Rarest form of CM, 4.5% of the total, incidence of 0.03 to 0.04/ 100.000 children. Majority are idiopathic or genetic causes (check Table below).

RCM is called CM with preserved systolic function, provokes mainly diastolic dysfunction, and at the end, systolic dysfunction. CM has higher risk of SD (due to ventricular arrhythmias) and irreversible pulmonary hypertension, so patient has to be included in heart transplant list when pulmonary resistance starts to increase, although patient feels asympthomatic. Conventional treatment of HF is not useful, just diuretics in early phase and ICD normally is required in advanced status of the disease.