Robotic and Minimally Invasive Mitral Valve Surgery

Robotic Systems

Three-dimensional vision and seven degrees of freedom are optimal to manipulate and freely orient objects in a three-dimensional space, such as a body cavity. Consequently, standard endoscopic surgery with only two-dimensional vision and four degrees of freedom reduces accuracy, efficiency, and dexterity of movement. Human motor skill, specifically eye-hand coordination, deteriorates with the indirect observation and manipulation of instruments and tissues in endoscopic surgery. In addition, instrument shaft shear, or drag, necessitates higher manipulation forces by the surgeon, leading to hand muscle fatigue. The surgeon must reverse hand motions in endoscopic surgery because the fixed entry point (fulcrum effect), such as a trocar, makes it a motor skill set that is nonintuitive to learn. Computer-enhanced systems have been developed to overcome these and other limitations. Through telemanipulation, the surgeon operates from a console with a three-dimensional view of the operative field. The surgeon's movements are reproduced in a scaled proportion by instruments mounted on robotic arms inserted through the chest wall. The robotic arms and “micro-wrist” instruments mimic the human arm and wrist with seven full degrees of freedom. For cardiac surgery, a robotic telemanipulation system, the da Vinci Surgical System (Intuitive Surgical, Inc., Sunnyvale, CA), is currently available, with two different versions.

The da Vinci S Surgical System has three components: a surgeon console, a patient-side cart, and a vision cart. The surgeon console is separated physically from the patient and allows the surgeon to sit ergonomically with his or her head positioned in a three-dimensional vision system, arms at the side, and hands beneath the vision system. This natural eye-hand-instrument alignment replicates the experience of open surgery. The surgeon's analog finger and wrist movements, along with any tremor, are converted to digital signals by sensors in the console. The movements are scaled, whereby movements of the surgeon at the console are larger than movements of the instruments in the patient. The tremors are filtered and smoothed, which removes inherent human tremor with a frequency of 8 to 10 Hertz. This motion scaling and tremor suppression enhance precision at the tissue level. A clutching mechanism at the console, which temporarily disconnects the surgeon's and instruments' movements, enables readjustment of hand positions to maintain optimal ergonomics. The surgeon's movements are transferred to the patient cart digitally, where the instruments move synchronously through one of the four independent effector arms. For cardiac surgery, the arms are used to control the camera, the surgeon's left and right hands, and the atrial retractor. The vision cart houses the image-processing equipment and a large viewing monitor, which provides the operating room team, including the patient-side assistant, a view of the operative field. The three-dimensional vision system facilitates natural depth perception with high-power magnification (10×) via both 0-degree and 30-degree endoscopes.

The da Vinci Si Surgical System, the most recent version, incorporates dual-console capability, enhanced three-dimensional 1080i high-definition visualization, an updated user interface, and improved operating room integration. The dual-console feature supports training and collaboration by allowing two surgeons to sit at separate consoles and easily and quickly take control of the instruments at any time during surgery. Three-dimensional high-definition visualization with capability of 10× magnification increases viewing resolution, providing improved clarity and detail of the anatomic structures. The updated user interface with easy-to-use touchscreen controls simplifies intraoperative system and vision adjustments. Addressing the increasing trend toward operating room integration, vision system components traditionally housed in the vision cart can be installed on an operating room boom, and a multiple-input display allows viewing of up to three video sources, such as the operative field, ultrasound, and electrocardiogram (ECG), at one time.

Evolution of Robotic Cardiac Surgery

Initially, advances in minimally invasive surgery were based on modifications of previously used approaches performed under direct vision. Mini-sternotomies, partial sternotomies, parasternal approaches, and mini-thoracotomies simply reduced the size of the incisions and the degree of tissue manipulation. Advances in cannulation methods and video-optics opened the door for totally endoscopic robotic surgery.

