Pediatric CHD Quick Reference Notes (Acyanotic & Obstructive)

Classification of Congenital Heart Disease

• CHD broadly split into cyanotic vs acyanotic based on systemic hemoglobin saturation.
• Three main pathophysiologic groups:
  • Left-to-right shunts
  • Right-to-left shunts
  • Outflow tract obstructions
• Acyanotic lesions include left-to-right shunts and outflow tract obstructions.
• Left-to-right shunts (increased pulmonary circulation): VSD, ASD, PDA, AVSD.
• Outflow tract obstructions typically have normal pulmonary blood flow and include AS, PS, CoA.
• Consequences of increased pulmonary flow: pulmonary edema, dilation/hypertrophy of heart, congestive heart failure.

Ventricular Septal Defect (VSD)

• Most common congenital heart defect; can be isolated or part of other defects.
• Ventricular septum components: muscular, posterior/inlet, supracristal, membranous.
• VSDs classified by location: muscular vs perimembranous (margin of muscular septum just below aortic valve).
• Shunt size and pulmonary vascular resistance (PVR) determine presentation and murmur:
  • Small VSDs: loud murmur, often asymptomatic; turbulent flow.
  • Moderate-large VSDs: quieter murmur; risk of pulmonary hypertension and heart failure.
• Classic murmur: pansystolic, loudest at left lower sternal border; may have accompanying thrill and a split S2.
• Pathophysiology: left-to-right shunt → increased pulmonary flow → left heart volume overload → dilation/hypertrophy; long-standing can cause pulmonary hypertension and right ventricular hypertrophy.
• Investigations: ECG and chest X-ray depend on defect size; echocardiography is mainstay to define size, location, valves, and associated lesions.
• Treatment:
  • Small VSDs: often close spontaneously; surgical closure not always needed.
  • Moderate-large VSDs: diuretics, afterload reduction, caloric supplementation; consider closure if symptoms persist or pulmonary hypertension develops.
  • Closure: surgically or by device via cardiac catheterization when indicated.

Atrial Septal Defect (ASD)

• Left-to-right shunt; most common type is secundum ASD (foramen ovale region).
• Other types: primum ASD (near endocardial cushions, part of AVSD spectrum), sinus venosus defects, coronary sinus defects.
• Embryology: failure of septal growth toward endocardial cushions.
• Clinical features: many children asymptomatic; older individuals may have arrhythmias, heart failure, pulmonary hypertension.
• Murmur findings: fixed and widely split S2; systolic ejection murmur at right or left upper sternal border; possible RV heave.
• Pathophysiology: shunt size and ventricular compliance determine extent of RV dilation.
• Investigations: ECG may show right axis deviation; RV enlargement; CXR with cardiomegaly and enlarged right heart; echocardiography to define type/size and flow.
• Treatment:
  • Closure recommended if significant shunt around age 3-5 ext{ years}.
  • Secundum ASDs often closed with transcatheter device closure.

Patent Ductus Arteriosus (PDA)

• Left-to-right shunt; more common in premature neonates.
• Ductus arteriosus is normal fetal connection between aorta and pulmonary artery; closes spontaneously within 24-74 ext{ hours} after birth.
• PDA results when closure fails, allowing left-to-right shunt as PVR falls.
• Size of PDA and PVR determine shunt magnitude and symptoms.
• Clinical features: small PDAs often asymptomatic; larger shunts cause congestive symptoms (failure to thrive, increased work of breathing, recurrent infections, fatigue).
• Murmur: continuous, machine-like murmur best heard at the left infraclavicular area; may radiate to the back/ lungs; may be systolic-only or absent in very large PDAs with pulmonary hypertension; wide pulse pressure and hyperdynamic precordium.
• Investigations: echo best for ductal anatomy and flow; chest X-ray may show cardiomegaly and increased pulmonary vascularity; ECG may show LVH/LA enlargement and possible RV effects if pulmonary hypertension present.
• Treatment:
  • Spontaneous closure unlikely after a few weeks; NSAIDs (e.g., indomethacin/ibuprofen) close moderate-large PDAs in premature neonates by inhibiting prostaglandins.
  • Older children: diuretics to manage symptoms; closure via catheter-based devices or surgery.

