Figura 1. A and B. Photograph of the Melody Medtronic valve.

Figura 2. Photograph of the Ensemble delivery system.

Figura 3. Illustration of the anatomic characteristics of a right ventricle to pulmonary artery con...

Figura 4. A. Image in AP/Caudal projection demonstrates a selective coronary angiography in a patien...

Figura 5. A. In lateral projection the right ventriculogram demonstrates a stenotic right ventricle ...

Figura 6. Photograph of the Edwards SAPIEN valve.

Introduction

The development of right ventricular outflow tract (RVOT) dysfunction due to progressive pulmonary valve stenosis and insufficiency is not uncommon after surgical repair of congenital heart disease.1 Therapeutic options have traditionally consisted of surgical implants in the form of homografts, valved conduits and bioprosthetic valves. Since the early 90s, when the main lesion is stenosis, bare metal stenting has been considered as an approach to prolong conduit longevity.2 The drawback of this approach is that it only treats pulmonary stenosis leaving behind severe pulmonary valve insufficiency. It is well known that chronic severe pulmonary valve insufficiency leads to progressive right heart failure, decreased exercise tolerance and life threatening arrhythmias.3-5

Although surgical intervention in the RVOT is considered to have relatively low morbidity and mortality,6,7 it carries the inherent risks of surgery plus the known limitations in lifespan of the surgical implants such that subjects continue to require multiple open-heart procedures.8,9 Percutaneous valve therapies have emerged in the last 10 years to decrease the need for open surgical procedures and prolong the lifespan of existing valve implants. As a consequence there has been a major change in the treatment of RVOT dysfunction. Currently, two transcatheter heart valves systems exist: the Melody (Medtronic Inc., Minneapolis, MN) and the Edwards SAPIEN (Edwards Lifesciences, Irvine, CA) valves. The Edwards SAPIEN valve in the pulmonary position has been studied as part of the COMPASSION (COngenital Multicenter Trial of Pulmonic VAlve Regurgitation Studying the SAPIEN InterventIONal) clinical trial, whereas the Melody valve received Humanitarian Device Exemption from the FDA in 2010 and is commercially available in the United States.

Percutaneous pulmonary valve implantation has been categorized as a Class II AHA recommendation for conduits with moderate to severe stenosis or insufficiency provided the patient meets the inclusion/exclusion criteria for the available valve (Level of evidence B).10

Melody Percutaneous Pulmonary valve

A. History and characteristics

Dr. Phillip Bonhoeffer implanted the first percutaneous pulmonary valve in the year 2000.11,12 This original design, conceived by Dr Bonhoeffer, was subsequently modified, and eventually resulted in what we now know as the Melody ValveTM, manufactured by Medtronic (Minneapolis, MN, USA), commercially available in the United States as a Humanitarian Use Device since March of 2010. This valve is a bovine jugular venous valve sewn into a platinum iridium balloon expandable stent (Figure 1A and 1B). The valve is mounted manually by the implanter on the Ensemble® Transcatheter Valve Delivery System, which consists of a balloon-in-balloon catheter with a retractable polytetrafluoroethylene (PTFE) sheath (Figure 2). The distal cup is large enough to front-load the stented valve after crimping. The delivery system has a 22 Fr crossing profile and comes in outer balloon sizes of 18, 20, and 22 mm (Figure 2). The valve is delivered in a similar fashion to conduit stents (Figure 3).

B. Indications

The Melody valve was the first percutaneous valve approved for human use in the United States by the Food and Drug Administration.13 Specifically, it is approved only for use in:

• dysfunctional conduits with either a mean gradient of 35 mmHg or

• at least moderate pulmonary valve insufficiency.

And:

• Original conduit implantation size has to have been at least 16 mm when implanted.

Although there are no specific contraindications, in the United States it is not recommended for implantation in the following:

• Aortic or mitral position, since preclinical bench testing of the Melody valve suggests that valve function and durability will be extremely limited when used in these locations.

• When patient’s anatomy precludes introduction of the valve, if the venous anatomy cannot accommodate a 22-Fr size introducer, or if there is significant obstruction of the central veins.

• There are clinical or biological signs of infection including active endocarditis.

