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Acyanotic Congenital Heart Disease

Learning Objectives

Core Knowledge & Clinical Reasoning

  • [ ] Classify acyanotic CHD into shunt lesions vs obstructive lesions
  • [ ] Describe hemodynamics of VSD, ASD, PDA, coarctation, AS, and PS
  • [ ] Recognize clinical presentations at different ages
  • [ ] Identify when intervention is needed

Communication & Counseling

  • [ ] Explain common diagnoses to families in understandable terms
  • [ ] Counsel on prognosis after repair

Classification

Category Lesions Pathophysiology
Left-to-Right Shunts VSD, ASD, PDA, AVSD Volume overload
Obstructive Lesions Coarctation, AS, PS Pressure overload

LEFT-TO-RIGHT SHUNT LESIONS

Ventricular Septal Defect (VSD)

Most common CHD (30-35%)

Types by Location

Type Location Frequency Notes
Perimembranous Membranous septum 70-80% Most common
Muscular Muscular septum 5-20% High spontaneous closure
Inlet AV canal area 5-8% Associated with Down syndrome
Outlet Below aortic valve 5-7% Risk of aortic regurgitation

Hemodynamics

  • L→R shunt (high pressure LV → lower pressure RV)
  • Shunt volume depends on defect size + PVR
  • Large VSD → volume overload → CHF as PVR drops

Clinical Presentation

VSD Size Murmur Symptoms Timing
Small Loud holosystolic None Any age
Large Softer holosystolic CHF (tachypnea, FTT, poor feeding) 4-8 weeks

Physical Exam

  • Murmur: Holosystolic at LLSB
  • Thrill: May be present
  • Smaller VSD = Louder murmur (more turbulence through restrictive defect)

Natural History

  • Small muscular: 80-90% close by age 2
  • Perimembranous: ~35% close spontaneously
  • Outlet: Do NOT close, risk aortic valve prolapse

Management

  • Small, asymptomatic: Observation
  • Large with CHF: Diuretics → Surgical closure 3-6 months
  • IE prophylaxis: NOT needed for unrepaired simple VSD

Atrial Septal Defect (ASD)

Types

Type Location Frequency Notes
Secundum Fossa ovalis 70% Device closure possible
Primum Adjacent to AV valves 20% Part of AVSD spectrum
Sinus venosus Near SVC/IVC 10% Often with PAPVR

Hemodynamics

  • L→R shunt at atrial level
  • RA/RV volume overload
  • Well-tolerated for decades

Clinical Presentation

  • Often asymptomatic in childhood
  • Fixed split S2 - CLASSIC finding (no respiratory variation)
  • Systolic ejection murmur at LUSB (increased pulmonary flow)
  • RV heave if significant

Complications if Untreated

  • Pulmonary hypertension (3rd-4th decade)
  • Atrial arrhythmias (flutter/fibrillation)
  • Paradoxical embolism
  • Right heart failure

Management

  • Secundum ASD: Device closure if suitable anatomy
  • Primum/Sinus venosus: Surgical closure required
  • Timing: Typically 3-5 years if significant shunt (Qp:Qs >1.5)

Patent Ductus Arteriosus (PDA)

Hemodynamics

  • Aorta → PA shunt (L→R when PVR normal)
  • LA/LV volume overload
  • Wide pulse pressure

Clinical Presentation

PDA Size Findings
Small Continuous murmur only
Moderate Continuous murmur, bounding pulses
Large CHF, wide pulse pressure, active precordium

Physical Exam

  • "Machinery" continuous murmur - left infraclavicular area
  • Loudest at end-systole, continues through S2
  • Bounding peripheral pulses
  • Wide pulse pressure

Management

  • Term infants/children: Catheter or surgical closure
  • Preterms: See Topic 24 (PDA in Preterms)
  • Closure recommended to eliminate IE risk

Atrioventricular Septal Defect (AVSD)

Anatomy

  • Common AV valve
  • Primum ASD + Inlet VSD (complete form)
  • Strong association with Down syndrome (40-50%)

Types

  • Complete AVSD: Large primum ASD + inlet VSD + common AV valve
  • Partial AVSD: Primum ASD + cleft mitral valve, no VSD

Clinical Presentation

  • Complete: CHF in infancy
  • Partial: May be asymptomatic; MR murmur

Management

  • Surgical repair typically by 4-6 months (complete)
  • Monitor for AV valve regurgitation long-term

