Congenital Heart Defects in Adults (ACHD) - Differential Diagnosis

Overview

Classification Framework

Specific Defects in Adults

1. Bicuspid Aortic Valve (BAV)

• Most common congenital cardiac anomaly in adult populations, present in ~2% of the general population
• Accounts for up to half of surgical aortic stenosis cases in adults
• Clinical: Systolic ejection click + murmur; progressive AS or AR; aortic root dilation/dissection risk
• Complications: Infective endocarditis, aortic coarctation association, aortopathy
• Differential: Acquired/calcific tricuspid AS (older patients), rheumatic AS, hypertrophic obstructive cardiomyopathy (HOCM)

2. Atrial Septal Defect (ASD)

• Constitutes 30-40% of CHD in adults; ostium secundum ASD accounts for 7% of all congenital lesions
• Types: Ostium secundum (most common), ostium primum, sinus venosus, coronary sinus
• Clinical: Often silent for decades. Presents in 3rd-5th decade with exertional dyspnea, atrial fibrillation, RV volume overload. Fixed splitting of S2 is the hallmark auscultatory finding. Pulmonary hypertension develops after the 4th decade; Eisenmenger syndrome occurs in 5-10%.
• ECG: Right bundle branch block (rSR' pattern in V1), right axis deviation in secundum ASD; left axis deviation in primum ASD
• Echocardiographic finding: Left-to-right flow across the atrial septum on color Doppler (see figure below)
• Differential: Pulmonary hypertension (primary or secondary), right heart failure from any cause, mitral stenosis, anomalous pulmonary venous drainage

3. Ventricular Septal Defect (VSD)

• Most common congenital lesion in children (15-20% of all CHD); less prevalent in adults due to high spontaneous closure rates
• Types: Perimembranous (up to 80%), infundibular/supracristal, inlet, muscular/trabecular
• Clinical: Small (restrictive) VSDs - asymptomatic with a harsh holosystolic murmur at the left sternal border. Moderate/large VSDs - LV volume overload, pulmonary hypertension, dyspnea. Eisenmenger complex develops in ~10% of unrestricted VSDs.
• Differential: Mitral regurgitation (murmur radiates to axilla), tricuspid regurgitation, HOCM (murmur increases with Valsalva), aortic stenosis

4. Patent Ductus Arteriosus (PDA)

• Accounts for 5-10% of all CHD in infants with normal birthweight
• Clinical: Small PDAs - asymptomatic. Moderate/large PDAs - continuous "machinery" murmur at left infraclavicular area, wide pulse pressure, LV volume overload. Eisenmenger reversal causes lower-limb cyanosis and clubbing (differential cyanosis).
• Differential: Aortic regurgitation + stenosis, coronary arteriovenous fistula, sinus of Valsalva aneurysm rupture, aortopulmonary window

Left-to-right shunt diagram (ASD, VSD, PDA):

5. Pulmonary Stenosis

• Accounts for 3-10% of all congenital lesions
• Clinical: Mild-moderate PS is usually well-tolerated into adulthood. Severe PS causes exertional dyspnea, RV hypertrophy, right heart failure. Ejection click that decreases with inspiration + crescendo-decrescendo systolic murmur at LUSB with radiation to the back.
• Differential: Atrial septal defect, dynamic RVOT obstruction in HOCM, pulmonary artery stenosis, tetralogy of Fallot

6. Coarctation of the Aorta

• 3-10% of CHD; associated with bicuspid aortic valve in up to 50% of cases; Turner syndrome association
• Clinical hallmarks:
  • Hypertension in upper extremities, reduced pressure and weak/delayed pulses in lower extremities
  • Blood pressure differential: arm systolic > popliteal systolic; >30 mmHg difference between right and left arms if left subclavian artery is involved
  • Systolic murmur heard posteriorly in the mid-thoracic region
  • Systolic ejection click from associated BAV
  • Collateral flow murmurs in infraclavicular areas
• CXR: Classic "3 sign" (dilated left subclavian artery + descending aorta indentation) and posterior rib notching of 3rd-8th ribs
• Differential: Essential hypertension, renal artery stenosis, Takayasu arteritis (in young women), mid-aortic syndrome

7. Tetralogy of Fallot (TOF)

1. Pulmonary stenosis (infundibular, most common)
2. Ventricular septal defect (large, perimembranous)
3. Overriding aorta
4. Right ventricular hypertrophy

• Clinical: Cyanosis (degree depends on severity of RV outflow obstruction), clubbing, polycythemia, hypertrophic osteoarthropathy. "Boot-shaped" heart on CXR (coeur en sabot). Most adults have had prior surgical repair; residual complications include pulmonary regurgitation, RV dilation/failure, arrhythmias, and sudden cardiac death.
• Genetic: 15% have 22q11 deletion (DiGeorge/CATCH-22 syndrome)
• CXR post-repair: Right aortic arch, upturned RV apex, sternal wires
• Differential: Large VSD with Eisenmenger, primary pulmonary hypertension, double-outlet right ventricle, pulmonary atresia with VSD