There is however increasing experience in the use of the vale in off-label applications,14-16 such as in tricuspid valve or other valve positions, inside bioprosthesis or outflow tract patches. For patients in whom venous access is limited, hybrid perventricular approach can be used. In addition, intraoperative implants can also be performed in young patients in whom the potential for late re-dilation of the valve stent gives an alternative which could accommodate to growth.

C. Implantation considerations

Similar to when stenting RVOT conduits, prior to deployment of a transcatheter pulmonary valve careful assessment of the coronary artery anatomy for the risk of coronary artery compression should be performed in all patients. Certain coronary anatomies are at increased risk of compression (anomalous left anterior descending from right coronary artery; single right coronary or single left coronary) (Figure 4 ). When the coronaries course in proximity of the conduit, selective coronary angiography with simultaneous conduit balloon dilation to the expected ending diameter must be performed (Figure 4) to evaluate for coronary compression at the time of conduit expansion. If compression or distortion is seen, the patient would be considered not a candidate for stent placement17,18 nor percutaneous pulmonary valve implantation.

In addition, restrictions with regards to diameter of balloon to expand the conduit do exist. To minimize the risk of conduit rupture, it is recommended not to use a balloon with a diameter greater than 110% of the nominal diameter (original implant size) of the conduit for pre-dilation of the intended site of deployment, or for deployment of the TPV.

The size and shape of the RVOT must be evaluated prior to PPV implantation. The RVOT will need to measure between 16 and 22 mm in diameter to accommodate the Melody Valve.TM Morphologically, a straight or hour glass shaped conduit is more favorable for Melody ValveTM implantation than a divergent or pyramidal shape19. However the shape of the RVOT is rarely a limitation to proceed.

The major component of the procedure is the preparation of an adequate “landing zone”. This can be particularly challenging in patients in whom the predominant indication for pulmonary valve implantation is stenosis, as these conduits are commonly resistant to dilation. The RVOT is prepared using sequential angioplasties and stent implantations within the conduit, almost always with use of ultrahigh pressure balloons. Once the target diameter has been achieved implantation of the Melody ValveTM is a relatively simple component of the procedure.

D. Experience and results

Melody percutaneous pulmonary valve implantation is currently performed in over 170 centers worldwide, with more than 5,000 implants to date.

USA

In the United States, there have been 2 major studies carried out. One was the original Investigational Device Exemption (IDE) study prior to approval 13. The second is the post market approval study, which is still on going. Among to initial 100 patients of the IDE study, the incidence of serious adverse events related to the device or procedure was 5.1%, including 4 four procedure-related events (homograft rupture, branch pulmonary artery rupture, supra-ventricular tachycardia, and coronary dissection) and one device-related SAE (stent fracture that necessitated repeat TPV placement). There was one death from intracranial hemorrhage after coronary artery dissection, and one valve was explanted after conduit rupture. The median peak right ventricular outflow tract gradient was 37 mm Hg before implantation and 12 mm Hg immediately after implantation. Before implantation, pulmonary regurgitation was moderate or severe in 92 patients (81%); no patient had more than mild pulmonary regurgitation early after implantation or during follow-up (1 year in 65 patients). Freedom from diagnosis of stent fracture was 77.8+/-4.3% at 14 months. Freedom from Melody valve dysfunction or reintervention was 93.5+/-2.4% at 1 year. A higher right ventricular outflow tract gradient at discharge (P=0.003) and younger age (P<0.01) were associated with shorter freedom from dysfunction.

Since this original study, experience has demonstrated that pre-stenting helps lower the chances of fracture and restenosis during follow up. A more aggressive approach to prepare an optimal “landing zone” for the valve will likely lead to improved long term results.

With regards to the post market approval study, it included 127 patients who were enrolled at 10 U.S. centers. There have been no deaths to date and a rate of 5.6 per 100 person-year significant adverse events, including stent fractures and endocarditis. Follow up data is still being collected for this study.

As it is known for stents in cardiac conduits, there is a risk of stent restenosis and fracture. In a series of 123 patients who underwent Melody valve placement, Nordmeyer et al. 20 reported an incidence of 25% of stent fracture at a two-year-follow- up.

Radiographic assessment of the stent with chest radiography or fluoroscopy should be included in the routine post-procedural evaluation of patients who receive a percutaneous pulmonary valve. Stent fracture is typically associated to restenosis. If a stent fracture is detected, continued monitoring of the stent should be performed in conjunction with clinically appropriate hemodynamic assessment. In patients with stent fracture and significant associated RVOT obstruction or regurgitation, reintervention should be considered in accordance with usual clinical practice. The presence of a fracture may indicate the increased risk of restenosis, but in the absence of a gradient, it is of little significance. If there is no loss of stent integrity, fractures are considered benign.

