Mitroflow aortic pericardial bioprosthesis

We read with great interest the article ‘Mitroflow aortic pericardial bioprosthesis – clinical performance’ published by Jamieson and colleagues [1] and we have a few queries regarding the contents and conclusions of the article. First, this is a retrospective study, performed with patients from three different hospitals (Bad Oeynhausen, Berlin and Vancouver) operated on between 1992 and 2003 using the Mitroflow pericardial bioprosthesis, model 12. The study involved a total of 381 patients. Minami (from Bad Oeynhausen) reported in 2005 the implantation of 1024 valves of Mitroflow model 12 [2]. Yankah (from Berlin) published in 2005 the clinical results of 1037 Mitroflow bioprosthesis implanted between 1986 and 2003 [3] (a great number of these valves probably were Mitroflow model 12). So, the first question is if there are now 381 patients included in the article, why were the other patients excluded? What kind of bias was made in the population data? Second, in the given data and Table 1, the authors made two groups: less than 70 years old and older. Nevertheless, in Fig. 2, the graphic captions are ‘≥60 years’ and ‘≥65 years’. Even more, the patients at risk in the older than 65-year-old group are greater in number than patients older than 60 years old (385 vs 374). How is it possible? Third, there were 20 early deaths and, of the 361 survivors, 24 patients were lost to follow-up (6.6%), and 228 were late deaths; 66 deaths were due to undetermined causes and 35 deaths were due to valve-related causes. Of these, only two were structural valve deterioration (SVD). Of the 66 undetermined deaths, we do not know the rate of structural failure or deterioration. Only 19 cases were re-operated on due to SVD, but how many patients had SVD without re-operation? Were they studied? If the follow-up was performed by telephone interview, as Minami reported [2], this may have limited the detection of valve-related pathology. Structural valve deterioration is a process occurring over a prolonged period of time and the real incidence may have been less than the rate that would be detected by periodic echocardiographic studies [4]. How many patients had SVD without clinical significance? The authors concluded in their exposure ‘The Mitroflow…, has very acceptable durability, at 10 years, for patients >60 years.’ We think that with these data, we cannot conclude that affirmation.

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