Ann Thorac Surg 2002;74:1488-1493
© 2002 The Society of Thoracic Surgeons
Original article: cardiovascular
Novel suture device for beating-heart mitral leaflet approximation
Ottavio Alfieri, MDa,
John A. Elefteriades, MDb*,
Robert J. Chapolini, MDc,
Robert Steckel, DVMd,
William J. Allen, PEd,
Scott W. Reed, BSd,
Stefan Schreck, PhDe
a Hospital San Raffaele, Milan, Italy
b Yale University School of Medicine, New Haven, Connecticut, USA
c BioAccess, Baltimore, Maryland, USA
d Synectic Engineering, Inc, Milford, Connecticut, USA
e Edwards Lifesciences, LLC, Irvine, California, USA
* Address reprint requests to Dr Elefteriades, Section of Cardiothoracic Surgery, Yale University, 121 FMB, 333 Cedar St, New Haven, CT, 06510, USA.
e-mail: john.elefteriades{at}yale.edu
Presented at the Poster Session of the Thirty-eighth Annual Meeting of The Society of Thoracic Surgeons, Fort Lauderdale, FL, Jan 28–30, 2002.
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Abstract
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BACKGROUND: This investigation evaluates the potential of using a novel suturing device to achieve mitral valve repair (Alfieri type) on a beating heart without cardiopulmonary bypass.
METHODS: Eight healthy adult sheep were anesthetized and the chest was opened via a left thoracotomy. The suture device was directly inserted into the appendage of the left atrium. Suction ports on the distal tip of the device grasped and approximated the mitral leaflets while the heart was beating. Two-dimensional echocardiography and intracardiac pressure monitoring at the tip of the device were utilized to guide the procedure. The device was used to place two single sutures across the two leaflets at the center of the mitral valve. A knot pusher with integrated cutter was used to tie the sutures and cut the suture ends.
RESULTS: In all animals, the free margins of the mitral leaflets were successfully grasped and approximated by this device. Echocardiography confirmed successful deployment of the sutures in all cases, with a figure-of-eight appearance of the valve and normal valve hemodynamic function after placement of the sutures. Mid-leaflet approximation was verified at autopsy immediately after the procedure. No tissue damage was observed.
CONCLUSIONS: This study demonstrates that mitral valve repair (Alfieri type) can be performed safely and consistently on a beating heart without cardiopulmonary bypass using this new tissue approximation suture device. This technique may be applicable to the treatment of ischemic mitral regurgitation in conjunction with revascularization procedures or to mitral regurgitation in heart failure patients.
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Introduction
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| Drs Alfieri, Elefteriades, and Chapolini disclose that they have a financial relationship with Edwards Lifesciences. Dr Schreck is an employee of Edwards Lifesciences, LLC. Mr Allen, Mr Reed, and Dr Steckel are employees of Synectic Engineering, Inc.
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The importance of mitral insufficiency in contributing to symptoms and poor prognosis in patients with ischemic disease and those with advanced heart failure is being increasingly recognized. Dion [1] reported that approximately 10% of patients undergoing coronary bypass surgery are affected by mitral regurgitation. The degree of mitral regurgitation is moderate or more severe in 4% of these patients. Mitral annulus dilatation is the root cause of regurgitation in half of the patients. Ring annuloplasty is currently the most common surgical treatment for ischemic mitral regurgitation [2]. Annuloplasty is also utilized for the treatment of patients with mitral regurgitation associated with heart failure [3–5]. In recent years, evidence has been accumulating that a simple "leaflet-to-leaflet" or "edge-to-edge" mitral valve repair (Fig 1)
can significantly improve mitral insufficiency [6–9]. The edge-to-edge technique may provide a simple alternative to more complex annuloplasty procedures. Concerns have been raised about the edge-to-edge technique in terms of its potential for mitral stenosis [10] and long-term durability [11]. However, clinical data collected to date indicate that the edge-to-edge procedure provides an effective and efficient means for the treatment of mitral regurgitation, at least in the short term [6–8].