In the series of patients who underwent Melody valve implant as part of the US IDE trial, it was demonstrated21 that stent fractures were more likely in patients with severely obstructed right ventricular outflow tract conduits and when the Melody was directly behind the anterior chest wall and/or clearly compressed, whereas a valve implant site protected by a pre-stent or bioprosthetic valve was associated with lower risk of fracture and reintervention.

Since approval, the experience at Children’s Hospital of Pittsburgh of UPMC includes 41 Melody ValveTM implantations, one intraoperative and the rest percutaneous. Review of the data demonstrates that on average, the conduits had narrowed by 33% of their original size by the time of implant. All but one patient required pre-stenting with one or more bare metal stents, which significantly expanded the conduits (Figure 5). Melody ValveTM implantation further expanded the area by an average of 10%. Intracardiac echocardiography was used to evaluate for paravalvular leaks whenever there was any regurgitation seen on post implantation angiograms. During follow up, there was one death unrelated to the procedure in an adult patient with diabetic end stage renal disease and severe biventricular dysfunction, who died from non-cardiac causes. The Melody Valve was functioning well. During follow up (up to 3 years) one valve was explanted due to endocarditis, and all others remain in place. There were 2 paravalvular leaks, one treated at the time of implantation with a second Melody valve implant. Another (which had been an intraoperative implantation in a small child) was managed medically. All patients have mild or less regurgitation during follow up, and gradients have been in mild to moderate range. Many of these patients are followed in the post market approval study.

European experience

The original experience by Dr Bonhoeffer 1 included 155 patients who underwent percutaneous pulmonary valve implantation between September 2000 and February 2007 with stenosis and/or regurgitation. There was significant reduction in right ventricular systolic pressure and right ventricular outflow tract gradient. Follow-up ranged from 0 to 83.7 months (median 28.4 months). Freedom from reoperation was 93%, 86%, 84% , and 70% at 10, 30, 50, and 70 months, respectively. Freedom from transcatheter reintervention was 95% , 87% , 73% , and 73% at 10, 30, 50, and 70 months, respectively. Survival at 83 months was 96.9%. On time-dependent analysis, the first series of 50 patients and patients with a residual gradient > 25 mm Hg were associated with a higher risk of reoperations, showing the effect of the learning curve on clinical outcome.

A prospective, observational, multi-centric survey by means of a web-based database registry of the Italian Society of Pediatric Cardiology22 reported 63 patients between October 2007 and October 2010 aged 11 to 65 years, who underwent Melody valve implantation due to pure stenosis (21 patients), pure regurgitation (12 patients), combined disease (30 patients) . Implantation was performed in 61 subjects (97%). Pre-stenting was performed in 85%. Immediate results demonstrated no significant regurgitation, with a significant decrease in gradient. Early major complications occurred in 7 subjects (11%). One death occurred in the early post-operative period in a severely ill subject. At a median follow-up of 30 months (range 12-48 months), three patients died due to underlying disease. Major complications occurred in six patients during follow-up, which included arrhythmias, viral encephalitis, Melody valve endocarditis (2 pts) and major stent fractures requiring second valve implant (2 pts). Freedom from valve failure at latest follow-up was 81.4% ± 9%.

Other reports reflecting the world experience with the Melody valve implant indicate similar early results. 16

Edwards SAPIEN Pulmonic Valve

Edwards SAPIEN TM Pulmonic Valve (Edwards Lifesciences LLC, Irvine, CA) consists of three bovine pericardial leaflets hand-sewn to a tubular, slotted, stainless steel, balloon expandable stent (Figure 6). The leaflet pericardial tissue is processed with the same ThermafixTM anti-calcification treatment utilized in the Carpentier-Edwards PERIMOUNT MagnaTM surgical valves. There is a fabric sealing cuff covering the lower portion of the stent to facilitate a seal with the calcified conduit and prevent paravalvular leak. The valve is available in 23 and 26 mm diameter sizes with heights of 14.5 and 16 mm, respectively. A 29 mm diameter valve is also available for the aortic position. The valve requires a specific delivery system: the RetroflexTM I or II catheters (Edwards Lifesciences LLC, Irvine,CA.). These catheters consist of a balloon catheter and a deflectable guiding catheter, and require either 22 or 24 Fr hydrophilic sheaths for the 23 and 26 mm valves, respectively. A specialized manual crimping tool is used to symmetrically compress the valve onto a valvuloplasty balloon.

