Progressive dilatation of pulmonary autografts after the Ross operation may refle
ct in
adequate remodeling of the native pulmonary root to
adapt to systemi
c cir
culation. Understanding the biome
chani
cs of autograft root dilatation may aid designing strategies to prevent dilatation. We have previously
chara
cterized normal human pulmonary root material properties; however, the me
chani
cal properties of failed autografts are unknown. In this study, failed autograft roots explanted during reoperation were a
cquired, and their material properties were determined.
c_2">Methods
Failed pulmonary autograft specimens were obtained from patients undergoing reoperation after the Ross operation. Fresh human native pulmonary roots were obtained from the transplant donor network as controls. Biaxial stretch testing was performed to determine tissue mechanical properties. Tissue stiffness was determined at patient-specific physiologic stresses at pulmonary pressures.
c_3">Results
Nonlinear stress-strain response was present in both failed autografts and normal pulmonary roots. Explanted pulmonary autografts were less stiff than were their native pulmonary root counterparts at 8 mm Hg (134 ± 42 vs 175 ± 49 kPa, respectively) (p = 0.086) and 25 mm Hg (369 ± 105 vs 919 ± 353 kPa, respectively) (p = 0.006). Autograft wall stiffness at both 8 and 25 mm Hg was not correlated with age at the Ross procedure (p = 0.898 and p = 0.813, respectively) or with time in the systemic circulation (p = 0.609 and p = 0.702, respectively).
c_4">Conclusions
Failed pulmonary autografts retained nonlinear response to mechanical loading typical of healthy human arterial tissue. Remodeling increased wall thickness but decreased wall stiffness in failed autografts. Increased compliance may explain progressive autograft root dilatation in autograft failures.