Chapter 44. Minimally Invasive and Robotic Mitral Valve Surgery

Minimally invasive mitral valve surgery (MIMVS) does not refer to a single approach, but rather to a collection of new techniques and operation-specific technologies. These include enhanced visualization and instrumentation systems as well as modified perfusion methods, all directed toward minimizing surgical trauma by reducing the incision size. Cohn and Cosgrove, along with several European surgeons, first modified cardiopulmonary bypass techniques and reduced incision sizes to enable safe, effective, minimally invasive aortic and mitral valve surgery.1–3 Concurrently, port-access methods using endoaortic balloon occluders were developed.4 Despite expanding enthusiasm for minimally invasive valve surgery, many surgeons remained skeptical and became critical of complex operations done through small incisions, owing to possibilities of unsafe operations, unknown operative complexities, and inferior results.5,6

Despite circumspect reticence, significant advances were made and various institutions have published favorable results as single-center observational and comparative studies. Most surgeons who performed MIMVS in this era selected either a variation of a sternal incision or a minithoracotomy, and used direct vision with longer instruments. Simultaneous advances in cardiopulmonary perfusion, intracardiac visualization, instrumentation, and robotic telemanipulation hastened a technologic shift, with more surgeons adopting minimally invasive valve surgery in their practice. Less surgical trauma, blood loss, transfusions, and pain, translating into shorter hospital stays, faster return to normal activities, less use of rehabilitation resources, and overall healthcare savings, has driven further development in this field. Today, replacing and repairing cardiac valves through small incisions have become standard practices for many surgeons as patients become more aware of its increasing availability. Changes in surgical indications, largely because of a better understanding of the natural history of organic mitral regurgitation and improved repair techniques, have increased the number of less symptomatic patients with degenerative disease being referred for an elective repair.7,8 For MIMVS to become widely accepted, equivalent, if not better, short- and long-term outcomes have to be demonstrated compared with sternotomy operations.

To perform the ideal cardiac valve operation (Table 44-1) surgeons need to operate in restricted spaces through tiny incisions, which necessitate assisted vision and advanced instrumentation. Although the ultimate goal of a completely endoscopic mitral valve repair has not been widely achieved, MIMVS has continued to evolve, with many surgeons performing procedures along the minimally invasive continuum, utilizing a variety of techniques including either limited incisions, video-assistance, video-directed operations, or robotic techniques. Heretofore, completely endoscopic mitral valve repair was difficult but telemanipulators now offer ideal endoscopic techniques to mitral valve surgeons and their patients. However, the steep learning curve still can be an impediment to more widespread adoption. Video-assisted and direct vision techniques have placed MIMVS within the reach of most cardiac surgeons.

Minimally invasive cardiac surgery has not enjoyed a standardized nomenclature. The terms minimally invasive or limited access cardiac surgery have suggested reduced size of the incision, the avoidance of a sternotomy, the use of a partial sternotomy or mini-thoracotomy, or lack of need for cardiopulmonary bypass. The development of less invasive heart surgery may be considered analogous to the ascent of Mount Everest. Embarking from a conventional median sternotomy-based operation or “base camp,” surgeons advance progressively toward less invasiveness through experience and methodological acclimatization. Nomenclature paralleling this “mountaineering” analogy is shown in Table 44-2. In this schema entry levels of technical complexity are mastered before advancing past small-incision, direct-vision approaches (Level 1), toward more complex video-assisted procedures (Level 2 or 3), and finally to completely endoscopic robotic valve operations (Level 4). With the constant evolution of new technology and surgical expertise, many established surgeons have already attained “comfort zones” along this trek. Advancements in robotic surgery have allowed more and more surgeons to flatten this curve, favoring robotic mitral repairs.

Level 1: Direct Vision

The first steps toward MIMVS were to establish the safety and efficacy of less invasive cardiac operations. Early minimally invasive valve operations were based solely on modifications of previous incisions, and nearly all operations were done under direct vision. In 1996 the first truly minimally invasive aortic valve operations were reported.3,9 At that time surgeons found that minimal access incisions provided adequate exposure of the mitral valve.10–12 Using either a ministernal or parasternal incision, Arom, Cohn, Cosgrove, and Gundry showed encouraging results with low surgical mortality (1 to 3%) and morbidity.1,2,13,14 In Cosgrove's first 50 minimally invasive aortic operations, perfusion and cardioplegia times approximated those of conventional operations and his operative mortality was 2%. Over half the patients were discharged by postoperative day 5.2 In early 1997 Cohn described 41 minimally invasive aortic operations and first defined the economic benefits of these operations.1

In early 1996, the Stanford group performed the first MIMVS using intra-aortic balloon occlusion (port-access) and cardioplegia.11,14–16 Subsequently, surgeons at the University of Leipzig reported 24 mitral valve repairs done through a minithoracotomy using port-access techniques.4 This group later reported a high incidence of retrograde aortic dissections and neurologic complications with their initial cases, seemingly related to new catheter technology and limited surgeon experience.17 By early 1997 Colvin and Galloway had performed 27 direct-vision, port-access mitral repairs or replacements with a single death. None of their patients experienced an aortic dissection, and 63% of patients had mitral valve repairs with no reoperations for leakage.18 By December 1998, Cosgrove had performed 250 minimally invasive mitral valve operations through either a ministernotomy or parasternal incision with no mortality.3 The successes of these early MIMVS procedures became the springboard to the current direct-vision techniques described herein.

Level 2: Direct Vision/Video Assisted

Radical endoscopic surgical techniques of the 1980s became routine general, urologic, orthopedic, and gynecologic operations in the 1990s. This advancement was related primarily to successes with extirpative or ablative endoscopic operations. In contrast, fine vascular anastomotic and complex reparative procedures are the centerpieces of cardiac surgery. Limited video technology and instrumentation with only four degrees of freedom hindered the fine dexterity required for these operations, and cardiac surgeons were reluctant to explore the benefits of operative video assistance.

