AKT · Child health/Congenital heart

Tetralogy of Fallot

Cyanotic CHD: pulmonary stenosis + VSD + overriding aorta + RV hypertrophy

Overview

The commonest CYANOTIC congenital heart disease beyond the neonatal period — four features: PULMONARY STENOSIS, a large VSD, an OVERRIDING AORTA and RIGHT VENTRICULAR HYPERTROPHY. The degree of RV outflow obstruction determines cyanosis. Hypercyanotic 'TET SPELLS' (acute cyanosis relieved by SQUATTING/knee-chest) are characteristic. Boot-shaped heart on CXR. Surgical repair in infancy.

Recognise

Cyanosis (variable, often after the neonatal period), ejection systolic murmur (the pulmonary stenosis) at the upper left sternal edge
'TET SPELLS' (hypercyanotic episodes — crying/feeding/waking; relieved by SQUATTING or knee-chest, which raises systemic resistance)
CXR: 'BOOT-SHAPED' heart (coeur en sabot); RV hypertrophy on ECG; associations: 22q11 (DiGeorge), Down

Red flags

Hypercyanotic 'tet' spell → knee-chest position, oxygen, morphine, IV fluids, beta-blocker/phenylephrine — can be life-threatening
Profound cyanosis in a duct-dependent neonate (severe RVOT obstruction) → prostaglandin

Differentials & how to tell them apart

Transposition of the great arteriescyanosis from DAY 1-2 (vs Fallot often later); egg-on-string CXR, no tet spells

Other cyanotic CHD (tricuspid atresia, truncus, TAPVR)echo defines; the 5 Ts

Severe pulmonary stenosiswithout the VSD/overriding aorta

Investigations

Echocardiography (the four features); CXR (boot-shaped heart, reduced pulmonary markings); ECG (RVH/right axis); pulse oximetry screening; consider 22q11 testing.

Management

Manage tet spells; surgical repair in infancy (prostaglandin/BT shunt if duct-dependent)

1Confirm on echo. Treat hypercyanotic 'tet' spells acutely (knee-chest position, oxygen, morphine, fluids, ± beta-blocker/phenylephrine). Plan surgical repair in infancy.Gate: A 'TET SPELL' is relieved by manoeuvres that RAISE systemic vascular resistance (knee-chest/squatting, phenylephrine) — increasing pulmonary flow; a severely cyanotic neonate (duct-dependent) needs prostaglandin
2Surgical repair (close the VSD, relieve RV outflow obstruction); BT shunt as a bridge; lifelong follow-up (pulmonary regurgitation, arrhythmia).

Tet spell: knee-chest position + O2 + morphine + IV fluids ± beta-blocker/phenylephrine — raises systemic vascular resistance / calms the spell

Prostaglandin (severe neonatal/duct-dependent) — maintain pulmonary flow before surgery

Surgical repair (VSD closure + relieve RVOT obstruction) — definitive, usually in infancy; a BT shunt as a temporising measure

Key points

PS + VSD + overriding aorta + RVH = Fallot, the commonest cyanotic CHD beyond the neonate. Tet spells relieved by SQUATTING; boot-shaped heart. Manage spells by raising systemic resistance. Think 22q11/DiGeorge.

Monitor & prognosis

Saturations, spells, surgical follow-up.

Good after repair; long-term pulmonary regurgitation/arrhythmia.

Source: RCPCH; paediatric cardiology