Author: Nicholas Houska, DO - University of Colorado, Children’s Hospital Colorado
A newborn boy with a prenatal diagnosis of Tetralogy of Fallot develops respiratory distress shortly after birth, subsequently requiring intubation and extracorporeal membrane oxygenation. A portable computed tomography scan of the chest demonstrates severe main pulmonary artery dilation and bronchial compression. Which of the following types of Tetralogy of Fallot is the MOST likely diagnosis in this neonate?
EXPLANATION
Tetralogy of Fallot (TOF) with absent pulmonary valve (TOF/APV) is a rare type of TOF (3%) associated with high fetal and neonatal morbidity and mortality. In this defect, severe pulmonary insufficiency due to the lack of pulmonary valve cusps leads to massive main and proximal pulmonary artery dilation and thus extrinsic airway compression. Volume and pressure overload of the right ventricle (RV) can lead to dysfunction, and tricuspid regurgitation with associated left ventricular dysfunction. Chromosomal anomalies are found in 46% of TOF/APV patients who undergo genetic testing, with 35% having the 22q11.2 deletion. The clinical presentation of TOF/APV lies on a spectrum, ranging from fetal hydrops or severe postnatal respiratory distress to mild cardiopulmonary symptoms during infancy. The necessity for postnatal respiratory or cardiovascular support is common, and many patients do not survive to surgical repair.
Given the increased utilization and diagnostic capabilities of fetal imaging and the poor prognosis of TOF/APV, pregnancy termination is common after prenatal diagnosis. A 2021 study found that in patients with intention to treat after birth, 9% died in utero and 27% died postnatally. Right ventricular dysfunction independently predicted overall mortality, while pulmonary artery z-scores did NOT correlate with outcomes. Management of TOF/APV includes respiratory support based on symptoms. Patients with mild obstructive symptoms may be supported with medical management, oxygen therapy, or non-invasive positive pressure ventilation until surgical repair. These patients are often prone to frequent respiratory infections, which may require hospitalization. Conversely, patients born with more severe respiratory distress may require prone positioning to alleviate compression and/or intubation and mechanical ventilation. Patients with the most severe respiratory failure or cardiovascular dysfunction may require extracorporeal membrane oxygenation and early surgical repair. Surgical repair includes addressing the ventricular septal defect, the right ventricular outflow tract with a valved or non-valved conduit, and pulmonary arterioplasty. There have also been case reports of combining cardiac repair of TOF/APV with external bronchial stenting to relieve airway compression.
Tetralogy of Fallot with Pulmonary Stenosis and Tetralogy of Fallot with Pulmonary Atresia are associated with normal, small, or discontinuous main and/or branch pulmonary arteries. The patient in the stem has a presentation most consistent with TOF/APV.
REFERENCES
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Chelliah A, Moon-Grady AJ, Peyvandi S, et al. Contemporary outcomes in Tetralogy of Fallot with absent pulmonary valve after fetal diagnosis. J Am Heart Assoc. 2021;10(12):e019713.
Sakamoto T, Nagase Y, Hasegawa H, Shin'oka T, Tomimatsu H, Kurosawa H. One-stage intracardiac repair in combination with external stenting of the trachea and right bronchus for tetralogy of Fallot with an absent pulmonary valve and tracheobronchomalacia. J Thorac Cardiovasc Surg. 2005;130(6):1717-1718.
