Mosaic®-Bioprothese nach fünf Jahren

Zusammenfassung

Ziel der Studie war die Evaluation der klinischen und hämodynamischen Funktion der Mosaic^® Bioprothese in Aortenposition. Die Prothese ist seit Februar 1994 in klinischer Verwendung.

Die Mosaic^®-Bioprothese ist eine gestentete porcine Aortenklappe, die mit der so genannten Null-Druck-Technik fixiert und mit Aminoölsäure gegen Gewebsmineralisation behandelt ist. Zwischen Februar 1994 und Mai 1999 unterzogen sich in unserer Abteilung 100 Patienten einem Aortenklappenersatz mit der Mosaic^®-Prothese. 49 der Patienten waren weiblich, das mittlere Alter am Tag der Operation betrug 73,4±7,3 Jahre (31 bis 87 Jahre). In 40% der Fälle wurden Begleiteingriffe am Herzen vorgenommen. Die Patienten wurden in einer prospektiven Studie in jährlichen Abständen mittels transthorakaler Echokardiographie nachuntersucht. Der mittlere Untersuchungszeitraum betrug 2,7 Jahre, die gesamte Beobachtungszeit 273,7 Patientenjahre. Das Follow-up ist zu 100% komplett.

Die operationsbedingte Mortalität (innerhalb der ersten 30 Tage) betrug 3,0%, die postoperative Mortalität (ab 30. Tag) war 4,4%/Patientenjahr und schloss eine klappenbedingte Mortalität von 0,7%/Patientenjahr ein. Nach fünf Jahren ergab die Kaplan-Meier-Statistik eine Freiheit von 97,3±1,9% für prolongierte neurologische Ausfälle, 99,0±1,0% für vorübergehende neurologische Defizite, 95,9±3,2% für thrombosierte Bioprothesen, 95,6±2,2% für Blutungen infolge antikoagulatorischer Therapie, 96,2±3,8% für eine strukturelle Dysfunktion der Klappe, 96,9±3,0% für eine nicht strukturelle Klappendysfunktion, 100% für eine Endokarditis und 92,0±4,9% für die Explantation der Klappe. Der mittlere Druckgradient war 15,2±3,0 mm Hg für die 21-mm-Klappe, 13,1±4,6 mm Hg für die 23-mm-Klappe und 10,0±3,1 mm Hg für die 25-mm-Klappe.

Die hämodynamische Evaluation der Mosaic^®-Klappe erbrachte im Vergleich zu anderen gestenteten Bioprothesen niedrige Druckgradienten und große Klappenöffnungsflächen. Die Inzidenz von prothesenbedingten Komplikationen war gering.

Abstract

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 wich 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^® 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 of other beiological 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.