Author's Accepted Manuscript
Myxomatous Mitral Valve Repair: Loop Neochord Technique Robert C. Neely MD, Michael A. Borger MD, PhD
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S1522-2942(15)00132-4 http://dx.doi.org/10.1053/j.optechstcvs.2015.10.003 YOTCT382
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Operative Techniques in Thoracic and Cardiovasculary Surgery
Cite this article as: Robert C. Neely MD, Michael A. Borger MD, PhD, Myxomatous Mitral Valve Repair: Loop Neochord Technique, Operative Techniques in Thoracic and Cardiovasculary Surgery, http://dx.doi.org/10.1053/j.optechstcvs.2015.10.003 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting galley proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Myxomatous mitral valve repair: Loop neochord technique
Robert C. Neely MD, Michael A. Borger MD, PhD
For: Operative Techniques in Thoracic and Cardiovascular Surgery
Address for correspondence: Michael A. Borger, MD, PhD Division of Cardiac, Vascular and Thoracic Surgery Columbia University Medical Center-New York Presbyterian Hospital Milstein 7GN-435 177 Fort Washington Ave New York, NY 10032 [email protected]
Key words: mitral regurgitation, minimally invasive, loop technique, neochord
Surgical repair techniques for myxomatous mitral regurgitation have evolved over time, with multiple different methods in current use. The Loop neochord technique provides a versatile and reproducible method that can be used for anterior, posterior, or bileaflet prolapse, as well as Barlow’s disease. Preoperative planning and careful intraoperative valvular assessment are used in order to determine the appropriate Loop length. Prefabricated commercial Loops are available, but Loops can also be created at the time of operation with polytetrafluroethylene 4-0 sutures and pledgets. We herein describe specific leaflet and subvalvular landmarks and suture placement techniques to ensure an accurate and durable mitral valve repair. While these principles can be applied via a full sternotomy, we illustrate our preferred approach using the Loop technique via a right mini thoracotomy and femoral cardiopulmonary bypass.
Introduction Mitral valve (MV) repair remains the preferred treatment for myxomatous mitral regurgitation [1,2,3]. Although MV repair techniques have evolved over the preceding decades, no particular method has emerged as the predominant technique in current day practice [4-6]. In order to be a successful MV repair surgeon, one should be comfortable performing several different repair techniques that can be tailored to a patient's individual valvular pathology. Nonetheless, we prefer using the Loop neochord technique for the majority of patients with MV prolapse [7-9].
A variety of approaches to expose the MV have been described including minimally invasive approaches with an array of cannulation strategies for cardiopulmonary bypass (CPB) [8,10-12]. The advantages and disadvantages of minimally invasive cardiac surgery have been discussed at length in the literature [12-15]. We herein describe our preferred method for treating myxomatous mitral regurgitation using the Loop neochord technique for MV repair. Although the approach described herein is via a right minithoracotomy (our preferred approach for patients requiring MV surgery and / or tricuspid valve repair, closure of atrial septal defects, and atrial fibrillation ablation), the Loop technique can also be applied via a full sternotomy. We use the Minimal Invasive Valve XS system (Aesculap, Melsungen, Germany) and femoral cannulation for minimal invasive MV surgery.
Figure 1: Set up and patient positioning includes double lumen endotracheal intubation, central line placement and a Swan Ganz catheter inserted high in the neck to allow for supplemental internal jugular venous cannulation, if needed. A foley catheter is placed. The patient is positioned supine with a roll under the right chest, and the right arm is tucked slightly posteriorly in order to expose the anterolateral chest wall. External defibrillator pads are placed and transesophageal echocardiography (TEE) is standard. Figure 2: A 5-8cm curvilinear incision is made at the right inframammary crease (or just above) for women, or 1-2 cm below the nipple in men. The chest x-ray (CXR) should be examined prior to opening the pleural space to help guide which intercostal space is to be opened. The pleural space is entered 1-2 rib spaces above the skin incision for women, and at the incision or one rib space higher for men. The
intercostal space opening is extended several centimeters medially and laterally using cautery along the superior aspect of the rib. A 5mm incision is made just lateral to the sternum in the third or fourth intercostal space for the atrial retractor. An additional small incision is made a few centimeters cranial and posterior to the thoracotomy for introduction of the aortic cross clamp. A final 5mm incision is made directly cranial to the mini-thoracotomy for the thoracoscope port with CO2 inflation, which passes through the third intercostal space.
