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Robotic Mitral Valve Surgery

 Robotic Mitral Valve Surgery
Keywords : mitral valve, repair, replacement, prolapse, robotic
Abstract
Robotic mitral valve surgery was introduced in 1998 to reproduce excellent conventional sternotomy results with less invasive techniques. This technology is now routinely performed for delivering complete anatomic correction of all categories of mitral valve prolapse, regardless of disease complexity, with or without concomitant tricuspid valve repair and atrial fibrillation ablation procedures. Recent studies have demonstrated broad advantages of robotic mitral valve surgery, including reduced bleeding, extubation on the operating room table, shorter hospital length of stay, quicker return to normal activities, and a superior cosmetic result. Here we discuss the current status of robotic mitral valve surgery techniques.


· The 2014 American College of Cardiology (ACC)/American Heart Association (AHA) guidelines strongly recommend (class I) prompt surgical correction of mitral regurgitation (MR) for patients in stages D (severe symptomatic MR) and C2 (severe asymptomatic MR with left ventricular ejection fraction [LVEF] < 60% or left ventricular end-systolic diameter [LVESD] > 40 mm).1 Recently, several studies have supported the advantages of surgical correction of primary MR, even in patients in stage C1 (severe asymptomatic MR with LVEF > 60% or LVESD < 40 mm) to prevent excess long-term mortality and heart failure risks.
·    Modified cardiopulmonary bypass techniques were introduced in 1995 and enabled safe and effective minimally invasive mitral valve surgery. However, difficulties performing complex mitral valve repair using two-dimensional vision and long-shafted instruments limited their adoption. During the late 1990s, development of the da Vinci Surgical System (Intuitive Surgical, Sunnyvale, CA) made safe robotic cardiac surgery possible. The da Vinci Surgical System has allowed surgeons to perform complex reconstructive operations using a combination of telemanipulation and three-dimensional (3D) visualization. The first robotic mitral valve operation was performed by Carpentier et al. in 1998 using the da Vinci Surgical System. In 2000, Dr. Chitwood and colleagues at East Carolina University (ECU) performed the first mitral valve repair in the United States as part of the initial US Food and Drug Administration (FDA) clinical trial.
·    The most important benefits of robotic mitral valve surgery include excellent surgical dexterity with precise movements of instruments in the closed chest, high-definition 3D visualization with the line of vision parallel to the flow of the blood into the valve, excellent visualization of the subvalvular apparatus, and superior cosmetic results, with more rapid recovery than with the use of conventional approaches.

Step 1. Surgical Anatomy
·   The heart is covered anteriorly by the body of the sternum and the third to sixth costal cartilages of both sides. The coronary sulcus, separating the atria and ventricles, spans from the upper medial end of the third left costal cartilage to the middle of the right sixth chondrosternal joint. The anterior interventricular sulcus spans from the third left intercostal space (ICS) 2.5 cm to the left of the midline to a point 1.2 cm medial to the apex. The aortic valve is at the level of the third ICS behind the sternum. The pulmonary valve is at the level of the left third ICS. The tricuspid valve is behind the sternum at the level of the fourth to fifth intercostal junction. The mitral valve is located behind the sternum at the level of the fourth intercostal junction.
·  The mitral valve apparatus consists of the anterior and posterior leaflets, two commissures, which are the areas where the anterior and posterior leaflets meet, the mitral annulus, and the subvalvular apparatus, including the chordae tendineae and papillary muscles (Fig. 21.1).
·    Each leaflet has three segments including the A1 (anterior segment), A2 (middle segment), and A3 (posterior segment) of the anterior leaflet and P1 (anterior scallop), P2 (middle scallop), and P3 (posterior scallop) of the posterior leaflet. The anterior mitral annulus shares fibrous continuity with the aortic valve annulus (left coronary cusp and half of the noncoronary cusp) and is also adjacent to the atrioventricular node and the bundle of His. The circumflex artery courses along the posterior annulus and is at risk of injury during mitral valve repair or replacement (Fig. 21.2). The subvalvular apparatus includes two papillary muscles (anterolateral and posteromedial) and the thin fibrous structures chordae tendineae that support both leaflets and prevent leaflet prolapse. The primary chordae attach to the free margin of the leaflets, and the secondary and tertiary chordae insert into the leaflet body, closer to the annulus.
 
