ROBOTIC TELEMANIPULATION SYSTEMS

Six degrees of freedom are required to allow free orientation in space. Thus, standard endoscopic instruments with only four degrees of freedom reduce dexterity significantly. When working through a fixed entry point, such as a trocar, the operator must reverse hand motions (fulcrum effect). At the same time, instrument shaft shear, or drag, induces the need for higher manipulation forces, leading to hand muscle fatigue.³ Also, human motor skills deteriorate with visual-motor incompatibility, which is associated commonly with endoscopic surgery. Computer-enhanced instrumentation systems have been developed to overcome these and other limitations. These systems provide both telemanipulation and micromanipulation of tissues in small spaces. The surgeon operates from a console, immersed in a three-dimensional (3D) view of the operative field, and through a computer interface, the surgeon’s motions are reproduced in scaled proportion through “micro-wrist” instruments that are mounted on robotic arms that are inserted through the chest wall. These instruments emulate human x–y–z axis wrist activity through seven full degrees of freedom.

Thus, robotic telemanipulation systems have helped to overcome the limitations of conventional endoscopic instruments. Originally invented to facilitate fine manipulations done under either remote or hazardous conditions, these machines are controlled by an operator working at some distance from a console. Connected mechanically or electronically through a controller panel, the operator’s motions direct the remote manipulator or end-effector. Tremor filtering and motion scaling enable dexterous manipulations to be done in confined spaces. For cardiac surgery there exists one robotic telemanipulation platform, the da Vinci (Intuitive Surgical, Inc., Sunnyvale, CA), with two different versions.

The da Vinci system is composed of three components: a surgeon console, an instrument cart, and a visioning platform. The operative console is removed physically from the patient and allows the surgeon to sit comfortably, arms resting ergonomically and head positioned in a 3D vision array. The surgeon’s finger and wrist movements are registered digitally, through sensors, in computer memory banks, and then these actions are transferred efficiently to an instrument cart, which operates the synchronous end-effector instruments. Through 1-cm ports, instruments are positioned near cardiac operative sites in the thorax, and the camera is passed via a 4-cm working port used for suture and prosthesis passage. Every analog finger movement, along with inherent human tremor at 8 to 10 Hz/sec, is converted to binary digital data, which are smoothed and filtered to increase microinstrument precision. Wrist-like instrument articulation emulates precisely the surgeon’s actions at the tissue level, and dexterity is enhanced through combined tremor suppression and motion scaling. A clutching mechanism enables readjustment of hand-positions to maintain an optimal ergonomic attitude with respect to the visual field. This clutch acts like a computer mouse, which can be reoriented by lifting and repositioning it to reestablish unrestrained freedom of computer activation. The 3D digital visioning system enables natural depth perception with high-power magnification (×10). Both 0-degree and 30-degree endoscopes can be manipulated electronically to look either “up” or “down” within the heart or thoracic cavity. Access to and visualization of the internal mammary artery, coronary arteries, and mitral apparatus are excellent.

The da Vinci S (Fig. 83-1) is an updated version that incorporates 3D high-definition visioning that increases viewing resolution, providing improved clarity and detail of anatomic structures. A fourth arm is now fully integrated and all instrument arms are smaller, providing better patient access. The patient cart is motorized, allowing rapid setup at the patient bedside. Ergonomics have been improved and interfaces have been streamlined to provide the latest in robotic telemanipulation systems.

Figure 83–1 A, Surgeon seated at the console of the da Vinci S. B, The instrument cart of the da Vinci S with four arms, three of which are labeled (1 to 3). The camera arm is in the center and not labeled. A, cross-clamp.

EVOLUTION OF ROBOTIC CARDIAC SURGERY

Initially, minimally invasive cardiac valve surgery was based on modifications of previously used incisions and performed under direct vision. Mini-sternotomies, parasternal incisions, and mini-thoracotomies were used in the first truly minimally invasive aortic valve operations.^4–6

Since its introduction in 1996 at Stanford University,^1,2 Port-Access (Cardiovations, Inc., Ethicon, Somerville, NJ) technology combined a minimal surgical approach (avoidance of median sternotomy) with total cardiopulmonary bypass and an arrested heart. The system provides extrathoracic cardiopulmonary bypass with a specialized set of endovascular cannulas and catheters that allow antegrade or retrograde cardioplegic arrest, as well as ventricular decompression. Initial encouraging results confirmed the feasibility and safety of these techniques and further advanced the next level of minimal invasiveness.

