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.