OBSTRUCTIVE LESIONS

Coarctation of the Aorta

Anatomy

  • Narrowing at aortic isthmus (near ductus insertion)
  • 50-80% have bicuspid aortic valve
  • Associated with Turner syndrome

Clinical Presentation

Neonate (Critical Coarctation)

Finding Mechanism
Shock when ductus closes Loss of lower body perfusion
Absent/weak femoral pulses Obstruction
Acidosis, poor perfusion Inadequate cardiac output
Differential cyanosis If PDA with R→L shunt

Older Child

Finding Mechanism
Upper extremity hypertension Obstruction
Weak/delayed femoral pulses Obstruction
BP gradient >20 mmHg (upper > lower) Classic finding
Leg claudication with exercise Inadequate flow

Management

  • Neonate: PGE1 → Surgical repair
  • Older child: Surgical or balloon angioplasty ± stent
  • Lifelong surveillance: Re-coarctation, hypertension, aneurysm risk

Aortic Stenosis (AS)

Types

Type Location Associations
Valvar Aortic valve Bicuspid AV (most common)
Subvalvar Below valve Fibromuscular ridge, HCM
Supravalvar Above valve Williams syndrome

Clinical Presentation

  • Systolic ejection murmur at RUSB → carotids
  • Ejection click (valvar AS)
  • Severe: Syncope, chest pain with exertion, CHF

Management

  • Mild-moderate: Follow with echo
  • Severe/symptomatic: Balloon valvuloplasty or surgical repair

Pulmonary Stenosis (PS)

Clinical Presentation

  • Systolic ejection murmur at LUSB
  • Ejection click (decreases with inspiration)
  • Usually well-tolerated
  • Severe: RV failure, cyanosis (if ASD/PFO present)

Management

  • Mild-moderate: Follow
  • Severe (gradient >50 mmHg or symptoms): Balloon valvuloplasty

Quick Recognition Guide

Finding Think...
Holosystolic murmur at LLSB VSD
Fixed split S2 ASD
Continuous "machinery" murmur PDA
Upper > lower extremity BP Coarctation
Ejection click + murmur at RUSB AS
Ejection click + murmur at LUSB PS
CHD + Down syndrome AVSD, VSD
CHD + Turner syndrome Coarctation, bicuspid AV
CHD + Williams syndrome Supravalvar AS, branch PA stenosis

Board Pearls

Pearl: Small VSD = Loud murmur; Large VSD = Soft murmur

Restrictive defect creates more turbulence

Pearl: Fixed split S2 = ASD

Pathognomonic - S2 splitting doesn't vary with respiration

Pearl: Upper/lower BP gradient >20 mmHg = Coarctation

Always check 4-extremity BP in hypertensive child

Pearl: VSD murmur appears at 4-8 weeks

As PVR drops, L→R shunt and murmur increase

Pearl: Down syndrome + CHD = Think AVSD

40-50% of Down syndrome patients have CHD

Self-Assessment

Q1: A 6-week-old presents with tachypnea, poor feeding, FTT, and hepatomegaly. Exam shows holosystolic murmur at LLSB. Most likely diagnosis?

Answer **Answer**: Large VSD with heart failure **Rationale**: Presents at 4-8 weeks as PVR drops, increasing L→R shunt. Holosystolic LLSB murmur + CHF signs = large VSD.

Q2: An 8-year-old has upper extremity hypertension found at well-child visit. Femoral pulses are weak and delayed. What confirms the diagnosis?

Answer **Answer**: 4-extremity blood pressures showing >20 mmHg upper-to-lower gradient **Rationale**: Classic coarctation presentation. Echo confirms anatomy; may need CT/MRI for surgical planning.

Q3: A newborn with Down syndrome has a murmur. What CHD is most commonly associated?

Answer **Answer**: Atrioventricular septal defect (AVSD) **Rationale**: ~40-50% of Down syndrome patients have CHD; AVSD is the most common, followed by VSD.

Key Guidelines

2018 AHA/ACC Guideline for the Management of Adults With Congenital Heart Disease J Am Coll Cardiol. 2019;73(12):e81-e192 PMID: 30121239

References

  • Stout KK, et al. J Am Coll Cardiol. 2019;73(12):e81-e192
  • ACC/AHA 2018 Guidelines for Adults with CHD