Advances in video-optics initiated a wave of new endoscopic approaches in orthopedic, urologic, general, and gynecologic procedures. Cardiac surgery has lagged behind these specialties in utilizing the benefits of video assistance because fine coronary anastomoses and complex valve reconstructions are the centerpiece of contemporary adult cardiac surgery. Nevertheless, video assistance was used first for closed chest internal mammary artery harvests and congenital heart operations.^7–9 Carpentier and colleagues performed the first video-assisted mitral valve repair via a mini-thoracotomy using ventricular fibrillation in February 1996.¹⁰ Three months later, our group at East Carolina University performed a mitral valve replacement using a microincision, videoscopic vision, percutaneous transthoracic aortic clamp, and retrograde cardioplegia.^11,12

In 1997, Mohr first used the AESOP (Intuitive Surgical, Inc., Sunnyvale, CA) voice-activated camera robotic arm in minimally invasive videoscopic mitral valve surgery, and cardiac surgery entered the robotic age.¹³ This technology enabled the use of even smaller incisions with better valve and subvalvular visualization. In June of 1998, our group performed the first video-directed mitral operation in the United States, using the voice-controlled AESOP 3000 robotic arm and a Vista (Vista Cardiothoracic Systems, Inc., Westborough, MA) 3D camera.^11,12 Visual accuracy was improved by voice manipulation of the camera by the operating surgeon. We now routinely use the robotic arm, endoscope, and a conventional two-dimensional (2D) monitor and have done more than 800 videoscopic mitral operations successfully with this method. The addition of 3D visualization, robotic camera control, and instrument tip articulation were the next essential steps toward a totally endoscopic mitral operation, in which wrist-like instruments and 3D vision could transpose surgical manipulations from outside the chest wall to deep within cardiac chambers.

Finally, by 1998, Carpentier performed the first mitral valve repair using an early prototype of the da Vinci articulated intracardiac “micro-wrist” robotic device.¹⁴ Two years later, our group performed the first complete repair of a mitral valve in North America using the da Vinci system.¹⁵ Using the articulated wrist instruments, a trapezoidal resection of a large P₂ was performed, with the defect closed using multiple interrupted sutures, followed by implantation of a #28 Cosgrove annuloplasty band. Although a 4-cm incision is still used for assistant access, advancements in 3D video and robotic instrumentation have progressed to a point where totally endoscopic mitral procedures are feasible. In fact, Lange and associates in Munich were the first to perform a totally endoscopic mitral valve repair using only the 1-cm ports with da Vinci.¹⁶

In contrast, minimizing incisions and performing closed-chest (or nonsternotomy) coronary artery bypass surgery could be done only once the robotic telemanipulation system had been developed. Conventional thoracoscopic instruments could not be used to perform technically complex maneuvers such as a coronary anastomosis secondary to the lack of movement in all three axes. The “endo-wrist” was critical in achieving this goal. Early reports of success originated from several centers that were pioneering this effort.^17–20 To date, only a few centers continue this work, and most recent contributions to the literature include case series and retrospective reviews. Robotic coronary surgery has gained less traction than mitral valve surgery. Future refinements in these devices will be needed to apply this new technology more widely.

CLINICAL APPLICATIONS/PATIENT SELECTION

In the development of any robotic cardiac surgical program, essential steps for each surgical operation (e.g., mitral repair, coronary artery bypass) should be learned and integrated in a stepwise fashion. This will allow the surgical team to build on its experience until the entire operation can be performed effortlessly. Furthermore, strict inclusion and exclusion criteria should be followed. In our initial experience, all patients had isolated mitral insufficiency without the valvular or coronary artery disease that might have required operative intervention (Box 83-1). Patients with a severely calcified mitral annulus were not candidates. Decalcification requires further development of instruments, as well as a reliable means of evacuating any calcium that falls into the left ventricle. Those with a previous right thoracotomy were excluded from the da Vinci procedures. Patients with mitral valve stenosis were excluded in the early trials of the U.S. Food and Drug Administration (FDA); however, patients treatable by commissurotomy would be suitable candidates for robotic repair. The improved visualization of the valve and subvalvular apparatus along with improved maneuverability of bladed microinstruments would facilitate performance of a commissurotomy.

