Acyanotic Congenital Heart Defects (ACHDs)

1. Definition

• ACHDs are congenital cardiac malformations affecting:

  • Atrial or ventricular walls

  • Heart valves

  • Large blood vessels (e.g., aorta, pulmonary artery)

• Characteristic feature: Left-to-right shunt → increased pulmonary blood flow → right-sided heart hypertrophy without cyanosis initially.

Common causes / risk factors:

• Genetic disorders: trisomies (Down syndrome)

• Maternal infections: rubella, TORCH infections

• Maternal exposures: drugs, alcohol, diabetes

• Syndromes: Turner syndrome (coarctation), Loeys-Dietz (PFO)

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2. Common Types of ACHDs

CHD	Pathophysiology	Clinical Features	Diagnostic Findings	Management
Atrial Septal Defect (ASD)click here	Left-to-right atrial shunt → RA & RV volume overload	Often asymptomatic; exercise intolerance, fatigue; widely split fixed S2	Echocardiography: interatrial communication; CXR: enlarged RA/RV, prominent pulmonary vessels; ECG: RBBB pattern, right axis deviation	Small: observation; Large: percutaneous/surgical closure
Ventricular Septal Defect (VSD)click here	Left-to-right ventricular shunt → LV & RV volume overload → pulmonary hypertension	Small: asymptomatic, harsh holosystolic murmur; Large: HF signs, failure to thrive, tachypnea	Echocardiography: interventricular communication, left-to-right flow; CXR: cardiomegaly, pulmonary congestion; ECG: LVH ± RVH	Small: observation; Large/symptomatic: surgical closure
Atrioventricular Septal Defect (AVSD / Endocardial Cushion Defect)	Partial: ASD + minor AV valve anomaly; Complete: ASD + VSD + common AV valve → left-to-right shunt	Complete: HF early, pulmonary hypertension; Partial: may remain asymptomatic until later	Echocardiography: defect size, AV valve anatomy; CXR: cardiomegaly, pulmonary congestion	Medical management for asymptomatic; surgical repair usually 3–6 months (complete) or 2–4 years (partial)
Patent Foramen Ovale (PFO)	Persistence of fetal foramen ovale → mild left-to-right shunt; may reverse during maneuvers (Valsalva)	Usually asymptomatic; may cause paradoxical embolism or cryptogenic stroke	TTE with agitated saline: right-to-left shunt; TEE if TTE inconclusive; Transcranial Doppler optional	Asymptomatic: none; Post-embolism: antiplatelets/anticoagulation, possible closure
Patent Ductus Arteriosus (PDA)click here	Left-to-right shunt from aorta → pulmonary artery → pulmonary overcirculation	Continuous “machinery” murmur, HF in large PDA; bounding pulses; widened pulse pressure	Echocardiography: patent ductus; CXR: cardiomegaly, pulmonary overcirculation	Closure (surgical or device) if significant; maintain PDA with PGE1 in ductal-dependent lesions
Coarctation of the Aorta (CoA)	Narrowing of aortic arch → LV outflow obstruction → collateral circulation	Hypertension in upper extremities, weak femoral pulses, HF if severe; differential cyanosis in distal body	Echocardiography/CT/MRI: aortic narrowing; CXR: rib notching, LVH	Balloon angioplasty or surgical repair; maintain PDA in critical neonatal cases
Pulmonary Valve Stenosis (PVS) click here	RV outflow tract obstruction → RV hypertrophy	Systolic ejection murmur at LUSB; mild: asymptomatic; severe: dyspnea, fatigue	Echocardiography: valve thickening/narrowing; RV hypertrophy	Balloon valvuloplasty; maintain PDA if ductal-dependent lesion

Mnemonic for common ACHDs (frequency): “3 Ds” → VSD, PDA, ASD

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3. Pathophysiology

• Shunts:

  • Left-to-right: oxygenated blood returns to pulmonary circulation → pulmonary hypertension, right-sided hypertrophy, heart failure without cyanosis

  • Right-to-left (secondary / Eisenmenger): chronic left-to-right shunt → pulmonary vascular resistance rises → reversal of flow → cyanosis, digital clubbing, polycythemia

• Volume vs. pressure overload:

  • ASD → RA/RV volume overload

  • VSD → LV/RV volume overload

  • Obstructive lesions (CoA, PVS) → pressure overload → hypertrophy

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4. Clinical Features

General / Nonspecific

• Failure to thrive

• Recurrent respiratory infections

• Exercise intolerance, fatigue, pallor, diaphoresis

• Tachycardia, dyspnea, grunting, nasal flaring, retractions, head bobbing (infants)

Heart Failure Signs

• Right HF: hepatomegaly, peripheral edema (rare in infants)

• Left HF: tachypnea, pulmonary edema, low cardiac output → pallor, sweating, cool extremities

Murmurs / Auscultation

Defect	Murmur / Heart Sounds
ASD	Mid-diastolic murmur, widely split S2
VSD	Harsh holosystolic murmur at LLSB
PDA	Continuous “machinery” murmur at LUSB
PVS	Systolic ejection murmur at LUSB
CoA	May be systolic murmur; BP difference upper vs lower limbs

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5. Diagnostics

• Echocardiography (TTE/TEE): defect type, shunt direction, chamber sizes

• Chest X-ray: cardiomegaly, pulmonary vascular markings

• ECG: chamber hypertrophy, arrhythmias (supraventricular in ASD, LVH ± RVH in VSD/CoA)

• Advanced imaging: cardiac CT, MRI, catheterization for surgical planning

• Special tests: Agitated saline for PFO detection

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6. Medical Management

• General care: nutrition, immunizations, regular exercise, counseling

• Heart failure: diuretics, ACE inhibitors, inotropes (digoxin)

• Ductal-dependent CHDs: maintain PDA with prostaglandin E1 infusion

• Arrhythmia management: monitor and treat as needed

• Pulmonary hypertension / Eisenmenger: bosentan, PDE-5 inhibitors (sildenafil/tadalafil)

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7. Surgical / Interventional Management

• ASD/VSD/AVSD: patch closure, AV valve repair

• PDA: ligation or device closure

• PVS: balloon valvuloplasty

• CoA: balloon angioplasty or surgical repair

• Timing depends on size, symptoms, and risk of complications (e.g., heart failure, pulmonary hypertension)

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8. Complications

• Eisenmenger syndrome (late cyanosis due to shunt reversal)

• Heart failure (right or left)

• Arrhythmias (atrial fibrillation, supraventricular tachycardia)

• Embolic events (especially with PFO)

• Pulmonary hypertension

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9. Prognosis & Follow-up

• Lifelong cardiology follow-up recommended

• Early detection and timely surgical or catheter interventions improve outcomes

• Most patients with ACHDs can participate in moderate physical activity if no significant residual lesion

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