Mitral Valve Surgery by Means of Minimally Invasive Right Mini-Thoracotomy Compared with Standard Sternotomy: Technical Surgical Aspects, Clinical Results in the Current Era

Background. Surgical treatment of mitral insufficiency has undergone a radical change in the last two decades, changing from a predominantly or in most cases replacement to reparative surgery, based on the better knowledge of the pathophysiology of the valve insufficiency. Mitral valve surgery using conventional full sternotomy (MVS-FS) represents the standard approach. Despite this approach has shown excellent postoperative outcomes, in the last decade, minimally invasive mitral valve surgery, i.e., right mini-thoracotomy approach (MIMVS-RM), has gained consensus among surgeons as it can provide greater patient satisfaction as long as maintains the same quality and safety of the standard mitral valve surgery approach. According to a statement from the American Heart Association, the term “minimally invasive” refers to a smaller chest incision not including the full sternotomy. The rationale for its use is based on the fact that reducing the surgical invasiveness, the expected results should be excellent both in terms of mortality and morbidity, and for what concerns a faster recovery in the performance of the normal physical activities of the patient, with a consequent less use of rehabilitation resources and healthcare costs. However, some criticisms have been raised as minimally invasive surgery is technically more complex, requires a specific learning curve, and may be associated with serious complications, for example full sternotomy conversion for cardiac injuries, lack of adequate myocardial protection during cardiac arrest. Thus, on one hand MIMVS-RM has the rationale of being able to reduce postoperative hospitalization with a faster recovery of daily activities, and to offer an aesthetic advantage; on the other hand, full sternotomy allows a greater operative field for a safer response to the treatment of any intraoperative complications, a lower intra-operative cost and, consequently, a well-established safety. Objective of the investigation. The aim of the study is to highlight the differences between the two surgical approaches in terms of intra- and post-operative results, looking for possible limitations and advantages of both approaches (MIMVS-RM versus MVS-FS), by analyzing the results present in the literature, in particular focusing on cardiac surgery centers that perform a high volume of MIMVS-RM procedures. We will also analyze those obtained in the most recent five-year experience of our cardiac center of the Tor Vergata University of Rome, which has carried out a medium volume of MIMVS-RM procedures. Study. The study considered a sample of 152 patients, comparable for the preoperative characteristics, who performed mitral replacement or repair operations at our center from May 2014 to December 2018. Mitral valve surgery was done through a standard full sternotomy (MVS-FS Group or Group C, n = 106 patients) and the right mini-thoracotomy (MIMVS-RM Mitral Valve Surgery by Means of Minimally Invasive Approach 3 Group or Group Mini, n = 46 patients) and compared both intraoperative and postoperative results. Clinical results of our study in terms of operative mortality (1.9% vs. 2.2%, P = NS), postoperative complications, intensive care unit stay, need for blood product transfusion, release of cardiac enzymes, did not show substantial differences between the two types of approach (P = NS, for all comparisons). Operative surgical times were significantly longer in the MIMVS-RM Group (P < 0.001, for all comparisons). Interestingly, in the MIMVS-RM Group in comparison with Group C, mitral valve repair was more frequent than replacement with a biological or mechanical valve prosthesis (P < 0.01). Our data appear to be in line with those presented in the literature. The conversion rate in full sternotomy was 6.5%, but no intraoperative death occurred. In the last 7-month period (January-July, 2019) we are continuing to perform MIMVS-RM procedures, that currently represent about 20-25% of the total mitral valve surgery procedures performed at our center. Conclusion. The short-to-mid-term clinical results of the treatment of mitral valve disease by means of a right mini-invasive thoracotomy or by standard full sternotomy approach are substantially overlapping. The conversion of the right mini-thoracotomy into the full sternotomy should be safely performed in an emergency setting. In our experience, conversion has not been associated with an increase in surgical risk. However, larger randomized and retrospective observational studies with longer follow-up duration are needed to highlight any significant differences between the two types of surgical approach. At mid-term follow-up, MIMVS-RM procedures have shown satisfactory survival rate, freedom from operation and freedom from recurrent mitral regurgitation.