One symptom is cyanosis, usually seen as a bluish discoloration of the lips, fingers, and toes.

Some children have dyspnea (breathing problems) and adopt a squatting position after physical activity to relieve breathlessness. Others have hypoxic spells, where their bodies are suddenly starved of oxygen. These are characterized by anxiety, hyperventilation, and a sudden increase in cyanosis.

Syncope (fainting) and chest pain may occur.

Other symptoms depend on the specific type of cyanotic heart disease.

Physical examination confirms cyanosis.

The child may have clubbed fingers, an obvious thickening of the fingertips in response to the poor oxygenation.

Abnormal heart sounds, a heart murmur, and lung crackles may be heard.

Tests will vary depending on the suspected cause, but may be extensive and include a chest X-ray, a complete blood count (CBC), arterial blood gas analysis, ECG (echocardiogram), echo-Doppler, transesophageal echocardiogram (TEE), nuclear imaging tests, cardiac catheterization, and electrophysiologic study (EPS).