Less is Mohr - Minimally Invasive Mitral Valve Surgery
23 February 2017
23 February 2017
07 April 2017 (online)
The history of the Heart Center in Leipzig is rich in contributions to the evolution of mitral valve repair and replacement. As early as 1996, and within 2 years of its existence, a minimally invasive mitral valve program had been established there. The so-called port-access technique originally invented and engineered in Stanford, California, United States, included a perfusion platform for femoro–femoral cannulation, intra-aortic balloon occlusion, a percutaneous retrograde cardioplegia delivery system, and a pulmonary artery vent. A specially designed set of long-shafted instruments completed the port-access system, which allowed access to the mitral valve through a very limited right thoracotomy. After extensive training in animals, the procedure was performed in humans in a “CE” certification trial in Leipzig. Along with the proof of concept that the procedure was feasible and good repairs were achieved without a median sternotomy, at the same time several severe complications immediately dampened the initial enthusiasm. The initial series revealed a dismal clinical outcome with a 9.8% mortality and a high incidence of iatrogenic aortic dissection that could be largely attributed to the relatively stiff catheter system in conjunction with retrograde perfusion. When these data were first presented at the 77th Annual Meeting of The American Association for Thoracic Surgery in May 1997, the audience was thrilled by two facts: first Friedrich Mohr showed the feasibility of a true minimally invasive approach, but at the same time he honestly admitted the procedural risks and limitations of the technique. In the subsequent discussion, some judged Friedrich Mohr as an irresponsible and technically inferior surgeon while others, among them later friend and mentor Randolph Chitwood, acknowledged the pioneering effort and the courage it took to present these data truthfully. This landmark presentation held early in his career as the chief of a largely unknown hospital in former East Germany laid the foundation for the great respect among his peers and created the branding of the Heart Center as a center promoting innovation in conjunction with a sound evaluation of technologies.
As soon as 2 years after the first successful attempt of a minimally invasive mitral valve repair, the procedure had been standardized and was performed on a daily basis. At the same time, a voice-controlled robot was introduced as a camera holding device to allow seamless steering of the endoscope. Initially used in laparoscopic procedures the AESOP 3000 was used to enable “solo mitral valve surgery.” This was arguably the first report of “robot-assisted cardiac surgery.” At East Carolina University, Randolph Chitwood and his team had meanwhile developed a transcutaneous aortic clamp to facilitate minimally invasive mitral surgery. This technique simplified the procedure and was rapidly adopted by the team in Leipzig, which now got the attention of referring cardiologists throughout Germany as an emerging center for mitral valve repair.
While limited access surgery continued to evolve the focus was also on refining repair and replacement techniques. Together with von Oppeln, a new technique for chordal replacement, the so-called “loop”-technique was developed ([Fig. 1]). This technique followed a philosophy of “respect rather than resect,” which was later adopted and modified by many surgeons. In 2008, Kuntze et al reported the outcomes of 632 patients who underwent mitral valve repair using the premeasured loop-technique. In the same year, the results of a randomized controlled trial comparing this technique with standard resection techniques for P2-prolapse showed improved leaflet coaptation with the loop technique.
While trying to improve mitral valve repair the Leipzig group also participated in several valve replacement trials. Among them, a chordally supported stentless mitral valve replacement preserving the atrioventricular continuity was explored.
The millennium marked the event of total endoscopic computer enhanced “robotic” surgery. California-based Intuitive Surgical, Inc., Sunnyvale, USA, had developed a telemanipulator which was able to transfer six degrees of freedom of motion of the human wrist into the tip of remotely controlled instruments. For the first time, this masterpiece of engineering allowed wrist-like motion through a trocar. Together with the team of Prof. Carpentier and Dr. Loulmet in Paris, the Leipzig team systematically explored the potential of telemanipulator-assisted surgery ([Fig. 2]). After extensive animal and cadaver research, the first commercially available Da Vinci system was installed at the Heart Center in Leipzig and used for endoscopic mitral valve repair procedures ([Fig. 3]). In 2001, the group reported the outcomes of the first 148 patients undergoing this kind of surgery in Leipzig, then the largest series in the world. The article documented the feasibility and safety of minimally invasive mitral valve repair using remotely controlled instruments with six degrees of freedom along with three-dimensional (3D) endoscopic vision. In the following years, many surgical groups visited Leipzig to learn the technique of robotic surgery.
