Differential Diagnosis of Congenital Heart Defects in Adults

Diagnostic Framework

1. What is the native anatomy?
2. Has this patient undergone prior surgery?
3. What residual hemodynamic sequelae are present?

• 12-lead ECG
• Chest radiograph (CXR) + baseline O2 saturation
• Transthoracic echocardiography (TTE) with Doppler/color flow
• Cardiac MRI (best for aortic anatomy)
• Transesophageal echocardiography (TEE) for complex/interventional cases

Category I: Acyanotic Shunt Lesions (Left-to-Right)

1. Atrial Septal Defect (ASD)

• Prevalence: 30-40% of CHD in adults; ostium secundum type = 7% of all congenital lesions
• Presentation: Often asymptomatic until 3rd-4th decade; exertional dyspnea, palpitations, paradoxical embolism, stroke
• Physical exam: Wide, fixed splitting of S2 (hallmark); soft systolic ejection murmur at upper left sternal border (relative pulmonary stenosis); diastolic rumble (tricuspid flow) if large shunt
• ECG: Ostium secundum: right axis deviation, incomplete RBBB (rSR' in V1); Ostium primum: left axis deviation, PR prolongation
• CXR: Cardiomegaly (RA/RV enlargement), increased pulmonary vascular markings, prominent pulmonary artery
• Echo: Dilated RA/RV, septal defect on color flow; TEE best for sinus venosus ASD
• Distinguishing features vs. other shunts: Fixed S2 splitting is unique to ASD; no thrill; no continuous murmur

2. Ventricular Septal Defect (VSD)

• Prevalence: 15-20% of all congenital lesions; high spontaneous closure - fewer adults affected
• Presentation: Small VSDs often asymptomatic (maladie de Roger); large VSDs cause pulmonary hypertension, dyspnea, eventually Eisenmenger syndrome
• Physical exam: Holosystolic murmur, best at left lower sternal border; thrill common; no fixed S2 splitting (unlike ASD)
• ECG: Small VSD: normal; large VSD: biventricular hypertrophy
• CXR: LA and LV enlargement (vs. ASD where RA/RV enlarge); increased pulmonary vascularity
• Echo: Identify location (perimembranous, muscular, supracristal), size, and shunt direction

3. Patent Ductus Arteriosus (PDA)

• Prevalence: 5-10% of congenital cardiac lesions in infants with normal birthweight
• Presentation: Small PDA asymptomatic; large PDA causes dyspnea, differential cyanosis (lower limbs cyanotic/clubbed, upper normal), Eisenmenger physiology
• Physical exam: Continuous "machinery" murmur, best at left infraclavicular area; bounding pulse; widened pulse pressure
• ECG: Left ventricular hypertrophy (volume overload)
• CXR: Enlarged aortic knuckle, dilated pulmonary artery, increased pulmonary flow
• Key differentiator: Continuous murmur (systolic + diastolic) - no other CHD produces this characteristic sound

4. Atrioventricular Septal Defect (AVSD / Endocardial Cushion Defect)

• Associations: 50% of patients with Down syndrome (trisomy 21); AV valve regurgitation
• Physical exam: Features of both ASD and VSD; mitral regurgitation murmur
• ECG: Left axis deviation + right bundle branch block pattern (characteristic combination)
• Echo: Common AV valve, primum ASD, inlet VSD

Category II: Obstructive Lesions

5. Bicuspid Aortic Valve (BAV)

• Prevalence: ~2% of general population - the most common congenital cardiac anomaly in adults; accounts for up to 50% of surgical aortic stenosis cases in adults
• Presentation: Aortic stenosis symptoms (angina, exertional dyspnea, presyncope, syncope, heart failure); aortic regurgitation; ascending aortic aneurysm risk
• Physical exam: Systolic ejection click (high-pitched, best at apex - distinguishes it from acquired AS); aortic stenosis murmur; click disappears once valve calcifies
• ECG: Left ventricular hypertrophy
• Echo: Two cusps with systolic doming; may show eccentric closure line; assess gradient, regurgitation, and aortic root size
• Key differentiator: Ejection click at apex in a young/middle-aged adult strongly suggests BAV

