Interact CardioVasc Thorac Surg 2007;6:430-432. doi:10.1510/icvts.2007.153494
© 2007 European Association of Cardio-Thoracic Surgery
Work in progress report - Valves |
Acceptance and introduction of disruptive technologies – simple steps to build a fully functional pulmonary valved stent
Christoph H. Huber*,
Bettina Marty and
Ludwig K. von Segesser
Division of Cardiovascular Surgery, University Hospital of Lausanne, CHUV, Switzerland
Received 2 February 2007;
received in revised form 23 April 2007;
accepted 26 April 2007
 Supported in part by the Swiss National Science Foundation grant 3200B0-113437, Bern, Switzerland and by HeartLAB International, Hergiswil, Switzerland. Materials for valved stent assembly provided by Medtronic International, Tolochenaz, Switzerland and Tyco, Switzerland.
*Corresponding author. Service de Chirurgie Cardiovasculaire, Centre Hospitalier Universitaire Vaudois CHUV, 1011 Lausanne, Switzerland, Tel.: +41 21 314 2421; fax: +41 21 314 2278.
E-mail address: huberch{at}gmail.com (C.H. Huber).
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Abstract
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Valved stents are new land for cardiac surgeons even though they are being used more frequently by interventional disciplines. This paper presents simple steps to build a patient-specific pulmonary valved stent and its delivery device. The design concept was tested by random participants at a med-tech meeting. The valved stent is constructed by linking an endoprosthetic graft with a valved-jugular-vein. The delivery device is made from a modified 5-ml syringe. Of 72 participants, 66 (92%) built and 60 participants implanted the device successfully into the targeted pulmonary position via a trans-infundibular access.
Key Words: Valved stent; Percutaneous valve replacement; Pulmonary valve replacement; Off-pump; Minimally invasive valve surgery; Congenital cardiac surgery; Right ventricular outflow tract reconstruction
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1. Introduction
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Transcatheter therapy of structural heart disease is an emerging alternative for the treatment of heart valve disease. Pioneering interventional cardiologist and cardiac surgeons are the driving forces constructing the fundaments of what might become the next choice for the treatment of cardiac valvulopathies [1–3]. For most cardiac surgeons endoluminal therapies still present untouched new land even though the direct access valve replacement via the transapical procedure – a surgery based technique – has first been proposed by a cardiac surgeon [4] and gained wide popularity after validation by a peer reviewed position statement [5, 6]. In order to further sensitise and to ease introduction of those promising new technologies, med-tech meetings have set out to expose surgeons with the new devices. One way to familiarise with valved stents is presented in this paper by disclosing some simple steps to build a patient-specific pulmonary valved stent. The design concept has first been tested in an acute animal study (data previously presented) [7] and then by random participants at two consecutive Swiss Med-Tech meetings, the HeartLAB 2005 and 2006 in Zürich. Participants were asked to build and implant a self-made valved stent in a porcine model via a trans-infundibular approach.
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2. Technique
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The valved stent is constructed from two components. An endoprosthetic graft and a valved jugular vein conduit (see Figs. 1 and 2). Both parts are chosen to approximate their respective diameter. It is generally advisable to slightly oversize the device by 15–20% of the target vessel diameter, an experience gained from endoprosthetic therapies of aortic aneurysm as well as from the recent studies on aortic valved stent implantation. Then the carrier stent is built by shortening the endoprosthetic graft to a length including two rows of Z-stents. It is recommended to leave a maximum of 1 mm cloth rim to allow for future suturing. Next the valved-bovine-jugular-vein is trimmed down to fit the carrier stent. The aim of the cutting is to keep the valve in the middle between the two future suturelines.
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Fig. 1. Starting from top left to bottom right. Shortening of the endoprosthetic graft and of the valved conduit. Both components are placed within the stabiliser. Three Ti-Cron 2-0 sutures are placed at equidistance in a fashion to join the graft end and the valved segment. The three running sutures are completed. Last, the obtained valved stent is removed, turned upside-down and reinserted into the stabiliser to finalise the distal sutureline with three more Ti-Cron 2-0 sutures.
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Fig. 2. Starting from top left to bottom right. Manual loading into the 5-ml delivery tool. The delivery device is then reassembled. The maximum outer diameter of 14.5 mm allows insertion via a small infundibular incision.
