Truncus arteriosus

Background

• A cyanotic congenital heart defect
• Blood is pumped through a single truncal valve into a truncal artery which gives rise to the aorta and the pulmonary arteries
• Associated with large VSD in most patients
• Incidence ranges from 6 to 10 per 100,000 live births, accounts for 4% of all congenital heart disease

Physiology

• PVR is high in the newborn infant, so there is little left to right shunting at birth
• Over first several weeks of life, PVR drops, left to right shunting increases, leading to heart failure
• Mixing of systemic and pulmonary blood leads to mild to moderate cyanosis
• Pulmonary vascular obstructive disease may develop in surgically uncorrected patients

Clinical Features

• Most present within the first weeks of life with
  • Cyanosis
  • Pulmonary congestion and heart failure
    • Poor feeding, lethargy, signs of respiratory distress (tachypnea, costal-sternal retractions, grunting, and nasal flaring), tachycardia, hyperdynamic precordium, and hepatomegaly
  • Cardiovascular findings
    • Loud second heart sound
    • Prominent ejection click at the apex or left sternal border
    • Systolic ejection murmur at the left sternal border
    • Bounding peripheral pulses
    • Increased pulse pressure

Differential Diagnosis

Congenital Heart Disease Types

• Cyanotic
  • Tetralogy of fallot
  • Total anomalous pulmonary venous return
  • Transposition of the great arteries
  • Tricuspid atresia
  • Truncus arteriosus
  • Ebstein anomaly
  • Hypoplastic left heart syndrome
• Acyanotic
  • AV canal defect
  • Atrial septal defect (ASD)
  • Ventricular septal defect (VSD)
  • Cor triatriatum
  • Patent ductus arteriosus (PDA)
  • Pulmonary/aortic stenosis
  • Coarctation of the aorta
• Differentiation by pulmonary vascularity on CXR
  • Increased pulmonary vascularity
    • Large ASD
    • Large VSD
    • Total anomalous pulmonary venous return
    • Transposition of the great arteries
    • Truncus arteriosus
  • Decreased pulmonary vascularity
    • Tetralogy of fallot
    • Rare heart diseases with pulmonic stenosis

Evaluation

• ECG
  • May be normal
  • May have evidence of left or right ventricular hypertrophy
• Chest x-ray
  • Enlarged cardiac silhouette
  • Increased pulmonary vascular markings
  • May see absent thymus in patients with TA associated with DiGeorge syndrome
• Echocardiography

Management

• Stabilize cardiopulmonary function prior to surgery
• Diuretic therapy, (eg, furosemide) reduce preload, relieve volume overload and pulmonary congestion
• Inotropic agents (eg, dopamine and dobutamine) improve myocardial contractility
• ACEI reduces afterload
• Noninvasive positive pressure ventilation often used in patients with respiratory distress due to pulmonary congestion
• Supportive care to correct metabolic acidosis, hypoglycemia, and anemia that may contribute to heart failure
• Prostaglandin E1 if patient also has critical coarctation of the aorta
• Primary surgical repair during the neonatal period (less than 30 days of age)
  • Improved survival rate at one year of age of >80% vs 15% in uncorrected patients

Disposition

• Admit

See Also

• Congenital heart disease