Which cardiac condition is characterized by the heart's inability to pump efficiently due to stiffened muscle?

The condition characterized by the heart's inability to pump efficiently due to stiffened muscle is diastolic heart failure. In this condition, the heart's ventricles become stiff and cannot relax properly during the diastolic phase, which is when the heart fills with blood. This impaired relaxation leads to a reduced ability to accommodate the incoming volume of blood, resulting in elevated pressures in the heart and lungs.

Diastolic heart failure is often associated with conditions such as hypertension, aging, and diabetes, which contribute to the stiffness of the heart muscle. As a result, while the heart may still be able to contract normally (preserving systolic function), it struggles to fill adequately, leading to symptoms such as shortness of breath and fluid overload.

In contrast, coronary artery disease primarily involves the obstruction of coronary arteries, affecting blood flow to the heart muscle itself, rather than the muscle’s ability to fill with blood. Systolic heart failure is related to the heart's decreased ability to contract and pump blood effectively, rather than the filling process. Atrial fibrillation is an arrhythmia that can complicate heart failure but does not specifically pertain to the stiffening of the heart muscle affecting its pumping ability.