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Before starting suturing, a stabiliser is prepared from a 60-ml syringe by cutting-off the tip at the 10-ml mark. Next the syringe is fixed on a plane working surface by double-sided sticky tape or fixed within the two blades of a sternal retractor. Then the carrier stent is inserted into the obtained stabiliser and, finally, the trimmed valve conduit is introduced into the graft. Both components are arranged to show congruent ends. Following this, three Ti-Cron 2-0 sutures (Tyco, Waltham, Massachusetts) are placed at equidistance on the presenting end of the future valved stent. Sutures are placed in a fashion to join the graft and the valved conduit. Each suture is tied down to prevent a purse string effect over the running sutureline. Then, with each of the three Ti-Cron 2-0, a short running suture is started and tied with the next suture at each third of the circumference. The obtained double-walled cylinder is then removed, turned upside-down and reinserted into the stabiliser. Slight manual crimping might ease insertion of the device. The suturing is now repeated in the same manner. Then the finalised valved stent is removed from the stabiliser. Next the valve is inspected visually and tested by filling with saline solution.
It is recommended to mark the future flow direction by drawing an arrow onto the outer wall of the valved stent before insertion into the delivery device.
The delivery device for the trans-infundibular insertion is easily constructed from a 5-ml syringe by removing its distal portion in order to obtain an open cylinder. Next the valved stent is loaded manually facing into the appropriate delivery direction for an antegrade approach. Loading can further be assisted by a heavy silk suture wrapped around the stent and temporarily tightened by a second person until loaded into the delivery device. Now the system is ready for implantation. Delivery of the device is performed by pushing the piston and a slight pull back movement of the delivery tool during deployment to compensate for the forward shift (see Video 1).
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Video 1. Valved stent deployment by pushing of the delivery piston. Note the slight backward movement of the delivery system during deployment in order to compensate for the forward shift of the device.
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To validate the concept, a total of 72 participants of two consecutive Med-Tech meetings in Switzerland in the years 2005 and 2006 (HeartLab, Zürich) were asked to build and implant the self-made device in the pulmonary position of a porcine heart.
After a 30-min introduction on the topic and a live demonstration on how-to-build the device, on each meeting groups of six participants were divided into six teams and invited to join the work-benches for the hands-on session. The allocated time for construction and insertion was set to 45 min. All implants were tested for adequacy of delivery and anchoring capacity within their delivery location by a simple pull-test as well as correctness of construction and valve function by static leakage testing after explantation. Finally, the over-stented native pulmonary valve was macroscopically assessed for traumatic lesions.
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3. Results
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This pulmonary valved stent concept was first validated in vitro and in vivo within an experimental animal setting. Data previously presented [8].
Subsequently the simplicity of the design concept was further challenged by integration into a hands-on-session of two Med-Tech events. Within an allocated time window of 45 min, 11 of 12 groups of participants successfully built their own pulmonary valved stent. A total of ten groups implanted the device into the targeted pulmonary position by using the self-made delivery tool. Only one group delivered the valved stent too distally, above the native valve. Anchoring capacity of all ten implanted valved stents was excellent; none could be dislodged back into the right ventricle. On gross inspection, 11 valved stents were correctly constructed and showed no obvious signs of malfunction. At static leakage testing, two of the 11 valved stents were identified to have a minor valve insufficiency due to size mismatch between the graft and the valved conduit. None of the native pulmonary valves showed macroscopic signs of trauma.
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4. Discussion
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The device's specific design limits its use strictly to the right side of the heart as the covered stent might occlude the coronaries. The described valved stent/delivery device setup is only to be used in an experimental setting as there are no long-term or clinical data available. The mild valvular insufficiency of two of the 11 devices at the post-implantation static leakage test might have resulted from an inappropriate handling of the components while assembling or during device harvest after delivery. Every surgical therapy is a ‘hand-made’ activity and, as such, fully recognised as a rather major advantage by allowing precise and individualised patient-adapted therapy. A custom-built prosthesis is a further advantage to allow quick and effective production of a patient-adapted prosthesis and, furthermore, avoids the off-the-self bottleneck. The authors very strongly believe device construction to be simple and safe enough to be introduced into clinical practice when handled by an experienced surgeon's hands. Regarding bio-tolerance, functionality and approval of all components, no issues are expected to arise as the endograft and the bovine jugular vein conduit have widely been implanted clinically. The first, for endoluminal aortic aneurysm grafting and the latter for right ventricular outflow tract (RVOT) reconstruction in congenital cardiac surgery. The valve has also shown its validity in percutaneous procedures in over 100 patients within a commercially available device. The primary indication for this device is to be found in congenital cardiac surgery. One of the most frequent procedures, the repair of tetralogy of Fallot, might have an important benefit from the device. An insufficient pulmonary valve after RVOT enlargement could temporarily be replaced by this pulmonary valved stent until re-operation for graft outgrowth becomes necessary. Slight oversizing of the device with successive later balloon dilation, or even percutaneous reinsertion of a second valved stent, could further delay the point of outgrowth and successive surgery. Two groups have reported their clinical results of a similar device manufactured by Shelhigh recently [9, 10]. The device is based on a valved stent first published in 2003 by our group; constructed from a valved conduit schaffolded by two rows of self-expanding stents [11]. The clinical results confirm the clinical feasibility of intraoperative implantation for pulmonary regurgitation. Six patients (9–27 years) received an injectable porcine pulmonary valved stent after total correction of tetralogy of Fallot at 4.2±4.0 years. All implantations were uneventful and, except for one patient with a major paravalvular leak requiring surgical reintervention, the 6–12-month follow-up was very promising. Unfortunately, the valved stent insertion requires surgical access to the RVOT for device insertion. The valved stent reported in this publication is designed to be inserted via a guide-wire to allow for a minimally invasive insertion via the previously reported direct access trans-apical procedure [6] by puncturing the right ventricle via a small thoracotomy. Visualisation for delivery monitoring is achieved either by intracardiac or trans-esophageal echo with or without contrast enhanced fluoroscopy.
