Congenital Heart Defects: Step 1 review notes and self-test
Notes for the Congenital Heart Defects rapid review: the clue that separates each of its 5 confusion pairs, with timestamps and a self-test.
October 21, 2026
This video covers key clues that separate congenital heart defects that can look alike. Watch the video, then use these notes to test yourself.
Atrial septal defect vs Ventricular septal defect
You identify ASD by a wide fixed split S2 and VSD by a harsh holosystolic murmur at the lower left sternal border. Do not confuse them because both initially cause left-to-right shunts and can lead to Eisenmenger syndrome if large and unrepaired.
Atrial septal defect vs Ventricular septal defect ASD: wide fixed split S2; VSD: harsh holosystolic murmur at the lower left sternal border. Open the comparison and video →Patent ductus arteriosus vs Coarctation of the aorta
You identify PDA by a continuous machinery murmur with widened pulse pressure and bounding pulses. You identify coarctation by upper-extremity hypertension with delayed, weak femoral pulses. Both can be asymptomatic in childhood, and differential cyanosis can appear in either lesion when right-to-left shunting develops.
Patent ductus arteriosus vs Coarctation of the aorta PDA is continuous machinery murmur; coarctation is upper-lower extremity pulse and pressure difference. Open the comparison and video →Tetralogy of Fallot vs Eisenmenger syndrome
You identify tetralogy of Fallot as primary cyanotic anatomy with RV outflow obstruction and a VSD, while Eisenmenger syndrome is late reversal of an initially left-to-right shunt. Do not use cyanosis alone because it cannot distinguish congenital right-to-left anatomy from acquired shunt reversal.
Tetralogy of Fallot vs Eisenmenger syndrome TOF is primary cyanotic anatomy; Eisenmenger is late shunt reversal after an initially left-to-right lesion. Open the comparison and video →Truncus arteriosus vs Tetralogy of Fallot and transposition
You identify truncus arteriosus by one arterial trunk overriding a VSD, tetralogy of Fallot by RV outflow obstruction with a VSD, and transposition by switched great arteries that create parallel circuits. All are conotruncal cyanotic defects, so count the great arteries and decide whether the circuits are mixed or parallel.
Truncus arteriosus vs Tetralogy of Fallot and transposition Truncus is one trunk; TOF is obstructed RV outflow with VSD; TGA is parallel switched arteries. Open the comparison and video →Infantile/preductal coarctation vs Adult/postductal coarctation
You identify infantile or preductal coarctation when a neonate worsens as the ductus closes, while adult or postductal coarctation presents later with an arm-leg pressure difference and collateral flow. Weak femoral pulses can occur in both, so use timing and ductal dependence to separate them.
Infantile/preductal coarctation vs Adult/postductal coarctation Preductal coarctation presents as ductal-dependent neonatal shock; postductal presents later with arm-leg pressure gradient and collaterals. Open the comparison and video →Quick self-test
Name the diagnosis from the clue, then tap to check.
Neonate worsens when ductus closes because lower-body perfusion is ductal-dependent.
Infantile/preductal coarctation · Infantile/preductal coarctation vs Adult/postductal coarctation
Continuous machinery murmur below the left clavicle with bounding pulses from persistent aorta-to-pulmonary artery flow.
Patent ductus arteriosus · Patent ductus arteriosus vs Coarctation of the aorta
Primary cyanotic defect with VSD, overriding aorta, RV outflow obstruction, RVH, tet spells, and squatting relief.
Tetralogy of Fallot · Tetralogy of Fallot vs Eisenmenger syndrome
Fixed wide split S2 with systolic flow murmur from increased right-sided volume.
Atrial septal defect · Atrial septal defect vs Ventricular septal defect
Harsh holosystolic murmur at the lower left sternal border from LV-to-RV systolic flow.
Ventricular septal defect · Atrial septal defect vs Ventricular septal defect
Aortic narrowing with upper-extremity hypertension, weak femoral pulses, leg symptoms, and rib notching in older patients.
Coarctation of the aorta · Patent ductus arteriosus vs Coarctation of the aorta
Single arterial trunk overriding a VSD supplies systemic, pulmonary, and coronary circulations.
Truncus arteriosus · Truncus arteriosus vs Tetralogy of Fallot and transposition
Late pulmonary hypertension from chronic left-to-right shunt causing reversal to right-to-left shunt, cyanosis, and clubbing.
Eisenmenger syndrome · Tetralogy of Fallot vs Eisenmenger syndrome
TOF has two great arteries with RV outflow obstruction; TGA has switched great arteries creating parallel circuits requiring mixing.
Tetralogy of Fallot and transposition · Truncus arteriosus vs Tetralogy of Fallot and transposition
Keep going
Every pair in this review has a free page in the library with a side-by-side comparison and a practice question. Work through the ones you missed in the self-test first.