Figure 3: Femoral cannulation is performed through a 3-4cm transverse incision over the right femoral pulse. Heparin is dosed to achieve an activated clotting time >400 seconds. 5-O prolene overlapping pursesting sutures are placed in the femoral vein and artery at the cephalad most aspect of exposure, in order to optimize the angle of cannulae insertion. We perform venous cannulation with a multistage BioMedicus (Medtronic, Minneapolis, MN) using the Seldinger technique. TEE is used to confirm that the guidewire crosses the inferior vena cava(IVC), right atrium(RA), and superior vena cava(SVC) before advancing the tip of the cannula to a few centimeters above the SVC/RA junction. In patients weighing more than 80 kg, a second small venous cannula can be inserted via the right internal jugular vein. We use a 16 or 18mm FemFlex arterial cannula (Edwards Lifesciences, Irvine, CA) to cannulate the femoral artery. (Reprinted, with permission, from Elsevier. Seeburger J et al. Op Tech Thorac Cardiovasc Surg. 2008;13:83-90)
Figure 4: Adequate venous drainage and a decompressed right atrium are ensured. Vacuum-assisted venous drainage (-25 to -40 mm Hg) is nearly always required. The pericardium is opened vertically 3-5cm anterior to the phrenic nerve. Using blunt dissection, the ascending aorta is carefully mobilized from the right pulmonary artery. A 4-O prolene pursestring is placed on the anterior aspect of the ascending aorta and an antegrade cardioplegia cannula is inserted. CPB is briefly stopped and the aortic cross clamp (Chitwood Debakey Clamp, Scanlan; Saint Paul, MN) is applied. CPB is resumed and cardioplegia is administered. The oblique sinus is opened with blunt dissection, and then the left atrium is opened along Waterston's groove with an 11 blade. After achieving adequate diastolic arrest, the atriotomy incision is extended superiorly and inferiorly and a left atrial retractor is used to expose the entire MV apparatus. A combination of direct and thoracoscopic visualization is used throughout the remaining procedure.
Figure 5: The first step in the Loop technique is a comprehensive assessment of MV pathology, which confirms the TEE findings. In this case, extensive prolapse of the P2segment with a ruptured chordae tendinae is present.
Figure 6: The prolapsing P2-segment is laid down into the ventricle in order to visualize location of the papillary muscles. The proximity of each papillary muscles to the prolapsed cusp determines where the Loops are attached. Specifically, Loops that are fixed to the posteromedial papillary muscle should be attached to the medial half of the MV, and Loops attached to the anterolateral papillary muscle should be attached to the
lateral half. Attaching a neochord from the posteromedial papillary muscle to the lateral aspect of the valve, for example, will lead to restriction and must be avoided. Visualizing the midline of the valve aids this step and this so-called ‘do not cross the midline’ rule prevents such excessive tethering of the leaflet free edge.
Figure 7: The lengths of the Loops are determined by measuring the distance between the papillary muscle and the envisioned line of leaflet coaptation with a caliper (ValveGate Suture Ruler, Geister; Tuttlingen, Germany). Remember that the level of leaflet coaptation is several millimeters below the annulus for the posterior mitral leaflet (PML) and nearly at the level of the annulus for the anterior mitral leaflet (AML). In addition, AML sizing must be more precise in order to prevent residual MR. The distal jaw is positioned 3-5mm below the tip of the chosen papillary muscles, and the proximal jaw is placed at the expected level of coaptation.
Melnitchouk’s Rule can also be used prior to beginning the operation in order to determine Loop sizing. The distance between the mitral annulus and the left ventricular (LV) apex is measured using the two chamber long-axis view in TEE: For PML neochords: mitral annulus distance to LV apex (cm) x 2 = # mm Loop length.
For AML neochords: (mitral annulus distance to LV apex (cm) x 2) + 10 = # mm Loop length.
In general, Loop sizes fall within the following ranges in the vast majority of patients: PML 10-16 mm; AML 20-26 mm; commissures 16-20mm.
