Innovations: Technology & Techniques in Cardiothoracic & Vascular Surgery:
Neochordae Implantation Made Easy With an Adjustable Device: Early Report of Acute and Chronic Animal Experiments
Maisano, Francesco MD*; Denti, Paolo MD*; Vanermen, Hugo K. MD†; Seeburger, Joerg MD‡; Falk, Volkmar MD§; Mohr, Friedrich Wilhelm MD, PhD‡; Mack, Michael J. MD¶; Alfieri, Ottavio R. MD*
From the *San Raffaele Hospital, Milano, Italy; †Onze Lieve Vrouwziekenhuis, Aalst, Belgium; ‡Herzzentrum Universitaet Leipzig, Leipzig, Germany; §University of Zürich, Zurich, Switzerland, ¶Cardiothoracic Surgery Associates of North Texas, Dallas, TX USA.
Accepted for publication May 21, 2010.
Supported by Valtech Cardio LTD, Or Yehuda, Israel.
Disclosures: Francesco Maisano, MD, Hugo K. Vanermen, MD, Joerg Seeeburger, MD, Volkmar Falk, MD, Michael J. Mack, MD, and Ottavio R. Alfieri, MD, are consultants for Valtech Cardio, Or Yehuda, Israel.
Address correspondence and reprint requests to Francesco Maisano, MD, Cardiochirurgia, Ospedale San Raffaele, Via Olgettina 60, 20132 Milano, Italy. E-mail: email@example.com.
Objective: Neochordae implantation is a well-established surgical solution for the treatment of mitral valve prolapse. The main limitation to wide usage of the technique has been the difficulty associated with accurate determination of neochordal length. We describe a system specifically designed to facilitate rapid, uncomplicated implantation and off-pump, beating heart adjustment of neochordae.
Methods: Five swine underwent implantation of the adjustable neochordal system (V-Chordal; Valtech Cardio LTD, Israel) while on cardiopulmonary bypass after cutting native chordae to create a significant lesion. Neochordae length was adjusted with millimeter-level resolution, off-pump after discontinuation from bypass.
Results: In all animals, the implant was successful. Under echocardiographic monitoring, flail lesions were corrected in all cases, using the anatomic landmarks or the degree of mitral regurgitation for real-time guidance. At postmortem gross examination, the implant and the neochordae were completely healed with evidence of tissue ingrowth.
Conclusions: Preliminary animal experience suggests that the V-Chordal-adjustable neochordae system can be safely and effectively implanted, with accurate and precise adjustment of chordal length. The design of the device is suitable for a minimally invasive environment because of the long, flexible shafted design of the delivery system.
Neochordae implant is a well-established surgical solution for the treatment of mitral valve prolapse.1–3 The main advantage of this technique, predominantly used to treat anterior leaflet prolapse, is the restoration of the mitral anatomy with preservation of leaflet tissue to create the largest surface of coaptation and thereby enable improved functional performance of the mitral valve apparatus through minimization of residual mitral regurgitation (MR). The main drawback of the procedure is the complex and time-consuming process of determining optimal neochordal length, particularly in the flaccid heart during cardioplegic arrest. We investigated a new concept to implant adjustable length neochordae using a new system specifically designed to allow rapid and predictable adjustment of neochordae length during surgical mitral valve repair procedures. The system (V-Chordal-Adjustable System; Valtech Cardio LTD, Israel) is composed of a chronically implanted neochordae and a flexible delivery device for achieving papillary fixation and precise, high-resolution neochordae adjustment. To evaluate the safety and performance of the V-Chordal-adjustable system in an animal model of MR caused by flail leaflet, we report the early results of preclinical studies in an animal model of mitral valve dysfunction.
