Symptoms of HF reflect the inability of the myocardium to satisfy the circulatory and metabolic demands of the organism. Pediatric patients usually present symptoms when cardiac output has declined beyond moderate impairment and in 87% of cases of new-onset HF only reach a diagnosis when the patient is in a state of severe decompensation.

Infant and young children: The typical presentation is characterized by difficulty in feeding (from prolonged feeding time intake to frank intolerance). Cyanosis, tachypnea, sinus tachycardia, and diaphoresis can be present, but less often edemas and ascitis.
Older children and adolescence: Fatigue, shortness of breath, tachypnea, and exercise intolerance are the main symptoms. Abdominal pain, oliguria, and leg pitting edema may also be present. The severity of HF in children must be staged according to functional classes with increasing severity of clinical features.