The introduction of Port-Access technology (Cardiovations, Inc., Ethicon, Somerville, NJ) in 1996 combined a minimally invasive surgical approach (nonsternotomy) with total cardiopulmonary bypass and an arrested heart. The system provides extrathoracic cardiopulmonary bypass with a specialized set of endovascular cannulas and catheters to provide antegrade or retrograde cardioplegic arrest, and ventricular decompression. Encouraging results confirmed the feasibility and safety of these techniques and paved the way for the development of less invasive operations. Advances in video-optics started a wave of new endoscopic approaches in general, urologic, gynecologic, and orthopedic surgery. Video assistance in cardiac surgery was first used for closed chest internal mammary artery harvests and congenital heart operations. In 1996, Carpentier and colleagues performed the first video-assisted mitral valve repair using ventricular fibrillation via a mini-thoracotomy. Soon thereafter, Chitwood and coworkers performed a video-assisted mitral valve replacement using a microincision, percutaneous transthoracic aortic clamp, and retrograde cardioplegia.

Cardiac surgery entered the robotic age in 1997 when Mohr first used the AESOP (Intuitive Surgical, Inc., Sunnyvale, CA) voice-activated camera robotic arm in mitral valve surgery. In addition to freeing up the surgeon's hands during surgery, this device allowed for better valve and subvalvular visualization with even smaller incisions. In 1998, Chitwood performed the first video-directed mitral operation in the United States, using the voice-controlled AESOP 3000 robotic arm and a Vista three-dimensional camera (Vista Cardiothoracic Systems, Inc., Westborough, MA). The combination of robotic camera control and three-dimensional visualization was an essential step toward the totally endoscopic mitral operations performed today. The first mitral valve repair using an early prototype (the da Vinci articulated intracardiac wrist robotic device) of the present da Vinci robot was done by Carpentier and colleagues in 1998. The first complete repair in North America using the da Vinci system was performed by Chitwood and colleagues in 2000. A 4-cm incision was used for assistant access, but advancements in three-dimensional video and robotic instrumentation progressed to a point where totally endoscopic procedures were feasible. Lange and coworkers performed the first totally endoscopic mitral valve repair using only 1-cm ports with the da Vinci in 2000.

In contrast to mitral valve surgery, closed-chest (nonsternotomy) coronary artery bypass surgery could be performed only after the robotic telemanipulation system had been developed. Technically complex maneuvers, such as coronary anastomosis, could not be done with conventional thoracoscopic instruments because dexterity was lacking. Freedom of movement with the “endo-wrist” instruments, where additional articulation occurs within the patient near the tip of the instrument, was critical in achieving this goal. Early reports of success originated from several centers that were pioneering the effort. Although robotic coronary surgery has gained less traction than mitral surgery, today it can be performed safely with reproducible results at dedicated centers.

Clinical Applications and Patient Selection

The da Vinci robot is used for mitral valve repair and single-vessel coronary artery bypass. It is less frequently used for mitral valve commissurotomy and tricuspid valve repair. In our experience, patients are offered robotic mitral valve surgery if they meet strict criteria ( Box 84-1 ). Patients who have coronary artery disease or other valvular disease that would warrant surgery are excluded. Although tricuspid valve repair and coronary artery bypass graft surgery can be done using a robotic approach, the port placement and patient positioning are different. Mild aortic regurgitation (1+) or greater is also a contraindication because of the inability to reliably arrest the heart with retrograde cardioplegia alone. Patients with a prior sternotomy or right thoracotomy, or who have significant chest wall deformities that would limit access, are also excluded in our current practice, although there is some early experience with operations on such patients at other centers. Patients with a severely calcified mitral annulus are not candidates because decalcification requires further refinement of instruments and a more reliable means of evacuating any calcium that falls into the ventricle. Lastly, aortic, iliac, or femoral atherosclerosis greater than minimal, and femoral vessel diameter less than 7 mm, are relative contraindications; however, in such cases axillary perfusion may be substituted for femoral artery perfusion.