Echo Assessment of Congenital Heart Defects

1. ASD (Atrial Septal Defect) - 10 marks

Types to identify on echo:

• Secundum ASD (most common, 70%) - central fossa ovalis
• Primum ASD - inferior near AV valves; associated with cleft anterior mitral leaflet
• Sinus venosus ASD - posterosuperior near SVC/IVC
• Coronary sinus ASD - unroofed coronary sinus

2D Echo Findings:

• TTE views: Subcostal (best view), parasternal short axis, apical 4-chamber
• TEE: Mandatory if TTE inadequate; shows all 4 types clearly; 3D TEE gives precise anatomic detail of the defect rim for closure planning

Doppler Findings:

• Color Doppler: Left-to-right shunt across the atrial septum (red/orange jet toward tricuspid valve)
• Pulsed/CW Doppler: Low-velocity flow (0.5-1.5 m/s) through the defect - laminar
• Qp:Qs ratio - calculated from RVOT (pulmonic) vs LVOT (aortic) stroke volume ratios; significant shunt if >1.5:1
• TR jet velocity - estimate RV systolic pressure (RVSP); pulmonary hypertension if elevated
• Diastolic dysfunction pattern of RA/LA

Additional Echo Assessment:

• Measure defect size and location for closure eligibility (Amplatzer device needs ≥5 mm rim on all sides)
• Check for associated anomalous pulmonary veins (PAPVR)
• Check MV for cleft in primum ASD
• Contrast/bubble study - agitated saline shows right-to-left passage if PH reverses shunt (Eisenmenger)

Key Equations:

• RVSP = 4 x TR-velocity² + RAP (RAP estimated from IVC)
• Qp:Qs = (RVOT VTI x RVOT area) / (LVOT VTI x LVOT area)

2. VSD (Ventricular Septal Defect) - 10 marks

Types:

• Perimembranous (most common, 80%) - adjacent to tricuspid valve
• Muscular - within muscular septum (multiple "Swiss cheese" possible)
• Outlet/Supracristal/Subpulmonary - below pulmonic valve; associated with AR
• Inlet - part of AVSD

2D Echo Findings:

• Defect in ventricular septum - best seen in parasternal long axis, short axis, and apical 4-chamber views
• LA and LV dilation (volume overload from left-to-right shunt)
• RV dilation with large defects
• Small VSD - 2D echo may miss; rely on color Doppler

Doppler Findings:

• Color Doppler: High-velocity turbulent jet from LV to RV (left to right across septum); mosaic color pattern
• CW Doppler: High-velocity jet (3-5 m/s typical), allowing estimation of RV pressure:
  • RV systolic pressure = Systemic SBP - 4V² (if no PS)
  • E.g., if VSD jet = 4 m/s and SBP = 120 mmHg → RVSP = 120 - 64 = 56 mmHg
• Pulmonary hypertension assessment via TR jet
• AR - look for aortic valve prolapse/regurgitation in outlet VSDs

Hemodynamic Significance:

3. TOF (Tetralogy of Fallot) - key findings

The 4 Components to Identify:

1. VSD - large, non-restrictive perimembranous/malalignment type
2. RVOT obstruction (subvalvular infundibular stenosis + often pulmonic valve stenosis)
3. Aortic override - aorta overrides the VSD (>50% if "double outlet RV")
4. RVH - right ventricular hypertrophy

2D Echo Views:

• Parasternal long axis: Shows large VSD + aortic override; aorta straddles the interventricular septum
• Parasternal short axis: RVOT obstruction, pulmonic valve anatomy, MPA/branch PA size
• Apical 4-chamber: RVH, RV dilation, VSD
• Subcostal views: Helpful in children

Doppler Findings:

• RVOT CW Doppler: High velocity across infundibulum and pulmonary valve - calculate gradient
• VSD jet direction: Right-to-left (desaturated) if severe RVOTO; left-to-right if mild
• TR jet: Estimate RVSP
• Branch PA Doppler: Assess PA stenosis (post-repair concern)
• PR (pulmonary regurgitation): Very important in repaired TOF - assess severity (holodiastolic flow reversal, pressure half-time)

Key Measurements (especially post-repair):

• RV size and function - RVFAC, TAPSE, S' velocity
• RV volumes by 3D echo or CMR - RV EDVi >160 mL/m² = severe dilation (re-operation threshold)
• PR fraction - significant if >25-40%
• Residual RVOTO gradient - significant if >36 mmHg
• Residual/recurrent VSD

4. PDA (Patent Ductus Arteriosus) - 5 marks

Anatomy:

• Connection between main PA / proximal LPA and descending aorta just distal to left subclavian artery

2D Echo Findings:

• Parasternal short axis (high): Shows ductal flow entering MPA/LPA junction
• Suprasternal notch view: Best view of ductus itself; shows tubular structure connecting descending aorta to PA
• LA and LV dilation (left-sided volume overload)
• Enlarged MPA and branch PAs

Doppler Findings:

• Color Doppler: Continuous retrograde jet entering pulmonary artery from the posterior (ductal ampulla side); seen in PSAX view as a jet entering the PA at the LPA origin
• CW/PW Doppler: Continuous flow (both systole and diastole) toward the PA - "continuous machinery murmur" pattern on spectral Doppler
• Velocity: Reflects aorto-pulmonary pressure gradient; normally high velocity (3-4 m/s)
• If Eisenmenger (severe PH): Flow reverses to right-to-left (bidirectional or pure R-to-L)

Hemodynamic Assessment:

• PA diastolic pressure = Diastolic BP - 4 x Vend-diastole² (end-diastolic PDA velocity)
• Qp:Qs calculation
• RVSP via TR jet

5. COA (Coarctation of Aorta) - 5 marks

Anatomy:

• Discrete narrowing of the descending thoracic aorta at or just distal to the ductus arteriosus / ligamentum arteriosum (juxtaductal)
• ~50% have associated bicuspid aortic valve

2D Echo Findings:

• Suprasternal notch (SSN) view - PRIMARY view; shows the narrowing of the descending aorta
• Bicuspid aortic valve on parasternal short axis
• Ascending aorta and arch: May be hypoplastic in severe cases
• LVH (pressure overload)
• Collateral vessels (intercostal) - not well seen on echo

Doppler Findings:

• Color Doppler (SSN): Turbulent mosaic flow at the coarctation site
• CW Doppler (SSN): High-velocity jet in the descending aorta with characteristic "sawtooth" or diastolic runoff pattern - continuous antegrade flow throughout diastole due to collaterals (holosystolic-diastolic antegrade flow)
• Peak gradient: ΔP = 4(Vjet² - Vprox²); significant if peak-to-peak >20 mmHg
• Descending aorta pulsed Doppler: Blunted, dampened waveform distal to coarctation
• Abdominal aorta: Small amplitude, blunted systolic pulse - "tardus parvus" waveform

Key Points:

• Doppler gradient underestimates true gradient if poor angle alignment (descending aorta goes posterior/out of plane in SSN view)
• Cardiac MRI/CT often needed for full anatomical assessment
• Associated findings: Bicuspid AV (50%), ventricular septal aneurysm, Turner syndrome association (45,X0)

Quick Memory Aid for Doppler patterns:

• ASD = Low-velocity L→R flow across atrial septum + RV volume overload
• VSD = High-velocity mosaic jet L→R across septum; RVSP = SBP - 4V²
• TOF = High-velocity RVOTO jet + bidirectional VSD + aortic override
• PDA = Continuous (systolo-diastolic) retrograde PA jet in PSAX
• CoA = High-velocity + diastolic runoff pattern in descending aorta at SSN