RESULTS
Of the 595 patients enrolled, 159 (26.7%) of them received a biological prosthesis, while 436 (73.3%) received a mechanical prosthesis. The baseline characteristics of patients with biological and mechanical valves are presented in Table 1. Patients with biological valves were significantly older than patients with mechanical valves (69.9 +7.7 years vs. 62.6 + 12.1 years, p < 0.001). A mechanical prosthesis was more frequently implanted in men than a biological prosthesis (60.4% vs. 49.1%, p = 0.014). Also, in the mechanical prosthesis group, 5.5% of patients had native valve endocarditis compared to 0.6% of patients in the biological prosthesis group (p = 0.009). There was no statistically significant difference in the other preoperative characteristics and demographics.
The operative characteristics are presented in Table 2. There was no significant difference between the groups in EuroSCORE II, CPB or aortic cross-clamp times. Ejection fraction and mean ICU stay were similar between groups. PPM (moderate and severe, iEOA < 0,85 cm2/m2) was present in 69.8% of patients in the biological prosthesis group in comparison to 3.7% in the mechanical prosthesis group (p < 0.001) (Table 3). Severe PPM (iEOA < 0,65 cm2/m2) was present in 5.1% of patients in the biological group and 1.3% of patients in the mechanical prosthesis group, with a statistically significant difference (p < 0.001). There was no difference in the number of redo surgeries or the frequency of postoperative endocarditis in the follow-up period between the mechanical and biological prostheses groups. Freedom from angina at the time of the latest follow-up was also similar between the groups (85.1 % vs. 88.8%, p = 0.28). The distribution of prosthesis manufacturers and models in compared groups is shown in Table 4.
The median follow-up was 31.8 (1-74) months. When analysed overall for mechanical and biological prostheses combined, mean survival was significantly shorter in the PPM group (57.0 months, 95% confidence interval [CI] 51.9-62.2) when compared to the no-PPM group (65.2 months, 95% CI 63.1-67.4) (log-rank test p = 0.008) (Fig. 2). When data were analysed separately for biological prosthesis, mean survival was significantly shorter in the PPM group (50.2 months, 95% CI 45.2-55.3) when compared to the no-PPM group (60.1 months, 95% CI 55.7-64.4) (log-rank test p = 0.035) (Fig. 3). Analysis of survival in patients who had a mechanical prosthesis implanted did not show a difference in mean survival in the PPM group (66.6 months, 95% CI 58.3-74.9) when compared to the no-PPM group (64.9 months, 95% CI 62.6-67.2) (log-rank test p = 0.50) (Fig. 4). Also, there was no statistically significant difference in baseline characteristics between the PPM and NO PPM groups in both patients with mechanical or biological valves, especially in age, BSA and body mass index.
The response rate for the QoL survey was 87.6 % for all patients enrolled in the study. The SF-12 questionnaire was analysed separately in patients with mechanical and biological prostheses (Table 5). There was no significant difference between the physical and mental scores in patients with PPM and patients with no-PPM who had a mechanical prosthesis. (43.9 ± 9.4 vs. 46.9 ± 8.3, p = 0.18). The physical score was significantly lower in patients with PPM vs. patients without PPM in those with an implanted biological prosthesis (39.4 ± 8.4 vs. 45.7 ± 10.1, p < 0.001) compared to those with an implanted mechanical prosthesis (43.9 ± 9.4 vs 46.9 ± 8.3, p = 0.18), respectively. There was no significant difference between the mental score in patients with PPM and without PPM, irrespective of the type of prosthesis (Table 5).