What is the condition characterized by stiff heart syndrome due to protein deposits?

The correct choice refers to a condition known as cardiac amyloidosis, which is characterized by the abnormal buildup of amyloid proteins in the heart tissue. This accumulation leads to stiffness in the heart muscle, making it less able to fill with blood during diastole, which ultimately affects the heart's function. This condition often results in heart failure due to impaired cardiac relaxation and elevated filling pressures.

In cardiac amyloidosis, the protein deposits disrupt normal cardiac structure and function, which can lead to symptoms such as shortness of breath, swelling in the legs, fatigue, and arrhythmias. The diagnosis often involves imaging and biopsies to confirm the presence of amyloid deposits.

Understanding this condition is crucial because it is distinct from the other options, which involve different cardiovascular issues. Cardiac arrest involves a sudden cessation of heart activity, cardiac cachexia is associated with severe weight loss and muscle wasting in chronic heart disease, and cardiomegaly refers to an enlargement of the heart that can be caused by various conditions but does not specifically involve protein deposits.