Tetralogy of Fallot


Tetralogy of Fallot was originally described as a combination of four abnormalities: ventricular septal defect (VSD), right ventricular outflow tract obstruction, overriding aorta and right ventricular hypertrophy. There is typically an anterior malalignement of the conal septum. The right ventricular hypertrophy is a consequence of the overriding aorta exposing the RV to systemic pressures, the large VSD equalizing pressure +/- RVOT obstruction. The VSD is a perimembranous defect. In some cases, TOF can be associated with complete atresia of the pulmonary valve (TOF-Pulmonary Atresia) or with coronary anomalies. The rare form of TOF with absent pulmonary valve is associated with an absent / rudimentary pulmonary annulus which is stenotic. Because of the free pulmonary insufficiency, there is progressive dilation (aneurysmal) of the pulmonary arteries, which may lead to severe obstruction of the airways. Some are associated with an absent ductus. 

More of Fetal TOF with absent pulmonary valve syndrome.

Case 1: Tetralogy of Fallot (TOF) no pulmonary stenosis

Parasternal long axis view indicating overriding aorta and sub-aortic large ventricular septal defect shunting bidirectionally. 

PSAX showing the VSD in 2D. The pulmonary valve can be seen and is opening nicely with no evident RVOT obstruction. Mild deviation of the conal septum with no obstruction.

Apical views indicating the Tetralofy of Fallot, the large perimembranous central ventricular septal defect with aortic override. The mild deviation of the conal septum with no significant obstruction and the pulmonary valve and main pulmonary artery of normal size without obstruction.

Subcostal views showing the aorta override and the mild deviation of the conal septum

Small patent arterial duct (PDA) measuring 0.21 cm, shunting briefly right to left in early systole and left to right most of the cardiac cycle.

Case 2: Tetralogy of Fallot (TOF) mild pulmonary stenosis

PLAX with sweep in 2D and in Colour indicating the overriding Aorta and the malalignement ventricular septal defect

Flow acceleration by colour in the pulmonary artery in the PLAX

Mild narrowing of the pulmonary valvular annulus

Apical view with sweep in 2D and 2D colour showing the overriding aorta, malalignement VSD and some mild aortic insufficiency. 

Case 3: Tetralogy of Fallot (TOF) with major aortopulmonary collateral arteries (MAPCAs)

Parasternal long axis (PLAX) indicating a ventricular septal defect with overriding aorta

In PLAX, the anterior sweep indicates a small pulmonary artery with a thick pulmonary valve likely atretic (confirmed with colour to be virtual atresia)

MAPCAs by colour flow

PSAX showing the VSD and the narrow RVOT

PLAX indicating pulmonary valvular atresia - virtual, trickle colour passing.

Apical views by 2D and 2D-Colour showing the VSD and the overriding aorta with flow from LV and RV going to the Aorta

Sweep in the apical view showing the relationship between the RV/LV and Aorta with VSD

Subcostal view for visualization of the VSD, Pulmonary valvular atresia (virtual) and some MAPCAs observed by Colour

Catheterism indicating the MAPCAs

Presentation on TOF - Absent Valve by Louise Gervais and Jean-Francois Trudel

TOF with APVS - Combined _GA (1).pdf

Presentation on Tetralogy of Fallot by Laila Wazneh NNP &  Kathryn Jones NNP - NNPs at Montreal Children's Hospital

TOF 2024 (2 Final).pdf

Hallmark: Anterior cephalad deviation of the infundibular septum, which leads to: 

TET spell

Main principle is to use non-pharmacological intervention to revert the TET spell crisis:

If these non-pharmacological elements fail - will need pharmacological opiates to reduce distress:

If this fails (refractory Tet spell):

Echocardiography in TOF with pulmonary stenosis and a small PDA

Overriding aorta

Acceleration (aliasing) in the RVOT, outlining some degree of pulmonary obstruction.

Visualization of the RPA and LPA by colour which are of good calibers for the eventual repair. 

Perimembranous VSD visualized here. The infundibular septum (anteriorly displaced) is seen obstructing the RVOT. 

Sweep outlning the perimembranous VSD and the infundibular septum and RVOT.

Short axis outlining the RCA and the pulmonary valve. The thymus is well vizualized on top (although this is not sufficient to rule out Di George syndrome)

Flow seen with acceleration at the level of the subpulmonary infundibular septum anteriorly displaced. 

Normal coronary configuration. It is important to evaluate coronary configuration in TOF, as there may be up to 10% of abnormal coronary configuration. Some infants may even have coronary fistula feeding pulmonary vascular flow in severe TOF. 

Apical view with flow through the perimembranous VSD in the overriding aorta.

Flow in the RVOT with acceleration.

Peak gradient through the RVOT is at 12 mmHg. This infant is at day 1 of life. Once PVR will drop and PDA closes, this needs ot be reassessed as the gradient may increase with the drop of PVR and less blood flow feeding the PA through the PDA

Right sided aortic arch in this particular scan by evaluation of the branching pattern of the first aortic vessel. 

Pathological example from the Maude Abbott Medical Museum

Created by Gabriel Altit - Neonatologist / Créé par Gabriel Altit (néonatalogiste) - © NeoCardioLab - 2020-2024 - Contact us / Contactez-nous