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Case 003: Cyanotic Newborn

Presentation

Chief Complaint: 12-hour-old newborn with cyanosis noted by nursing staff

History: - Full-term male, born via SVD - Apgars 8 and 9 - Prenatal care: Late entry, no fetal echo - Appeared well initially, but progressive cyanosis noted - No respiratory distress - Feeding well

Physical Examination: - Weight: 3.4 kg - HR: 155, RR: 44 (comfortable), SpO2: 75% on RA - Mild cyanosis, especially with crying - Cardiac: Single loud S2, Grade 2/6 systolic ejection murmur at LUSB - Lungs: Clear - Pulses: 2+ and equal in all extremities - No hepatomegaly

Question 1

What is the differential diagnosis for a cyanotic newborn with minimal respiratory distress?

Answer **Cyanotic Congenital Heart Disease (CHD)** is most likely given: - Cyanosis without respiratory distress ("happy hypoxemia") - Single S2 (suggests absence of separate PA component) - No improvement with oxygen **Differential of Cyanotic CHD:** 1. **D-Transposition of Great Arteries (D-TGA)** - Most common cause of cyanosis in first day of life 2. **Tetralogy of Fallot** - Usually presents later, but can be severe 3. **Pulmonary atresia** - Would expect severe cyanosis 4. **Total anomalous pulmonary venous return (TAPVR)** - Often has more distress 5. **Tricuspid atresia** - Variable presentation 6. **Truncus arteriosus** - Often presents with CHF **Single S2** suggests: - Only one semilunar valve heard (pulmonary atresia, severe PS) - Or PA is posterior (D-TGA) **D-TGA** is highest on differential given: - Day 1 cyanosis - Minimal distress - Single S2 - Well-perfused (intact systemic output)

Initial Workup

Hyperoxia Test: - SpO2 on 100% FiO2: 78% (no significant improvement) - ABG on 100% O2: PaO2 = 38 mmHg

What does this indicate?

Answer **Failed hyperoxia test** - Confirms cardiac etiology for cyanosis Interpretation: - PaO2 <100 mmHg on 100% O2 = cardiac shunt - PaO2 typically >150 mmHg with pulmonary disease This newborn has **obligate mixing** or **parallel circulations** requiring cardiac evaluation.

Chest X-ray: - Mild cardiomegaly - Narrow mediastinum ("egg on a string" appearance) - Increased pulmonary vascular markings

ECG: - Sinus rhythm - RAD (normal for newborn) - RVH (normal for newborn)

Question 2

Based on the chest X-ray finding, what is the most likely diagnosis?

Answer **D-Transposition of the Great Arteries (D-TGA)** Classic findings: - **"Egg on a string"** silhouette on CXR: - Egg-shaped heart (from RV prominence) - Narrow mediastinum (great arteries are parallel, not crossing) - Increased pulmonary vascular markings (unrestricted pulmonary blood flow) - Day 1 cyanosis **Pathophysiology:** - Aorta arises from RV (systemic) - PA arises from LV (pulmonary) - Two parallel circuits with no mixing = profound hypoxemia - Survival depends on mixing: ASD, VSD, or PDA

Echocardiogram

  • D-Transposition of the Great Arteries confirmed
  • Aorta anterior and rightward, arising from RV
  • PA posterior, arising from LV
  • Intact ventricular septum
  • Small restrictive PFO (mean gradient 8 mmHg)
  • Moderate PDA with bidirectional shunting
  • Normal ventricular function

Question 3

What is the immediate management?

Answer **Immediate Steps:** 1. **Start Prostaglandin E1 (PGE1)** - 0.05-0.1 mcg/kg/min IV - Maintains PDA patency - Allows mixing between circulations - Be prepared for apnea (may need intubation) 2. **Balloon Atrial Septostomy (BAS)** - Indicated because PFO is restrictive - Creates larger atrial communication for mixing - Can be done bedside with echo guidance or in cath lab - Improves oxygenation 3. **Supportive Care:** - IV access, NPO - Avoid high FiO2 (can close PDA) - Monitor for metabolic acidosis **Goal:** Improve systemic oxygenation to SpO2 75-85% until definitive surgery

Clinical Course

After PGE1 initiation: SpO2 improves to 72%

Balloon atrial septostomy performed: SpO2 improves to 82%

Question 4

What is the definitive surgical repair and when is it typically performed?

Answer **Arterial Switch Operation (ASO)** **Procedure:** - Great arteries are transected and "switched" to correct positions - Aorta reconnected to LV - PA reconnected to RV - Coronary arteries reimplanted into neo-aorta **Timing:** - Typically within first 1-2 weeks of life - LV must be "prepared" to support systemic pressure - In D-TGA with IVS, LV rapidly deconditions after birth - Delay beyond 2-3 weeks → LV may not tolerate systemic pressure **Outcomes:** - Excellent (survival >95%) - Long-term issues: Coronary stenosis at reimplantation sites, neo-aortic root dilation, supravalvar PS

Question 5

What if this baby had D-TGA with a large VSD?

Answer **D-TGA with VSD:** **Advantages:** - More mixing → better oxygenation - BAS often not needed - Surgery can be delayed if stable **Disadvantages:** - Risk of developing pulmonary vascular disease (unrestricted pulmonary blood flow) - Higher risk of heart failure **Surgical timing:** - Still typically within first 1-2 weeks - But can be delayed up to 4-6 weeks if needed - VSD closed at time of ASO

Surgical Outcome

  • ASO performed on day of life 7
  • Uncomplicated operative course
  • Discharged day of life 14

Long-term Follow-up Issues

Potential Late Complications After ASO: 1. Supravalvar pulmonary stenosis (most common) 2. Neo-aortic root dilation and neo-aortic regurgitation 3. Coronary artery stenosis at reimplantation sites 4. Rhythm disturbances (rare)

Surveillance: - Annual cardiology follow-up - Serial echocardiograms - Exercise testing in older children - Coronary evaluation if symptoms

Board Pearls

Pearl

D-TGA is the most common cyanotic CHD presenting on day 1 of life

Pearl

"Egg on a string" CXR = D-TGA (narrow mediastinum from parallel great arteries)

Pearl

PGE1 is lifesaving in duct-dependent lesions - start empirically when suspecting cyanotic CHD

Pearl

Balloon atrial septostomy improves mixing in D-TGA with restrictive ASD

Learning Points

  1. Day 1 cyanosis + minimal distress = cardiac
  2. Failed hyperoxia test confirms cardiac shunt
  3. PGE1 is first-line for all suspected duct-dependent lesions
  4. ASO is performed in first 1-2 weeks (LV deconditioning window)
  5. Long-term outcomes are excellent but require surveillance

References

  • AHA CCHD Screening Guidelines
  • Pediatric Cardiology (Park)