cyanotic heart disease
Cyanotic heart disease is the family of congenital defects in which oxygen-poor blood reaches the body without being fully refreshed by the lungs, so the skin and lips can take on a bluish tint. The word cyanosis comes from the Greek for dark blue. The blue color appears when enough hemoglobin in the circulation is carrying little or no oxygen.
These defects share a common theme: blood is allowed to bypass or under-fill the lungs, either because a right-to-left shunt diverts blood around them, or because the plumbing mixes oxygenated and deoxygenated blood before it leaves the heart. Classic examples include tetralogy of Fallot, transposition of the great arteries, and pulmonary atresia.
Because the body is chronically short of oxygen, it may respond by making extra red blood cells and, over years, the fingertips and toes can become clubbed. Recognizing cyanosis early matters because some causes are surgical emergencies in the newborn period, while others allow planned repair.
A blue newborn whose oxygen levels do not rise despite supplemental oxygen is suspected of having cyanotic heart disease and undergoes urgent echocardiography.
Cyanosis that fails to correct with oxygen points toward a cardiac cause.
Cyanosis from heart disease (called central cyanosis) involves the lips and tongue and does not improve with extra oxygen, which helps distinguish it from cold hands or lung problems.