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Fig 1. The edge-to-edge technique. Double-orifice repair on the left and paracommisural repair on the right.
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The purpose of this study was to determine if a suture device currently being developed for soft tissue approximation could be used to perform "edge-to-edge" mitral valve repair on the beating heart without the need for cardiopulmonary bypass. Availability of such a less-invasive technology for mitral valve repair could be of considerable benefit in the treatment of these seriously ill patient categories. In patients with end-stage heart failure, availability of such a technique could delay the need for heart transplantation. A schematic of a potential clinical use of this novel system for less-invasive edge-to-edge repair is illustrated in Figure 2.
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Fig 2. Overview of the surgical approach utilizing the suture device as it may be envisioned for use in a clinical procedure.
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Material and methods
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Device overview
The experimental mechanical suturing system (LifeStitch; Edwards Lifescience, Irvine, CA) consists of a long trocar-type device that is placed through an access cannula port into the left atrium and then through the mitral valve. The cannula port (see Fig 2), which is placed inside a purse-string suture in the left atrium, provides a reliable, reusable access to the cardiac chambers for the required technical maneuvers. A duck-bill valve in the access port cannula prevents retrograde bleeding and discourages entrainment of air into the left atrium. A pistol-grip firing mechanism is incorporated (Fig 3A).
The trocar contains lumens for two sutures and their needles, as well as for two suction channels used to grasp the mitral valve leaflets (Fig 3B).
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Fig 3. The experimental device. (A) The suture device on the top, the knot pusher on the bottom, and the monofilament sutures with straight needles in the middle. The device passes into the cardiac chambers through a port access cannula in the left atrium (pictured in Fig 2). (B) Close-up view of the distal end of the suture device showing the two suction parts and the four needles partially deployed. (C) Schematic depiction of the method of firing of the stitches through the mitral valve (MV) leaflets. (LA = left atrium; LV = left ventricle.)
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Device positioning
Epicardial echocardiography (7.5-MHz probe) is utilized to visualize and adjust the position of the trocar device vis-à-vis the left atrium, mitral valve annulus, and left ventricle (Fig 4A). By echocardiography, the tip of the device is positioned through the center of the mitral valve into the left ventricle. The device is then withdrawn gently and slowly until the suction ports are located at the level of the mitral valve leaflets. Pressure monitoring through the suction ports assists this positioning. When the leaflet level is reached, a distinct "clipping" of the systolic pressure waveform is seen on the pressure monitor, due to covering of the pressure ports by the leaflets.
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Fig 4. Edge-to-edge approximation of the mitral valve in sheep. (A) Echocardiographic positioning images. (Left) Short-axis view. Note device going through circular image of mitral valve (MV) into left ventricle (LV) (into the plane of the figure). (Right) Long-axis view of same. (B) Echocardiographic image of the mitral valve approximated at the A2-P2 portions of the leaflets. (C) Mitral valve in situ taken immediately after completion of the edge-to-edge procedure. (LA= left atrium.)
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Leaflet grasping
Once the trocar-type device has been placed into the left ventricle through the mitral valve, the leaflets must be grasped. This is done by means of suction ports at the sides of the trocar tip (see close-up in Fig 3B). These are protected by a grate, which permits exertion of suction force but prevents the leaflets from being aspirated into the ports. Application of suction is accomplished via two suction lumens, one for each leaflet, which run the length of the device. The suction force originates from 1-L evacuated bottles next to the operating field, which also measure any blood aspirated before leaflet approximation. Once the leaflets are grasped, blood effluent ceases, as the leaflets themselves occlude the suction ports.
Suture deployment
Two double-armed monofilament sutures with two straight needles at the ends are housed in the distal tip of the device. As the device is fired, the needles are deployed out from the housing (points facing back toward the handle of the device) (Fig 3C). When the trigger is pulled, the two sets of two needles are fired through the mitral valve leaflets, from the left ventricular to the left atrial sides of the valve. Once through the valve leaflets, the needles are captured by clips constrained behind the vacuum port grates, to prevent their migration.
