When is diastolic blood pressure measured?

Diastolic blood pressure is specifically measured when the heart muscle is relaxed, particularly when the left ventricle is refilling with blood from the left atrium. This phase of the cardiac cycle allows for the heart chambers to prepare for the next contraction while the body maintains a steady flow of blood. During this time, the pressure in the arteries is at its lowest point, which is what diastolic blood pressure indicates. It reflects the resistance in the blood vessels and helps to assess the overall cardiovascular health of an individual.

While it's true that the heart is at rest during diastole, the emphasis here is on the filling of the left ventricle, which is a critical part of the cardiac cycle. Other options relate to different phases of the heart's activity and do not accurately describe when diastolic pressure is measured.