Absent Pulmonary Valve Syndrome

Definition and Morphology

Absent pulmonary valve syndrome is a rare congenital cardiac malformation that was first described anatomically by Chevers in 1847. The first clinical case report was published in 1927, the typical anatomy described in a 58-year-old with chronic cyanosis and clubbing. Fundamentally, the intracardiac anatomy is that of tetralogy of Fallot, but the characteristic morphologic feature of this lesion is the complete absence of the pulmonary valve leaflets or the presence of vestigial remnants that are usually dysplastic nodules guarding a small ventriculopulmonary junction. This results in a variable degree of right ventricular outflow tract obstruction, significant pulmonary regurgitation, right ventricular enlargement, and often gross dilation of the pulmonary arteries ( Fig. 49.1 ). This last anomaly has been attributed to absence of the arterial duct in utero, which is the norm, although there are occasional reports in which a patent duct is present. Case series and reports have also described the characteristic outflow tract and pulmonary artery features in the presence of an intact ventricular septum, and association with other cardiac malformations, including tricuspid atresia, type B interrupted aortic arch, and atrioventricular septal defects.

Epidemiology and Genetics

The overall frequency of this defect remains unknown because it was often miscategorized in earlier epidemiologic studies. More recent reports quote a prevalence that ranges from 1% to 6% of patients with tetralogy of Fallot, corresponding to approximately 1 in 500 (0.2% to 0.4%) liveborn infants with congenital heart disease. Prenatal echocardiographic studies report a higher prevalence (1%); however, this difference can be attributed to significant intrauterine and perinatal mortality.

Although the association with microdeletion of chromosome 22q11 and phenotypic features of DiGeorge syndrome has been widely reported in patients with tetralogy of Fallot and absent pulmonary valve syndrome, it has not been identified in patients with isolated agenesis or dysplasia of the pulmonary valve. Smaller reports have also identified similar phenotypes with deletions in the 18q chromosome in humans and as an effect of exposure to the teratogenic agent bis -diamine in rat models.

Tetralogy of Fallot with Absent Pulmonary Valve