between aortic diastolic pressure and the left ventricular end-diastolic pressure (LVEDP). During diastole, the heart relaxes and the aorta’s diastolic pressure pushes blood into the coronary arteries, while the LV endures a back pressure from its own filling pressure. A larger gap between these two pressures means more driving force for coronary flow; a smaller gap reduces flow and risks subendocardial ischemia if the LVEDP rises or the aortic diastolic pressure falls. LV preload and LVEDP alone don’t capture this driving force, and heart rate changes diastolic duration rather than directly setting the gradient. Hence, the difference between aortic diastolic pressure and LVEDP is the direct determinant of LV coronary perfusion pressure.