6. Pulmonary Stenosis (PS)

• Prevalence: 3-10% of all congenital lesions
• Presentation: Usually well-tolerated; exertional dyspnea with severe PS; right heart failure in advanced cases; cyanosis if associated atrial communication with right-to-left shunting
• Physical exam: Systolic ejection click at upper left sternal border (pulmonary area); harsh crescendo-decrescendo murmur that increases with inspiration; widely split S2 (P2 delayed and soft)
• ECG: Right ventricular hypertrophy with right axis deviation (proportional to severity)
• CXR: Post-stenotic dilation of the pulmonary artery; RV enlargement; normal pulmonary vascularity (unlike shunt lesions)
• Echo/Doppler: Peak gradient >30 mmHg indicates significant stenosis; doming of pulmonary valve cusps
• Intervention: Valvuloplasty for peak gradient ≥50 mmHg or symptoms

7. Coarctation of the Aorta

• Anatomy: Discrete narrowing just distal to the left subclavian artery at the aortic ductal attachment
• Associations: Turner syndrome (45,X); bicuspid aortic valve in 50%; berry aneurysms (intracranial)
• Presentation in adults: Hypertension (upper extremities), headache, epistaxis; leg claudication; heart failure; aortic dissection/rupture
• Physical exam: Blood pressure differential: elevated in arms, reduced/absent in legs; bounding upper limb pulses vs. weak/delayed femoral pulses; systolic murmur heard posteriorly (mid-thoracic); infraclavicular and axillary collateral flow murmurs; ejection click if bicuspid AV present
• CXR: "3 sign" (indentation between dilated left subclavian artery above and post-stenotic aortic dilation below); bilateral rib notching (ribs 3-8, posterior) from enlarged collateral intercostal arteries
• ECG: Left ventricular hypertrophy
• Best imaging: MRI for anatomy; catheterization measures gradient before intervention
• Key differentiator: Upper-lower extremity BP differential + rib notching on CXR is pathognomonic

8. Left Ventricular Outflow Tract Obstruction (Subvalvular/Supravalvular)

• Discrete subaortic stenosis: Fibromuscular ring below aortic valve; 15-20% of congenital LVOT obstruction; 50% have concomitant aortic insufficiency
• Supravalvular aortic stenosis: Thickened aorta above sinuses; associated with Williams syndrome (chromosome 7q11.23 deletion); risk of early coronary ostial stenosis
• Distinguishing from valvular AS: No ejection click; regurgitation more prominent in subaortic stenosis; echo shows level of obstruction

Category III: Complex / Cyanotic Lesions

9. Tetralogy of Fallot (TOF)

• Most common cyanotic CHD in adults
• Four components: Large VSD + right ventricular outflow tract obstruction (RVOTO) + overriding aorta + right ventricular hypertrophy
• Presentation in adults: Most are post-repair (surgical correction common since 1960s); residual/recurrent RVOTO, pulmonary regurgitation (major post-repair concern), arrhythmia (VT/SVT), right heart failure; unrepaired patients have cyanosis, clubbing, polycythemia
• Physical exam (unrepaired): Cyanosis + clubbing; single S2 (absent P2 due to RVOTO); harsh systolic murmur from RVOTO (not VSD); squatting posture (increases SVR, reduces right-to-left shunt)
• ECG: Right ventricular hypertrophy; post-repair: right bundle branch block (RBBB) with QRS duration >180 ms = risk marker for sudden death
• CXR: "Boot-shaped heart" (coeur en sabot) - upturned apex, concave pulmonary bay; decreased pulmonary vascularity
• Key differentiator: Boot-shaped heart + decreased pulmonary markings + RBBB post-repair

10. Eisenmenger Syndrome

• Definition: Severe pulmonary hypertension with reversal of a previously left-to-right shunt to right-to-left (any uncorrected large shunt - VSD, ASD, PDA, AVSD)
• Presentation: Central cyanosis, clubbing, exertional dyspnea, hemoptysis, polycythemia/hyperviscosity (headache, visual disturbance), paradoxical embolism, sudden death
• Physical exam: Central cyanosis; loud P2; prominent RV heave; clubbing; the original shunt murmur often disappears (equalized pressures)
• Differential cyanosis (lower limbs cyanotic, upper normal) = PDA with Eisenmenger (aortic flow to legs, reversed shunt)
• Complications: Hyperviscosity (hematocrit >65% - phlebotomy indicated); hyperuricemia/gout; hemostatic abnormalities; increased infection risk; endocarditis
• Management: Pulmonary vasodilators (bosentan); avoid dehydration, iron deficiency; oxygen therapy for long flights; chronic oxygen unlikely to benefit (fixed PVR)