In early 1996, Carpentier performed the first video-assisted mitral valve repair through a minithoracotomy using hypothermic ventricular fibrillation.19 Shortly thereafter, we reported the first video-assisted mitral valve replacement, completed through a mini-thoracotomy, using a percutaneous transthoracic aortic clamp and antegrade cardioplegia.20,21 This clamping and visualization technique was simple, cost-effective, and has remained the mainstay of isolated mitral valve operations at several centers.17,22 In 1997, Mohr reported 51 minimally invasive mitral valve operations, performed with port-access cardioplegia techniques, a 4-cm incision, and for the first time three-dimensional (3D) videoscopy.23 In this series 3D assistance aided mitral replacement; however, these surgeons found that even simple reconstructions were significantly more difficult than those done through a sternotomy. At about the same time Loulmet and Carpentier deployed an intracardiac “mini-camera” for lighting and subvalvular visualization; however, they also concluded that two-dimensional (2D) visualization was inadequate for detailed repairs.24 Concurrently, our group reported 31 successful mitral valve operations done using 2D video-assistance.25 Complex repairs were possible, and these included quadrangular resections, sliding valvuloplasties, chordal transfers, and synthetic chordal replacements. Our initial results were encouraging.

Level 3: Video-Directed

In 1997, Mohr first used the Aesop 3000 voice-activated camera robot (Intuitive Surgical, Inc., Mountainview, CA) in minimally invasive videoscopic mitral valve surgery.23 Six months later we began using the Aesop 3000 routinely to perform both video-assisted and video-directed minimally invasive mitral valve repairs.26 We continued to use this device during most isolated mitral valve operations, including reoperations. This device provided surgeons camera-site voice activation, precluding translation errors inherent with verbal transmission to an assistant. Camera motion was shown to be much smoother, more predictable, and requiring less lens cleaning than during manual direction. At one point along our progression, we completed over 90% of mitral repairs under video direction with the Aesop 3000. This device, however, is no longer in production and other camera scope holders have been found to be equally effective. Mohr first termed this method “solo mitral surgery” and reported 8 patients undergoing successful mitral repairs using this semirobotic technique.23 Vanermen perfected his method to perform repairs completely endoscopically with excellent results. In nearly 1000 mitral valve operations, he and his colleagues have shown that after a significant learning curve totally video-directed repairs could be done with excellent results using long-shafted instruments.27,28

Level 4: Robotic (Computer Telemanipulation)

In June 1998, Carpentier and Mohr completed the first true robotic mitral valve operations using the da Vinci surgical system.29,30 In May 2000, the East Carolina University group performed the first da Vinci mitral valve repair in the United States.31 This computer-driven system provides both tele- and micromanipulation of tissues in small spaces. The surgeon operates from a console through end-effecter, microwrist instruments, which are mounted on robotic arms that are inserted through the chest wall (Fig. 44-1). These devices emulate human X-Y-Z axis' wrist motion throughout seven degrees of manipulative excursion. Movement occurs through two joints that together control pitch, yaw, and rotation. Additionally, arm insertion and rotation, as well as variable grip strength, give additional freedom to the operating “wrist.”30,32 Grossi and associates performed a partial mitral valve repair but had limited ergonomic freedom using the Zeus system.33 Lange and associates in Munich were the first to perform a totally robotic mitral valve repair using only 1-cm ports and the da Vinci device.34 To date, Chitwood, Murphy, and Smith have the largest experiences with robotic mitral valve repairs, and have independently shown da Vinci to be very effective, even for performing complex bileaflet repairs.32,35 Together, they have successfully completed well over 1000 mitral valve repairs and now routinely perform these procedures using only ports and a 2- to 4-cm mini-incision. Still further technological development will eventually lead to better improved learning curves. To this end, we are on the cusp of developing a closed-chest operation that can be done by many surgeons.

The type and size of the musculoskeletal incision remains central to discussions around minimally invasive cardiac surgery. A myriad of modified small sternal, para-sternal, and minithoracotomy incisions are used to access the cardiac valves. In the largest patient series modified sternal incisions have been used.36–38 Although many surgeons prefer the hemisternotomy approach, a right minithoracotomy yields excellent exposure for both direct-vision and videoscopic mitral valve access (Fig. 44-2A and B). To access the left atrium for direct vision, using a limited access mini-thoracotomy, a 4- to 6-cm submammary incision is placed along the anterior axillary line. The small sections of the pectoralis and intercostal muscles fibers are divided, and the thorax is entered through the fourth intercostal space with minimal rib distraction and no rib cutting. The New York University group has been quite successful in combining this incision with port-access methods and direct vision for both mitral and tricuspid repairs/replacements.39,40 A smaller 3- to 5-cm incision with minimal rib retraction can be used in video-assisted cases and is large enough for prosthesis passage (Fig. 44-3). Vanermen and Mohr perform video-assisted mitral operations routinely through 4-cm, nonretracted thoracic incisions with excellent results.41–43 Minimal rib spreading to prevent intercostal nerve injury and use of intraoperative local anesthetics are the keys to minimize postoperative discomfort. We generally use a soft tissue retractor to enhance visualization without the need for rib spreading. Tricuspid operations can be performed through this incision when combined with bicaval cannulation and drainage isolation. Murphy and colleagues prefer a more lateral approach for access in robotic mitral valve surgery.44

We consider the term minimally invasive to include the size of the actual cardiac incision. Most superior and transseptal mitral valve approaches, through a hemisternotomy, require a larger cardiac incision. For aortic, mitral, and tricuspid valve operations, surgeons at the Cleveland Clinic use a hemisternotomy, extended to the fourth interspace, with direct aortic arch and right atrial cannulation.3,9 To access the mitral valve, they extend the atriotomy from the right atrium, across the left atrial roof, and continuing caudally to divide the interatrial septum (Fig. 44-4A and B). This incision provides excellent exposure for aortic, mitral, and tricuspid valve replacements as well as repairs. Although the septal artery is divided, the incidence of atrial arrhythmias seems to parallel traditional interatrial groove atriotomies. For mitral and aortic surgery, Gundry suggested a similar hemisternotomy with single right atrial cannulation. This incision provides similar exposure to that described by opening the atrial roof, between the superior vena cava and aorta, without entering the right atrium.14 Cohn now prefers a lower hemisternotomy for mitral surgery and uses a transseptal approach for valve exposure.45 Loulmet and Carpentier reported using a midsternal, C-shaped, partial sternotomy for exposing mitral valves through the interatrial septum.24 All of these incisions provide generous direct-vision exposure, if combined with pericardial retraction.

