Brunsting, Louis A. III MD; Rankin, J Scott MD; Braly, Kimberly C. MSN; Binford, Robert S. MD
From the Centennial Medical Center, Nashville, TN USA.
Accepted for publication May 14, 2009.
Color reproduction costs for this article supported by the Sorin Group.
Presented at the Annual Meeting of the International Society for Minimally Invasive Cardiothoracic Surgery, Boston, MA, June 11–14, 2008.
Address correspondence and reprint requests to Louis A. Brunsting III, MD, 2400 Patterson Street, Suite 223, Nashville, TN 37203 USA. E-mail: firstname.lastname@example.org.
In recent years, two trends in mitral valve repair have been developed simultaneously. First, the conversion to minimally invasive approaches, which have been shown to be safe and effective, and clearly facilitate patient recovery.1–3 Second, the increasing use of Gore-Tex artificial chordal replacement (ACR) for correction of mitral valve prolapse.4–15 As a component of standard mitral reconstruction, ACR allows virtually all prolapse valves to be repaired, while achieving excellent long-term stability and low late-failure rates.16,17 These two methods are ideal to combine, as described by several authors,10,18 and this article describes a simple method of robotic ACR, as currently practiced in our center.
All patients referred to our practice with isolated mitral valve degenerative disease and prolapse are considered for a minimally invasive, robotically assisted approach. Solitary posterior leaflet prolapse has been routinely operated robotically, as well as straightforward anterior leaflet or bileaflet prolapse. Patients with Barlow’s or complex valves are currently being approached by median sternotomy. The excellent visualization of the mitral valve afforded by high-definition robotic system may allow all open repair techniques to eventually be replicated in a minimally invasive setting.
Preoperative 64-slice computed tomographic angiography provides screening for the presence of significant coronary or aortic atherosclerosis, as well as measurement of aortic and femoral artery diameter. Relative contraindications to the robotic approach include morbid obesity, prior thoracic or cardiac operations, and greater mild aortic valve insufficiency. Absolute contraindications to this approach include inability to perform peripheral cardiopulmonary bypass and ascending aortic aneurysm.
After anesthetic induction with dual-lumen endotracheal intubation, a retrograde coronary sinus catheter is placed under echocardiographic guidance from the right internal jugular vein. Patients are positioned with the right chest and flank mildly elevated and the back flexed. The right femoral vessels are exposed. Two ports are placed in the fourth intercostal space lateral to the nipple—a 12-mm camera port and a 15-mm soft plastic “working” port (Fig. 1). Right and left robotic arm ports are inserted in the fifth or sixth and the third intercostal spaces more laterally. The atrial retractor port is positioned in the fifth intercostal space medial to the nipple line. If the diaphragm interferes with the right robotic arm function, a pledgetted retraction suture is placed in the tendinous portion and brought out inferolaterally. The pericardium is opened and retraction sutures to the posterior edge exteriorized laterally. A vent is placed across the chest wall. After initiation of femoral cardiopulmonary bypass and cardioplegic cardiac arrest using endoaortic balloon occlusion, the left atrium is opened just anterior to the right pulmonary veins. The robotic atrial retractor provides exposure to all aspects of the mitral valve in a flexible, adjustable manner, including the subvalvular apparatus and papillary muscles. The mitral valve is thoroughly examined, including functional testing with cold saline insufflation, using an endoscopic irrigation system.
Technique of Chordal Placement
For prolapsing segments of the left half of either leaflet, artificial chords are placed to the anterior papillary muscle, and for the right half, chords are placed to the posterior papillary muscle. As a first step before ring placement, and with good exposure of the submitral apparatus, a pledgetted mattress suture of 2-0 Gore-Tex is placed in the appropriate papillary muscle, oriented longitudinally, and tied (Fig. 2). Another 2-0 Gore-Tex vascular suture is passed through the anchor pledget, left untied, and stuffed into the ventricle. The pledgetted anchor suture prevents disruption of the Gore-Tex chord from the papillary muscle. A full annuloplasty ring (CarboMedics Memo three-dimensional) is then sutured to the mitral annulus with horizontal mattress sutures of 2-0 Teflon-coated braided suture, with knots being tied by the bedside surgeon or assistant.
After ring placement, the two arms of the Gore-Tex chord are retrieved from the ventricle and woven into the flail leaflet (straddling the prolapsing segment) in three full-thickness bites: (1) fairly close together in the free edge, (2) flaring laterally in the surface of coaptation, and (3) angling back together through the line of coaptation and onto the atrial surface. This loop pattern stabilizes the lateral aspects of the prolapsing segment, and leaving the suture untied through the anchor pledget allows the two arms to adjust to equal lengths and tensions once the heart starts beating. Weaving the suture from the free edge to the atrial surface produces a “hockey stick” shape to the leaflet, facilitating the creation of a surface area of coaptation. Again, it is important to take full-thickness bites to prevent subsequent dehiscence from the leaflet.
The length of the 2-0 Gore-Tex suture is held initially with the robotic forceps while valve competence is tested by injecting cold saline across the leaflets. If a chord seems too short or long, and the knot is lengthened or tightened by 1 cm, the process is repeated until the leaflets are symmetrically seated into the annular plane and the valve is fully competent. Then, the Gore-Tex suture is tied tightly against the robotic forceps by the bedside surgeon, and a permanent small clip is placed on the knot to further prevent unraveling. This is important because tying Gore-Tex off the tissue can increase the chances of unraveling. By “adjusting” the Gore-Tex chords at the end, a symmetrical and large surface area of coaptation can be achieved, routinely producing a competent valve with good leaflet opening and minimal diastolic gradients.
