American Journal of Cardiovascular and
Thoracic Surgery

Objective: To systematically evaluate the postoperative cardiac function and complications after mitral valve replacement with complete preservation of subvalvular apparatus versus posterior subvalvular.

Method: The literature of the randomized controlled study, cohort study and case-control study of the two preservation of subvalvular apparatus was searched via the databases of the Pubmed, embase, Cochrane, Web of science, CNKI, Wanfang, CBM, VIP.RevMan5.3 software was used for meta-analysis of outcome indicators evaluation of postoperative cardiac function and postoperative complications.

Results: 31 cases of researches were selected, including 17 cases of case-control researches, 11 cases of cohort researches, and 3 cases of randomized controlled trials, with a total of 3468 patients. Left ventricular end diastolic dimension: 6 months after operation, 12 months after operation; Left ventricular end systolic dimension: 6 months after operation, 12 months after operation; Left ventricular ejection fraction: 6 months after operation, 12 months after operation; Early mortality of postoperative, left ventricular rupture, the differences of above outcome indicators between the two groups have statistical significance.

Conclusion: There is no significant difference in after postoperative cardiac function in the short term after mitral valve replacement with complete preservation of subvalvular apparatus versus posterior subvalvular. However, in terms of left ventricular function, long term follow-up shows that the complete preservation of subvalvular apparatus is superior to that of the preservation of posterior subvalvular apparatus. In terms of complications, complete preservation of subvalvular apparatus is superior to preservation of posterior subvalvular apparatus.

Key words: Mitral valve replacement; preservation of subvalvular apparatus; randomized controlled study; cohort study; case control study; Meta analysis.

Standard mitral valve replacement removes all valve leaflets, chordae, and papillary muscles, which disrupts the left ventricular structure and leads to impaire left ventricular function, with the further study of the relationship between submitral valve structure and left ventricular wall in anatomy and physiology. Mitral valve replacement with preservation of the subvalvular apparatus has a protective effect on left ventricular systolic function. However, the reported results of cardiac function and complications after total and partial preservation of subvalvular structures are inconsistent. The purpose of this meta-analysis is to evaluate the difference of cardiac function and complications between the two surgical methods and provide the most powerful basis for guiding clinical surgical decision-making to develop effective treatment methods.

Search formula (“subvalvular apparatus” OR “subvalvular apparatus” OR “preservation of chordae tendineae” OR “preservation of chordal-sparing”) AND (“Mitral Valves” OR “mitral valve” OR “Bicuspid Valve” OR “Bicuspid Valves” Search for Pubmed, embase, Cochrane, Web of science, CNKI, Wanfang, CBM and Weipu. All search strategies are determined by multiple pre-searches. All literature languages were Chinese and English.

1. Patients with valvular disease undergoing mitral valve replacement

2. Randomized control, cohort study, and case-control study of complete subvalvular apparatus and preserved posterior subvalvular

3. Outcome measures

•postoperative cardiac function: left ventricular end diastolic diameter, left ventricular end systolic diameter, left ventricular ejection fraction, left ventricular fractional shortening

• Postoperative complications: early postoperative mortality, left ventricular rupture

1. Documents from repeated publications of the same study were selected with the most detailed information.

2. The data could not be extracted.

Two reviewers evaluated the quality of the randomized controlled trials according to the quality evaluation method recommended by the Cochrane systematic review manual [1]. Independent evaluation of literature quality in case-control and cohort studies based on the Newcastle-Ottawa scale [2, 3].

Formulate a data extraction form and back-to-back extract. The main contents of the extracted data included: general data, research characteristics, exposure factors, follow-up time, research results, and research types.

Meta-analysis was performed using RevMan5.3 software. The heterogeneity test between the included studies was performed using the I² test. (I² < 50%, P > 0.05) the analysis was performed using a fixed-effect or random-effect model. If there is statistical heterogeneity (I² > 50%, P < 0.05), a random effect model was used. After exploring the sources of heterogeneity and eliminating the relatively poor quality literature, sensitivity analysis was conducted again to assess the stability of the merged results. Qualitative analysis of publication bias of funnel charts was performed for more than 10 studies with outcomes.

The literature screening flow chart was shown in Figure 1.

A total of 17 case-control studies were included, all of which were retrospective studies, including 1096 patients in the experimental group and 1554 patients in the control group. A total of 11 cohort studies were included, all of which were prospective studies, including 291 patients in the trial group and 407 patients in the control group, 3 randomized controlled trials, including 67 patients in the experimental group and 53 patients in the control group. The postoperative cardiac function indexes and postoperative complications were shown in Table 1.

According to the Newcastle-Ottawa Scale (NOS), the cohort study and case-control study literature were evaluated according to the type of study with Methodological Quality Assessment, the quality evaluation method recommended by the Cochrane System Evaluation Manual, use for the quality of the literature of randomized controlled trials was evaluated in Table 2- 4.

The combined effect of the two groups [SMD=-0.65, 95% CI (-1.09, -0.22), P=0.003], the random effect model meta-analysis showed statistically significant differences, indicating that the complete retention of the subvalvular apparatus group was better than the posterior subvalvular group. 11 case-control studies were included. There was significant difference between the two groups after the combined effect. Five cohort studies were included, and there was no statistically significant difference after the combined effect between the two groups. Two randomized controlled trials were included, and there was no statistically significant difference after the combined effect between the two groups Figure 2.

