Right-to-left circulatory shunt

Alternative names

Right-to-left cardiac shunt; Cyanotic heart disease

Definition

Cyanotic heart disease is a defect or group of defects in the structure or function of the heart or the great vessels, present at birth, consisting of abnormal blood flow from the right to the left part of the circulatory system (either at the level of the atria, the ventricles, or the great vessels).

This abnormal communication (called right-to-left shunt) results in poor oxygenation of the body and therefore cyanosis (bluish coloration of the body).

Causes, incidence, and risk factors

Cyanotic heart diseases are congenital heart defects (heart diseases present at birth) that result in low oxygen levels in the blood and cause the child's skin to look blue (cyanosis).

This bluish coloration is most often detected on the lips, fingers, and toes or during exercise. Some heart defects cause major problems immediately after birth, and some cause few if any problems until adulthood.

Not all congenital heart diseases are cyanotic. Congenital heart defects that cause cyanosis include the following:

• Tetralogy of Fallot
  
• Transposition of the great vessels
  
• Ebstein's anomaly
  
• Tricuspid atresia (a deformity of the tricuspid heart valve)
  
• Total anomalous pulmonary venous return
  
• Pulmonic stenosis
  
• Truncus arteriosus
  
• Hypoplastic left heart syndrome
  

Most congenital heart disease occurs as a birth defect limited only to the heart, but some conditions occur as part of genetic and chromosomal syndromes that affect many organs.

Some syndromes that include congenital heart disease (not all cyanotic) are Down syndrome, trisomy 13, Turner's syndrome, Marfan syndrome, Noonan syndrome, and Ellis-van Creveld syndrome.

Some congenital heart diseases are caused by drugs, chemical exposure, or infections during pregnancy. Fetal rubella, infection by cytomegallovirus (CMV), maternal alcohol use (fetal alcohol syndrome), lithium carbonate use (for manic-depressive disorder), and retinoic acid use (for acne) are examples of infections and drugs that can cause congenital heart disease.

Symptoms

One symptom is cyanosis, usually seen as a bluish discoloration of the lips, fingers, and toes.

Some children have dyspnea (breathing problems) and adopt a squatting position after physical activity to relieve breathlessness. Others have hypoxic spells, where their bodies are suddenly starved of oxygen. These are characterized by anxiety, hyperventilation, and a sudden increase in cyanosis.