Date Published: April 13, 2017
Publisher: Public Library of Science
Author(s): Ende Tao, Li Wan, WenJun Wang, YunLong Luo, JinFu Zeng, Xia Wu, Davide Pacini.
Surgery remains the primary form of treatment for infective endocarditis (IE). However, it is not clear what type of prosthetic valve provides a better prognosis. We conducted a meta-analysis to compare the prognosis of infective endocarditis treated with biological valves to cases treated with mechanical valves.
Pubmed, Embase and Cochrane databases were searched from January 1960 to November 2016.Randomized controlled trials, retrospective cohorts and prospective studies comparing outcomes between biological valve and mechanical valve management for infective endocarditis were analyzed. The Newcastle-Ottawa Scale(NOS) was used to evaluate the quality of the literature and extracted data, and Stata 12.0 software was used for the meta-analysis.
A total of 11 publications were included; 10,754 cases were selected, involving 6776 cases of biological valves and 3,978 cases of mechanical valves. The all-cause mortality risk of the biological valve group was higher than that of the mechanical valve group (HR = 1.22, 95% CI 1.03 to 1.44, P = 0.023), as was early mortality (RR = 1.21, 95% CI 1.02 to 1.43, P = 0.033). The recurrence of endocarditis (HR = 1.75, 95% CI 1.26 to 2.42, P = 0.001), as well as the risk of reoperation (HR = 1.79, 95% CI 1.15 to 2.80, P = 0.010) were more likely to occur in the biological valve group. The incidence of postoperative embolism was less in the biological valve group than in the mechanical valve group, but this difference was not statistically significant (RR = 0.90, 95% CI 0.76 to 1.07, P = 0.245). For patients with prosthetic valve endocarditis (PVE), there was no significant difference in survival rates between the biological valve group and the mechanical valve group (HR = 0.91, 95% CI 0.68 to 1.21, P = 0.520).
The results of our meta-analysis suggest that mechanical valves can provide a significantly better prognosis in patients with infective endocarditis. There were significant differences in the clinical features of patients receiving a biological valve compared to patients receiving a mechanical valve. A large, multicenter retrospective study included in our meta-analysis suggested that any mortality risk of the biological valve group was significant higher than that of the mechanical valve group. However, the risk was no different after risk was adjusted. So, we thought the reason for this result may be related to the characteristics of the patient rather than valve dysfunction. It is still necessary to future randomized studies to verify this conclusion.
Despite improvements in managements, IE remains a deadly disease associated with an in-hospital mortality of 10–30%, and 50% of patients required cardiac surgery during the acute phase[1,2]. The two primary objectives of surgery are the complete removal of the infected tissue and reconstruction of cardiac morphology, including repair or replacement of the affected valves. During the operation, the type of valve including biological valve, mechanical valve, autograft and homograft is selected.The 2014 American College of Cardiology/American Heart Association(ACC/AHA) guidelines recommended a biological valve in patients 65 years of age or older, while a mechanical valve is suitable for patients under 65 years of age, but the guidelines do not provide specific recommendations for surgery for IE. The Task Force for the Management of Infective Endocarditis of the 2015 European Society of Cardiology (ESC) does not support any specific valve substitute but recommends a tailored approach for each individual patient and clinical situation. Guidelines from the STS recommend the following: (1)When surgery is indicated for native aortic valve endocarditis, a mechanical or stented tissue valve is acceptable, if the infection is limited to the native aortic valve or to the aortic annulus. Valve choice should be based upon age, life expectancy, comorbidities, and compliance with anticoagulation therapy (Class IIa, Level of evidence B); (2) When surgery is indicated for prosthetic valve aortic endocarditis, it is reasonable to implant a mechanical or stented tissue valve (Class IIa, Level of evidence B). A homograft may be beneficial in aortic valve prosthetic endocarditis when a periannular abscess or extensive destruction of anatomic structures has occurred (Class IIa, Level of evidence B). The choice of valve remains controversial. Some studies[7,8,9,10,11] have found no significant differences in survival between biological valves and mechanical valves, but there are also some studies[4,12] reporting that the survival rate with biological valves is inferior to mechanical valves. Presently, there are no randomized controlled trials or meta-analysis studies compare the prognosis of biological valves with that of mechanical valves. We performed a meta-analysis with available evidence to analyze the prognosis of IE patients treated with biological and mechanical valves to assist clinicians in the selection of valve type.
Infective endocarditis (IE) is a fatal disease with a yearly incidence of approximately 3–10 per 100,000 people. Overall, 40–50% of patients with IE require surgical treatment; the main choices for the valve replacememt are prosthetic valves and autografts or homografts. The application of allografts and homografts, however, is limited by poor availability and difficult surgical techniques. Since its initial report by Osler William in 1885, the epidemiology of IE has evolved from predominantly a disease of young adults with rheumatic heart valve disease to a disease affecting the elderly, and those with prosthetic valves and intra-cardiac devices. A study from The Society of Thoracic Surgeons Adult Cardiac Surgery (STS ACSD) showed that, for primary operations, biological valve use increased from 57% to 67%, while mechanical valve use decreased from 30% to 24% during 2005 to 2011. For reoperation, the use of biological valves increased from 38% to 52%, and the use of mechanical valves decreased from 20% to 17%. We found that the utilization rate of biological valves was higher than mechanical valves in the primary operation and reoperation, but it was not clear whether biological valves can lead to a better prognosis compared to mechanical valves. A meta-analysis from Lund et al.  including 17,439 patients suggested that there was no significant difference in the all-cause mortality between the biological valve group and the mechanical valve group after adjusting for age and other common risk factors. However, this meta-analysis was not aimed at patients with IE. Only 2.2% of the patients had IE in the biological valve group, and only 6.8% patients had IE in the mechanical valve group. Therefore, the results of this meta-analysis did not apply to patients with IE.
Our study has several limitations. First, our research consists of prospective or retrospective studies without randomized studies. Additionally, the patients in the biological valve group were inferior physical condition than those in the mechanical valve group, and the follow-up time of a study was too short to completely reflect the prognosis of the patients. Moreover, several studies with small sample size raised some concerns regarding the reliability of their results [7, 8, 12, 28]. Second, the data were first selected from the literature, then extracted from the Kaplan-Meier curve, which may lead to bias. Third, individual studies mentioning prosthetic valve endocarditis, recurrence of endocarditis, reoperation and embolic events were limited in number.
Results of our meta-analysis suggest that mechanical valves can provide a significantly better prognosis than biological valves in patients with infective endocarditis. There were significant differences in the clinical features of patients receive a biological valve compared to patients receive a mechanical valve. A largest, multicenter retrospective study included in our meta-analysis suggested that any mortality risk of the biological valve group was significant higher than that of the mechanical valve group, however, the risk was no different after risk adjusted. So, we thought the reason for this result may be related to the characteristics of the patient rather than valve dysfunction. Although several prospective studies have investigated this issue, the results were not consistent. Further randomized studies are necessary to verify the conclusions.