The combined effect of the two groups [SMD=-0.88, 95% CI (-1.42, -0.35), P=0.001], the random effect model meta-analysis showed statistical differences, The results showed that the complete preservation of subvalvular apparatus group was superior to the preservation of posterior subvalvular structure group. Four case-control studies were included, and the combined effect of the two groups showed statistically significant differences. Two cohort studies were included, and the difference between the two groups showed statistically significant differences. A randomized controlled trial was included and the difference was not statistically significant Figure 3.

The meta-analysis results of left ventricular ejection fraction at Postoperative 6 months, left ventricular ejection fraction at Postoperative 12 months, left ventricular ejection fraction at Postoperative 6months, left ventricular ejection fraction at Postoperative 12 months, left ventricular fractional shortening at Postoperative 6 months, early postoperative mortality, left ventricular rupture have statistical significance Table 5.

The left ventricular end-diastolic diameter, the left ventricular end-systolic diameter, early postoperative mortality were included in more than 10 case-control studies in Postoperative 6 months and the funnel plot analysis was published. The results showed that the studies were distributed in the funnel. The two sides were basically symmetrical. A few studies were located outside the funnel, this suggests that the publication bias of this study may be small.

Excluding the outside of the funnel plot and the study with poor quality of the index, left ventricular end-diastolic diameter and left ventricular end-systolic diameter postoperative 6 months, The results of each outcome index did not reverse, suggesting that the results were stable Table 6.

Complete preservation of the mitral valve leaflet and subvalvular apparatus and retention of the posterior leaflet and its subvalvular apparatus are two surgical methods for mitral valve replacement retaining the subvalvular apparatus. Current studies on cardiac function and complications due to different preservation of subvalvular apparatus are inconsistent. This article mainly expands the sample size, which improves the effect quantity estimation and makes the conclusion more comprehensive and accurate, so as to evaluate the difference of postoperative cardiac function and complications between the two surgical methods. Thirty-one studies were included; a total of 3468 patients, 17 case-control studies, 11 cohort studies and 3 randomized controlled studies.

The main indicators of this systematic evaluation include postoperative cardiac function indicators and complications. In terms of left ventricular end-diastolic diameter, left ventricular end-systolic diameter and left ventricular ejection fraction, the combined effect of postoperative 6 and 12 months showed that the complete preservation of subvalvular apparatus group was superior to the preservation of posterior subvalvular apparatus group. In terms of left ventricular fractional shortening, there was no statistical difference between the two surgical methods postoperative 6 months. In terms of postoperative complications, the combined effect of postoperative early mortality and left ventricular rupture showed that the fully preserved subvalvular apparatus was lower than the retained posterior subvalvular apparatus.

SáMPBDO et [35] performed a meta-analysis of the structure of fully preserved and partially preserved mitral valve structures. A total of 1535 patients in eight research centers were included. Data of 30-day mortality, low cardiac output syndrome and left ventricular ejection fraction were extracted and analyzed. Finally, there was no statistical difference. There were no significant differences in 30-day mortality, low cardiac output syndrome and left ventricular ejection fraction between the complete preservation and posterior subvalvular apparatus. This article only included data from 8 foreign research centers, which was not included in the Chinese data study, the results of early postoperative mortality and left ventricular ejection fraction were inconsistent. The literature included in this paper was the data of several national research centers. The sample size of the included literature was larger. The outcomes of the extraction included: postoperative left ventricular end diastolic diameter, left ventricular end systolic diameter, left ventricular ejection fraction, Early postoperative mortality and left ventricular rupture made the outcome indicators more comprehensive, the evaluation was more adequate, and the evidence was more reliable.

According to the systematic review, the two surgical methods showed that the complete preservation was superior to the retained posterior subvalvular apparatus after longterm follow-up. The postoperative complications of the fully preserved subvalvular apparatus were better than the posterior subvalvular apparatus. Therefore, for patients undergoing mitral valve replacement, it is suggested that the surgical procedure of the complete preservation of subvalvular apparatus should be selected under the same conditions. Which preserves the normal physiological structure of the heart, maintains the left heart function, and reduces postoperative complications.

The overall quality of this paper is fine. Random effect models are used in all cases. The meta-analysis of more than 10 studies has done a funnel plot for publication bias analysis. The comprehensive analysis shows that the meta-analysis results are scientific and reliable. For the outcome Indicators, the sensitivity analysis was carried out. After excluding the outside of funnel diagram and the poor quality of research, the results were not reversed, which showed that the results were stable.

The limitations of this study, Some of the studies included in the literature have a small sample size, meanwhile the casecontrol study are retrospective studies, the existence of recall information bias and confounding factors, which will affect the authenticity of the meta-analysis results, it is recommended that Prospective cohort studies and randomized controlled trials should be performed to improve the quality of the study. Are there racial and regional differences in the studies included in the literature for many countries. Because of the lack of longer followup data in the included literature, it is impossible to evaluate the results of longer follow-up.

In summary, long-term follow-up of mitral valve replacement showed that complete preservation of subvalvular structure was superior to preservation of posterior subvalvular structure in left ventricular function and complications. In view of the limitations of this systematic review, more high-quality and large-sample prospective studies are expected to provide more reliable evidence for the clinic.

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