Suture tying
The needles are brought out of the heart as the trocar device is withdrawn backwards from the cardiac chambers. The two continuous monofilament sutures are deployed out of the device as it is withdrawn. The needles are cut off and the knots tied externally and advanced into the left atrium through the port cannula using a knot pusher. After six throws are delivered and seated, spring-loaded cutting blades integrated into the tip of the knot pusher are deployed, cutting the suture 2 mm above the last knot.
Surgical procedures (table 1)
Eight
ovine females ranging from 4 to 8 years in age were premedicated with buprenorphine IM and administered general anesthesia according to a preapproved protocol at the T. D. Morris facility in Reisterstown, MD. All animals received humane care in compliance with the "Guide for the Care and Use of Laboratory Animals." Induction of general anesthesia was accomplished with a ketamine/diazepam combination IV, followed by endotracheal intubation and maintenance of general anesthesia with a combination of isofluorane and oxygen in a semiclosed breathing circuit. The animals were then positioned on the operating table in a right lateral decubitus position. Because the surgical procedures were intended to be terminal, aseptic technique was not necessary. Before positioning the animals for surgery, the left femoral artery and vein, plus the left jugular vein, were cannulated with 8- or 9-Fr catheters by direct surgical cut-down. The three catheters permitted direct arterial blood pressure monitoring and blood gas sampling, rapid fluid replacement therapy, and intraoperative cardio-specific drug administration, respectively. Left thoracotomy was performed. The cartilaginous portion of the scapula was removed with a large bone cutter to enhance access over the dorsal wound margin. The chest was entered through the removed fifth rib. The pericardium was then incised to expose the left heart chambers. Beating-heart mitral valve repair was then performed by applying the methodology described above.
The surgeon and the assistant confirmed capture of both mitral leaflets by the creation of the double-lumen or "bow-tie" appearance of the mitral valve image with the epicardial ultrasound. Further confirmation of leaflet capture was obtained by inspection of the vacuum bottles, which were observed to be aspirating negligible or no blood once the leaflets completely covered the suction openings at the tip of the device. At that point, the surgeon fired the device, delivering the needles and attached sutures through both mitral leaflets. Again, the ultrasound image was monitored continuously to assure the surgical team that the first step of the "edge-to-edge" repair had been accomplished (Fig 4B).
The surgeon then withdrew the device slowly to allow the integral 4-0 sutures to pay out along the length of the instrument and through the self-sealing port access cannula valves. After the suture device had been removed from the cannula completely, the assistant surgeon would identify the correct suture pairs and tie them externally. As the surgeon made individual throws of a square knot, and the ultrasonographer provided a continuous image of the mitral valve, the assistant surgeon would advance the individual throws with the specially designed knot pusher passed down through the self-sealing cannula, thus suturing the mitral leaflet edges together. The end of knot passage was determined both by the feel of a "stop" by the operator, and by the image created by ultrasound that the metal tip of the knot pusher had contacted the mitral leaflet tissue. This process was performed for the first five throws of each respective suture. After the sixth knot throw was formed, the suture blades integrated in the knot pusher were spring-deployed. As the surgeon held mild tension on the suture strands, the assistant activated the cutting function of the knot pusher, severing the sutures approximately 2 mm above the end of the knot. The port access cannula was removed from the left atrium. A final ultrasound image of the "edge-to-edge" mitral repair was documented on video film before humane euthanasia according to the preapproved protocol. At postmortem, the heart was opened and the mitral valve exposed to confirm proper placement of the sutures. The valve was subsequently excised for a more detailed visual inspection of the edge-to-edge placement.
