Discussion
Minimal access cardiac surgery has undergone continuous development over
the past twenty years and has become in certain settings the gold
standard for the treatment of atrioventricular valve pathologies.
Several institutional have reported outstanding results as a minimally
invasive surgical approach provided to be safe and effective, and
propensity matched studies showed comparable early and mid-term results
between right mini-thoracotomy access and conventional sternotomy
approach [8][9][10][11]. However, all these experiences
collaterally highlighted that patients in sternotomy surgery cohorts had
a higher preoperative risk score and a higher prevalence of redo
procedures, rheumatic disease and mitral valve replacement. Furthermore,
patients who underwent cardiac surgery through sternotomy were more
likely to receive an associated procedure involving the tricuspid valve.
Our experience suggest that the performance of tricuspid valve surgery
through a minimally invasive approach is safe and effective.
In our practice, the reasons favouring a sternotomy approach were
limited to the presence of pleural adhesions from previous thoracic
operations, severe peripheral arterial disease, or active endocarditis
with abscess involving the mitro-aortic continuity. During the study
period, more than 95% of surgical operations on atrioventricular valves
have been performed through a right mini-thoracotomy access and in 20%
of the cases they included a combined procedure on mitral and tricuspid
valves [12]. Recent guidelines recommend intervention for severe
symptomatic tricuspid valve regurgitation at the time of left-side heart
valves operation (ACC and ESC) and in case of severe primary tricuspid
regurgitation in patients who are symptomatic despite an optimal medical
therapy (ESC). There is still a big gap in knowledge regarding the
benefit associated with tricuspid valve intervention and its timing,
however, an untreated moderate/severe TR has been associated with a
worse survival both in primary tricuspid valve regurgitation or in case
of tricuspid disease secondary to mitral dysfunction. Tricuspid valve
surgery has been increasingly performed during the last decade, however
it is still associated with high early mortality (8-10%) and morbidity
rate and long period of hospitalisation [13]. A minimally invasive
approach aiming a less invasive access and a faster recovery could be
beneficial in this frail and comorbid patients but few reports in
literature have focused on mini thoracotomy tricuspid valve surgery
[14] [15].
Our data showed the minimally invasive approach has been safe and has
shown good results. The times of mechanical ventilation and ICU stay are
in line with the values reported in the literature. Although
neurological complications are present in a small number of cases, 3
patients (4%) are an element still present in valve surgery, in our
experience they have mostly occurred with the use of endo-aortic
clamping with endo-clamp. Despite the presence of a share of blood in
the right atrium, the visualization of the tricuspid valve was optimal,
the echocardiographic results at discharge and follow-up are
satisfactory, shows an efficacy of the surgical technique performed.
External snaring of the caval veins is commonly performed before the
opening of the right heart chambers. This manoeuvre can be hazardous
through a right mini thoracotomy approach, especially in presence of
frail tissue or in case of redo procedure as bleeding control can be
challenging or impossible without conversion to sternotomy. Previous
reports have underlined this technical issue and described alternative
solutions of management of the venous drainage without the external
snaring of the caval veins. Murzi et al. reported in 2009 their
experience with a single two-stage femoral venous cannula able to
provide a satisfactory drainage directly from the superior and inferior
caval vein. In seventeen redo cases, this strategy allowed a
satisfactory venous drainage while opening the right atrium without
snaring the caval veins [16]. The same group confirmed these results
on a larger scale reporting the safety and effectiveness of using a
double-stage femoral venous cannula with two distal perforated sections
separated by a nonperforated segment of 15 cm in length in
right-minithoracotomy surgery requiring the opening of the right atrium
without occluding the venae cavae [17]. A similar solution with a
single-stage femoral venous cannula was described by Peng et al as they
reported a successful CPB management and surgical repair of tricuspid
valve in 8 patients who underwent redo surgery through a right
minithoracotomy approach [18]. A different trick has been proposed
in 2011 by Sansone et al. reporting an internal occlusion of the two
caval veins by a Foley catheter in 3 redo cases of combined mitral and
tricuspid valve surgery [19]. This technique has been subsequently
developed by the same authors with the implementation of an endovascular
balloon catheter [20]. Dandolu et al. described in 2005 the
incidental observation that the opening of the right atrium without
caval snaring did not lead to air entry in the venous reservoir. They
further studied this finding on an animal model characterised by double
venous cannulation and no caval veins occlusion and reported that, after
the opening of the right atrium, the venous drainage remained
satisfactory with a minimal entering of air in the superior vena cava
[21].
In our experience no type of caval veins occlusion was used and all
procedures were performed with the usual setting of double venous
cannulation: surgical technique is simpler, there is a reduction in
tissue dissection, especially in reoperations, reducing the chances of
damage and bleeding. In mini-thorototomy the detection of bleeding and
its repair can be complex. Venous drainage should be modulated to
maintain a blood level in the right atrium below the tricuspidal valve
plane. In order to guarantee the visualization of the tricuspid valve in
all its parts we recommend that blood level should be approximately 1 cm
below the septal leaflet. Through the venous cannulas with active
drainage a mixture of air and continuous blood is guaranteed, this
allows that an air column does not form without blocking the
cardiopulmonary pump. The continuous passage of blood in the venous
circuit pushes the air bubbles from the cannula to the reservouir. For
this reason it is necessary to maintain a minimum level of blood in the
right atrium. Generally the mixture of air and blood is managed by the
active vacuum drainage, changing the sucking intensity. In the event
that the amount of air is excessive and causes a temporary letup of the
venous return, the surgeon can pull the draining tip of the cannula into
the inferior vena cava. This shift allows an increase in blood drainage
and a mobilization of air from the venous circuit to the reservoir.
Conclusions.
Our results show that performing tricuspid surgery without caval
occlusion is safe. The air was captured by the active vacuum drainage
system without causing damage. There is no clinical evidence of gas
embolism. Vacuum-assisted drainage in centrifugal pump could cause an
increase in wall stress on red blood cells but only in few cases
perioperative hematuria occurred without clinical repercussions.
Mid-term follow up data confirm that minimally invasive approach does
not alter the quality of surgery.