The first use of the Edwards SAPIEN(™) valve in a human was reported by Garray et al.23 in a 16-year-old patient after a Ross procedure based on a compassionate use approved by the FDA. The first use of the Edwards Sapien valve in Europe was reported by Ewert et al. in 2010.24 The new Edwards SAPIEN(™) pulmonic valve reached European CE certification at the end of 2010, thus offering an attractive alternative for percutaneous valve implantation with extended sizes (23 and 26 mm).

The experience with the SAPIEN valve in the RVOT in the United States has been relatively small, as access to the valve is restricted in the US to the COMPASSION clinical trial and is limited to insertion within a pre-existing homograft. Results of phase 1 FDA approved COMPASSION trial using the SAPIEN valve demonstrated efficacy and safety in reducing RVOT pressure gradient and establishing pulmonary valve competence.25 Thirty-six patients from 4 centers were recruited between April 2008 and May 2010 Successful valve deployment was achieved in 33 of 34 attempts (97.1%). Valve migration occurred in 3 patients, with 2 requiring surgical retrieval. Procedure complications also included pulmonary hemorrhage in 2, ventricular fibrillation in 1, and stent migration in one. Pullback gradient across the conduit decreased significantly. At 6-month follow-up, all patients were alive. The number of patients with New York Heart Association functional class I increased from 5 at baseline to 27 at follow-up. Pulmonary regurgitation was ≤2+ in 97% of patients. Freedom from reintervention was 97% with 1 patient undergoing elective placement of a second valve due to conduit-induced distortion of the initial implant.

It is not clear whether this valve will demonstrate superior resistance from fracture relative to the Melody valve. The fact that the valve has been implanted in the aortic position in over 20,000 patients with excellent valve function reported at 2-year follow-up in large clinical trials is very encouraging.25

A study on the experience in Germany 27 reviewed the results during a one year period using the Edwards SAPIEN™ pulmonic valve in 22 patients. Implantation was successful in 21 (10 received a 23 mm valve and 11 received a 26 mm one). Invasive data showed a significant decrease of right ventricular systolic pressure with reduction of RVOT gradient. There was a substantial reduction of pulmonary regurgitation from before (none/trivial n = 0, mild n = 2, mode rate n = 9, severe n = 11) to after implant (none/trivial n = 20, mild n = 1). During the short-term follow-up of 5.7 months there was persistent favorable valve function.

In the meantime, further data assessing long-term functionality and durability of both valves are needed to evaluate their long-term outcome.

Limitations of available percutaneous valve implants

Only approximately 15 percent of potential patients with RVOT dysfunction can accommodate the currently approved implantable valves.18 Many patients remain poor Melody ValveTM candidates due to their small physical size, limited vascular access, or the size and shape of their RVOT. At times, pre-stenting with bare-metal stents can be used as a way to “prime” the RVOT in patients with prior RVOT patch repair, permitting subsequent successful PPV implantation.29 In patients with large and distensible RVOT conduits, a hybrid approach combining intra-operative PPV implantation with simultaneous conduit down-sizing has been undertaken with some success.31 Alternatively, Melody ValveTM implantation into the bilateral branch pulmonary arteries has been proposed as a minimally invasive, though still experimental, option in patients with large and insufficient conduits.32

These limitations have led some physicians to explore innovative techniques, including self expanding nitinol pulmonary valve stents. 30

Concluding comments

The development of percutaneous pulmonary valve stents such as the Medtronic Melody ValveTM and the Edwards SAPIENTM pulmonic valve haves revolutionized the treatment of RVOT dysfunction. The pulmonary stenosis and insufficiency that previously required an open-heart procedure, can now be safely and effectively treated with minimally invasive percutaneous techniques. Pulmonary valve stent technology continues to evolve with the goal of treating a larger percentage of patients with RVOT dysfunction with the percutaneous technique. The Edwards SAPIENTM transcatheter heart valve can be used in patients with larger RVOT conduits, as it is sized as large as 26 mm, and possibly up to 29 mm. It’s use will likely increase significantly once it becomes widely available for use. Self-expanding nitinol pulmonary valve stents offer the potential of treating larger RVOT morphologies with a low-profile design, but are still under investigation.

