Which of the following clinical signs would be most obvious on examination of a patient with either tetralogy of Fallot or transposition of the great vessels?

D. Marked cyanosis is a distinct clinical sign in both tetralogy of Fallot and transposition of the great vessels. Any congenital cardiac malformation that allows right-to-left shunting of blood is sometimes called cyanotic heart disease. Right-to-left shunting allows poorly oxygenated blood from the right side of the heart to mix with highly oxygenated blood on the left side of the heart. This causes decreased oxygen tension to peripheral tissues, leading to a characteristic blue tinge (cyanosis) and bulbous thickening of the fingers and toes (clubbing).