“…Primary endocardial fibroelastosis in children is diagnosed when there are no valvular heart lesions, no inflammation, or no exactly defined myocardial degeneration (Mitchell, Froehlich, Banas, and Gilkeson, 1966). The results of our own investigations, as also those of otherauthors (Andersen andKelly, 1956;Kelly and Andersen, 1956;Boj and Pikiel, 1964), show that even in the so-called primary endocardial fibroelastosis the endocardial changes are secondary to the myocardial damage.…”