What is the key physical finding in a patient with tetralogy of Fallot (TOF)?

In tetralogy of Fallot (TOF), the key physical finding is cyanosis. This condition is a congenital heart defect characterized by four specific anatomical issues: ventricular septal defect, pulmonary stenosis, right ventricular hypertrophy, and an aortic override. The presence of these defects leads to inadequate oxygenation of the blood, resulting in decreased oxygen delivery to the tissues, which causes the bluish discoloration of the skin and mucous membranes known as cyanosis.

Cyanosis typically presents in infants and children with TOF when demands for oxygen increase, such as during feeding, crying, or physical activity. It can manifest as peripheral cyanosis (bluish coloration of the extremities) or central cyanosis (bluish discoloration of the lips and face). The severity of cyanosis can vary depending on the degree of right-to-left shunting of blood through the ventricular septal defect and the extent of pulmonary stenosis.

Other symptoms such as persistent cough, diarrhea, or a swollen abdomen may occur in various clinical contexts but are not specific indicators of TOF. These symptoms could arise from other respiratory, gastrointestinal, or systemic disorders, making them less relevant in diagnosing or identifying the specific congenital heart defect of tetralogy of Fall