Explore Congenital Heart Disease (CHD) with our comprehensive guide. Learn about acyanotic & cyanotic types like ASD, VSD, TOF, TGA, causes, and symptoms.
Congenital Heart Disease (CHD) Anatomy · March 3, 2026 --- Summary Congenital Heart Disease (CHD) encompasses structural or functional abnormalities of the heart present at birth, typically classified as acyanotic or cyanotic . These defects arise from altered embryonic development, affecting approximately 0.8% of live births . Etiology is frequently unknown, but genetic and environmental factors contribute to conditions like Tetralogy of Fallot, VSD, ASD, and TGA. --- Key Points Topic Detail --- --- Definition Abnormality in cardio-circulatory structure or function present at birth Epidemiology ~0.8% of live births; extracardiac anomalies are common Etiology Unknown in ~90%; associated with maternal rubella, thalidomide, alcohol, and genetic factors (Trisomies, Turner syndrome) Classification Acyanotic (Left-to-Right shunt) vs. Cyanotic (Right-to-Left shunt) ASD Types Ostium secundum (most common), Ostium primum (Down syndrome), Sinus venosus, Coronary sinus PFO Present in ~25% of adults; linked to paradoxical embolism VSD Most common CHD (25%); haemodynamic effects depend on size PDA Persistence of ductus arteriosus; associated with prematurity; causes a machinery murmur Eisenmenger Syndrome Irreversible reversal of L→R shunt to R→L due to pulmonary hypertension TOF Most common cyanotic CHD; VSD + pulmonary stenosis + overriding aorta + RVH TGA Aorta from RV, PA from LV; incompatible with life without mixing (ASD/VSD/PDA) Ebstein's Anomaly Apical displacement of tricuspid leaflet; associated with maternal lithium use Coarctation of Aorta Narrowing of aorta → hypertension in upper limbs, hypotension in lower limbs --- Detailed Notes Introduction and Classification CHD refers to structural or functional abnormalities of the heart and circulatory system present at birth, arising from altered embryonic development. It affects ~0.8% of live births and can be associated with extracardiac anomalies. Broadly classified as: - Acyanotic (left-to-right shunts): ASD, VSD, PDA, Coarctation of Aorta - Cyanotic (right-to-left shunts): TOF, TGA, Ebstein's anomaly, Truncus arteriosus, Eisenmenger syndrome Etiology is often unknown but involves environmental factors (maternal infections, substance use) and genetic factors (chromosomal abnormalities). --- Embryonic Development Month 1 — Cardiac Tube Formation: Sinuatrium → Primitive ventricle → Bulbus cordis → Truncus arteriosus Month 2 — Septation and Folding: - Atrial Septum: Septum primum grows → ostium primum → perforates → ostium secundum. Septum secundum forms the fossa ovalis. - Ventricular Septum: Cephalic growth of main ventricular septum fuses with endocardial cushions. - Great Arteries: Truncus arteriosus divides and rotates to create the spiral relationship between the aorta and pulmonary artery. --- Atrial Septal Defect (ASD) Type Frequency Notes --- --- --- Ostium secundum 75% Midseptal; associated with mitral valve prolapse Ostium primum 15% Lower septal; associated with Down syndrome and AV valve clefts Sinus venosus 10% Upper septal; associated with anomalous pulmonary venous return --- Ventricular Septal Defect (VSD) Most common CHD overall. - Types: Muscular, Membranous (most common), Doubly committed subarterial - Pathophysiology: Large defects → LV volume overload → may progress to Eisenmenger syndrome --- Patent Ductus Arteriosus (PDA) Persistent connection between the proximal left pulmonary artery and the descending aorta. - Clinical: Continuous machinery murmur - Treatment: Indomethacin to close; Prostaglandins to keep open (e.g., in TGA where mixing is essential) --- Tetralogy of Fallot (TOF) Most common cyanotic CHD. Four components: 1. VSD 2. Pulmonary Stenosis 3. Overriding Aorta 4. RVH (Right Ventricular Hypertrophy) - "Tet spells": Episodes of cyanosis, often relieved by squatting (↑ systemic vascular resistance → improves oxygenation) - CXR: "Boot-shaped heart" --- Transposition of the Great Arteries (TGA) Aorta arises from RV; pulmonary artery arises from LV → two parallel circulations. Incompatible with life without a shunt (ASD, VSD, or PDA) to allow mixing. --- Ebstein's Anomaly Apical displacement of tricuspid leaflets → "atrialization" of part of the RV. - Associated with Wolff-Parkinson-White (WPW) syndrome - Linked to maternal lithium use --- Coarctation of the Aorta Narrowing of the aorta, typically in the juxtaductal region. Feature Detail --- --- Radiofemoral delay Delayed/weak femoral pulses vs. radial pulses Rib notching Due to collateral vessel development (on CXR) "Figure 3 sign" On imaging Associations Turner syndrome, bicuspid aortic valve --- Practice Questions Presentation Diagnosis --- --- Cyanosis at birth, aorta from RV, PA from LV TGA Boot-shaped heart + Tet spells TOF Stroke in young adult with PFO Paradoxical embolism Continuous machinery-like murmur PDA Down syndrome + ASD near AV valves Ostium primum ASD HTN in upper limbs, weak lower pulses, rib notching Coarctation of the Aorta Maternal lithium + tricuspid displacement Ebstein's anomaly Irreversible reversal of L→R shunt due to pulmonary HTN Eisenmenger Syndrome