SURGICAL TECHNIQUES

Preoperative and postoperative surface and transesophageal echocardiographic (TEE) studies should be done in every patient. Patients are anesthetized and positioned with the right chest elevated 30 degrees and with both arms tucked aside. Single left-lung ventilation is used for complete intrathoracic exposure.

Cardiopulmonary bypass is established at 28° C using femoral arterial inflow cannula (19 or 21 French) and kinetic venous drainage through a femoral (22 or 23/25 Fr) and right internal jugular vein (17 Fr) cannula in the majority of cases. If the femoral artery is too small or atherosclerotic, either a Bio-Medicus (Medtronic, Minneapolis, MN) or Directflow (Cardiovations, Inc., Somerville, NJ) cannula can be placed through a second interspace port for antegrade aortic perfusion. Sometimes the right axillary artery can be cannulated as well. A 3- to 4-cm inframammary incision is used, and a subpectoral 4th intercostal space (ICS) mini-thoracotomy is developed to provide cardiac access. The pericardium is opened under direct vision, 2 cm anterior to the phrenic nerve (Fig. 83-2). Antegrade cardioplegia is given by an aortic needle or vent placed either under direct vision or videoscopically. To minimize intracardiac air entrainment, the thoracic cavity is flooded continuously with carbon dioxide at 1 to 2 L/min via a 14-gauge plastic catheter. A transthoracic aortic cross-clamp (Scanlan International, Inc., Minneapolis, MN) is positioned in the midaxillary line via a 4-mm incision in the 2nd ICS, and intermittent antegrade cold blood cardioplegia is used to maintain cardiac arrest and myocardial protection. Under video-assisted guidance, the posterior tine of the clamp is passed through the transverse sinus with care taken not to injure the right pulmonary artery, left atrial appendage, left main coronary, or aorta. After cardioplegic arrest, a 3- to 4-cm left atriotomy is made medially to the right superior pulmonary vein, and, after valve inspection, positions for da Vinci left, right, and fourth arm port incisions are determined. The right trocar is placed in the 4th ICS posterolateral to the incision and parallel to the right superior pulmonary vein. Occasionally, the 5th ICS provides a better angle for the right robotic arm. The left trocar is generally placed 6 cm cephalad and medial to the right trocar, ensuring internal clearance between arms to avoid both external and internal conflicts. Optimal robotic arm convergence avoids left atrial wall tearing during instrument manipulations. The fourth arm is positioned 1 to 2 cm lateral to the right internal mammary artery and one intercostal space cephalad to the working port incision (Fig. 83-3). A “high-magnification” camera is used with a 30-degree, 3D endoscope placed through the medial portion of the mini-thoracotomy. The remainder of the incision is used as a working port for the assistant. Needles are retrieved using a long magnetic device, and suture remnants are removed from the surgical field using vacuum assistance.

Figure 83–2 The 4-cm working port incision. The pericardium is opened under direct vision. The mechanical retractor is removed later, when the patient cart is in place.

Figure 83–3 Operative setup with soft tissue retractor in place. Three trocars are in position; the robotic arms will be placed through them. The cross-clamp has been applied as well.

Operative procedures are performed from the surgeon’s console placed approximately 10 feet from the operating table but in the same operating room. The patient-side assistant changes instruments and supplies and retrieves operative materials. An annuloplasty band (Edwards Lifesciences, LLC, Irvine, CA) has most often been used to support repairs or provide annular reduction. In video-assisted robotic cases, early placement of annuloplasty sutures facilitates exposure during complex repairs. Exposure of each new suture often becomes predicated on retraction of the previous one. Leaflet resections, papillary muscle reconstruction, and cord insertions or transpositions should be performed after annular sutures are completed and suspended. In da Vinci cases, each suture is placed and tied intracorporeally. On completion of the repair, the left atrium is closed robotically. Thereafter, robotic arms are removed and standard de-airing and weaning procedures are performed under TEE control. Intraoperative time metrics are collected and cataloged in spreadsheets. One month after discharge, all patients return for a follow-up visit and a transthoracic echocardiogram.

CLINICAL OUTCOMES