The influence of sizing and method of fixation on the hydrodynamic function of stentless, free-hand inserted porcine bioprosthesis: an in vitro study.
OBJECTIVE
There is increasing interest in the use of stentless porcine bioprostheses implanted by the free-hand suturing technique. However, preservation of normal valve geometry and function is a matter of concern. This in vitro study was conducted to investigate the influence of sizing and method of fixation in glutaraldehyde on the hydrodynamic function of stentless, free-hand inserted porcine bioprosthetic valves in the aortic position.


METHODS
Three sets of porcine aortic roots were used, with six specimens in each set. Group A comprised 2-3 mm larger aortic valve (oversizing) fixed in glutaraldehyde under zero pressure inserted by free-hand suturing technique in fresh aortic roots; group B comprised size-for-size placement of aortic valve fixed in glutaraldehyde under zero pressure inserted by free-hand suturing technique in fresh aortic roots; and group C comprised size-for-size placement of aortic valve fixed in glutaraldehyde under zero pressure with permanent predilatation before fixation inserted by free-hand suturing technique in fresh aortic roots (undersizing). Hydrodynamic function and leaflet bending deformations were analyzed in a modified pulsatile flow simulator which incorporated the elastic aortic roots.


RESULTS
The hydraulic effective orifice area (EOA) of the valve (derived from flow and pressure measurements) was divided by actual orifice area of the annulus to determine the performance index. Although statistically non-significant, the performance index of 0.50 in group A (oversizing) was higher than that of size-for-size placement in group B (0.39). The performance index in group C of 0.41, following use of a permanent predilatation technique, was again not significantly different. The mean pressure difference during peak flow followed a correspondingly reversed order, with 11.4 mmHg in group B, 8.86 mmHg in group C, and 7.75 mmHg in group A. No significant difference was observed between the groups in terms of open leaflet bending deformations, nor was there any inter-group difference in regurgitation.


CONCLUSIONS
No beneficial effect was seen to suggest that size-for-size placement was superior to the currently followed practice of over-sizing. In contrast to previous studies of whole root replacement, permanent predilatation and fixation was also not shown to have any additional advantages in a stentless scalloped free-hand inserted porcine valve.
Revanna
P
P
Killingbeck Hospital, Leeds, UK.
Fisher
J
J
Watterson
K G
KG
D000818:Animals; D001021:Aortic Valve / Q000601:surgery*; D001696:Biomechanical Phenomena; D001705:Bioprosthesis; D006350:Heart Valve Prosthesis; D066298:In Vitro Techniques; D011474:Prosthesis Design; D012212:Rheology; D015607:Stents; D013552:Swine