[Mosaic bioprosthesis after 5 years]

The Mosaic bioprosthesis is a stented porcine aortic valve, which combines the zero pressure differential fixation technique (by applying equal pressure to the in- and outflow ends of the valve, the aortic root is pressurized to maximize the flow area while no pressure is exerted on the leaflets) and an antimineralization treatment with alpha amino oleic acid for improved tissue durability. The device is in clinical use since February 1994. The purpose of this study was to collect intermediate term data of the Mosaic bioprosthesis in the aortic position to evaluate its clinical and hemodynamic function. From February 1994 to May 1999, 100 patients underwent aortic valve replacement with the Mosaic prosthesis at our department. There were 49 female patients, mean age at implant was 73.4 +/- 7.3 years (range 31 to 87). Concomitant procedures were done in 40%. Preoperative and operative clinical data are shown in Tables 1 and 2. When assessing the size of the bioprosthesis, it is important to use the original Mosaic sizer. Because of the possibility of the so-called supra-x placement, the specific construction of the sizer and the Mosaic valve often allow the implantation of a 1-size larger valve compared to the conventional supra-annular placement. By this a significant increase in the effective flow orifice is possible. This proceeding is depicted in Figure 1. All patients have been anticoagulated with phenprocoumon at least for 3 months postoperatively, INR was aimed at 2.5 to 3.5. Patients have been followed up prospectively, within the initial hospitalization for valve replacement, 6 months postoperatively and at annual intervals including an hematological check and transthoracic echocardiography. The mean follow-up was 2.7 years with a total follow-up of 273.7 patient years. The follow-up was 100% complete. After 5 years the mean systolic pressure gradient was 15.2 +/- 3.0 mm Hg for the 21-mm, 13.1 +/- 4.6 mm Hg for the 23-mm, 10.0 +/- 3.1 mm Hg for the 25-mm valve size, the effective orifice area 1.6 +/- 0.3 cm2 (21-mm), 1.9 +/- 0.3 cm2 (23-mm) and 2.5 +/- 0.8 cm2 (25-mm) (see Table 3). The freedom from prosthesis-related event rates, calculated according to Kaplan-Meier, at 5 years were: 97.3 +/- 1.9% for permanent neurological, 99.0 +/- 1.0% for transient neurological, 95.9 +/- 3.2% for thrombosed prosthesis, 95.6 +/- 2.2% for antithromboembolic related hemorrhage, 96.2 +/- 3.7% for structural valve deterioration, 96.9 +/- 3.0% for non-structural dysfunction, 100% for endocarditis and 92.0 +/- 4.9% for explant (see Table 4). The total operative mortality (within 30 days) was 3.0%, the late postoperative mortality was 4.4% per patient year and included a valve related mortality rate of 0.7%/patient year. In Figure 2 the survival function after aortic valve replacement is depicted, arranged in freedom from all deaths, from Mosaic-related deaths and from Mosaic-related plus sudden/unexplained deaths. Before implantation of the Mosaic bioprosthesis 95% of the patients were in NYHA Classes III and IV, whereas 6 months postoperatively 98% could be classified in NYHA Classes I and II (see Figure 3). In relation to other biological prostheses (Intact, Carpentier-Edwards Pericardial and Porcine, Hancock Modified Orifice, Biocor, Freestyle) the Mosaic bioprosthesis showed very satisfactory and predominantly better hemodynamic results than the compared stented valves and approached the performance of stentless prostheses. The freedom rates from prosthetic-related adverse events of the Mosaic bioprosthesis were at least equivalent to the compared prostheses. However, the satisfactory freedom rates, especially from structural valve deterioration, should be qualified by considering the experience that most incidences appear from the 5th year on after implantation. The clinical and hemodynamic performance of the Mosaic prosthesis has been very satisfactory during the first 5 years after clinical introduction. Further data will be necessary to confirm long-term durability.