VCU Department of Radiology

Definition and Incidence

The most common type of cyanotic congenital heart disease in children, accounting for 8% of congenital heart disease.

The four classic components:

1. Large, subaortic ventricular septal defect 

2. Obstructed right ventricular outflow tract

   • invariable infundibular

   • +/- pulmonary annulus

   • main pulmonary valve artery

   • right or left pulmonary artery

   • absent pulmonary value 

3. Right ventricular hypertrophy

4. Overriding aorta

Anatomic Associations:

• Right aortic arch - 25%

• Coronary arteries anomalies - 5%

Clinical Features

• Age at which symptoms begin depends on the degree of right ventricular outflow tract obstruction, which determines the amount of right-to-left shunting. Because infundibular stenosis is usually progressive, eventual right-to-left shunting and cyanosis may not appear until 3-4 months or later. 

• Symptoms include episodic loss of consciousness and squatting when fatigued (to increase pulmonary flow and thus 02 saturations).

• ECG reveals right ventricular hypertrophy.

Radiolographic Features

Plain Film

• Normal to slightly enlarged cardiac silhouette

• "Boot-shaped" heart or Coeur-en-sabot appearance

  • (due to 1) RVH --> uplifting of cardiac apex and 

  • 2) small pulmonary arteries --> concave main pulmonary artery segment)

• Large aorta

  • (because almost all blood flow from both ventricles is delivered to the aorta)

• Right aortic arch - 25% of patients

• Decreased pulmonary vasculature

• Pulmonary vasculature may be asymmetric

  • (secondary to left pulmonary artery stenosis)

MRI

• Used to delineate main, right, and left pulmonary arteries, and assess extent of aortopulmonary collateral flow to help both palliative treatment and definitive surgical correction. 

Treatment

• Palliative shunts (symptomatic but poor surgical candidates)

• Blalock-Taussig: any surgical connection between the subclavian artery and the pulmonary artery.

• Total corrective repair: VSD closure, removing infundibular muscle causing obstruction, and inserting either a transannular patch or external conduit to relieve obstruction between right ventricle and main pulmonary artery.