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Ann Thorac Surg 2007;83:1921
© 2007 The Society of Thoracic Surgeons

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Correspondence

Can Cryopreservation Destroy the Extracellular Matrix of Pulmonary Allografts?

Department of Cardiovascular Surgery, Charité Hospital, Medical University Berlin, Berlin, D-10117 Germany

(Email: pascal.dohmen{at}charite.de; wolfgang.konertz{at}charite.de).

To the Editor:

We have read the article by Schenke-Layland and associates [1] regarding the impact of cryopreservation on extracellular structures with great interest. Cryopreserved allografts are still the gold standard with excellent hemodynamics and low reoperation rates during long-term follow-up in demanding surgical procedures, such as infective endocarditis and complex congenital cardiac surgery [2].

Several studies show good conservation and function of endothelial and interstitial cells of cryopreserved allografts and a positive impact on durability. However, few studies concentrate on preservation of extracellular matrix structures. This study compares fresh and cryopreserved porcine pulmonary heart valves in an attempt to explain tissue deterioration. The results show that cryopreservation destroys the extracellular matrix; these findings need to be discussed.

First the authors write that obtaining slaughterhouse valves and transport to the laboratory should be as short as possible. It is indeed important to keep the ischemic time as short as possible. Aidulis and colleagues [3] describe the importance of having warm ischemic time no longer than 30 minutes, and cold ischemic time during transport on ice no longer than 180 minutes. Although immediate transport to the laboratory was mentioned, the authors may have exceeded these time frames.

Furthermore, Goffin and colleagues [4] mentioned the importance of giving dimethylsulfoxide (DMSO) as a cryoprotective solution to the allograft and waiting at least 40 to 60 minutes to allow DMSO to penetrate completely into the tissue. In this study the leaflets show ice crystals; thus the cryopreserved wall of these allografts may have been injured.

A further important issue of this study is an analysis of the freezing curve. Goffin and colleagues [4] have always taken interest in this issue and use a grading scale for the quality of the allografts. Fifteen percent of cryopreserved pulmonary allografts were judged second grade in quality due to a poor freezing curve. If the chamber temperature decreases too fast, the program should be manually corrected. Of course, this does not always guarantee a perfect freezing process. The authors of this recent study apparently had no cryopreservation failures.

Finally, thawing fractures, which are due to early manipulation before ice has melted completely, should be discussed. Adam and colleagues [5] have shown that this will happen especially at temperatures as low as –196°C as occurred in this study. It is extremely important not to manipulate tissue during this period to prevent tissue deterioration.

Several investigators, including our group, are developing new generation heart valves with the use of tissue-engineering techniques [6]. Early follow-up of these heart valves show promising results. Nevertheless, it must be mentioned that cryopreserved allografts are still the gold standard and produce acceptable long-term results.

	References

Top References

 

1. Schenke-Layland K, Madershahian N, Riemann I, et al. Impact of cryopreservation on extracellular matrix structures of heart valve leaflets Ann Thorac Surg 2006;81:918-927.[Abstract/Free Full Text]
2. Crescenzo DG, Hilbert SL, Barrick MK, et al. Donor heart valves: electron microscopic and morphometric assessment of cellular injury induced by warm ischemia J Thorac Cardiovasc Surg 1992;103:253-257.[Abstract]
3. Aidulis D, Pegg DE, Hunt CJ, et al. Processing of ovine cardiac valve allografts: 1. effects of preservation method on structure and mechanical properties Cell Tissue Bank 2002;3:79-89.[Medline]
4. Goffin Y, Grandmougin D, van Hoeck B. Banking cryopreserved heart valves in Europe: assessment of a 5 year operation in an international tissue bank in Brussels Eur J Cardio-thoracic Surg 1996;10:505-512.[Abstract]
5. Adam M, Hu JF, Lange P, Wolfinbarger Jr L. The effect of liquid nitrogen submersion on cryopreserved human heart valves Crybiology 1990;27:605-614.
6. Erdbruegger W, Posner S, Ellerbrock H, et al. Deoxycholic acid treatment offers improved prospects in heart valve replacement Tiss Eng 2006;8:2059-2068.

This article has been cited by other articles:

				K. Schenke-Layland and U. A. Stock Reply Ann. Thorac. Surg., May 1, 2007; 83(5): 1921 - 1922. [Full Text] [PDF]

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Add to Personal Folders Download to citation manager Author home page(s): Pascal Maria Dohmen Wolfgang Konertz Permission Requests Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Dohmen, P. M. Articles by Konertz, W. Search for Related Content PubMed PubMed Citation Articles by Dohmen, P. M. Articles by Konertz, W. Related Collections Valve disease Related Article