II. Epidemiology
- Incidence: 10-15% of Congenital Heart Disease
- Most common cause of CHD outside infancy
III. Pathophysiology
- See Tet Spell
- Cyanotic Congenital Heart Disease
- Four components
- Primary features responsible for symptoms (resulting in a right to left shunt)
- Large Ventricular Septal Defect (VSD)
- Right outflow tract obstruction
- Other features
- Right Ventricular Hypertrophy
- Aorta overides both ventricles (mixing oxygenated and deoxygenated blood)
- Primary features responsible for symptoms (resulting in a right to left shunt)
- Right to left shunt is the key mechanism of Tetralogy of Fallot
- Right outflow obstruction leads to pulmonary vascular resistance greater than Systemic Vascular Resistance
- Blood easily shunts across the Ventricular Septal Defect which re-circulates de-oxygenated blood
- Tet Spells occur from increased right sided pressures, or decreased left sided pressures
- Increased right sided pressures
- Decreased left sided pressures
- Right outflow obstruction leads to pulmonary vascular resistance greater than Systemic Vascular Resistance
IV. Associated Conditions
- Right aortic arch (25%)
- Atrial Septal Defect (15%)
- Absent pulmonary valve
- Pulmonary atresia
- Pulmonary stenosis
- Atrioventricular septal defect
- Left superior vena cava to coronary sinus
V. Signs: General
- Oxygen Saturation is always low (e.g. 80%)
- Systolic ejection murmur at left sternal border
- Grade III+ intensity, harsh Systolic Murmur
- Murmur diminishes in intensity during "Tet Spell"
- Single S2 Heart Sound
VI. Signs: Tet Spell
- Ill appearing child
- Refractory Hypoxia
- Right ventricular outflow related murmur decreases with a lowering of right sided-flow
- VSD-related murmur persists
VII. Diagnostics: Electrocardiogram
VIII. Labs
-
Arterial Blood Gas
- Normal arterial pH
- Normal arterial pCO2
- Low arterial pO2
IX. Imaging
-
Chest XRay
- Heart size normal or small
- Narrow mediastinum
- Heart may appear "boot shaped" in classic presentation
-
Echocardiogram
- Large Ventricular Septal Defect (VSD)
- Right outflow tract obstruction
- Right Ventricular Hypertrophy
- Overriding aorta
X. Management: Tet Spell
- Decrease stress (to reduce Heart Rate and allow for pulmonary vascular filling)
- Calming measures
- Treat pain and avoid painful procedures
- Use EMLA cream prior to IV insertion
- Intranasal anxiolysis and Analgesics
- Intranasal Fentanyl
- Intranasal Midazolam
- Intranasal Ketamine
-
Knee chest position
- Increases Systemic Vascular Resistance
- Manage Hypoxia (to reduce pulmonary vascular resistance)
- Supplemental Oxygen
- Critically ill children may require Endotracheal Intubation (high risk)
- Ensure adequate preoxygenation and hydration prior to intubation
- Have Phenylephrine or neorepinephine available bedside to immediately treat Peri-Intubation Hypotension
- Treat Hypovolemia and Hypotension
- Rehydration with IV fluid boluses
- Vasopressors that do not increase Heart Rate
XI. Management: Surgery
- Stabilized with PGE-1 infusion followed by endovascular ductus stent in first days of life before ductus closure
- Similar initial management as with other cyanotic ductus dependent lesions
- Subclavian to pulmonary artery shunt (Blalock-Taussig)
- Palliative or temporizing method
- Definitive, total repair
- Repair as newborn or at age 3 years
- Ventricular Septal Defect patch
- Right ventricular outflow tract widening
XII. Causes: Cyanotic Episodes ("Tet Spells")
-
Hypoxia responsive to Supplemental Oxygen
- Impaired alveolar gas exchange (e.g. Pneumonia, Pulmonary Edema)
-
Hypoxia UNresponsive to Supplemental Oxygen
- Decreased pulmonary Blood Flow via ductus arteriosus (ductus stent Occlusion, closure of unstented ductus)
XIII. Complications: Without repair (inoperable cases)
- Affects related to:
- Hypoxia
- Polycythemia
- Symptoms
XIV. Complications: Post-surgical correction
- Arrhythmia
- Right ventricular insufficiency
- Right Ventricular Failure
- Pulmonary insufficiency
- Left ventricular insufficiency
XV. Prognosis
- Survival post-surgical repair: >95%
- Cognitive development may be impaired
XVI. References
- Drapkin and Claudius (2024) Tetralogy of Fallot, EM:Rap, published 4/22/2024
- Broder (2023) Crit Dec Emerg Med 37(9): 22-3
- Civitarese and Crane (2016) Crit Dec Emerg Med 30(1): 14-23
- Cyran (1998) PREP review lecture, October, Phoenix
- Merenstein (1994) Pediatrics, Lange
- Tsze and Spangler in Herbert (2015) EM:Rap 15(4): 2-3
- Saenz (1999) Am Fam Physician 59(7):1857-66 [PubMed]