Cannulation for cardiopulmonary perfusion can be accomplished through a number of approaches for MIMVS. By combining modified traditional perfusion methods and new technology, surgeons have been able to speed the development of less invasive mitral operations. Thin-walled arterial and venous cannulas, transthoracic aortic cannulas, endoaortic balloon occluders, modified aortic clamping devices, longer direct aortic antegrade cardioplegia catheters, percutaneous retrograde coronary sinus cardioplegia catheters, and assisted venous drainage all have assisted the evolution of these operations.

We prefer to establish arterial access via femoral cannulation, employing a small wire-wound Bio-Medicus (Medtronic, Inc., Minneapolis, MN) arterial cannula (17 to 21F) inserted over a guidewire (Fig. 44-5). Exposure of the femoral artery is through a 1.5-cm transverse incision placed in the right groin crease. We ask our referring cardiologists to perform cardiac catheterizations via the left groin to avoid hematoma and scar formation. However, if the right groin vessels were used at catheterization, we still use the right femoral vessels for cannulation, because the trajectory is better when introducing the cannula into the femoral-iliac venous system. Minimal dissection of the femoral vessels is performed without encircling the vessels. Less dissection has reduced seroma formation, which is now rare. For both venous and arterial cannulation, we believe that transesophageal echocardiographic guidance is mandatory to ensure proper guidewire insertion before passing dilators and the cannulae. Using this method excellent flow rates have been attained with acceptable perfusion pressures in over 1200 cases. We have experienced only two retrograde aortic dissections, one of which was in a reoperative case. Mitral valve patients having either peripheral atherosclerosis or small iliac vessels may require direct aortic cannulation either through the incision or via a transthoracic Seldinger approach. Alternatively, cannulation of the right (as in aortic surgery) or left axillary artery also has proved to be very effective.46

Venous cannulation and drainage can be established in a variety of ways. At the Brigham and Women's Hospital, the right atrium is cannulated directly either through the incision or via a separate skin incision. Cosgrove introduces a small (23F) cannula directly into the right atrium through the mini-sternotomy.40 Gundry and Konertz insert an oval-flat or “pancake” cannula directly into the right atrium to maximize hemisternotomy exposure.9,14 Assisted venous drainage has been a major advancement by enhancing the efficiency of smaller cannulas. At our institution we use the Bio-Medicus centrifugal vortex pump to create variable negative pressures for venous drainage. Similarly, by combining wall suction (<40-cm H2O pressure) and a closed-bag or hard-shell cardiotomy reservoir, a safe, simple, and economical assisted venous drainage system can be developed. For superior caval drainage a 15 to 17F Biomedicus cannula is placed by the anesthesia team via the right internal jugular vein using the Seldinger technique, positioning the tip at the pericardial-caval junction (Fig. 44-6). In addition, a 22 or 25F Cardiovations (Johnson & Johnson, Inc., Sommerville, NJ) or a 21 or 23F Biomedicus cannula is inserted via the right femoral vein and advanced over a guidewire into the right atrium. Again, it is important to use transesophageal echocardiographic guidance for proper cannula placement and safety.

Myocardial preservation techniques used with MIMVS are similar to those used in sternotomy-based operations. We cool systemically to 28°C, because the ambient cardiac temperature generally is warmer than during conventional valve operations. With either a ministernotomy or minithoracotomy, a retrograde coronary sinus cardioplegia catheter can be inserted directly into the right atrium and its position confirmed by echocardiography. Alternatively, a percutaneous retrograde cardioplegia catheter can be introduced preoperatively using echocardiographic and/or fluoroscopic guidance via the internal jugular vein. Although retrograde cardioplegia seems preferable, we have found antegrade cold blood cardioplegia efficient and preferable to ensure uniform cardiac cooling and even distribution of cardioplegia solutions. In the presence of significant aortic insufficiency, a retrograde cardioplegia catheter is inserted before bypass is established. After aortic clamping, cold antegrade blood cardioplegia is infused every 15 minutes into the aortic root via a vent/cardioplegia cannula passed through the incision. An extra long Medtronic cardioplegia catheter facilitates its positioning in the aortic root. During both videoscopic and robotic mitral surgery, we place a flexible sucker via the left atriotomy directly into the left superior pulmonary vein to clear residual blood from the surgical field.

For partial sternotomy based mitral valve surgery, aortic occlusion can be achieved using a standard cross-clamp applied through the incision. Cosgrove developed a flexible-handle aortic clamp to increase exposure through the hemisternotomy while minimizing inadvertent dislodgment (Fig. 44-7). For minithoracotomy mitral operations we use a percutaneous transthoracic aortic cross-clamp (Scanlan International, Minneapolis, MN), which is inserted through a 4-mm incision placed in the lateral right third intercostal space toward the axilla. The posterior immobile “tine” of the clamp is positioned through the transverse sinus dorsal to the aorta (see Figs. 44-3, and 44-8A and B).47 During placement, attention is necessary to prevent injury to the left atrial appendage and right pulmonary artery behind the aorta. This clamp has provided very secure occlusion without any aortic injuries. Occasionally we will apply this clamp in the “verso” direction with the mobile tine posterior to the aorta in the transverse sinus. In a short aorta this approach provides more length for cardioplegia needle insertion, and also arches the clamp away from the atriocaval junction, improving atrial septal ventral retraction and avoiding left robotic arm collisions. The “verso” approach introduces a somewhat greater risk of pulmonary artery injury and inadequate aortic occlusion, and thus excellent visualization during deployment is essential.

