The five Ts, numbered by the great vessel count
Expansion
The five Ts, conveniently numbered:
- 1 - Truncus arteriosus: one great vessel
- 2 - Transposition of the great arteries: two vessels, swapped
- 3 - Tricuspid atresia: three letters in “tri”
- 4 - Tetralogy of Fallot: four features
- 5 - Total anomalous pulmonary venous return: five words
Cyanotic means a right to left shunt, so deoxygenated blood reaches the systemic circulation without passing the lungs. The hyperoxia test distinguishes it from lung disease: giving 100 per cent oxygen fails to raise the PaO2 much in a cardiac shunt.
Timing separates them: transposition presents within hours of birth as the ductus closes; tetralogy presents later, often at 1 to 2 months, with cyanotic spells.
Duct dependent lesions deteriorate as the ductus arteriosus closes, and are kept open with a prostaglandin E1 infusion until surgery.
Acyanotic lesions are the left to right shunts: ventricular septal defect (the commonest congenital lesion), atrial septal defect, patent ductus arteriosus, and the obstructive lesions coarctation and aortic stenosis. Untreated, a large left to right shunt can reverse when pulmonary pressures rise, producing Eisenmenger syndrome.