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State of the art for approaching the mitral valve: sternotomy, minimally invasive or total endoscopic robotic?

Mitral valve surgery (MVS) has continuously evolved over the past decades. Indications, repair techniques and surgical approaches represent the most important revolutions of the MVS. Mitral valve replacement has been considered the treatment of choice for mitral valve disease for many decades. Despite initial criticisms, repair is now considered the standard of care of most mitral valve diseases as a number of studies have demonstrated its superiority over replacement, in terms of mortality, morbidities and long-term results, while reducing the risk of infective endocarditis, thromboembolism events and bleeding complications related to anticoagulation [1, 2]. Median sternotomy is the common surgical approach for heart surgery. It provides excellent exposure to the heart and great vessels, allows central arterial and venous cannulation for cardiopulmonary bypass and guarantees a good myocardial protection. The operation can be performed precisely and expeditiously and if complications occur, the surgeon may have direct access to the heart. MVS has been performed through median sternotomy for more than 30 years and the clinical outcomes have significantly improved in the past years, despite gradual increase in patient age and overall risk profile. Recent data reported from STS database showed an overall operative mortality for isolated mitral valve repair of 1.2% and a 0.6% in asymptomatic patients [3]. Freedom from reoperation is very high in the setting of degenerative mitral valve disease, as Carpentier et al. have demonstrated a freedom from reoperation of 95% at 15 years [4]. Despite these excellent results, less-invasive procedures have been developed as an alternative to the conventional technique to reduce the surgical trauma and preserve the same quality, safety and efficacy of the full sternotomy approach. The term ‘minimally invasive’ refers to a small chest wall incision that does not include a full sternotomy [5]. The most common minimally invasive MVS (MIMVS) approach is the right minithoracotomy, followed by the lower ministernotomy. Potential benefits of the MIMVS approach are less surgical trauma and postoperative pain, better respiratory function due to the preservation of the sternum, faster recovery and better cosmesis. Compared with conventional procedure, several meta-analyses have shown that MIMVS is associated with low mortality and excellent postoperative outcomes [6, 7]. Specifically, MIMVS has the advantage of reducing bleeding, blood product transfusion, atrial fibrillation, sternal wound infection, ventilation times, intensive care unit, hospital length of stay as well as to reduce the time to return to normal activity. These benefits are even more evident in the setting of redo surgery [8]. At the last EACTS meeting held in Milan, we presented our 10-year experience on over 1600 patients undergoing MIMVS for any mitral valve disease, showing an overall mortality rate of 1.1%, a 95% rate of mitral valve repair in the setting of degenerative mitral valve disease and a freedom from reoperation of 94% at 10 years (Fig. 1). Despite these excellent results, many criticisms still remain regarding MIMVS. Traditionalists have claimed that MIMVS is technically more complex, requires dedicated instruments and reduces the rate of mitral valve repair. Despite the learning curve (generally at least 25 cases), results from experienced centres have confirmed that right minithoracotomy or ministernotomy approach is a safe and reproducible technique, can be taught successfully to cardiac trainees and enable excellent repairs, even in the setting of mitral valve Barlow disease [9–11]. A second criticism are related to morbidities associated with peripheral arterial cannulation in terms of neurological events, pseudoaneurysm and wound infections. In a meta-analysis of over 12 000 patients, Cheng et al. concluded that MIMVS was associated with higher incidence of stroke, aortic dissection and groin complications and phrenic nerve palsy [7]. We previously highlighted the importance of antegrade perfusion and the use of a CO2 line in reducing neurological complications and postoperative delirium [12]. Our preference is the direct aortic cannulation, which allows a more direct and physiological flow to the brain and reduces morbidities related to the groin cannulation. In addition, the use of direct aortic clamping in favour of balloon endoclamp has definitively reduced the rate of aortic dissection. To avoid phrenic nerve palsy, it is mandatory to identify the phrenic nerve after thoracotomy and the pericardium should be opened at least 3–4 cm above it. Third criticism is related to the cost of the surgical instrumentations and optical devices. Although these devices are more expensive and are not required in standard sternotomy, the low rate of complications and the faster recovery associated with the minimally invasive procedures