Vanermen, Murphy, Colvin, and Hargrove continue to be strong advocates for intra-aortic balloon occlusion for minimally invasive and robotic mitral surgery.27,28,44,48 Most commonly these devices are introduced retrograde through the femoral artery. The occlusive balloon should be positioned, under echocardiographic control, just above the sinotubular junction in the ascending aorta (Fig. 44-9).4,49 Balloon pressures often reach 400 torr during complete occlusion. Antegrade cardioplegia is delivered via the central lumen of the catheter. Balloon dislodgment can cause innominate artery occlusion, potentially causing neurologic injury, or prolapse into the left ventricle with inferior myocardial preservation. Thus, continuous echocardiographic monitoring and the comparison of right and left radial artery pressures are essential to detect balloon migration. Balloon occlusion may be advantageous compared with the transthoracic clamp method when there is limited access to the aorta. Aortic dissection is a feared complication of using the endoballoon, but experience with the technique dramatically reduces the risk of this adverse event. Regardless, Reichenspurner and colleagues demonstrated increased morbidity, cost, and operative/cross-clamp times when the endoballoon technique was used for mitral valve surgery.22

Meticulous intracardiac air removal is most important in these operations, because difficulty exists in manipulating and deairing the left ventricular apex. Also, in the right anterolateral minithoracotomy, air tends to be retained along the more dorsal ventricular septum and in the right pulmonary veins. Continuous carbon dioxide (CO2) insufflation has been helpful in minimizing intracardiac air and should begin before opening any cardiac chamber. CO2 displaces air efficiently and is much more soluble than air in blood. We continuously infuse CO2 (4 to 5 L/min) into the thorax via a 14-gauge angiocatheter throughout the case. Before releasing the cross-clamp, both lungs are ventilated vigorously to deair the pulmonary veins. After atriotomy closure and following cross-clamp release, suction is applied to the aortic root vent, and the right coronary artery origin is compressed during early ejection. As the heart beats, nonatherosclerotic aortas can be partially reclamped to expel residual air into the vent suction. Constant transesophageal echocardiographic monitoring is essential to ensure adequate air removal before weaning from cardiopulmonary bypass. We have found that during ventral retraction fixed transthoracic atrial retractors distort the aortic root, which can entrain air. The robotic retractor can be positioned to minimize this problem. Moreover, reducing retraction during antegrade cardioplegia delivery reduces aortic insufficiency and improves myocardial protection.

Preoperative Mitral Valve Repair Plan

Successful mitral valve repair begins with a comprehensive assessment and understanding of the mitral valve pathology by the surgeon in conjunction with the cardiologists and/or anesthesiologists. High quality intraoperative 3D transesophageal echocardiography (TEE) has become a critical aspect of planning mitral valve repair and is more accurate than 2D TEE in mapping mitral valve prolapse50; we now rely almost exclusively on TEE imaging to plan the repair. Each valve segment is measured using TEE. We pay particular attention to the angle between the mitral valve and the aortic annular plane (Fig. 44-10), the C-septal distance (distance between the septum at the hinge point of the aortic valve cusp and the coaptation point of the mitral valve leaflets), and the thickness of the interventricular septum, to minimize the potential for systolic anterior motion (SAM) of the anterior leaflet. We rely solely on measurements acquired by TEE to construct a topographic model, size the annuloplasty band, and plan the operation (Fig. 44-11). A saline test is performed intraoperatively to confirm the echocardiographic findings, but occasionally we still measure the valve segments directly (Fig. 44-12).

Mitral Valve Exposure

Using a hemisternotomy, exposure of the mitral valve is best accomplished through either an extended right to left atrial incision or the transseptal approach championed by Cosgrove and Cohn, respectively (see Figs. 44-2A and 44-4A and B). A hand-held retractor placed through the incision facilitates valvular exposure using these incisions. For endoscopic and robotic mitral repairs most of us have favored a fixed-blade transthoracic retractor immobilized by a table-mounted clamp. Blades of various sizes are available; however, after fixed-retractor deployment, movement to provide additional exposure becomes limited. For reoperative mitral surgery through a minithoracotomy, we prefer to use the hand-held retractor shown in Fig. 44-13. It allows variable access to all parts of the left atrium and subvalvular structures; moreover, it can provide access in very deep chests. The second and subsequent generations of the da Vinci system includes a fourth robotic arm that can be used to dynamically manipulate a left atrial retractor (Fig. 44-14) that is activated alternately through the left instrument arm control. This retractor provides variable exposure of the mitral valve by altering blade positions, length, rotation, and flexion. The retractor arm is inserted via a third interspace port in men and a fourth interspace port in women, medial to the anterior thoracotomy in both cases.

Robotic Mitral Valve Surgery

For both video-assisted and robotic mitral surgery we position the patient as shown in Fig. 44-15 with the right arm at the side facilitating application of the cross-clamp through the midaxilla. A simple Olympus endoscope holder attached to the operating table now is used for our minimally invasive video-assisted approach. Using video-assistance, surgeons operate with long instruments in a 2D operative field (Fig. 44-16). Knots are tied and sutures cut using specialized hand-held long-shafted instruments (Figs. 44-17A and B and 44-18).

