Pediatrics · Year 3 · from Pediatrics

Case 1: Tetralogy of Fallot with Hypercyanotic Spell

Patient Demographics

  • Age: 6-month-old male
  • Sex: Male

Chief Complaint

"My baby turned blue and went limp while crying."

History of Present Illness

A 6-month-old male with known tetralogy of Fallot (TOF) awaiting surgical repair is brought to the emergency department after experiencing an episode of sudden cyanosis and limpness while crying this morning. The mother reports that the infant was crying vigorously when he suddenly became deeply blue, appeared to be struggling to breathe, and then became limp and unresponsive for approximately 30 seconds. She instinctively brought his knees to his chest, and he slowly improved over the next few minutes. This is his third similar episode in the past two weeks, though the previous two were milder. He was diagnosed with TOF at 2 weeks of age after a murmur was detected at his newborn visit. He has been followed by cardiology and is scheduled for complete surgical repair next month.

Physical Examination

  • General: Alert infant, mildly tachypneic, visible cyanosis of lips and nail beds
  • Vital signs: HR 160 bpm, RR 44/min, SpO2 78% on room air, BP 75/50 mmHg
  • HEENT: Central cyanosis, no respiratory distress at rest
  • Cardiovascular: Hyperdynamic precordium, systolic ejection murmur at left upper sternal border (softer than previously documented), single S2
  • Respiratory: Clear breath sounds bilaterally
  • Abdomen: Soft, no hepatomegaly
  • Extremities: Clubbing of fingers, peripheral cyanosis

Workup

  • CBC: Hemoglobin 17.2 g/dL (polycythemia), Hct 52%
  • ABG: pH 7.28, pCO2 32 mmHg, pO2 45 mmHg, HCO3 15 mEq/L
  • Chest X-ray: Boot-shaped heart with decreased pulmonary vascular markings
  • ECG: Right axis deviation, right ventricular hypertrophy
  • Echocardiogram: Large VSD with overriding aorta, severe infundibular stenosis, RV hypertrophy; RV outflow tract gradient increased from baseline

Diagnosis

Tetralogy of Fallot with hypercyanotic (tet) spell

Clinical Reasoning

The classic presentation of a tet spell in an infant with known TOF is characteristic. The episode was triggered by crying, which increases oxygen demand and can precipitate infundibular spasm, worsening the right-to-left shunt. The softer murmur during the episode reflects decreased blood flow across the pulmonary outflow tract (less turbulence when more blood is shunted right-to-left). The polycythemia represents a compensatory response to chronic hypoxemia. The metabolic acidosis reflects tissue hypoxia during the spell.

Management

  1. Immediate treatment: Knee-to-chest position, supplemental oxygen, IV access
  2. Pharmacotherapy: Morphine 0.1 mg/kg IV for sedation and decreased catecholamine response; consider phenylephrine if persistent (increases SVR, decreases R-to-L shunt)
  3. If refractory: Propranolol IV to relax infundibular spasm
  4. Long-term: Oral propranolol 1 mg/kg/day divided Q6h until surgical repair
  5. Urgent surgical consultation: Expedite complete repair given recurrent tet spells
  6. Parent education: Knee-to-chest positioning, avoid excessive crying when possible

Clinical Image

Image Description: Anatomical diagram of tetralogy of Fallot showing the four characteristic features: ventricular septal defect, overriding aorta, right ventricular outflow tract obstruction, and right ventricular hypertrophy.

Source: Wikimedia Commons URL: https://commons.wikimedia.org/wiki/File:Tetralogy_of_Fallot.svg License: CC BY-SA 3.0

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