<unk>  refers to a type of congenital heart defect. Congenital means present at birth.<unk>  is classified as a cyanotic heart defect because the condition causes low oxygen levels in the blood. This leads to cyanosis (a bluish-purple color to the skin).
The classic form of tetralogy includes four related defects of the heart and its major blood vessels:
Ventricular septal defect (hole between the right and left ventricles)
Narrowing of the pulmonary outflow tract (the valve and artery that connect the heart with the lungs)
Overriding aorta (the artery that carries oxygen-rich blood to the body) that is shifted over the right ventricle and ventricular septal defect, instead of coming out only from the left ventricle
A thickened muscular wall of the right ventricle (right ventricular hypertrophy)
At birth, infants may not show signs of cyanosis. However, later they may develop sudden episodes (called Tet spells) of bluish skin from crying or feeding.<unk>  is rare, but it is the most common form of cyanotic congenital heart disease. Patients with<unk>  have a higher incidence of major non-heart congenital defects.
Tetralogy of fallot
Pentalogy of Fallot
Trilogy of Fallot
Tetralogy of Fallot
Persistent truncus arteriosus
Interrupted aortic arch
Transposition of the great vessels
Tricuspid atresia