The Valtech V-Chordal-adjustable system is composed of two main elements (1) the neochordal implant is formed by a metallic, helical fixation element, a Dacron-covered, microlocking, adjustment spool and two 3-0 sutures coated with expanded polytetrafluoroethelyne connected to tapered needles and (2) a delivery system comprising a proximal end affixed to a flexible shaft that securely engages the implanted microlocking spool mechanism during fixation and adjustment of neochordal length, and a distal adjusting handle that allows precise, high-resolution regulation of the neochordae length (either increasing or decreasing length) in the beating heart under physiological loading conditions before surgical closure (Fig. 1).
Five adult swines (three acute and two chronic experiments) underwent general anesthesia with a standardized protocol as described below. Induction and maintenance of anesthesia were performed by administration of isoflorane (2%). Preoperative transthoracic echocardiographic measurements of mitral valve anatomy and function were performed and recorded. A minimally invasive left thoracotomy approach (muscle sparing) was performed on all animals. After full heparinization, the descending aorta (arterial line) and pulmonary artery (venous line) were cannulated using standard entry and purse-string closure techniques. Cardiopulmonary bypass was initiated and the left atrium was opened longitudinally 2 cm above the atrioventricular groove without cross-clamping the aorta.
After opening the left atrium, the mitral valve leaflets could be easily and directly visualized. A model of mitral valve regurgitation was created by first isolating and then cutting two or more anterior chords in the area of A2. The V-Chordal delivery system was then inserted across the mitral valve. The head of the posterior papillary muscle was stabilized and the central region of the papillary head was engaged with the helical fixation element. Fixation was accomplished by slowly rotating (four turns clockwise from a proximal perspective) the distal mechanism on the adjustment handle. Appropriate engagement of the papillary muscle was verified by application of gentle traction. Then, the surgical sutures, connected to the microlocking, adjustment spool, were detached from the shaft of the delivery system and sutured to the edge of the mitral leaflet as usually performed for chordae replacement penetrating the leaflets with the attached needles (Fig. 2). The atrium was then closed with a running stitch, leaving shaft of the adjustment handle across the atriotomy line (Fig. 3), and the animals were weaned from cardiopulmonary bypass. The implanted neochordal length was adjusted by rotating the suture length control knob on the adjustment handle under real-time echocardiographic guidance until the desired reduction of MR was achieved (Fig. 4). After releasing the neochordae implant, the flexible delivery system shaft was withdrawn from the atrium.
The acute animals were euthanized and the hearts were removed for visual examination. In the chronic animals, the thoracotomy was closed in layers and air was removed from the chest. Antibiotics were given and animals recovered while being monitored. Chronic animals were housed and fed for 60 days before killing.
All animals survived the surgery. Anterior leaflet flail lesions were effectively simulated in all animals by cutting two primary chordae in the A2 region, toward the posteromedial commissure. The flail segment width was ∼5 mm. After discontinuation from cardiopulmonary bypass, flail leaflet was obvious in all animals, with evidence of a severe grade of eccentric MR. Under echocardiographic monitoring, flail lesions were corrected in all cases, using either the anatomic landmarks or the degree of MR for real-time guidance. In all cases, the Delivery System was easily disconnected from the implant, with no bleeding from the atriotomy line and no damage to the surrounding tissue. During final echocardiographic measurements, all animals showed no or trivial amount of MR with no evidence of residual flail lesions (Fig. 4B). The neochordae were visible on echo and the implant position in the tip of the posteromedial papillary muscle.
Two animals survived after the acute experiment for 60 days. At postmortem gross examination, the implant and the neochordae were completely healed with evidence of tissue ingrowth, with no gaps. Papillary muscles seemed to be normal with fibrous healing confined to the area of the implant and no evidence of damage to the surrounding tissue (Fig. 5).
In this initial experience with the Valtech V-Chordal, we have been able to implant adjustable length neochordae in an animal model of flail leaflet-related MR. Neochordae length was precisely regulated with high resolution on the beating heart, under echocardiographic guidance to safely and effectively optimize functional performance of the mitral valve.
Preliminary evidence from this study suggests that minimally invasive chordal repair and intraprocedure, real-time adjustment techniques are technically feasible and may lead to wider application of neochordae repair, enhancing the chance of a successful repair, thereby promoting the potential for more rapid and complete reverse remodeling subsequent to surgical intervention.
