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Cyanotic Congenital Heart Disease

Learning Objectives

Core Knowledge & Clinical Reasoning

  • [ ] Identify the 5 T's of cyanotic CHD
  • [ ] Differentiate cyanotic CHD from pulmonary causes of hypoxemia using hyperoxia test
  • [ ] Recognize ductal-dependent lesions requiring PGE1
  • [ ] Manage hypercyanotic (Tet) spells

Communication & Counseling

  • [ ] Explain cyanotic CHD to families in understandable terms
  • [ ] Counsel on expected surgical pathway

Key Concept

Cyanosis = Right-to-left shunting or parallel circulations

Deoxygenated blood reaches systemic circulation without passing through lungs

The 5 T's of Cyanotic CHD

Lesion Mechanism Ductal-Dependent?
Tetralogy of Fallot R→L shunt via VSD (RVOTO) Variable
Transposition of Great Arteries Parallel circulations Yes (for mixing)
Tricuspid Atresia No RV inlet → obligate R→L Yes (pulmonary)
Total Anomalous Pulmonary Venous Return All PVs drain to RA Variable
Truncus Arteriosus Single outflow with mixing No

Other cyanotic lesions: HLHS, Pulmonary atresia, Ebstein anomaly, Single ventricle

Hyperoxia Test

Purpose: Distinguish cardiac from pulmonary cyanosis

Condition Room Air SpO2 On 100% FiO2
Pulmonary disease Low Improves significantly (>95%)
Cyanotic CHD Low Minimal improvement (<85-90%)

If SpO2 doesn't improve with 100% O2 → Think cardiac cause

Method: Place on 100% FiO2 for 10 minutes, check ABG - PaO2 >150 mmHg → Pulmonary disease likely - PaO2 <100 mmHg → Cyanotic CHD likely

Tetralogy of Fallot (TOF)

Most common cyanotic CHD (~10% of all CHD)

Four Components

  1. VSD - Large, unrestrictive, malalignment type
  2. Overriding aorta - Straddles VSD
  3. RV outflow tract obstruction (RVOTO) - Infundibular ± valvar
  4. RV hypertrophy - Secondary to RVOTO

Hemodynamics

  • Degree of cyanosis depends on severity of RVOTO
  • More RVOTO → More R→L shunt across VSD → More cyanosis
  • VSD is unrestrictive, so RV and LV pressures equalize

Clinical Spectrum

Type RVOTO Severity Presentation
"Pink Tet" Mild Murmur, minimal cyanosis
"Blue Tet" Severe Significant cyanosis at birth
TOF with absent pulmonary valve Variable Respiratory symptoms from PA dilation

Physical Exam

  • Cyanosis (variable)
  • Harsh systolic ejection murmur at LUSB (RVOTO)
  • Single S2 (absent/soft P2)
  • RV heave
  • Boot-shaped heart on CXR (coeur en sabot)

Hypercyanotic (Tet) Spells

Triggers: Crying, feeding, defecation, awakening, dehydration

Mechanism: Dynamic RVOTO worsens → More R→L shunt → Hypoxemia → Acidosis → Catecholamines → More RVOTO (vicious cycle)

Management (in order):

Step Intervention Mechanism
1 Knee-chest position Increases SVR
2 Calm the child Reduces catecholamines
3 Oxygen May help marginally
4 IV fluid bolus Improves preload
5 Morphine (0.1 mg/kg) Reduces hyperventilation, sedation
6 Phenylephrine Increases SVR
7 Propranolol Relaxes RVOT
8 Emergent surgery If refractory

Surgical Management

  • Complete repair: Typically 3-6 months of age
  • Earlier if severe cyanosis or frequent spells
  • Palliative BT shunt: If not candidate for early complete repair

Transposition of Great Arteries (TGA)

Anatomy (D-TGA)

  • Aorta arises from RV (anterior)
  • PA arises from LV (posterior)
  • Parallel circulations - incompatible with life without mixing

Hemodynamics

  • Deoxygenated blood: RA → RV → Aorta → Body → RA (systemic circuit)
  • Oxygenated blood: LA → LV → PA → Lungs → LA (pulmonary circuit)
  • Must have mixing via PDA, ASD, or VSD to survive

Clinical Presentation

  • Cyanosis within hours of birth - often profound
  • May have minimal or no murmur
  • Single loud S2 (anterior aorta)
  • Tachypnea without respiratory distress ("happy tachypnea")
  • "Egg on a string" cardiac silhouette on CXR

Management

Step Intervention Purpose
1 PGE1 (0.05-0.1 mcg/kg/min) Maintain ductal patency for mixing
2 Balloon atrial septostomy (BAS) Create/enlarge ASD for mixing
3 Arterial switch operation Definitive repair in first 1-2 weeks

Do NOT give 100% O2 thinking it will help

May accelerate ductal closure and worsen mixing

Tricuspid Atresia

Anatomy

  • No tricuspid valve → No RV inlet
  • Hypoplastic RV
  • Obligate R→L shunt at atrial level (ASD/PFO required)
  • Pulmonary blood flow via VSD and/or PDA

