Current status of the mechanical valve and bioprosthesis in Japan

Tricuspid valve replacement with mechanical versus biological prostheses: a systematic review and meta-analysis

BACKGROUND AND OBJECTIVE

Tricuspid valve replacement (TVR) is required when repair is not feasible, and it continues to be a relatively high-risk procedure owing to the complex medical and/or surgical profile of patients. The choice between mechanical and biological prostheses for TVR remains a subject of debate owing to their distinct advantages and disadvantages. This study aimed to analyse and compare the clinical outcomes of these two types of prostheses in the tricuspid position.

METHODS

PubMed, EMBASE, Web of Science, and the COCHRANE library were searched from 1995 to April 2023 for studies comparing clinical outcomes of mechanical versus biological valves in the tricuspid position. Data on 30-day mortality, reoperations, 5-year valve failure rates, thrombotic/thromboembolic events, and long-term survival were extracted, pooled, and analysed. Forest plots were generated using a random-effects model.

RESULTS

From an initial pool of 4716 citations, 37 studies meeting our inclusion criteria were assessed, collectively encompassing 8316 prostheses (3796 mechanical, 4520 bioprostheses). Our analysis revealed that mechanical valves exhibited a non-significant trend towards diminished 30-day mortality (RR = 0.85, 95% CI = 0.69-1.06). A distinct disparity emerged in valve durability, with mechanical valves demonstrating a significantly increased risk of 5-year valve failure (RR = 2.21, 95% CI = 1.38-3.56). Strikingly, mechanical valves displayed a substantial six-fold elevated risk of thrombotic events (RR = 6.29, 95% CI = 3.98-9.92). In contrast, the long-term survival and reoperation rates demonstrated no statistically significant differences between the two valve types.

CONCLUSIONS

This systematic review and meta-analysis provides insights into the selection of mechanical and bioprosthetic valves for TVR. These findings highlight the potential advantages and disadvantages of mechanical and bioprosthetic valves in terms of early mortality, valve durability, and thrombotic risk. Our analysis provides clinicians with evidence-based guidance for optimizing outcomes in TVR, offering a foundation for informed decision-making in this intricate surgical landscape. Despite these insights, clinicians must overcome the limitations of retrospective studies, evolving healthcare, and anticoagulant disparities to ensure careful consideration in tricuspid valve replacement decisions.

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.