11. Ebstein Anomaly

• Anatomy: Apical displacement of the tricuspid valve leaflets into the right ventricle; "atrialized" portion of RV; associated ASD/PFO in 50% (causes cyanosis)
• Presentation: Palpitations (Wolff-Parkinson-White, SVT), cyanosis (if ASD/PFO with right-to-left shunt), right heart failure
• Physical exam: Widely split S1 (delayed tricuspid closure); "sail sound" of the large anterior tricuspid leaflet; pansystolic murmur (TR)
• ECG: Right bundle branch block; tall peaked P waves (Himalayan P waves); delta waves if WPW (10-25%); PR prolongation
• CXR: Massive cardiomegaly with "wall-to-wall heart" (globe-shaped) and decreased pulmonary vascularity
• Key differentiator: RBBB + WPW pattern + massive cardiomegaly in a young adult

12. Transposition of the Great Arteries (D-TGA) - Post-repair Adults

• Anatomy: Aorta arises from RV; pulmonary artery from LV
• Prevalence: Together with TOF, accounts for 5-12% of CHD in infants
• Adults encountered: Post-Mustard/Senning repair (atrial switch) or post-arterial switch operation
• Post-atrial switch complications: Systemic RV failure, atrial arrhythmias (sick sinus syndrome), baffle obstruction/leak, sudden death
• ECG: Right axis deviation, RV hypertrophy (systemic RV pattern)

13. Congenitally Corrected Transposition (L-TGA / ccTGA)

• Anatomy: Double discordance - AV discordance + ventriculo-arterial discordance; RV is the systemic ventricle
• Presentation: Often incidental; progressive systemic RV failure; complete heart block (develops at ~2%/year); Ebstein-like tricuspid valve anomaly common
• ECG: Q waves in right precordial leads (V1-V4) but absent in V5-V6 (reversed septal depolarization); varying degrees of heart block

14. Sinus of Valsalva Aneurysm (Ruptured)

• Typical presentation: Young man with sudden onset chest pain + progressive dyspnea, often after exertion
• Right or non-coronary sinus involved in >90%; rupture into right atrium or right ventricle
• Physical exam: Continuous to-and-fro murmur (loud); signs of acute heart failure
• Key differentiator: Acute presentation of continuous murmur in young adult, different from PDA which is chronic

15. Pulmonary Arteriovenous Malformation (PAVM)

• Association: Osler-Weber-Rendu syndrome (hereditary hemorrhagic telangiectasia)
• Presentation: Cyanosis, clubbing, platypnea-orthodeoxia (worse when upright), paradoxical embolism/brain abscess
• Physical exam: Bruit over chest wall sometimes audible
• Differentiator: Cyanosis that worsens in upright position; no murmur of a cardiac shunt; telangiectasias on skin/mucosa

Summary Differential Table

Genetic Associations to Remember

Key Diagnostic Pearls

1. Fixed wide splitting of S2 = ASD until proven otherwise
2. Continuous machinery murmur = PDA
3. Boot-shaped heart + decreased pulmonary vascularity = Tetralogy of Fallot
4. "3 sign" + rib notching on CXR = Coarctation of the aorta
5. Ejection click best at apex in a young adult = Bicuspid aortic valve
6. Differential cyanosis (legs > arms) = PDA with Eisenmenger
7. Globe-shaped cardiomegaly + WPW on ECG = Ebstein anomaly
8. Cyanotic CHD without cardiac murmur = Eisenmenger syndrome (equalized pressures)
9. Left axis deviation + RBBB = AVSD (endocardial cushion defect)
10. QRS >180 ms post-TOF repair = High risk for sudden cardiac death

• Goldman-Cecil Medicine (International Edition), Chapter 55: Congenital Heart Disease in Adults, pp. 604+