Figure 8: Commercially available non-absorbable polytetrafluroethylene (ePTFE) loops (Implant Chordae Loop, Santech Medical; Grosswallstadt, Germany (pictured) or Chord-X suture, On-X Life Technologies; Austin, TX) simplify the procedure, although Loops can be handmade using Goretex 4-O CV sutures (W.L. Gore and Associates; Flagstaff, AZ), two pledgets, and the Loop sizing caliper.
Figure 9: Loops of the appropriate length are sutured to the papillary muscle head approximately 3-5 mm below its tip. The needles are then passed through a free pledget and the Gore-Tex sutures are knotted several times to avoid slippage.
Figure 10: The Loops should protrude away from the papillary muscles and into the ventricular cavity without entrapment of any of the surrounding chordae. Each Loop is then attached to the free edge of the prolapsing segment with a separate, non-pledgeted anchoring suture (Gore-Tex 4-0) passed through the Loop. The anchoring suture can be placed through more than one Loop if the prolapsing segment is narrow, but no less than two anchoring sutures should be used.
Figure 11: A) One end of the anchoring suture is passed through the prolapsing segment of the leaflet, approximately 5 – 8 mm from its free edge, and the two ends are tied over the free edge of the leaflet. The distance between anchoring sutures on the leaflet free edge is also 5 – 8 mm. B) The distance from the free edge of the prolapsing leaflet progressively decreases as the anchoring sutures advance towards the middle of the valve in order to compensate for the fact that the distance to the papillary muscle progressively increases. Note the ‘do not cross the midline rule’.
Figure 12: A water-sealing test is performed using a laparoscopic suction-irrigator such as the StrykFlow 2 (Stryker, Kalamazoo, MI) both: A) prior to ring annuloplasty and B) after lowering of the ring annuloplasty into place (but prior to tying sutures). Any required adjustments to the Loops are easier to perform prior to fixing the annuloplasty ring in place. Note the Gore-Tex suture knots shift below the level of coaptation when the ventricle is full.
Figure 13: The annular sutures are tied with a knot pusher and a final water-sealing test is performed. Automatic tying devices may reduce the myocardial ischemic time.
Figure 14: The left atrium is closed with a Prolene 3-0, being sure to inject the cavity with saline prior to tying the suture. Suction is placed on the aortic vent, CPB flow is reduced, and the aortic cross clamp is removed. A single epicardial ventricular wire is placed along the inferior RV wall prior to filling the heart. A second wire can be placed at the skin for grounding. The presence of significant air emboli is ruled out by TEE prior to
removing the aortic root vent. CPB flow should be reduced again during tying of the aortic root vent suture. The pericardium is closed, leaving a small window for a mediastinal drain. The patient is weaned from CPB and decannulated. Protamine is given and the thoracoscope is used to look for residual chest wall bleeding prior to closing. A pleural chest tube and mediastinal drainage tube (via a small opening in the inferior pericardium) are placed. The thoracotomy is closed in standard fashion. 0.25% Marcaine is injected for anesthetic rib blockade.
The Loop neochord technique is a reproducible operation and can be used routinely for a variety of valvular pathologies. Applying the tenents of ‘respect rather than resect’, this technique allows the operator to correct nearly all different forms of MV prolapse while achieving maximal leaflet coaptation. Determining the correct Loop length, however, can be challenging. In the only randomized controlled trial to date, Loop neochords resulted in similar clinical and echocardiographic outcomes, but greater line of coaptation, compared to classic leaflet resection techniques .
Our preferred approach to the MV is via a right mini-thoracotomy. In addition to improved cosmesis, the benefits of a minimally invasive approach include less blood loss, fewer transfusions, shorter length of stay and quicker return to normal activity levels without compromising patient safety or durability of MV repair [8,12,13]. Moreover, femoral cannulation for CPB is safe and simplifies the operative field . Although the
routine adoption of a minimal invasive technique can be achieved with very low rates of conversion to full sternotomy [18,19], a definite learning curve exists for this procedure . The Loop technique may facilitate the learning curve for minimal invasive MV surgery. Indeed, one may want to employ the Loop technique first via a full sternotomy before proceeding to the minimal invasive approach. Once mastered, we consider the Loop technique via a right, mini-thoracotomy the standard of care for patients with myxomatous MV disease.
We would like to thank Rob Gordon for his hard work preparing the expert illustrations presented in this manuscript.
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