Figure 21.1 Anatomy of mitral valve apparatus.
Figure 21.2 Cross-sectional view of the mitral valve.

Step 2. Preoperative Considerations
·   Degenerative, ischemic, rheumatic, and infectious processes are the major causes of mitral valve disease and can affect any component of the valve or subvalvular apparatus. Robotic mitral valve surgery is appropriate for both degenerative and functional mitral valve disease. However, degenerative mitral valve disease is the most common indication for robotic surgery. Furthermore, concomitant left atrial appendage (LAA) closure, ablation for atrial fibrillation, and tricuspid repair can also be performed using the same robotic platform.
·    Following the 2014 ACC/AHA guidelines,1 in centers with expertise in both mitral valve and robotic surgery, most patients with severe primary MR with appropriate vascular and coronary anatomy may reasonably be considered for early robotic mitral valve repair, regardless of the complexity of mitral valve disease. Patients should be screened for comorbid conditions that may preclude the selection of the robotic technique. Table 21.1 demonstrates plausible and relative contraindications to robotic mitral valve surgery. However, many of the relative contraindications can be managed to allow a safe robotic mitral valve operation.


·    Repair techniques in patients with functional valve disease relate to the degree of annular and ventricular dilation, papillary muscle displacement, dynamic cardiac function, and degree of leaflet tethering.
·   Patients at risk for coronary artery disease should undergo a cardiac catheterization or computed tomography (CT) angiography. Patients with significant risk factors for carotid or peripheral vascular disease should be screened by ultrasound and CT. A right heart catheterization may be indicated for patients who have significant pulmonary hypertension, particularly with depressed right ventricular function. Finally, patients with sternal or thoracic deformities should be evaluated by CT to determine whether robotic instrument trajectories will be compromised. A transthoracic echocardiography (TTE) or transesophageal echocardiography (TEE) study should be performed to confirm the diagnosis and determine the repair plan. TEE is also essential in the operative room to delineate mitral valve anatomy in detail, and intraoperative femoral ultrasound should be peformed to confirm the adequacy of vessels for cannulation.

Step 3. Operative Steps
·      All patients undergoing robotic mitral valve surgery undergo the following steps:
1.    Patient setup and port placement
2.    Cannulation, docking of robotic arms, and exposure of the mitral valve
3.    Mitral valve surgery, tricuspid valve repair, and atrial fibrillation procedures
4.    Weaning from bypass, decannulation, and closing of incisions

1. Patient Setup and Port Placement
·   The patient is intubated with a double-lumen endotracheal tube, and a TEE probe is placed. Pulmonary artery vent and retrograde coronary sinus cardioplegia catheters (CardioVations, Ethicon, Somerville, NJ) may be placed via the right internal jugular vein under TEE guidance. The patient is positioned at the right edge of the operating room table with a transverse roll under the chest and an arm board supporting the right arm. The right femoral artery and vein are exposed via an oblique incision above the groin crease and assessed for appropriateness for cannulation.
·  Port placement is done after femoral vessel exposure has confirmed adequacy for use in cannulation for cardiopulmonary bypass. Local anesthetic may be used at all port sites to aid with postoperative pain control. The endoscope camera port is placed in the fourth ICS, 2 to 3 cm lateral to the nipple. In female patients, the breast is retracted superiorly and the incision is placed in the inframammary crease to enter the chest in the fourth or fifth ICS. The working port incision (for a 15-mm soft rubber retractor) is placed in the fourth ICS 4 cm lateral to the camera port. The left instrument port is placed one interspace above and approximately halfway between the shoulder and the camera port. The right instrument port is two or three interspaces below and near the anterior axillary line. The fourth robotic port, for the atrial retractor instrument, is placed in the fifth ICS medial to the camera port. A 10-G angiocatheter, which can accommodate the so-called crochet hook for suture retrieval, is placed in the midaxillary line for posterior pericardial traction sutures. Two other angiocatheters are placed medially and laterally to the central angiocatheter. A Chitwood transthoracic cross-clamp and a small suction vent are placed via stab wounds in the axilla (Fig. 21.3).

