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Ann Thorac Surg 2002;74:1488-1493
© 2002 The Society of Thoracic Surgeons
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 2830, 2002.
| Abstract |
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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.
| 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 [35]. 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 [69]. 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 [68].
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| Material and methods |
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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.
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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.
| Results |
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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.
| Comment |
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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.
| Acknowledgments |
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| References |
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