Landmark based morphometric analysis of the pulmonary valve

The pulmonary valve comprises three leaflets which attach to the wall of the right ventricle via the annulus. The purpose of this study is to describe the leaflet attachment pattern of the pulmonary valve using landmark-based geometric morphometric techniques and explore the relationship between shape variables and size.

A total of 28 pulmonary valves were harvested from anatomical donors. The valves were opened and photographed in a standardized manner. A geometric morphometric landmark protocol was digitally applied to each photograph. Generalized Procrustes superimposition and an ordination analysis were used to assess valve shape. The relationship between major components of valve shape and centroid size were investigated. Ten valves were repinned and photographed by another researcher to evaluate the role of error in the results.

The principal component analysis (PCA) revealed several patterns in pulmonary valve leaflet attachment. Principal component 1 (PC1) accounted for 40.6% of the variation in the sample; its major axis of variation reflects a curvature in the ends of the open outflow tract which corresponds with natural variability in the circumference of the tract between the level of the annulus and sinotubular junction. Principal component 2 accounted for 19.2% of the variation in the sample and was associated with asymmetry in peak leaflet attachment. Uniform variation in sinus depth was seen along PC3 (12.7%). Principal component 4 was associated with non-uniform asymmetric variation in sinus depth and accounted for 7.5% of the variation in the sample. No association was found between the size and shape of the valve. Error study results demonstrated the process of pinning and photographing had a marginal effect shape outcomes.

Our results show notable variability in pulmonary valve leaflet attachment pattern. Shape variables had no relationship with valve centroid size. More nuanced morphologic analyses may stimulate physiologic questions aimed at assessing the relationship between valve morphology and performance.