A type of heart disorder referring to the inability of the ventricles to fill with blood because the myocardium (heart muscle) stiffens and looses its flexibility. Causes include replacement of the myocardium with scar tissue, abnormal cellular infiltration of the myocardium, or deposition of a substance (e.g., amyloid) in the myocardium. The disease is Monarch Disease Ontology term MONDO_0005201 (restrictive cardiomyopathy). Also known as: cardiomyopathy, constrictive, primary restrictive cardiomyopathy.