The da Vinci surgical system is comprised of three components: a surgeon console, an instrument cart, and a visioning platform (Fig. 44-19A and B).51 This system provides intracardiac telepresence and facile tissue micromanipulation. The operative console is removed physically from the patient and allows the surgeon to sit comfortably, resting the arms ergonomically with his or her head positioned in a 3D vision array. The da Vinci Si Surgical System released in April 2009 provides dual-console capability, extending the potential for either two surgeons to work together, or to enhance training with a “student-driver” model. Instruments are positioned through 8-mm ports around the operative sites in the thorax, and the camera is passed either through the working port used for suture and prosthesis passage (Fig. 44-20A) or a separate port incision. The surgeon's finger and wrist movements are registered by sensors in the masters, transformed by a computer and then transferred to the instrument cart, which operates end-effecter instruments. Wristlike instrument articulation emulates precisely the surgeon's actions at the tissue level, and dexterity becomes enhanced through combined tremor suppression and motion scaling. These features allow increased precision and dexterity with the surgeon becoming truly “ambidextrous.” A clutching mechanism enables readjustment of hand positions to maintain an optimal ergonomic attitude with respect to the visual field. The clutch acts very much like a computer mouse, which can be reoriented by lifting and repositioning it to reestablish unrestrained freedom of computer activation. The SI system provides the surgeon with depth perception as a 3D image of the surgical field in full high definition (1080i) with up to 10× magnification. The operator becomes ensconced in the 3D operative topography and can perform extremely precise surgical manipulations, devoid of traditional distractions. Both 0-degree and 30-degree endoscopes can be manipulated electronically to look either “up” or “down” within the heart. Access to and visualization of the internal thoracic artery, coronary arteries, and mitral apparatus have been shown to be excellent. Figure 44-20B shows the surgeon's operative field during a da Vinci mitral repair. Perfusion technology is the same as described above for video-assisted operations and a larger mini-thoracotomy.

Heretofore, many surgeons avoided repairing valves with large bileaflet defects. However, we have found that repairs of these maladies are particularly amenable to robotic telemanipulation because of high-definition 3D magnified vision and the ability to translocate multiple individual chordae tendineae to new leaflet sites. After the first 50 mitral repairs our group began to repair more complex valves as well as develop and use new adjunctive technology during robotic surgery. Figures 44-21, 44-22, 44-23, 44-24, 44-25, 44-26, 44-27, and 44-28 illustrate the variety of methods we use routinely for both simple and complex repairs. The mainstay of our repair techniques for posterior leaflet prolapse secondary to ruptured or redundant chordae has been a modification of the classic quadrangular resection. As seen in Fig. 44-21, a trapezoidal or triangular resection is made in the central portion of redundant posterior leaflet segment. By conserving the annular distance that must be closed, tension along the posterior annulus is limited, especially when one of the scallops is much larger than the others as is often the case in P2 prolapse, where P1 and P3 may be diminutive. The minor base of the trapezoid is closed with a figure-of-eight braided suture (2-0 Cardioflon [Peters, Inc., Paris, France]). Often we conserve leaflet tissue by decreasing the size of P2. When the leading edges are approximated, chordae are effectively shortened as they assume a new angle with the leaflet insertions which brings the line of coaptation below the annular plane. When there is an isolated anterior leaflet prolapse, chordae can either be transferred from the posterior leaflet (Fig. 44-22A and B) or the redundancy reduced using PTFE neochords (Fig. 44-23A and B). When any posterior leaflet scallop is radially higher than 2 cm or the anterior leaflet is longer than 3 cm, there is increased risk of systolic anterior motion of the anterior leaflet. This is especially true when the aortic outflow is narrowed by a thickened interventricular septum or a relatively acute angle exists (>120 degrees) between the aortic and mitral valve annular planes (see Fig. 44-10). Generally, systolic anterior motion can be avoided by reducing the posterior leaflet height with a sliding-plasty after prolapsing segments are resected (Fig. 44-24A through C).

Traditional repair techniques employing resection become complicated in the presence of a large P2 scallop with multiple ruptured or redundant chords and either significant annular calcification, thin leaflets, or deficient P1 or P3 scallops that are too small to slide successfully. In addition, standard repair techniques usually render the posterior leaflet immobile, leaving the MV with one functional leaflet. Advances in robotic technology, including three-dimensional visualization and improved dexterity with enhanced operative precision, have facilitated the development of new repair techniques for MR. In 2006 we introduced the “Haircut” repair technique. The limits of the prolapsing P2 segment with associated ruptured or redundant chords are identified (Fig. 44-25A) and the height (annulus to tip) of each scallop is measured. Lateral P2 scallop edges are imbricated concomitantly with P1-P2 and P2-P3 cleft closure (4-0 Cardionyl; Péters, Surgical, Bobigny, France). Incomplete natural clefts can be closed during imbrication. Completion of this part of the repair generally reduces the P2 segment prolapse substantially. Thereafter, excess P2 tissue is resected to the measured height of adjacent P1 and P3 scallops (Fig. 44-25B), with the goal of achieving a posterior leaflet height less than 15 mm. With this resection ruptured chords and excess P2 lengths get a “haircut.” Redundant chords are preserved along with a tiny piece of leaflet-anchoring tissue and are reattached to the free edge of the P2 chord, restoring the line of coaptation (Fig. 44-25C). If all P2 chords require resection, adjacent secondary chords can be transferred from either the posterior or anterior leaflet. Alternately, polytetrafluoroethylene neochords can be substituted. The repair is completed with an annuloplasty band (Cosgrove-Edwards; Edwards Lifesciences, Irvine, CA) (Fig. 44-25D). We implant the band using 2-0 Cardioflon sutures (Péters Surgical, Paris, France), which have excellent handling characteristics and require only four knots, facilitating a more expeditious repair. A photograph of the completed repair is shown in Fig. 44-25E.52

In patients with bileaflet prolapse, or Barlow's disease, part of the resected segments from the posterior leaflet are transposed to the redundant anterior leaflet segments and attached with 4-0 monofilament sutures. Again, “swinging” a chord-bearing piece of posterior leaflet to the undersurface of the anterior leaflet generally reduces the prolapse of the latter (Figs. 44-26A through E).