2. Cannulation and Docking
·      A purse-string suture is placed in the anterior surface of the femoral vein, and then a guidewire is passed through the femoral vein and into the superior vena cava (SVC) under TEE guidance. Seeing the guidewire pass up into the SVC is very important to ensure the proper positioning of the venous cannula. A 25F CardioVations Quickdraw venous cannula is passed over the wire and positioned so that the tip is several centimeters up the inferior vena cava (IVC). The femoral artery is cannulated using the Seldinger technique (Fig. 21.4). Cardiopulmonary bypass is initiated.
·  The pericardium is opened with electrocautery anterior to the phrenic nerve. The pericardiotomy extends from near the IVC to up over the ascending aorta. Two traction sutures are placed on the posterior pericardial edge to expose the site of the left atriotomy. A traction stitch on the anterior pericardium facilitates aortic exposure (Fig. 21.5).
·    The table is rotated 15 degrees to the left and placed in reverse Trendelenberg to lower the hips and gain extra clearance for the right instrument arm of the robot. The da Vinci robot is brought to the surgical field; the arms are connected to the ports, and the camera and instruments are introduced into the chest.
 
Figure 21.3 Patient setup and port placement.
Figure 21.4 Cannulation of the femoral vessels.

3. Aortic Occlusion, Cardioplegia, and Exposure
  Aortic occlusion is achieved using the endoballoon or Chitwood clamp; cardioplegia is delivered antegrade and readministered every 15 to 20 minutes throughout the cross-clamp time.
     A left atriotomy incision is made anterior to the right pulmonary vein (Fig. 21.6). The intuitive surgical atrial retractor is positioned to elevate the atrial septum and provide exposure. The atrial retractor position can be adjusted to optimize exposure for patent foramen ovale closure, closure of the LAA, or exposure of the mitral valve. The small suction vent is positioned in the left pulmonary vein to clear the surgical field of blood.
 
Figure 21.5 Opening of the precardium.
Figure 21.6 Left atriotomy.
4. Mitral Valve Repair
Triangular Resection With Ventricularization
·    This technique is ideal for patients who need posterior leaflet repair with prolapsing, redundant, and myxomatous tissue. The mitral valve is exposed and evaluated. The normal chordae on either side of the prolapsing portion are identified to determine the extent of resection. A triangular-shaped segment of tissue, with the base at the free edge of the posterior leaflet and the apex at or near the annulus, is excised with curved scissors (Fig. 21.7A). Running 4-0 Prolene sutures (see Fig. 21.7B), with or without a ventricularization technique, are used to close the defect in the leaflet.
·  The ventricularization technique is performed to normalize the height of the posterior leaflet and reduce the risk of systolic anterior motion. After triangular resection, each needle of a double-armed suture is passed through the free edge of one leaflet remnant and then through the midportion of that leaflet segment to ventricularize the free edge (i.e., move closer to the ventricle), thereby reducing the leaflet height (see Fig. 21.7C). Each needle is then used for a running closure of the posterior leaflet defect (see Fig. 21.7D), and the stitch is tied at the base of the resection (see Fig. 21.7E). The assistant may tie the suture with a knot pusher or the surgeon can tie it intracorporeally.

Quadrangular Resection With Sliding Repair
·  A quadrangular resection of the posterior leaflet is necessary for the management of an extensive, redundant, prolapsing leaflet. The excessively tall posterior leaflet is excised, and then the remaining portions of the posterior leaflet are detached from the annulus and advanced centrally, sliding it over to meet the other leaflet component. The leaflet base is reattached to the annulus with two layers of running 4-0 Prolene sutures, and the leaflet edges are reapproximated with 4-0 Prolene sutures.
 
Figure 21.7 (A) Triangular resection of the posterior leaflet. (B) Posterior leaflet repair using running technique. (C) Repair of the posterior leaflet using ventricularization technique. (D) Running closure of the posterior defect. (E) Final stitch next to the annulus.

