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[Surgical pathology analysis of the causes of failure of 48 bioprosthetic heart valves in 40 Chinese cases].

OBJECTIVE
To investigate the pathological changes and related factors leading to failure of bioprosthetic valves.


METHODS
The surgical explanted bioprosthetic valves in Fuwai Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College from January 2006 to December 2014 were retrospectively reviewed. Calcification, cusp tears, pannus and infectious endocarditis of bioprosthetic valves were evaluated by gross examination, X ray photography and histopathological analysis. Meanwhile, the age and the site at implantation, and the tissue type of bioprosthetic valves, the implantation duration were obtained by chart review and used to be analyzed with the modes of valve failure. U test, χ(2) test and Fisher exact test were used to analyze the data.


RESULTS
Total 48 bioprosthetic valves were collected from 40 cases with 26 females. Their age at the time of implantation was 12 to 71 years (median 58 years). The tissue types of bioprosthesis included 24 bovine pericardial valves and 24 porcine aortic valves respectively. The implantation sites included mitral in 29 valves, aortic in 14 valves and tricuspid in 5 valves. The implantation duration ranged from 5 days to 27 years (mean (111±77) months). The study showed that the commonest mode of valve failure was structural valve deterioration (32 valves, 66.7%). The fewer modes of valve failure were infectious endocarditis (9 valves, 18.7%) and non-structural valve deterioration (7 valves, 14.6%). No thrombosis was found in this series. The degree of calcification was correlated positively with implantation duration (r=0.52, P=0.000). The implantation duration of bovine pericardial valves was longer than that of porcine aortic valves ((146±74) months vs. (77±68) months, Z=-3.24, P=0.001). Porcine aortic valves had a higher incidence of cusp tears than bovine pericardial valves (66.7% vs. 16.7%, χ(2)=12.34, P=0.000) despite they had a relatively lower incidence of calcification (41.7% vs. 75.0%, χ(2)=5.37, P=0.019). For the age at the time of implantation, the patients ≤60 years old had more calcification of bioprosthetic valves compared with those >60 years old (45.1% vs. 2/17, χ(2)=5.51, P=0.019) whereas the patients ≤60 years old had fewer cusp tears (12.9% vs. 58.8%, P=0.002). Infectious endocarditis was found more frequently in the valves failure within 5 years than those failure after 5 years (6/14 vs. 8.8%, P=0.006).


CONCLUSIONS
Structural valve deterioration is the principle cause of bioprosthetic valve failure while infectious endocarditis mainly involves the valves failure in early and middle terms after surgery. The mode of valve failure in the patients ≤60 years old is different from that in the patients >60 years old at the time of implantation. More calcification would occur in bioprosthetic valve in the younger patients.