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. 2012 Jan;33(1):1-8.
doi: 10.1016/j.biomaterials.2011.09.027. Epub 2011 Oct 10.

Porcine vena cava as an alternative to bovine pericardium in bioprosthetic percutaneous heart valves

Amy E Munnelly  1 , Leonard Cochrane, Joshua Leong, Naren R Vyavahare
Affiliations

Porcine vena cava as an alternative to bovine pericardium in bioprosthetic percutaneous heart valves

Amy E Munnelly et al. Biomaterials. 2012 Jan.

Abstract

Percutaneous heart valves are revolutionizing valve replacement surgery by offering a less invasive treatment option for high-risk patient populations who have previously been denied the traditional open chest procedure. Percutaneous valves need to be crimped to accommodate a small-diameter catheter during deployment, and they must then open to the size of heart valve. Thus the material used must be strong and possess elastic recoil for this application. Most percutaneous valves utilize bovine pericardium as a material of choice. One possible method to reduce the device delivery diameter is to utilize a thin, highly elastic tissue. Here we investigated porcine vena cava as an alternative to bovine pericardium for percutaneous valve application. We compared the structural, mechanical, and in vivo properties of porcine vena cava to those of bovine pericardium. While the extracellular matrix fibers of pericardium are randomly oriented, the vena cava contains highly aligned collagen and elastin fibers that impart strength to the vessel in the circumferential direction and elasticity in the longitudinal direction. Moreover, the vena cava contains a greater proportion of elastin, whereas the pericardium matrix is mainly composed of collagen. Due to its high elastin content, the vena cava is significantly less stiff than the pericardium, even after crosslinking with glutaraldehyde. Furthermore, the vena cava's mechanical compliance is preserved after compression under forces similar to those exerted by a stent, whereas pericardium is significantly stiffened by this process. Bovine pericardium also showed surface cracks observed by scanning electron microscopy after crimping that were not seen in vena cava tissue. Additionally, the vena cava exhibited reduced calcification (46.64 ± 8.15 μg Ca/mg tissue) as compared to the pericardium (86.79 ± 10.34 μg/mg). These results suggest that the vena cava may provide enhanced leaflet flexibility, tissue resilience, and tissue integrity in percutaneous heart valves, ultimately reducing the device profile while improving the durability of these valves.

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Figures

Figure 1
Figure 1
Collagen and elastin stability against enzymes, represented as a percentage of dry tissue weight loss (n= 6, * p<0.05)
Figure 2
Figure 2
GAG content as represented by hexosamine content of tissue; * indicates difference with Fresh of same species; (n = 6; * p<0.05)
Figure 3
Figure 3
Representative uni-axial tensile stress strain curve for porcine vena cava
Figure 4
Figure 4
Effects of fixation on elastic moduli of porcine vena cava (PVC) and bovine pericardium (BP); (A) Lower modulus; (B) Upper modulus; (n = 6; All differences between PVC and BP are significant (p < 0.05) except GLUT in the lower modulus in circumferential direction)
Figure 5
Figure 5
Elastic modulus of tissue after crimping; A) Lower modulus B) Upper modulus; (n = 6; All differences between uncrimped and crimped tissues are significant (p < 0.05) * indicates difference between crimped PVC and BP tissues, p<0.05)
Figure 6
Figure 6
Scanning electron microscopy pictures: A) PVC control; B) PVC crimped; C) BP control; D) BP crimped, bar represents 500 μM.
Figure 7
Figure 7
Calcium and phosphorus content of subdermally implanted tissue; (n = 10; * p<0.05)
See this image and copyright information in PMC

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