Perfusion strategies and aortic clamping techniques for right mini-thoracotomy mitral valve surgery (MVS) have evolved over time; since the first video-assisted mitral valve (MV) repair performed by Alain Carpentier in 1996, new technologies and operation-specific methods have been introduced.1
Concomitantly, several centers all over the world have adopted this approach and have developed experience in this challenging field. Excellent short- and long-term results have been reported: right mini-thoracotomy MVS has established early and long-term mortality and valve function results comparable with those of the conventional sternotomy approach, as well as less pain, less blood loss, less transfusions, and re-explorations for bleeding, a trend toward shorter hospital stay, faster recovery, less use of rehabilitation resources, and overall healthcare savings.2,3
Despite these encouraging reports, broad adoption of the right mini-thoracotomy approach is still limited. A report from The Society of Thoracic Surgeons indicates that this approach is performed only in 20% of the overall isolated MV procedures.2 This limited compliance might be explain by the fact that the transition from the traditional approach to the right mini-thoracotomy approach requires demanding training and a challenging learning curve for surgeons, anesthesiologists, perfusionists, and scrub nurses and that investments in video assistance platforms, surgical instruments, and perfusion cannulas are required.4
Moreover, there is still debate regarding the rate of neurological events associated with the right mini-thoracotomy approach and regarding the role of perfusion strategies and clamping techniques in the occurrence of this complication.5,6
Several studies have suggested that retrograde arterial perfusion (RAP), particularly in patients with severe peripheral vascular disease, could be related to the potential drawback of neurological complications in right mini-thoracotomy MVS.5,6 Grossi et al.5 claimed that the only significant risk factor for neurological events during right mini-thoracotomy MV repair was the use of RAP in patients with severe peripheral vascular disease. Comparable results were reported also by Murzi et al.6 in a series of 1280 minimal access MVS: the use of RAP contributed to a 4.28-fold increase in the risk of stroke.
The different aortic clamping techniques have also been extensively reviewed. The standard set-up uses RAP through the femoral artery and endoaortic balloon clamping (EAC) or transthoracic aortic clamping (TTC). In the EAC, aortic occlusion and cardioplegia delivery are obtained through an endoluminar balloon catheter (Intraclude, Edwards Lifesciences Corp., Irvine, CA USA); in the TTC, aortic occlusion is obtained through a transthoracic direct clamping and a separate line into the ascending aorta is used for cardioplegia delivering.
The EAC setting has reported good results particularly in the subgroup of patients with previous cardiac operations.7 Concerns regarding neurological events within this setting are mainly related to the use of RAP and retrograde balloon manipulation in case of aortoiliac atheromatous disease.3,6,8
Different centers support the use of TTC to avoid retrograde balloon manipulation, even if it requires more demanding dissection to allow external clamp positioning and a separate line into the ascending aorta for cardioplegia.8 A subgroup revision of the International Society for Minimally Invasive Cardiothoracic Surgery showed that the increased risk of neurological complications in the minimal access approach appeared driven by a higher stroke rate in those studies reporting the EAC setting and not the TTC setting.9 A meta-analysis by Cheng et al.3 documented a 1.79-fold increase in the relative risk of stroke with the right mini-thoracotomy approach compared with the standard sternotomy approach, but on subgroup analysis, this appeared driven by a higher stroke risk in those studies reporting EAC.3
These findings are in contrast with more recent reports that demonstrate the safety of the EAC.4,8 A study performed by Barbero et al.7 on 460 consecutive patients who underwent right mini-thoracotomy MVS through three different approaches—RAP with EAC (247, 53.7%) or with TTC (150, 32.6%), and direct ascending aorta cannulation and EAC with the Endodirect (ED) setting (63, 13.7%)—showed that with a correct preoperative assessment and allocation to the most appropriate setting, the rate of early mortality and stroke is low and comparable between the different strategies: overall, no cases of aortic dissection were reported; no differences in terms of stroke rate (1.7% in the EAC, 2% in the TTC, and no cases in the ED group, P) and 30-day mortality (2.1% in the EAC, 2.7% in the TTC, and 1.6% in the ED group, P) were reported. Logistic regression model showed no influences of arterial perfusion and aortic clamping techniques on 30-day mortality and stroke.7 A multicenter study on right mini-thoracotomy MVS with the EAC setting carried on by Casselman et al.4 supported this suggestion with a stroke rate of 0.8% (4 of 500 patients) and no aortic dissections.