Meanwhile, minimally invasive techniques became routine and indications were expanded also to reoperations. The concept of avoiding reentry injury, extensive dissection of the heart and protecting patent grafts allowed for safe access to the mitral valve. In 2002, the outcomes of the first series of 39 patients undergoing minimally invasive mitral valve repair or replacement in a redo setting were reported. In 2009, the group again reported excellent outcomes in 181 patients undergoing redo surgery using the minimally invasive access. The technique was further expanded to treat functional mitral insufficiency in patients with cardiomyopathies and severely impaired left ventricular function as well as treating concomitant tricuspid regurgitation and atrial fibrillation. In 2008, Seeburger et al published the outcomes of 1,536 patients who had undergone minimally invasive mitral valve surgery in Leipzig. This was one of the largest series worldwide and demonstrated the evolution of this procedure into a routine operation. Further analysis revealed repair rates of over 90% for all pathologies including anterior and bileaflet prolapse with excellent long-term outcomes. Special reports on anterior leaflet repair and the special considerations of a minimally invasive approach in Barlow disease were subsequently published.  In 2012, the reported cohort included already more than 3,000 patients.
Along with the positive outcomes, the Leipzig group continued to raise awareness for potential pitfalls and problems and shared also the negative aspects of new techniques. A systematic analysis of circumflex coronary artery injury during mitral interventions, an underreported problem, got a lot of attention. In 2013, Holzhey presented a landmark article in circulation discussing the impact of individual surgical experience on outcomes of minimally invasive mitral valve repair. By analyzing the outcomes of 17 surgeons who had trained at the Heart Center in Leipzig and using CUSUM (cumulative sum) analysis he could show that a minimum number, frequency, and differences in talent determine the outcomes of this procedure.
With smaller access and more sophisticated repair concepts becoming routine the need for advanced imaging became obvious. The Leipzig group was among the first to explore the added benefits of 3D echo which initially was not real-time and required long acquisition and reconstruction times. With the evolution of the technique methods for augmented reality for advanced procedural planning were developed using ring templates superimposed on 3D echo data. 
As a pioneering center in transcatheter aortic valve implantation (TAVI) very early in the experience, the feasibility of minimally invasive transapical repeat valve-in-valve (VinV) and valve-in-ring implantation was systematically developed via a retrograde transapical and an antegrade transatrial approach.   This groundbreaking work, led by Walther and Kempfert, laid the foundation for transcatheter VinV therapy. The experiments were performed in the on-site experimental hybrid suite, which had been installed at the Leipzig Heart Center to facilitate research in the field of transcatheter techniques. Mohr had anticipated the potential of these techniques and wanted the center to be prepared as a preclinical and clinical teaching facility long before TAVI entered the clinical arena. The experimental hybrid suite was subsequently used by many surgical groups to train transcatheter techniques and became a cornerstone of the Leipzig Heart Center research and teaching facility.
In 2012, the next evolutionary step in minimizing the surgical trauma of mitral valve repair was achieved with transapical neochord implantation on the beating heart, first experimentally and later in clinical practice as the leading center of the TACT (Transapical Artificial Chordae Tendinae) trial.  It was also soon recognized that transcatheter techniques were entering the mitral arena and must be mastered by surgeons. As a result, surgeons in the Leipzig team resumed an active role in percutaneous repair and replacement techniques.
In close collaboration with national and international leaders as well as industry, countless innovations and modifications in technology and techniques have been developed for mitral valve disease at the Heart Center in Leipzig. The major contribution, however, was the constant effort to train surgeons in-house and from other institutions in mitral valve repair. Several courses, countless live transmissions to major meetings, including the EACTS Techno College (EACTS House, United Kingdom), and an active fellowship program have helped to spread the Leipzig school of mitral valve surgery nationally and internationally.
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