Intraoperative three-dimensional transesophageal echocardiography is used routinely to monitor the procedure. An example of a preoperative echocardiogram from a typical patient with isolated posterior leaflet prolapse is shown in Figure 3, along with a video frame showing the flail leaflet. After ACR and ring placement, the valve is completely competent with cold saline pressurization, and the echo shows full competence of the valve.
From 2006 to 2008, 12 patients have undergone robotic mitral valve repair with ACR, with no operative deaths. Valvular pathology was a degenerative disease in all patients, with the exception of a single patient with treated bacterial endocarditis. Intraoperative transesophageal echocardiography demonstrated no residual mitral insufficiency in nine patients and trace insufficiency in three. No patient had 1+ or greater insufficiency. On follow-up echocardiography, no patient has had worsened insufficiency, and there have been no reoperations in this cohort.
Over the past 15 years, considerable experience has been obtained using ACR without leaflet resection with open mitral repair. ACR has produced no residual leak in 95% of prolapse patients and mild leak in only 5%. In mitral prolapse, virtually all valves can be successfully repaired using ACR, independent of the anatomy and with negligible early or late conversion to replacement.15–17 Because the repair is not based on myxomatous chords (which can predispose to late chordal rupture)19 and because chordal support is actually augmented by the Gore-Tex material, the late failure/reoperation rate has been exceedingly low (2%–3% over 10 years of follow-up).16 The subsequent endocarditis rate has been around 1% (a real advantage of repair over replacement), and moderate mitral regurgitation (MR) recurrence treated medically has occurred in <2%. Finally, it is becoming increasingly evident that patient survival is improved by effective mitral valve repair, as compared with prosthetic replacement.20–22 If early robotic results using a similar ACR technique (as given above) are compared with these open data, it appears from early data that outcomes may be similar. Thus, we are cautiously optimistic that robotic methods of ACR will produce equivalent long-term outcomes to open approaches, although more long-term follow-up will be required to be certain.
With the ACR method, systolic anterior motion (SAM) of the anterior mitral leaflet has not occurred in either open or robotic series, because pulling both leaflets symmetrically down into the ventricle holds the anterior leaflet out of the outflow tract and prevents SAM. Leaflet tissue is never resected. The anterior and posterior leaflets are shaped differently but have the same surface area.23 Resecting posterior leaflet creates a relatively redundant anterior leaflet, predisposing to SAM. Sliding plasty can compensate by pulling the reconstructed posterior leaflet down into the ventricle. However, the easier solution is not to resect leaflet at all, especially because maintaining surface area promotes valve competence. The development of the fourth arm for the DaVinci robotic system (Intuitive Surgical, Inc., Sunnyvale, CA) has clearly facilitated its use for mitral valve repair, and from a technical viewpoint, merging ACR with robotic techniques is quite appealing. Leaflet resection and reconstruction was difficult with the robot because of long leaflet suture lines, whereas ACR placement into a papillary muscle is simple, or even easier with the robotic system, because of excellent exposure to the submitral apparatus. Long suture lines are not required, and because leaflet resection is not performed, leaflet surface area and valve competence are enhanced.
At present, only valves with clearly defined simple single leaflet or bileaflet prolapse are being approached robotically in our practice. More complex bileaflet prolapse or Barlow’s valves are still being exposed via sternotomy, because of concerns over the complexity of four-chord Barlow’s repairs17 or uncertainty regarding the exact anatomy of more complicated valves. The recent introduction of three-dimensional echocardiography may provide a more reliable assessment of the exact location of prolapsed segments, allowing a greater percentage of valves to be approached robotically. Moreover, as experience is gained, more difficult bileaflet repairs may be undertaken with the robot, perhaps routinely. The single overlying principle, however, is the importance of obtaining the best possible long-term valve repair.
It is not justifiable to compromise long-term outcomes for the sake of a smaller incision. For example, in the first robot trial,24 approximately 10% of patients left the hospital with moderate residual leak, and 5% required reoperation in the near term. Even in a more recent series,25 9% of patients with anterior or bileaflet prolapse required reoperation after 2 years, an unacceptable result by comparison to open ACR series.16 However, it is likely that merger of ACR with robot techniques will allow these cases to be performed robotically with better long-term results, perhaps with outcomes equivalent to open methods. At present, however, the authors try to recognize complex prolapse cases preoperatively and to repair them with ACR techniques through a median sternotomy approach.
Although early experience with robotic ACR suggests that results will be similar to open methods, several concerns need to be discussed. First, handling the Gore-Tex material with the robotic forceps could injure the material and facilitate late chordal rupture. With the use of 2-o Gore-Tex, a several fold margin of safety exists in the yield stress of the material,17 and it is unlikely that serious injury will occur. However, this potential problem is a cause of worry, and until 10-year follow-up is available, it should be kept in mind. It is also not known if the security of ring placement will be very good, but the initial results have been quite adequate. Although having properly qualified this new method, early experience suggests that results of robotic ACR in valves with simple prolapse will approximate the outcomes obtained with open methods, justifying continued liberal application in properly selected patients.
In summary, artificial chordal replacement for correction of mitral valve prolapse is extremely well suited for integration with robotic mitral repair. Techniques are now well established and are being applied to increasingly complex anatomies. It is suggested that robotic ACR without leaflet resection is an attractive alternative for repair of simple mitral valve prolapse.
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This is a nicely described technique on a method for placement of artificial chords using the da Vinci robotic system. This technique allows for adjusting of the chordal length as the valve is tested by injection of cold saline into the ventricle. The authors provide beautiful illustrations. This is another example that complex mitral valve repairs can be performed using robotic systems with excellent results in the hands of skilled surgeons.
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