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5. Conclusions
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Valved stents are slowly moving into clinical practice. Availability and familiarity are limiting factors for their acceptance. This study shows the feasibility to hand-build a valved stent and the simplicity of implantation. Furthermore, the off-the-self bottleneck is avoided by the self-constructed and custom-made design of the device.
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References
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- Bonhoeffer P, Boudjemline Y, Saliba Z, Merckx J, Aggoun Y, Bonnet D, Acar P, Le Bidois J, Sidi D, Kachaner J. Percutaneous replacement of pulmonary valve in a right-ventricle to pulmonary-artery prosthetic conduit with valve dysfunction. Lancet Oct 21, 2000; 356:1403–1405.[CrossRef][Medline]
- Cribier A, Eltchaninoff H, Bash A, Borenstein N, Tron C, Bauer F, Derumeaux G, Pontier G, Laborde F, Leon MB. Percutaneous transcatheter implantation of an aortic valve prosthesis for calcific aortic stenosis: first human case description. Circulation 2002; 106:3006–3008.[Abstract/Free Full Text]
- Huber CH, Tozzi P, Corno AF, Marty B, Ruchat P, Gersbach P, Nasratulls M, von Segesser LK. Do valved stents compromise coronary flow? Eur J Cardiothorac Surg 2004; 25:754–759.[Abstract/Free Full Text]
- Huber CH, Nasratulla M, Augstburger M, von Segesser LK. Ultrasound navigation through the heart for off-pump aortic valved stent implantation: new tools for new goals. J Endovasc Ther 2004; 11:503–510.[CrossRef][Medline]
- Vassiliades TA, Block PC, Cohn LH, Adams DH, Borer JS, Feldman T, Holmes DR, Laskey WK, Lytle BW, Mack MJ, Williams DO. The clinical development of percutaneous heart valve technology. A position statement of the Society of Thoracic Surgeons (STS), the American Association for Thoracic Surgery (AATS), and the Society for Cardiovascular Angiography and Interventions (SCAI). J Am Coll Cardiol 2005; 45:1554–1560.[Free Full Text]
- Huber CH, Cohn LH, von Segesser LK. Direct-access valve replacement a novel approach for off-pump valve implantation using valved stents. J Am Coll Cardiol Jul 19, 2005; 46:366–370.[Abstract/Free Full Text]
- Huber Ch, Zhou J, von Segesser LK. Transapical implantation of valved stents – or how to prevent reoperation for postoperative pulmonary regurgitation. Cardiology in the young, Abstractbook 2006 May O-18:7 Data presented at the 41st Annual Meeting of the Association for European Paediatric Cardiology in Basel, Switzerland 2006; Manuscript currently under submission.
- Oechslin EN, Harrison DA, Harris L, Downar E, Webb GD, Siu SS, Williams WG. Reoperation in adults with repair of tetralogy of Fallot: indications and outcomes. J Thorac Cardiovasc Surg 1999; 118:245–251.[Abstract/Free Full Text]
- Berdat PA, Schönhoff F, Pavlovic M, Pfammatter JP, Carrel T. Cardiology in the young, Abstractbook 2006 May O-39:15.
- Schreiber C, Hörer J, Vogt M, Fratz S, Kunze M, Galm C, Eicken A, Lange R. A new treatment option for pulmonary valve insufficiency: first experiences with implantation of a self-expanding stented valve without use of cardiopulmonary bypass. Eur J Cardiothorac Surg 2007; 31:26–30.[Abstract/Free Full Text]
- Zhou JQ, Corno AF, Huber Ch, Tozzi P, von Segesser LK. Self-expanding valved stent of large size: off-bypass implantation in pulmonary position. Eur J Cardiothorac Surg 2003; 24:212–216.[Abstract/Free Full Text]
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Abstract
1. Introduction