Atrioventricular Septal Defect (AVSD)

• Also known as endocardial cushion defect; failure of septum to fuse with endocardial cushion.
• Complete AVSD features: primum ASD, inlet VSD, common AV valve with a cleft left AV valve; AV valve insufficiency possible.
• Strong association: most common CHD in infants with Down syndrome.
• Pathophysiology: falling PVR leads to CHF symptoms (increased work of breathing, fatigue, failure to thrive) due to VSD and valve dysfunction.
• Murmurs vary with the extent of shunting.
• Investigations: echocardiography for anatomy and planning; chest X-ray for cardiomegaly/vascularity; ECG may show left axis or LVH.
• Treatment: diuretics, afterload reduction, caloric support; definitive treatment is surgical repair.

Pulmonary Stenosis (PS)

• Outflow tract obstruction; subtypes by location: valvular, subvalvular, supravalvular.
• Etiology: faulty development of valve leaflets; mild PS often asymptomatic; moderate-to-severe PS causes exertional dyspnea and fatigue.
• Neonatal severe PS can cause cyanosis due to right-to-left shunting at the atrial level.
• Murmur: systolic ejection murmur at the second left intercostal space with a systolic ejection click.
• Investigations: echocardiography to define site and severity; ECG may show RVH and right axis deviation in significant cases.
• Treatment: balloon valvuloplasty is first-line for valvular PS; surgical repair if balloon outcome is poor or if subvalvular/supravalvular PS present.

Aortic Stenosis (AS)

• Outflow obstruction; types: valvular, subvalvular, supravalvular; bicuspid aortic valve is a common cause.
• Symptoms: exertional dyspnea, syncope, reduced exercise tolerance, possible sudden death; neonates with severe AS may collapse when ductus closes.
• Murmur: systolic ejection murmur at the second right intercostal space, radiating to the neck; may have systolic ejection click; murmur intensity rises with severity.
• Investigations: ECG and chest X-ray may be normal with mild AS; echo to locate site, morphology, and gradient; assess ascending aorta dilatation.
• Treatment: balloon valvuloplasty as first-line; surgery for significant aortic insufficiency or failed balloon; monitor progression.

Coarctation of the Aorta (CoA)

• Etiology: failure of the aortic isthmus to develop; constricted segment with medial thickening.
• Presentation varies by age and ductus dependency:
  • Neonates: may be ductus-dependent; after ductus closure, poor perfusion, shock, feeding difficulty, respiratory distress.
  • Older children: headaches, upper-extremity hypertension, claudication; weaker femoral pulses; murmur best heard in the left interscapular area.
• Associated findings: bicuspid aortic valve in about half of cases; may have a systolic click/murmur of associated aortic stenosis.
• Investigations: imaging to locate extent; echo to define site and other lesions; older children may show LVH and cardiomegaly on ECG/X-ray; rib notching may appear on X-ray due to collateral vessels.
• Treatment:
  • Neonates: prostaglandin E1 (PGE1) to keep ductus open; inotropes/diuretics as needed; surgical repair is common.
  • Older children: medical management with beta-blockers for hypertension; balloon angioplasty; stenting is preferred in older children/adolescents; long-term follow-up for persistent hypertension and risk of complications.

Murmurs: Innocent vs Pathologic

• Innocent murmurs: physiologic, no heart disease; soft, vibratory; typically no extra sounds; may vary with position.
• Pathologic murmurs: suggest structural heart disease; harsh quality, higher grade, possible thrill; may have accompanying abnormal S2, clicks, S3/S4, or radiating patterns; do not rely on auscultation alone.
• Features to trigger concern/referral: multiple pathologic findings, persistent murmur with growth concerns, cyanosis, clubbing, failure to thrive, poor pulses, reduced exercise tolerance, family history of congenital heart disease.
• Practical guide: use the presence of ALL pathologic features to classify vs innocent murmurs; refer to a pediatric cardiologist when there is suspected pathology or uncertainty.

Summary

• CHD can be categorized into three main groups: left-to-right shunts, right-to-left shunts, and outflow tract obstructions.
• Acyanotic CHD includes left-to-right shunts and outflow tract obstructions.
• Left-to-right shunts include ASD, VSD, PDA, and AVSD.
• Clinical presentation varies with shunt size and associated lesions; follow-up is essential to address current symptoms and prevent deterioration.

Quick Investigations & Treatments (Reminders)

• Echo is the main diagnostic tool across CHD for size, location, type, and flow.
• ECG and chest X-ray findings depend on defect size and hemodynamics.
• Treatments often include: diuretics, afterload reduction, and caloric support for congestive symptoms; closure (surgically or via catheter) when indicated; balloon valvuloplasty or surgical repair for outflow tract obstructions; prostaglandin E1 for ductus-dependent lesions in neonates; beta-blockers for some CoA-related hypertension.