There are several possible explanations for the discrepancies reported, such as retrospective comparisons of small cohorts with baseline differences, different study periods with different cannulae and clamping devices (Endoreturn vs. Intraclude balloon; Edwards Lifesciences Corp., Irvine, CA USA), lack of peripheral vascular disease assessment during the preoperative screening, and different methods of deairing. The level of experience of the center and its learning curve may also play a critical role in achieving effective and safe results. Indeed, a recent European multicenter report collecting data from high-volume institutions with extensive experience in minimal access MVS and EAC setting showed neurological outcomes completely comparable with those of the standard sternotomy approach—major stroke occurred in 4 (0.8%) of 500 patients.10
Fibrillating or beating heart MVS avoids aortic clamping and manipulation of the ascending aorta; however, the safety of deairing can be questioned. The Society of Thoracic Surgeons database shows that fibrillatory arrest carried itself an adjusted threefold higher risk of stroke if compared with aortic cross-clamping.2
The EndoDirect cannula completes the alternative strategies of cannulation and perfusion for minimal access MVS, avoiding the limitations and the morbidity of a peripheral approach. Particularly, it allows antegrade flow, which is mandatory in case of severe peripheral arterial disease to prevent arterial injuries, aortic dissection, and strokes.5 Despite the fact that the production of the EndoDirect cannula has been suspended for regulatory reasons, recent reports underline that it is, definitely, a useful and safe tool to extend right mini-thoracotomy MVS also to high-risk patients.
Current evidence in this field shows that with a proper preoperative assessment of the patient—in terms of past medical history, comorbidities, and anatomy—and a following allocation to the most appropriate approach, the overall rate of neurological events in right mini-thoracotomy MVS is low and comparable between different strategies. Therefore, to guide the patient toward the safest approach, it is paramount to have a full preoperative screening (computed tomography scan or angiography) particularly based on the anatomy of the aortoiliac-femoral vessels. These data allow the surgeon to allocate the patient to the safest perfusion and aortic clamping setting.
In our opinion, all the settings available must be part of a safe right mini-thoracotomy program, and surgeons dedicated to it must be confident with all of them. In this way, the different perfusion and aortic clamping techniques can really be tailored to the individual patient to achieve the best possible clinical outcome.
1. Carpentier A, Loulmet D, Carpentier A, et al. Open heart operation under videosurgery and minithoracotomy. First case (mitral valvuloplasty) operated with success. Comptes Rendus de l'Academie des Sciences III
2. Gammie JS, Zhao Y, Peterson ED, et al. Less-invasive mitral valve operations: trends and outcomes from the Society of Thoracic Surgeons Adult Cardiac Surgery Database. Ann Thorac Surg
3. Cheng DC, Martin J, Lal A, et al. Minimally invasive versus conventional open mitral valve surgery: a meta-analysis and systematic review. Innovations
4. Casselman F, Aramendi J, Bentala M, et al. Endoaortic clamping does not increase the risk of stroke
in minimal access mitral valve surgery: a multicenter experience. Ann Thorac Surg
5. Grossi EA, Loulmet DF, Schwartz CF, et al. Evolution of operative techniques and perfusion strategies for minimally invasive mitral valve repair. J Thorac Cardiovasc Surg
6. Murzi M, Cerillo AG, Miceli A, et al. Antegrade and retrograde arterial perfusion
strategy in minimally invasive mitral-valve surgery: a propensity score analysis on 1280 patients. Eur J Cardiothorac Surg
7. Barbero C, Marchetto G, Ricci D, et al. Minimal access mitral valve surgery: impact of tailored strategies on early outcome. Ann Thorac Surg
8. Mazine A, Pellerin M, Lebon JS, et al. Minimally invasive mitral valve surgery: influence of aortic clamping
technique on early outcomes. Ann Thorac Surg
9. Falk V, Cheng DC, Martin J, et al. Minimally invasive versus open mitral valve surgery: a consensus statement of the International Society of Minimally Invasive Coronary Surgery (ISMICS) 2010. Innovations
10. Barbero C, Krakor R, Bentala M, et al. Comparison of endoaortic and trans-thoracic aortic clamping
in less-invasive mitral valve surgery. Ann Thorac Surg