Diastolic refers to the phase of the cardiac cycle when the heart relaxes and fills with blood. During this time, the heart's chambers, particularly the ventricles, expand to receive blood from the atria. This phase is crucial for ensuring that the heart has enough blood to pump out during the next contraction. In blood pressure readings, diastolic pressure is the lower number, indicating the pressure in the arteries when the heart is at rest between beats. For example, in a reading of 120/80 mmHg, 80 mmHg represents the diastolic pressure. Maintaining healthy diastolic pressure is important for overall cardiovascular health.