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Results
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The prototype suture device worked satisfactorily in all eight mitral valve repair procedures. All animals maintained acceptable hemodynamics throughout the procedure. Blood loss through suctioning to grasp the leaflets averaged 362 cm3 (range 150 to 675 cm3). Suctioning of blood from the chambers ceased once the leaflets were successfully grasped. In all cases, the suture device successfully captured the individual leaflets. Echocardiography confirmed successful deployment of sutures in all cases, with a figure-of-eight appearance of the valve in all cases (Fig 4B). Autopsy confirmed mid-leaflet approximation in all cases (Fig 4C). The needles penetrated the mitral leaflets consistently, approximately 3 to 4 mm away from the free edge of the tissue margin. The spacing between the two sutures was 5 mm in all cases. See again Figure 4C for the relation of the sutures to the leaflet edges and to each other. The paying out of the long sutures from the instrument shaft was again without mishap, and the self-sealing cannula allowed an acceptable degree of blood extravasation during the knot-tying portion of the procedure. The results for the individual animals are summarized in Table 1.
Knot tying of the mitral valve repair sutures did require a "delicate touch" and practice. The knots were consistently tied as six throw square knots, and the integral cutting function of the knot pusher consistently cut both suture strands about 2 mm from the knot.
Immediate postmortem examination of the intracardiac anatomy of the left heart chambers revealed that neither the vacuum applied to the tissue nor the suturing device or knot pusher produced any perceptible damage to the myocardium or associated structures.
The minimally invasive approach required some operator training, as the surgeons did not have direct visual access to the valve and the system permitted only limited tactile feedback through the instruments. Once the operators became familiar with reading the information on the echo screen and pressure monitor, capture of leaflets and knot tying could be completed in less than 15 minutes.
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Comment
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This study confirms that mitral repair of the edge-to-edge type can consistently be performed in the live animal with a beating, closed heart technique, using a novel tissue approximation suture device, without cardiopulmonary bypass. A combination of echocardiographic images and intracardiac pressure monitoring provided adequate information to guide leaflet approximation and suture deployment. Suction created by evacuated bottles generated sufficient force to capture and approximate the leaflets without damage to the tissue.
Although all sutures were successfully placed, without damage to cardiac structures, it is conceivable that misplacement of sutures or damage to the atrium, mitral valve leaflets, or left ventricle could occur. The experimental system reported here has no ability to correct such potential problems. An open heart approach on cardiopulmonary bypass would be required.
Other limitations of this investigation are as follows. The Alfieri technique, even with cardiopulmonary bypass, remains controversial, and not universally accepted. Specific concerns have to do with long-term follow-up and proof of effectiveness after Alfieri repair is performed. As well, this experiment was a short-term feasibility study. Long-term effectiveness of such beating-heart surgery techniques remains to be demonstrated.
Placement of the edge-to-edge stitch in a beating heart without the need for cardiopulmonary bypass may provide the clinician with an additional tool for managing patients with mitral regurgitation.
One potential setting for future application of this technology would be for adjuvant mitral valve repair at the time of coronary artery bypass grafting. Although controversy exists regarding the necessity for a direct repair of the mitral valve at the time of coronary artery bypass grafting in patients with ischemic mitral insufficiency, many authorities advocate mitral valve repair in this setting. The experimental technology evaluated in this study could permit concomitant mitral valve repair at the time of coronary bypass surgery without the need for a left atrial incision or additional cardiopulmonary bypass time.
This minimally invasive edge-to-edge technique may also be applicable to the treatment of ischemic mitral regurgitation in conjunction with coronary revascularization procedures performed with off-pump, beating-heart techniques.
Another group of patients who could benefit from this technology are those with advanced left heart failure and mitral insufficiency. The experimental technique reported in this study could permit minimally invasive correction of the mitral insufficiency. These patients are often not referred for surgical repair, because they are believed "too sick" for conventional surgery. The experimental technology described in this report would avoid cardiopulmonary bypass and its consequences, and thus represents a more palatable alternative for these patients. Symptomatic improvement, and even postponement of the need for cardiac transplantation, might be realized.
Although these experiments were performed in experimental animals via open thoracotomy, a port approach without chest incision (as depicted in Fig 2) can be envisioned for future human application.
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Acknowledgments
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Research funding was provided by Edwards Lifesciences, LLC.
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References
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Abstract
Introduction