Neochordae Implantation
·     Gore-Tex (WL Gore & Associates, Newark, DE) neochordae placement is greatly facilitated by the robotic approach due to the excellent exposure and magnified view of the subvalvular apparatus. The anterior leaflet is lifted upward using a dynamic left atrial retractor. The neochordae are created using 5-0 polytetrafluoroethylene (PTFE) sutures. One arm of the suture is passed twice through the fibrous tip of the papillary muscle and then twice through the free edge of the corresponding prolapsing segment. The second arm is then passed twice through the free edge of the prolapsing segment. The length of the chordae is adjusted based on the height of the nearest normal segment of the posterior leaflet, and the sutures are tied on the atrial side of the mitral valve leaflet (Fig. 21.8).
 
Figure 21.8 Repair of the mitral valve using artificial chordae.
Annuloplasty
·    All repairs are completed using a flexible, standard-length annuloplasty band. The band is first secured at the right (A3–P3) trigone, and additional sutures are placed from the medial to lateral part of the annulus using either running or interrupted Ethibond sutures.
·    For the interrupted suture technique, 10 to 12 2-0 braided polyester sutures are used to secure the annuloplasty ring in the standard fashion (Fig. 21.9). For the running suture technique, three 2-0 braided polyester sutures (Ticron, Covidien, MA) are used to secure the annuloplasty ring as follows. The first suture is tied down between right trigone and the ring and run clockwise to the midportion of the ring. The second suture (14 cm in length) is then passed through the ring and annulus in running fashion to the level of the midportion of the annulus. The second suture is started at this point with a single interrupted stitch and tied to the first suture. The remainder of the second suture is then run clockwise to the left trigone. The third suture (9 cm in length) is passed through the ring, through the left trigone, and then back through the ring. This third suture is tied down, and the tail is used to secure the second suture (Fig. 21.10).

5. Mitral Valve Replacement
·      The subvalvular apparatus and chordae are preserved whenever possible. Appropriate sizing is performed and 10 to 12 everting, double-armed, mattress sutures with Teflon pledgets are placed counterclockwise from the 11 o’clock position and fixed sequentially outside the incision with a small hemostat. The sutures are placed in the prosthesis sewing ring outside the chest. The prosthesis is lowered into the chest and positioned, and the knots are tied using the knot pusher or Cor-Knot device (LSI Solutions, Victor, NY) through the working port.

6. Atrial Fibrillation Procedure
     All lesions are created by applying the CryoMaze probe (ATS Medical, Minneapolis, MN) for 2 minutes directly to myocardial tissue, with temperatures reaching –140° to –160°C (–284° to –320°F). Following lesion creation, the probe is separated from the surrounding tissue by administering warm saline solution.
     The pulmonary veins are isolated with a single wide box lesion around all four veins. The first cryolesion extends from the right inferior pulmonary vein to the mitral annulus. The next lesion extends from the mitral annulus around the left pulmonary veins, reaching the upper border of the atriotomy. Great care is taken to ensure complete contact between the probe and atrial tissue. The complete box lesion can be constructed with two or three cryolesions; however, if the left atrium is particularly large and redundant, more lesions may be required. Additional lesions might be required from the pulmonary vein isolation box to the LAA if this area is not completely ablated.
     The final left atrial lesion is an epicardial lesion across the coronary sinus to ensure complete transmurality at the mitral valve annulus.
   The LAA is routinely closed as part of the CryoMaze operation unless there are significant pericardial adhesions keeping the appendage patent. The LAA is closed in a two-layer fashion using 3-0 Gore-Tex sutures.
Figure 21.9 Band annuloplasty using interrupted stitches.
Figure 21.10 Band annulolasty using running stitches.
7. Atrial Closure
·    Once the mitral surgery is complete, the left atriotomy is closed with running 4-0 Gore-Tex sutures, beginning a suture at each end of the atriotomy and meeting in the middle. The heart is allowed to fill and de-air via the atriotomy before tying the suture.

