Tetralogy of Fallot. (a, b) Tetralogy of Fallot, the most common cause of cyanotic congenital heart disease, consists of a membranous VSD right ventricular outow obstruction, rightward displacement of the aorta (AO), and secondary right ven­tricular hypertrophy. The right ventricular outow obstruction may take the form of hypoplasia of the pulmonary trunk (PT), pulmonary valvular malformation and ste­nosis, outow tract (infundibular) hypoplasia and narrowing, or a combination of all

Clubbing. (a) The angle at the junction of skin with the nail at the dorsal surface of digits is normally around 160°. (b) In children with cyanotic congenital heart dis­eases this angle becomes wider and may exceed 180°. This is the result of hypoxia in peripheral tissue, which causes the opening of normally collapsed capillaries to better perfuse the hypoxic tissue. Perfusion of these collapsed capillaries will result in expansion of the volume of these peripheral tissues (tips of digits) resulting in clubbing. This phenomenon is seen in other lesions causing hypoxia of peripheral tissue, such as with chronic lung disease and chronic anemia (causing hypoxia through reduction of level of hemoglobin and therefore reduction of oxygen carry­ing capacity) such as with ulcerative colitis, Crohn’s disease, and chronic liver dis­ease [Thompson WR, Mehrotra SM.Cardiac History and Physical Examination. In: Abdulla R, editor. Heart Diseases in Children [Internet]. Boston, MA: Springer US; 2011 [cited 2016 Jul 29]. p. 3–16. Available from: http://link.springer.