What form of cardiomyopathy is usually caused by infiltrative disease of the myocardium?

Restrictive cardiomyopathy is characterized by the stiffening of the heart muscle, which prevents the heart from filling properly with blood during diastole. This condition is often a result of infiltrative diseases such as amyloidosis or sarcoidosis, where abnormal substances accumulate in the myocardium. The infiltration of these substances leads to the loss of normal muscle function and elasticity, resulting in impaired cardiac filling and reduced overall cardiac output.

In contrast, hypertrophic cardiomyopathy primarily involves the thickening of the myocardium, which can be genetic in origin, while septal cardiomyopathy specifically refers to issues related to the interventricular septum. The term "infiltrative" may refer broadly to a category of diseases, but does not specifically define the functional impairment found in restrictive cardiomyopathy, which is the key issue of filling impairment caused by myocardial stiffness. Thus, restrictive cardiomyopathy is the appropriate answer in the context of infiltrative disease affecting the myocardium.