8. Tricuspid Valve Repair
·     After bicaval cannulation, the caval cannulas are backed into the SVC and IVC, and the tapes around the cavae are tightened. A vertical right atriotomy is made, and the dynamic atrial retractor is used to retract the anterior right atrial wall. Tricuspid valve repair has evolved from a classic De Vega repair (double-armed, running, vertical mattress purse-string sutures of 4-0 PTFE, tied over pledgets) to an annuloplasty band sewn into place with interrupted 2-0 polyester sutures. The right atrium is then closed in two layers with PTFE, and the caval tapes are released.

9. Removing the Cross-Clamp and Cardioplegia Catheter
·    All repairs are assessed using saline insufflation to fill and pressurize the left ventricle before closure, de-airing, and cross-clamp removal. Integrity of the repair (less than or mild residual MR) and adequacy of deairing should be confirmed with the patient off cardiopulmonary bypass before decannulation. Once the heart is beating (and preliminary evaluation of the repair by TEE looks good), the antegrade cardioplegia catheter is removed from the aorta, and the puncture site is closed with pledget-reinforced 4-0 Gore-Tex or Prolene mattress sutures.

10. Final Steps
·   The pericardium is loosely closed with two sutures to prevent cardiac torsion. A 19F Blake drain (Ethicon) is brought into the chest via the atrial retractor and the right instrument ports.
·    The instruments and ports are all removed, and both lungs are ventilated. The patient is then separated from cardiopulmonary bypass, and the repair is evaluated by TEE. While a protamine is administered, the cannulas are removed, the purse-string sutures in the femoral vein are tied, and the femoral arteriotomy is repaired primarily.
·    After a protamine is administered, the right lung is deflated, and the camera is reintroduced into the chest to examine the aortic cardioplegia site, as well as all port and angiocatheter sites, to ensure good hemostasis.
  
Step 4. Postoperative Care
·    Postoperative care is routine for cardiac surgery, with special attention to arrhythmia prevention and maintaining afterload reduction. In the area of postoperative pain control, several factors should be considered. Pain control after robotic surgery may be achieved with intercostal nerve block or using cryothermia to freeze the intercostal nerves prior to incision closure. Compared to sternotomy, patients who have robotic surgery require less intravenous narcotic, which may allow earlier extubation. All patients should undergo repeated TTE before discharge from hospital. Lifelong annual echocardiographic surveillance is necessary after mitral valve repair.

Step 5. Pearls and Pitfalls
·  Operating inside the heart with robotic instruments does not allow tactile feedback. However, this has not been a limitation in practice. Highly disciplined movement of robotic instruments, advanced echocardiographic imaging, and gaining ocular tactility through experience have addressed this issue. Furthermore, although cross-clamp and operative times are longer compared to those of conventional median sternotomy, there has been no significant difference with regard to postoperative morbidity and mortality.
· There are several potential advantages of robotic mitral valve repair in comparison to thoracotomy and thoracoscopic approaches. The robot facilitates precise movements of instruments in the closed chest and avoids the difficulties of using long, shafted, endoscopic instruments that may be experienced during minimally invasive procedures. The high-definition 3D view facilitates the visualization of the subvalvular apparatus and enables repair of any type of myxomatous pathology. The cosmetic results are appreciated by female and male patients, particularly in patients with prior breast reconstruction. Finally, the requirements for heterologous blood products, the incidence of atrial fibrillation, and postoperative pain have been reported to be lower, likely due to the reduced surgical trauma.
·    The collective results of robotic mitral valve repair in experienced groups have now reported a hospital mortality rate of less than 0.9%, stroke rate of 0.6% to 1.7%, reexploration for bleeding of 2.2% to 4.7%, and rare chest wall infections. Furthermore, the incidence of iatrogenic aortic dissection, phrenic nerve palsy, and groin infections have all decreased to almost 0%.
·  In summary, robotic mitral valve repair is now routinely performed, with or without concomitant tricuspid valve repair and atrial fibrillation ablation procedures. This approach is safe, effective, and durable for complete correction of all categories of mitral valve leaflet prolapse, regardless of complexity. Furthermore, robotic repair offers reduced blood loss, lower risk of incisional infection and atrial fibrillation, shorter hospital length of stay, quicker return to normal activities, and a superior cosmetic result. Therefore, the procedure may be particularly appealing in asymptomatic stage C1 patients according to ACC/AHA class IIa guideline recommendations.