4.Discussion
Detachment of the septal leaflet of tricuspid valve was first attempted by Hudspeth and colleagues in 1962 to achieve optimal visualization of VSD in surgical repair15. And in the last few decades several studies applied TVD techniques to repair hard-to-expose VSD sites, but the majority of which were single institution cohort studies with limited sample sizes and high risk of bias.
This meta-analysis was designed to evaluate and compare important procedural and clinical outcomes after VSD repair using TVD and non-TVD techniques. To date this is the most comprehensive comparative analysis focusing on the efficacy and safety of TVD in surgical repair of VSD. This analysis has drawn to the following conclusions. Firstly, TVD prolongs CPB time and cross-clamp time compared with non-TVD techniques in VSD repair surgeries. Secondly, no significant difference exists in LOS, length of ICU stay, postoperative atrioventricular block, implantation of pacemakers, incidence of ≥mild TR postoperatively and at discharge, as well as incidence of ≥small residual VSD after surgery and during follow-up. Thirdly, application of TVD increases the risk of TR during follow-up.
There have been worries that prolonged CPB and cross-clamp time during surgeries using TVD techniques may harbor additional ischemic damages, and that a more complicated technique may do harm to the conduction system and change the geometry of the heart. However, our meta-analysis has shown that although TVD procedure requires longer CPB and cross-clamp time to be completed, it did not result in any significant differences in clinically relevant outcomes except incidence of TR during follow-up compared with non-TVD procedures. The following factors may contribute to this finding. As has been exemplified in the study led by Sasson11, most included studies allocate patients into TVD group under strict criteria to maximize patients’ benefit from TVD: (1) multiple tricuspid valve chordal arrangement obscuring the margins of the defect; (2) tricuspid valve aneurysm that precludes easy access to the defect; and (3) high position of the defect with outlet extension requiring excessive traction on the tricuspid valve leaflet for exposure. During surgery, an incision parallel to the atrioventricular groove on the right atrium was suggested to reduce the risk of damaging the conduction system. In addition, marking sutures was used at the beginning and end of the detachment to enhance positioning accuracy. After closure, cold saline was injected into the ventricle to assess TV leaflet competence and coaptation, and reoperation was applied immediately should any issues occur.
As for why the incidence of TR is relatively high in the TVD group during follow-up, to date no studies have raised concerns on this topic. We speculate that the reason may be Prolene sutures used to reattach detached leaflets or chordae gradually become incompatible to the healing and renewing tissue. In addition, minor errors during reattachment after TVD maybe amplified by the change of heart size and adapting hemodynamics. This result serves as a reminder that achieving separation of the body and lung circulations should not be the only goal of VSD closure, mitigating trauma to the myocardium and preservation of heart geometry should also be surgeons’ main consideration4.