The Pulmonary Valve

Abstract

Pulmonary autografts have shown a low incidence of early failure and late structural deterioration when placed in the aortic position yet the potential value of the pulmonary valve as a replacement device has not been widely considered. Since the mechanical suitability of pulmonary valves for the high stress aortic position is unclear, we set out to define and compare the tensile mechanical properties of these two valves. We removed all 72 cusps from 12 fresh porcine aortic and pulmonary valves. Eighteen cusps from each of the two groups were fixed flat in 0.25% glutaraldehyde for greater than 24 hr. Circumferential or radial strips were cut from each cusp creating eight test groups, each with nine specimens. Stress-strain curves for each specimen were obtained using an Instron tensile testing machine. Stress-strain curves were obtained at 2, 10, 50, and 200 mm/min strain rates, each specimen was then strained to fracture. We found pulmonary leaflets were thinner than aortic leaflets (0.49 mm versus 0.67 mm) and glutaraldehyde fixation did not affect this relationship. The elastic moduli were comparable within the fresh and glutaraldehyde fixed treatment groups and within the circumferential and radial strip groups. Radial strips were more extensible than circumferential strips. Tissue viscous properties were similar and glutaraldehyde fixation produced minimal changes in stress relaxation rates. Tissue fracture tests emphasized tissue anisotropy with the failure point depending upon strip orientation. Glutaraldehyde had no effect on fracture stress but strain at fracture doubled due to increased collagen fiber crimping during fixation.(ABSTRACT TRUNCATED AT 250 WORDS)