8. Ebstein Anomaly

• Apical displacement of the tricuspid valve leaflets (particularly the septal and posterior leaflets) into the RV, causing "atrialization" of a portion of the RV
• Clinical: Wide spectrum from severe neonatal presentation to incidental adult diagnosis. Symptoms include cyanosis (via ASD/PFO with R-to-L shunting), exercise intolerance, palpitations (accessory pathways, WPW syndrome in up to 25%). Characteristic auscultatory finding: "sail sound" (loud widely split S1 from tricuspid closure), triple or quadruple rhythm.
• ECG: Right bundle branch block, tall peaked P waves, delta waves if WPW
• Differential: Tricuspid regurgitation (any cause), dilated cardiomyopathy with TR, ASD, RV cardiomyopathy (ARVC)

9. Transposition of the Great Arteries (TGA) - Congenitally Corrected TGA (ccTGA)

• Simple TGA (D-TGA): Rarely reaches adulthood unrepaired; adults are almost always post-Mustard/Senning repair or arterial switch operation, each with specific late complications (baffle obstruction, systemic RV failure, arrhythmias)
• Congenitally corrected TGA (ccTGA/L-TGA): AV and ventriculo-arterial discordance that is "physiologically corrected." The systemic ventricle is the morphologic RV, which tends to fail over decades. Adults may present with TR, complete heart block, or heart failure.
• Differential: Dilated cardiomyopathy, complex RV failure, ARVC

10. Sinus of Valsalva Aneurysm

• A previously asymptomatic young man typically presents with acute chest pain and rapidly progressive dyspnoea (sometimes after physical exertion) due to rupture into the right heart
• Rupture creates a large left-to-right shunt; continuous "to-and-fro" murmur
• Differential: PDA, aortic regurgitation, coronary AV fistula

11. Anomalous Coronary Arteries

• Present in 0.6-1.5% of patients undergoing coronary angiography
• Most dangerous: left main or LAD arising from the right sinus and coursing between the aorta and pulmonary artery (risk of ischemia, MI, sudden death with exertion)
• Clinical: Exertional chest pain, syncope, sudden cardiac death in young athletes
• Differential: Premature CAD, HOCM, exercise-induced spasm, myocarditis

Eisenmenger Syndrome

• Late cyanosis (central, differential in PDA)
• Clubbing and polycythemia
• Symptoms of right heart failure
• Once established, structural repair is contraindicated (defect acts as a "pop-off valve")
• Treatment: pulmonary vasodilators (bosentan, sildenafil, prostacyclins), transplant

Differential Diagnosis Summary Table

General Diagnostic Approach in Adults

1. History: Prior surgeries, cardiac catheterizations, known diagnosis in childhood, family history of CHD or genetic syndromes
2. Physical exam: Cyanosis, clubbing, differential cyanosis (PDA), blood pressure in all 4 limbs, character and location of murmurs, S2 splitting, precordial heave
3. ECG: RV hypertrophy/strain, bundle branch blocks, axis deviation, pre-excitation (WPW in Ebstein), arrhythmias
4. CXR: Cardiomegaly, pulmonary vascular markings (plethora vs. oligemia), rib notching (coarctation), "3 sign," boot-shaped heart (TOF), situs
5. Echocardiography: First-line modality; assesses anatomy, shunt direction/quantification (Qp:Qs), ventricular function, pressures
6. Cardiac MRI: Gold standard for RV volumes, TOF residua, complex anatomy, coarctation
7. Cardiac CT angiography: Coronary anomalies, aortic anatomy, vascular structures
8. Cardiac catheterization: Hemodynamic assessment (pulmonary vascular resistance), vasoreactivity testing before repair decisions in pulmonary hypertension

Genetic Associations to Keep in Mind

• Any adult with an unexplained stroke, TIA, or systemic embolism should be screened for PFO or ASD (paradoxical embolism)
• Differential cyanosis (lower limbs only) + clubbing in a young adult = PDA with Eisenmenger reversal
• New continuous murmur + acute dyspnea in a previously well young adult = suspect sinus of Valsalva aneurysm rupture
• Exertional syncope in a young athlete = coronary anomaly until proven otherwise (also consider HOCM, long QT, ARVC)
• All patients with repaired or unrepaired CHD need prophylaxis consideration; high-risk lesions (unrepaired cyanotic CHD, prosthetic valves, post-repair residua) require endocarditis prophylaxis for dental procedures