To date, all of our nearly 600 robotic repairs have been supported either by an annuloplasty using a Cosgrove-Edwards (Edwards Lifesciences, Inc., Irvine, CA) or an ATS annuloplasty band. We use either single-arm 2-0 braided sutures as shown in Fig. 44-27A or nitinol U-clips (Medtronic, Inc., Minneapolis, MN) as shown in Figs. 44-27B and C and 44-28 to secure the band. For insertion of a band alone or with limited resection, we prefer to use U-clips, which enable faster deployment. However, when greater tension is required, as in larger resections and sliding-plasties, the compressive force of sutures provides seemingly better reinforcement of the repair.

Cosgrove and Gundry have consistently promoted the hemi-sternotomy for mitral valve surgery. They have considered this technique to be the most reproducible for surgeons with variable experiences and abilities, as well as small clinical volumes. Complex replacements and repairs have been performed through this incision and to date few repair failures have resulted from this exposure method. Between 1995 and early 2004, Cosgrove and his Cleveland Clinic group performed 2124 minimally invasive mitral operations, using direct vision through either a right paramedian incision or partial sternotomy using modified perfusion methods, compared with 1047 standard sternotomy procedures during the same time period. As noted earlier, the extended atriotomy, first proposed by Guiardon and used continually by the Cleveland Clinic group, apparently has caused excessive atrial arrhythmias, which have been lessened by modifying the atriotomy.53 Of the patients undergoing a minimally invasive approach, 85% had degenerative and 9% had rheumatic disease and 90% were repaired using standard techniques. In a propensity-matched subset of 590 patient pairs, perfusion and aortic occlusion times averaged 85 and 65 minutes, respectively, and were only slightly longer compared with a full sternotomy. For propensity-matched patients, mortality was less than 1% for both groups with no differences in stroke, renal failure, myocardial infarction, or infection. However, patients undergoing minimally invasive procedures experienced less mediastinal drainage and received fewer blood transfusions. In addition, more patients in the minimally invasive group were extubated in the operating room and had higher postoperative forced expiratory volume in 1-second and lower pain scores. Their conversion rate to full sternotomy was 1.9%.54

After initially using a right parasternal incision Cohn and associates now prefer a lower hemisternotomy with direct aortic arterial cannulation and vacuum-assisted percutaneous femoral venous drainage, accessing the mitral valve via a standard left atriotomy. Of the 707 mitral patients operated between 1996 and 2007, the most common mitral valve pathology was myxomatous degeneration (88%) including 184 patients with anterior or bileaflet prolapse, rheumatic disease (3.5%), and endocarditis (3.1%). Their thirty-day mortality was 0.4%. Bleeding requiring reoperation occurred in 2% of patients. Strokes occurred in 1.7% of patients, myocardial infarctions in 0.7% and vascular complications in 4.4%. Patients were hospitalized for a mean of 5 days and 6.9% required additional rehabilitation before discharge. Survival at 11.2 years was 83% and freedom from reoperation was 92%. Late mitral regurgitation occurred in 12%. Anterior leaflet prolapse and lack of an annuloplasty ring were involved in 65% of failed repairs.55

In early 2002, Vanermen described 187 patients undergoing totally video-directed repairs using the port-access method and no rib spreading. He used a 2D endoscopic camera to perform complex repairs with excellent results at follow-up 19 months later.41 The hospital mortality was 0.5%, and there were only two conversions to a sternotomy for bleeding. Freedom from reoperation was 95% at 4 years. Over 90% of patients had minimal postoperative pain. Although this and other series had not been randomized, these series strongly suggest that mitral valve surgery has entered a new era, and that minimally invasive and video techniques can facilitate these operations.

In 2003 Vanermen and associates updated their results in 306 mitral patients (226 repairs and 80 replacements). Six patients were converted to median sternotomy because of peripheral cannulation complications, and 30-day mortality was 1% (n = 3). In this series 46% of patients were back to work within 4 weeks, and the overall freedom from reoperation was 91% at 4 years. Their results continued to suggest that endoscopic mitral valve surgery is safe with excellent results.56 Mohr and the University of Leipzig group recently reported 1536 patients undergoing video-assisted mitral valve surgery for mitral regurgitation using peripheral perfusion and Bretschneider cardioplegia administered at intervals of 90 to 120 minutes. The repair rate was 87.2% and the conversion rate was only 0.3%. Thirty-day mortality was 2.4% and 5 year Kaplan-Meier survival was 82.6%. Their freedom from reoperation was 96.3% at 5 years.57 Subsequently, this group compared results from a subset of patients undergoing complex mitral valve repair with patients undergoing simple posterior leaflet repairs. They determined that long-term results and reoperation rates for anterior mitral valve leaflet repair and bileaflet repair were similar to posterior leaflet repairs.58

