The pulmonary valve in tetralogy of Fallot: insights from a necroscopy series.

Background: Tetralogy of Fallot is the most common cyanotic congenital malformation of the heart. The right ventricular outflow tract is of great interest in this setting, but most of the focus on this feature has been on the size of the so-called pulmonary valvar "annulus". We aimed to characterise other aspects of the morphology of the pulmonary root in heart specimens with tetralogy of Fallot.

Methods: We reviewed archived hearts with tetralogy of Fallot from four registries. The pulmonary root was examined with specific attention to the number of sinuses, the number of leaflets, presence of any fusion of leaflets, and the direction of the zone of apposition between the leaflets. Cluster analyses were then conducted to see if the features permitted segregation into groups.

Results: We examined a total of 155 hearts. The pulmonary valve had two leaflets in 62%, three leaflets in 34%, and one leaflet in 3%. Irrespective of leaflet morphology, most hearts had two sinuses. Cluster analysis permitted segregation into three groups, with the direction of the zone of apposition being the most important feature for segregation.

Conclusion: In two-thirds of our hearts with tetralogy of Fallot, the pulmonary valve had two leaflets. Most frequently there were three sinuses. In the setting of a valve with two sinuses, the zone of apposition between the leaflets pointing towards the aorta. Cluster analysis permitted statistically sound segregation of the heart and highlights the importance of delineating these features, specifically the leaflet and sinus morphology, with clinical imaging.