While there are many types of heart disease that are congenital in nature, some are considered as complex. These involve intricate abnormalities of the heart’s structure and function, demanding specialized care. Some of the complex congenital heart diseases include the following:

1. Tetralogy of Fallot – as outlined above, this refers to a combination of four heart defects, as listed below. This condition causes symptoms such as cyanosis, difficulty breathing, and tiredness. Cyanosis refers to abnormal bluish skin color.

•       Ventricular Septal Defect – hole between the ventricles.
•       Pulmonary stenosis – narrowing of the tract between right ventricle and pulmonary artery.
•       Right ventricular hypertrophy – thickening of right ventricular wall.
•       Overriding aorta – improper position of the aorta.

2. Transposition of the great arteries – this refers to swapping of the aorta and pulmonary artery. This causes circulation of oxygen-poor blood through the body and oxygen-rich blood through the lungs. Symptoms include severe cyanosis, difficulty breathing, and reduced oxygen levels.
3. Truncus arteriosus – this refers to the condition of a single large vessel emerging from the heart instead of the aorta and pulmonary artery. This triggers symptoms like cyanosis, difficulty breathing, and reduced intake. 
4. Total anomalous pulmonary venous return – swapped connection of the pulmonary veins to the right atrium, instead of the left atrium. This causes symptoms like severe cyanosis, difficulty breathing, and heart failure.
5. Hypoplastic left heart syndrome – underdeveloped left ventricle, mitral valve, and aortic valve, affecting pumping of blood. This causes symptoms like severe cyanosis, rapid breathing, and heart failure.
6. Double outlet right ventricle – emergence of the aorta and pulmonary artery from the right ventricle, causing mixing of blood. This is indicated through symptoms like cyanosis, difficulty breathing, and lesser than average growth.
7. Ebstein’s anomaly – malformed tricuspid valve and incorrect positioning resulting in enlarged right atrium. Symptoms include cyanosis, heart murmur, heart failure and arrhythmias. 
8. Double outlet left ventricle – emergence of the aorta and pulmonary artery from the left ventricle, causing mixing of blood. Symptoms include cyanosis and difficulty breathing.
9. Complex single ventricle – multiple conditions due to underdeveloped ventricles, causing symptoms like cyanosis, heart failure, and impaired physical abilities.