The East Carolina University group reported a combined series with Hargrove consisting of 1178 successful video-assisted mitral valve operations between 1996 and 2008.59 At first, patients with anterior leaflet pathology and annular calcification were avoided. However, these patients are now operated on using video-assisted techniques. Table 44-3 details our current criteria for patient selection. The majority of patients had degenerative disease and 79.9% of the total group underwent a repair. In this series repairs included ring annuloplasties with quadrangular resections, sliding plasties, chordal transfers and PTFE neochordae placement procedures. The operative mortality for mitral valve repair and replacement for this two center series was 2.1% and 4.6%, respectively, but only 0.2% for isolated primary mitral valve repair. Cross-clamp (100 minutes) and perfusion (142 minutes) times still remained longer than those of conventional operations. Currently, at our institution cardiac arrest and perfusion times for video-assisted mitral operations have fallen to 70 and 100 minutes, respectively, Myocardial protection strategies included transthoracic clamping (48.7%), endoaortic balloon occlusion (40.7%), and hypothermic fibrillation (10.1%). A trend for increased stroke and aortic dissection was found, especially when using the endoballoon. Interestingly, we have seen no difference in bleeding and transfusion requirements between our conventional and minimally invasive cases. However, hospital length of stay averaged 6 days compared with 8 days for conventional operations. Of these 1178 patients there were 19 (1.6%) conversions to a sternotomy, 23 (2.0%) had strokes, 63 (5.4%) required re-exploration for bleeding, and 9 (0.8%) sustained aortic dissections. A total of 45.5% of the patients received a blood product transfusion. Postoperative repair transesophageal echocardiograms showed no more than trivial insufficiency in 97.1% of patients having mitral valve repair. We previously reported our series of reoperative procedures via this approach including 14 patients (4.3%) who required a mitral valve reoperation. We have operated on 71 patients (31 mitral valve repairs and 40 mitral valve replacements) having had prior coronary bypass operation or mitral surgery. These patients underwent video-assisted reoperations with 9.8% mortality as well as four re-explorations for bleeding and one stroke (1.4%) Midterm outcomes were favorable with only 22 (1.9%) of patients requiring reoperation at a mean of 732 days.60 Hargrove has become convinced that small-incision and videoscopic mitral surgery is safe, effective, economical, and better accepted by patients than conventional sternotomy operations. The long-term results of all of the above series continue to confirm that minimally invasive mitral operations have already taken a prominent position in the evolution of cardiac surgery.

In our recent meta-analysis of 43 manuscripts comparing minimally invasive mitral valve repair to sternotomy, we identified 10 papers published between 1998 and 2005 suitable for analysis, including 1358 minimally invasive patients and 1469 sternotomy patients. One report was a randomized control trial, and the remainder were case-control studies. Although cross-clamp and cardiopulmonary bypass times were longer in the minimally invasive group, there were no differences in mortality, stroke, reoperation for bleeding, new onset atrial fibrillation, or duration of ICU or hospital stay. Freedom from reoperation ranged from 91 to 99%.61

Grossi and associates at New York University have reported the longest outcomes for minimally invasive mitral surgery to date. Between 1996 and 2008 they performed 1071 minimally invasive mitral valve repairs and compared their results with a cohort of 1601 conventional procedures. This group uses a 6- to 8-cm minithoracotomy and operates under direct vision. They now prefer to use direct aortic cannulation with an external aortic clamp. Venous drainage is via a femoral cannula and cardioplegia is administered by a coronary sinus catheter inserted through the right atrium. Approximately one third of the minimally invasive repairs included an anterior leaflet procedure and all patients received an annuloplasty device. They reported a perioperative mortality of 1.3% in both groups with isolated mitral valve repair and no differences in major adverse events. Long-term results were equivalent to sternotomy techniques. In isolated mitral valve repair, eight-year freedom from reoperation or severe recurrent insufficiency was 93% and freedom from all valve-related complications was 90%. Their results suggest that minimally invasive mitral operations can be done safely using limited incisions and direct aortic clamping methods with similar results as conventional operations and with no added mortality or morbidity. At the same time they had fewer transfusions, shorter lengths of hospital stay, and fewer septic complications.62

The right chest minithoracotomy provides significant benefits in re-operative settings by avoiding sternal re-entry and limited dissection of adhesions, avoiding the risk of injury to cardiac structures or patent grafts, and limiting the amount of postoperative bleeding. Vanermen reported 80 adults undergoing endoscopic mitral valve and tricuspid valve re-operative surgery with an operative mortality of 3.8%. There were three perioperative strokes, and survival at 1 and 4 years was 93.6 and 85.6%, respectively.63 A recent case control study, comparing re-sternotomy to the right minithoracotomy for redo mitral valve surgery, noted no difference in mortality or perfusion times but significantly reduced intubation times, blood transfusions, and hospital stays with the minimally invasive approach.60

Robotic Mitral Valve Surgery

The East Carolina University group performed the first da Vinci system robotic mitral valve repair in North America in May 2000. Since then, we have performed nearly 600 robotic mitral valve repairs. The first Food and Drug Administration (FDA) safety and efficacy trial was conducted at our institution in 2000 and included 20 patients.32 Leaflet resections, sliding-plasties, chordal transfers, neochord insertions, and annuloplasties were all performed successfully. This initial study demonstrated that although operative times were longer, when compared with conventional mitral valve sternotomy operations, the results were comparable. There were no device-related complications. Postoperative hospital stays averaged 4 days, and all patients returned to normal activity by 1 month following surgery. Early postoperative echocardiograms at 3 months demonstrated that none of the patients had more than trace mitral regurgitation.

These initial results were encouraging and prompted a phase II multicenter FDA trial, which was completed in 2002.35 A total of 112 patients were enrolled at 10 different institutions and all types of repairs were performed. Following surgery, nine patients (8%) had grade 2 or higher mitral regurgitation, and six patients (5%) required a reoperation. Although the reoperative number was high for the number of patients, failures were distributed evenly among centers, with some centers having performed fewer than 10 procedures and were still early in their learning curve phase. There were no deaths, strokes, or device-related complications. These results prompted FDA approval (2002) of the da Vinci system for mitral valve surgery.

