Final answer:
Diastolic heart failure is characterized by the heart's reduced ability to relax and fill with blood due to stiffening of the heart muscle, leading to loss of ventricular diastolic relaxation.
Step-by-step explanation:
A patient diagnosed with diastolic heart failure is experiencing a condition where the heart's ability to relax and fill with blood between contractions is compromised. The most direct cause of diastolic heart failure is loss of ventricular diastolic relaxation. This occurs when the heart muscle (myocardium) becomes stiff and does not relax as it should, making it difficult for the ventricles to fill with blood during the resting phase between heartbeats. Unlike systolic heart failure, where the pumping action of the heart is weakened, in diastolic heart failure, the heart's pumping function during contraction may still be normal. Instead, the problem lies in the heart's reduced capacity to fill with blood, which can lead to inadequate blood flow to the body's tissues. Additionally, pressure may build up as the blood flow from the lungs to the heart faces increased resistance, which can result in fluid accumulation in the lungs, a condition known as pulmonary edema.