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.