Congenital Heart Disease, Cyanotic

Basics

Aberrant embryonic development results in mixing of deoxygenated and oxygenated blood returning to systemic circulation by 2 mechanisms:
- Right-to-left intracardiac shunt
- Anatomic defects of the aortic root
Subtypes: 5 T's, 2 E's, single ventricle:
- Tetralogy of Fallot (TOF):
  - Ventricular septal defect (VSD)
  - Right ventricular (RV) outflow obstruction
  - Overriding aorta
  - RV hypertrophy (RVH)
- Transposition of the great arteries (TGA):
  - Aorta arises from RV and pulmonary artery from left ventricle (LV)
- Tricuspid atresia:
  - No outlet from right atrium to RV
  - Obligatory atrial level connection
- Truncus arteriosus:
  - Single arterial trunk for systemic, pulmonic, and carotid circulations
- Total anomalous pulmonary venous return (TAPVR):
  - Pulmonary veins drain into systemic venous circulation
  - Supracardiac, cardiac, infracardiac, or mixed
- Ebstein anomaly of tricuspid valve:
  - Abnormal and displaced tricuspid valve divides RV resulting in poor RV function
- Eisenmenger syndrome:
  - Complication in longstanding acyanotic heart disease with L→R shunts
  - Pulmonary vascular resistance reaches suprasystemic levels; R→L shunt
- Single ventricle physiology:
  - Total mixing of systemic and venous return
Subdivide by amount of pulmonary blood flow:
- Decreased in TOF and tricuspid atresia
- Increased in TGA, truncus, and TAPVR

For most forms, cause is unknown:

Genetic cause: Chromosome 22 deletion in DiGeorge syndrome (conotruncal defects; TOF, truncus; also coarctation of aorta)
Environmental/teratogenic: TGA seen more often in infants of diabetic mothers

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