Surgical techniques that spare leaflet tissue seem to provide clear benefits when coaptation can be optimized and MR minimized. The creation of neochordae has been associated with larger orifice area after repair compared with leaflet resection.2 Moreover, the preservation of the leaflets is possibly associated with a wider surface of coaptation1 suggesting a potential for longer durability of the repair.4 Several techniques have been reported to accurately estimate the length of the neochordae that are created during surgery with sutures anchored in the head of the papillary muscle.5 The most frequently used technique involves estimating the length of other chordae as a reference, adjustment of chordal length during hydraulic testing of the static heart (on cardiopulmonary bypass), and the use of the annular to papillary muscle distance.6 Other methods include devices to guide chordal implant by adjusting the length using the annuloplasty level as a reference.7 More recently, the loop technique has been introduced as a method to improve reproducibility of the repair, implanting a presized group of chordae, with the length based on either anatomic or echocardiographic measurements.8 Maselli et al9 reported a method to modify the length of the neochordae while in cardioplegic arrest, using a special tying technique.
One important distinction is that all these traditional methods are based on the static determination of chordal length during cardioplegic arrest. In all these methods, hydraulic testing is used to assess the effect of chordal length on coaptation and resultant MR estimations.
More recently, transapical off-pump implant of neochordae has been proposed as an alternative to conventional techniques.10,11 By using this approach, chordal length is adjusted on the beating heart under echo guidance. Unfortunately, this approach is limited because there is no annuloplasty device available to combine with the therapy, although minimally invasive procedures could be performed early in the course of the disease, before annular dilatation develops.
We described a minimally invasive surgical device that simplifies the implant of neochordae under cardioplegic arrest and allows subsequent adjustment on the beating heart. The device has a flexible shaft that allows remote actuation of a fixation element in the head of the papillary muscle. The use of this mode of fixation improves simplicity, by reducing suture handling, and it is possibly safer as the papillary muscle implant interferes with the native chordae less than a conventional figure of eight suture. Once the papillary muscle fixation is completed, the neochordae are implanted on the free edge of the prolapsing segment as conventionally done. The device enables fine tuning of the neochordae length, after the implant, under physiological loading conditions.
In conclusion, we investigated the functionality of a device enabling a simple and a reliable technique for the implant and precise adjustment of neochordae. The system is designed to accommodate commonly practiced surgical and minimally invasive techniques with the addition of two elements of novelty. First, the papillary muscle attachment is obtained with a helical fixation element, and second, the length of the neochordae is precisely adjustable on the beating heart. Preliminary animal experience suggests that the procedure can also be safely and effectively performed in a minimally invasive environment because of the long, flexible shafted design of the delivery system. Potentially, multiple devices can be used to address more complex anatomies with multiple prolapsing segments. Further evaluations are warranted to assess critical issues related to durability and feasibility of the procedure in chronic MR animal models.
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This intriguing experimental report from Maisano et al describes early work with an adjustable neochordae implantation system. The use of artificial chords in mitral valve repair has gained increasing popularity as a physiological solution for the treatment of mitral valve prolapse. The main limitation to this technique has been the difficulty associated with the accurate determination of neochordal length. This can be particularly challenging in minimally invasive surgery. This report describes a system specifically designed to facilitate rapid, uncomplicated implantation of neochordae and their off-pump beating heart adjustment. In this small animal series, all the implantations were successful, and the flail lesions were corrected. At postmortem examination, the neochordae were healed with evidence of tissue ingrowth.
Although this report is promising, further evaluation is clearly needed to address critical issues such as the durability of this procedure and whether it could be used to address complex pathology. Only two chronic animals were studied, and more data would be needed to fully establish the feasibility of this approach. The authors are to be congratulated for their excellent work on this novel and exciting new technology.
Mitral repair; Dynamic devices; Neochordae implant
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