Other early robotic assisted mitral valve surgery reports included:

1. Tatooles et al. reported their experience with 25 patients and demonstrated excellent results with no mortality, device-related complications, strokes or reoperations for bleeding. One patient had a transient ischemic attack 7 days after surgery. The CPB and XC times were 126.6±25.7 minutes and 87.7±20.9 minutes, respectively. Eighty-four percent were extubated in the operating room, 8 were discharged home within 24 hours, and the mean hospital stay was 2.7 days. However, there was a 28% rate of readmission using this aggressive discharge policy and two patients required interval mitral valve replacement.64

2. Jones et al. reported a series of 32 robotic mitral repair patient from a community hospital. They performed concomitant procedures in five patients (tricuspid valve repair n = 3 and MAZE procedure n = 2). There were two deaths in this series where neither was reported as a device-related complication. Complications included reoperations for repair failure (n = 3), stroke (n = 1), groin lymphocele (n = 1) and pulmonary embolism (n = 1).65

3. In a nonrandomized single surgeon experience from the University of Pennsylvania, Woo et al. demonstrated that robotic surgery patients had a significant reduction in blood transfusions and length of stay compared with sternotomy patients.66

4. Folliguet et al. compared patients undergoing robotically-assisted mitral valve repair with a matched cohort undergoing a sternotomy (n = 25 each). The robotic group had a shorter hospital stay (7 days versus 9 days, p = 0.05) but besides this there were no differences between the 2 groups.67

More recent and larger series include:

1. Murphy et al. reported their experience in 127 patients undergoing robotic mitral surgery of which five were converted to a median sternotomy and one to a thoracotomy; seven patients had a valve replacement and 114 had a repair. There was a single in-hospital death, one late death, two strokes and 22 patients developed new onset of atrial fibrillation. Blood product transfusion was required in 31% of patients and two (1.7%) patients required a reoperation. Postdischarge echocardiograms were available in 98 patients at a mean follow-up of 8.4 months with no more than 1+ residual MR in 96.2%.44

2. Our report from the East Carolina University included the first 300 patients undergoing robotic mitral valve repair between May 2000 and November 2006. Mean patient age was 57 years and 36% were female. Cardiopulmonary bypass times were 159 minutes, and cross-clamp times were 122 minutes. Repairs included quadrangular resections, sliding-plasties, chordal transfers, chordal shortening, neochord insertion, edge-to-edge repairs, and annuloplasties. Echocardiographic and survival follow-up was complete in 93% and 100% of patients, respectively.68 There were 2 (0.7%) 30-day mortalities and 6 (2.0%) late mortalities. No conversions to sternotomy or mitral valve replacements were required. Immediate postrepair echocardiograms showed the following degrees of mitral regurgitation: none/trivial, 294 (98%); mild, 3 (1.0%); moderate, 3 (1.0%); and severe, 0 (0.0%). Complications included two (0.7%) strokes, two (0.7%) transient ischemic attacks, three (1.0%) myocardial infarctions, and seven (2.3%) reoperations for bleeding. The mean hospital stay was 5.2 ±4.2 (standard deviation) days. Sixteen (5.3%) patients required a reoperation. Echocardiographic follow-up demonstrated the following degrees of mitral regurgitation: none/trivial, 192 (68.8%); mild, 66 (23.6%); moderate, 15 (5.4%); and severe, 6 (2.2%). Within this series, 66 patients underwent complex repairs for anterior leaflet or bileaflet prolapse. In this subgroup, 90% of patients had moderate or less mitral regurgitation postoperatively, and the 5-year freedom from reoperation was approximately 90%.69

We have also used the da Vinci system to perform mitral valve replacements as well as combined mitral valve repairs with atrial fibrillation ablation.70 As we continue to perform further robotic mitral operations, the operative times have continued to decrease. In addition, we are able to repair more complex valves because of the enhanced visualization and fine dexterity offered by the evolved da Vinci system.

Over the last decade there has been a transformation in the way cardiac surgeons, cardiologists and patients approach cardiac therapies. Indeed, current STS data shows that 11.3% of isolated mitral valve repairs are performed with robotic assistance. Up to 20% of surgeons are using some minimally invasive method for their repairs. Nevertheless, fewer than 60% of repairable mitral valves are currently being repaired, no matter the approach. Less invasive mitral valve repair procedures are more demanding, but proven safety, efficacy, and durability are still demanded with new techniques. Evidence presented herein demonstrates that minimally invasive mitral valve surgery is associated with equal mortality and neurological events to sternotomy methods, despite longer cardiopulmonary bypass and aortic cross-clamp times. However, there is less morbidity in terms of reduced need for reoperation for bleeding, a trend towards shorter hospital stays, less pain, and faster return to preoperative function levels than conventional sternotomy-based surgery. It is expected that these results will translate into improved utilization of limited healthcare resources. With follow-up now of almost 7 years it is clear that long-term outcomes are equivalent to those of conventional surgery. Data for minimally invasive mitral valve surgery after previous cardiac surgery is limited but consistently demonstrates reduced blood loss, fewer transfusions and faster recovery compared with reoperative sternotomy. Almost all patients who undergo a minimally invasive mitral valve operation as their second procedure feel their recovery is more rapid and less painful than their original sternotomy.

As for the future, minimally invasive cardiac surgery is likely to become more widely adopted and less of a niche market. Although operative philosophies, patient populations, and surgeon abilities differ among centers, the compendium of recent results remains very encouraging. The ultimate goal is to perform safe completely endoscopic surgery. To successfully perform these operations, surgeons and engineers will need to continue to improve methods by which instruments are directed by computers. Recent successes with direct-vision, videoscopic, and robotic minimally invasive surgery all have reaffirmed that this evolution can be extremely fast, albeit through various pathways.

Patient requirements, technology developments, and surgeon capabilities all must become aligned to drive these needed changes. In addition, we must work closer with our cardiology colleagues in these developments. This is an evolutionary process, and even the greatest skeptics must concede that progress has been made. However, curmudgeons and surgical scientists alike must continue to interject their concerns. Caution cannot be overemphasized. Traditional valve operations enjoy proven long-term success with ever-decreasing morbidity and mortality, and remain the gold standard. Less invasive approaches to treating valve disease cannot capitulate to poorer operative quality or unsatisfactory valve and/or patient longevity. Nevertheless, patients are opting for less invasive operations.