Clinical Presentation

  • Cyanosis at birth
  • Degree depends on VSD size and presence of PS
  • Single S2 (no P2 if pulmonary atresia)

Management

  • Ductal-dependent for pulmonary blood flow → PGE1
  • Single ventricle palliation pathway:
  • Neonatal: BT shunt or PA band (depending on anatomy)
  • 4-6 months: Bidirectional Glenn (SVC → PA)
  • 2-4 years: Fontan completion

Total Anomalous Pulmonary Venous Return (TAPVR)

Anatomy

  • All pulmonary veins drain to systemic venous system (not LA)
  • Complete mixing in RA
  • ASD required for survival (oxygenated blood must reach LA)

Types

Type Drainage Site Frequency Obstruction Risk
Supracardiac SVC, innominate vein 50% Low
Cardiac Coronary sinus, RA 25% Low
Infracardiac Portal vein, IVC 20% HIGH
Mixed Multiple sites 5% Variable

Clinical Presentation

Obstructed TAPVR (usually infracardiac): - Severe cyanosis + respiratory distress at birth - Pulmonary edema (venous obstruction) - SURGICAL EMERGENCY - hours to live - CXR: "Snowman" or ground-glass (edema)

Unobstructed TAPVR: - Mild cyanosis - Volume overload physiology (like large ASD) - May present later in infancy

Management

  • Surgical repair - urgent/emergent if obstructed
  • Connect pulmonary venous confluence to LA

Truncus Arteriosus

Anatomy

  • Single arterial trunk arising from heart
  • Single semilunar (truncal) valve
  • VSD always present
  • PAs arise from truncus

Clinical Presentation

  • Mild cyanosis (complete mixing)
  • CHF symptoms (unrestricted pulmonary blood flow)
  • Wide pulse pressure, bounding pulses
  • Single S2 (one semilunar valve)

Associated Findings

  • DiGeorge syndrome (22q11 deletion) in 30-35%
  • Truncal valve regurgitation
  • Right aortic arch

Management

  • Surgical repair in neonatal period
  • Separate PAs from truncus, VSD closure, RV-PA conduit

Ductal-Dependent Lesions

Pulmonary Blood Flow Dependent (Cyanotic)

  • Severe TOF
  • Pulmonary atresia
  • Tricuspid atresia
  • Critical PS
  • Some Ebstein anomaly

Systemic Blood Flow Dependent

  • Critical coarctation
  • Interrupted aortic arch
  • HLHS
  • Critical AS

Mixing Dependent

  • TGA (needs PDA + ASD for adequate mixing)

START PGE1 if ductal-dependent lesion suspected

Dose: 0.05-0.1 mcg/kg/min IV Side effects (apnea, hypotension, fever) are manageable Missing a ductal-dependent lesion is fatal

Quick Recognition Guide

Presentation Think...
Cyanotic newborn, single S2, no/soft murmur TGA
Cyanosis + harsh ejection murmur + spells TOF
Cyanosis + severe respiratory distress at birth Obstructed TAPVR
Cyanotic + CHF + bounding pulses Truncus
Boot-shaped heart on CXR TOF
Egg-on-string silhouette TGA
Snowman silhouette Unobstructed supracardiac TAPVR

Board Pearls

Pearl: TGA = Cyanosis + Single loud S2 + No murmur

Needs PGE1 and urgent balloon septostomy

Pearl: Tet spell → Knee-chest position

Increases SVR, breaks the cycle by reducing R→L shunt

Pearl: Hyperoxia test - No improvement with O2 = Cardiac

PaO2 <100 on 100% FiO2 suggests cyanotic CHD

Pearl: Obstructed TAPVR = Surgical emergency

Cyanosis + pulmonary edema + respiratory distress at birth

Pearl: When in doubt, start PGE1

Side effects manageable; missed ductal-dependent lesion is fatal

Self-Assessment

Q1: A newborn is profoundly cyanotic with SpO2 65%. On 100% FiO2, SpO2 only rises to 70%. CXR shows "egg-on-string" silhouette. Most likely diagnosis?

Answer **Answer**: Transposition of Great Arteries (D-TGA) **Rationale**: Profound cyanosis unresponsive to O2 = cyanotic CHD. "Egg-on-string" (narrow mediastinum from great vessel relationship) is classic for TGA. Start PGE1 and arrange urgent balloon septostomy.

Q2: A 4-month-old with known TOF becomes deeply cyanotic while crying. What is the FIRST intervention?

Answer **Answer**: Knee-chest position **Rationale**: Tet spell management starts with knee-chest position to increase SVR and reduce R→L shunting. Then: calm child → O2 → fluids → morphine → phenylephrine → propranolol → surgery if refractory.

Q3: A newborn has severe cyanosis and respiratory distress at birth. CXR shows pulmonary edema with a small heart. Most likely diagnosis?

Answer **Answer**: Obstructed TAPVR (likely infracardiac) **Rationale**: Cyanosis + pulmonary edema + small heart = obstructed TAPVR. Pulmonary venous obstruction causes backup into lungs. This is a surgical emergency.

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
  • Allen HD, et al. Moss & Adams' Heart Disease in Infants, Children, and Adolescents