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Classify congenital heart disease. Describe the tetralogy of Fallot and Eisenmenger syndrome.

Pathology · 2nd Professional — Para-Clinical

Classification

Congenital heart disease comprises structural abnormalities of the heart or great vessels present at birth, affecting about 6 to 8 per 1000 live births.

Group	Lesions	Feature
Acyanotic — left-TO-right shunt	Ventricular septal defect (VSD), atrial septal defect (ASD), patent ductus arteriosus (PDA)	"The three Ds" — late cyanosis if the shunt reverses
Acyanotic — obstructive, no shunt	Coarctation of the aorta, pulmonary stenosis, aortic stenosis	No cyanosis
Cyanotic — right-TO-left shunt	Tetralogy of Fallot, Transposition of the great arteries, Truncus arteriosus, Tricuspid atresia, Total anomalous pulmonary venous return	"The five Ts" — cyanosis from birth or early infancy

VSD is the commonest congenital cardiac lesion overall; bicuspid aortic valve is the commonest congenital anomaly if valve variants are included
Tetralogy OF FALLOT is the commonest cyanotic lesion beyond infancy

Left-to-right Shunts

Lesion	Features
VSD	Harsh pansystolic murmur at the left sternal edge; small defects give louder murmurs and often close spontaneously; large defects cause failure and pulmonary hypertension
ASD	Wide fixed splitting of the second heart sound; ostium secundum is commonest; often presents in adulthood
PDA	Continuous "machinery" murmur; associated with congenital rubella and prematurity; closed with indomethacin, kept open with prostaglandin E

CLINICAL PEARL

Eisenmenger syndrome is what happens if a left-to-right shunt is left alone. Sustained high pulmonary flow causes pulmonary vascular disease; pulmonary pressure eventually exceeds systemic, and the shunt reverses to right-to-left. The patient becomes cyanosed, and the defect is now inoperable — closing it would leave the right ventricle facing an insurmountable resistance. Early correction exists to prevent exactly this.

Cyanotic Lesions

Tetralogy OF FALLOT — the four components: (1) ventricular septal defect, (2) overriding aorta, (3) pulmonary stenosis (right ventricular outflow obstruction), (4) right ventricular hypertrophy
All four arise from a single embryological error — anterosuperior displacement of the infundibular septum
The degree of pulmonary stenosis determines the severity, not the size of the septal defect
"boot-shaped" heart (coeur en sabot) on the chest radiograph, from right ventricular hypertrophy with a concave pulmonary bay
"tet spells" — hypercyanotic episodes relieved by squatting, which raises systemic vascular resistance and so reduces the right-to-left shunt
Transposition of the great arteries — two parallel circulations, incompatible with life unless a shunt (patent foramen ovale, ductus, VSD) allows mixing; prostaglandin E keeps the ductus open until surgery

Obstructive Lesions

Coarctation of the aorta — narrowing near the ductus arteriosus; hypertension in the upper limbs with weak, delayed femoral pulses (radiofemoral delay)
Rib notching on the chest radiograph from dilated collateral intercostal arteries, and a "figure of 3" aortic contour
Strongly associated with TURNER syndrome and with a bicuspid aortic valve

Applied Aspects

Causes and associations — congenital rubella (PDA, pulmonary stenosis), maternal diabetes, alcohol and lithium; down syndrome (atrioventricular septal defect, VSD), TURNER (coarctation, bicuspid valve), DiGeorge (truncus, tetralogy), Marfan (aortic root dilatation)
Pulse oximetry screening of newborns detects critical lesions before collapse and is cheap and effective
All significant lesions require endocarditis awareness, and the highest-risk groups need antibiotic prophylaxis
Early surgical correction has transformed outcomes, and most children now reach adulthood — creating a growing population of adults with congenital heart disease
In India, late presentation remains common, and Eisenmenger physiology is still seen because defects are recognised too late for repair

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