Current status of the mechanical valve and bioprosthesis in Japan

Bioprosthetic Aortic Valve Replacement in <50 Years Old Patients - Where is the Evidence?

Aortic valve disease is one of the most common valvular heart diseases in the cardiovascular category. Surgical replacement of the diseased aortic valve remains the definitive intervention for most diseases.

There is a clear consensus that in young patients who require aortic valve replacement, a mechanical prosthesis is the preferred choice due to its durable prosthesis without fear of wear and tear over time. However, this comes at the expense of increased risk of bleeding and thromboembolic events; in addition, there is a lack of strict evidence in using bioprosthesis in patients younger than 50 years. The objective of this review article is to assess the current evidence behind using bioprosthetic aortic valve in this young cohort.

Gal knockout pig pericardium: new source of material for heart valve bioprostheses

BACKGROUND

Although glutaraldehyde fixation is known to reduce immunogenicity and degeneration of heart valve bioprostheses, some degree of immunogenicity persists, which may trigger calcification. The aims of this study were to: (1) define the role of alpha-1,3-galactosyltransferase (alpha-Gal) antigen in valve calcification by comparing alpha-Gal-positive and alpha-Gal-deficient (GT-KO) pig pericardium; and (2) elucidate the role of human anti-Gal antibodies in the process of calcification and to determine the potential influence of different tissue-fixation techniques.

METHODS

Glutaraldehyde-treated pericardium from alpha-Gal-positive and GT-KO pigs, with or without pre-labeling with human anti-Gal antibodies, were implanted in rats during 1 month.

RESULTS

In glutaraldehyde-fixed pericardium, calcification levels were significantly lower in GT-KO pig pericardium (132.8 +/- 5.8 microg/mg) as compared with alpha-Gal-positive pig pericardium (155.7 +/- 7.1 microg/mg) (p < 0.015). In glutaraldehyde-fixed pig pericardium followed by a mix of formaldehyde, ethanol and Tween 80 (FET), the calcification levels were lower in GT-KO pig pericardium (0.35 +/- 0.1 microg/mg) as compared with alpha-Gal-positive pig pericardium (4.6 +/- 4.2 microg/mg). In glutaraldehyde-fixed pig pericardium + FET pre-incubated with human anti-Gal antibodies, calcification levels were significantly greater in alpha-Gal-positive pig pericardium (43.8 +/- 8.5 microg/mg) as compared with GT-KO pig pericardium (5.7 +/- 2.9 microg/mg) (p < 0.0001).

CONCLUSIONS

This study demonstrates the role of alpha-Gal antigen and human alpha-Gal antibodies in the calcification process of valvular bioprostheses. It is suggested that GT-KO pig pericardium could be beneficial as a new source of material for heart valve bioprostheses.