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).