Histological examination of the pulmonary artery and aorta in an adolescent undergoing the Ross procedure.

Background: The Ross procedure offers several advantages for adolescents requiring aortic valve replacement, but progressive pulmonary autograft dilation is a well-described risk. To provide novel insight into the pre-Ross histology in an adolescent with bicuspid aortic valve (BAV)-associated aortopathy, we describe the extracellular architecture of the pulmonary artery (PA) compared to the native ascending aorta.

Methods: A 15-year-old with BAV, symptomatic moderate aortic insufficiency and aortic stenosis, and ascending aortic dilation underwent Ross. Intraoperative specimens included the main PA and ascending aorta. Tissue specimens were fixed, stained using 1) haematoxylin and eosin, 2) Verhoeff's van Gieson, and 3) trichrome, and compared using light microscopy.

Results: Elastin van Gieson stain revealed that the aortic media in the dilated ascending aorta contained a greater concentration of dense elastin weaves and a regular distribution of collagen compared to the PA. In contrast to the dense and organised compaction of elastic fibres in the media of the aortic specimen, the PA, though grossly normal, demonstrated extensive disruption and fragmentation. Trichrome staining revealed minimal fibrosis in both specimens.

Conclusions: Notable pre-Ross histological differences include marked disruption of elastin in the PA compared to the aorta. Age-based differences in Ross outcomes suggest that adolescents may experience proportionally more significant autograft dilation over time, so future studies should include prospective collection and histological analysis of specimens across the age spectrum, both pre- and post-Ross, to allow comparison to age-matched controls.