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2. Kanter KR, Budde JM, Parks WJ, Tam VK, Sharma S, Williams WH, Fyfe DA. One hundred pulmonary valve replacements in children after relief of right ventricular outflow tract obstruction. Ann Thorac Surg. 2002;73(6):1801-1806; discussion 1806-1807.

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16. Boshoff DE, Cools BL, Heying R, Troost E, Kefer J, Budts W, Gewillig M. Off-label use of percutaneous pulmonary valved stents in the right ventricular outflow tract: Time to rewrite the label? Catheter Cardiovasc Interv. 2013 May;81(6):987-95.

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18. Demkow M, Biernacka EK, Spiewak M, Kowalski M, Siudalska H, Wolski P, Sondergaard L, Misko J, Hoffman P, Ruzyllo W. Percutaneous pulmonary valve implantation preceded by routine prestenting with a bare metal stent. Catheter Cardiovasc Interv.77(3):381-389.

19. Schievano S, Coats L, Migliavacca F, Norman W, Frigiola A, Deanfield J, Bonhoeffer P, Taylor AM. Variations in right ventricular outflow tract morphology following repair of congenital heart disease: implications for percutaneous pulmonary valve implantation. J Cardiovasc Magn Reson. 2007;9(4):687-695

20. Nordmeyer J, Khambadkone S, Coats L, Schievano S, Lurz P,Parenzan G, Taylor AM, Lock JE, Bonhoeffer P. Risk stratification,systematic classification and anticipatory managementstrategies for stent fracture after percutaneous pulmonary valveimplantation. Circulation 2007;115:1392–1397.

21. McElhinney DB, Cheatham JP, Jones TK, Lock JE, Vincent JA, Zahn EM, Hellenbrand WE. Stent fracture, valve dysfunction, and right ventricular outflow tract reintervention after transcatheter pulmonary valve implantation: patient-related and procedural risk factors in the US Melody Valve Trial. Circ Cardiovasc Interv. 2011 Dec 1;4(6):602-14.

22. Butera G, Milanesi O, Spadoni I, Piazza L, Donti A, Ricci C, Agnoletti G, Pangrazi A, Chessa M, Carminati M. Melody transcatheter pulmonary valve implantation. Results from the registry of the Italian society of pediatric cardiology. Catheter Cardiovasc Interv. 2013 Feb;81(2):310-6

23. Garray F, Webb J, Hijazi Z (2006) Percutaneous replacement of pulmonary valve using the Edwards-Cribier percutaneous heart valve. Catheter Cardiovasc Intervent 67:659–662

24. Ewert P, Horlick E, Berger F (2011) First implantation of the CEmarked ranscatheter Sapien pulmonic valve in Europe. Clin Res Cardiol 100(1):85–87

25. Kenny D, Hijazi ZM, Kar S, et al. Percutaneous implantation of the Edwards SAPIEN transcatheter heart valve for conduit failure in the pulmonary position: Early phase 1 results from an international multicenter clinical trial. J Am Coll Cardiol 2011;58:2248–2256.

26. Kodali SK, Williams MR, Smith CR, et al. Two-year outcomes after transcatheter or surgical aortic-valve replacement. N Engl J Med 2012;366:1686–1695.

27. Haas NA, Moysich A, Neudorf U, Mortezaeian H, Abdel-Wahab M, Schneider H, De Wolf D, Petit J, Narayanswami S, Laser KT, Sandica E. Percutaneous implantation of the Edwards SAPIEN(™) pulmonic valve: initial results in the first 22 patients. Clin Res Cardiol. 2013 Feb;102(2):119-28. doi: 10.1007/s00392-012-0503-8.

28. Capelli C, Taylor AM, Migliavacca F, Bonhoeffer P, Schievano S. Patient-specific reconstructed anatomies and computer simulations are fundamental for selecting medical device treatment: application to a new percutaneous pulmonary valve. Philos Transact A Math Phys Eng Sci.368(1921):3027-3038.

29. Momenah TS, El Oakley R, Al Najashi K, Khoshhal S, Al Qethamy H, Bonhoeffer P. Extended application of percutaneous pulmonary valve implantation. J Am Coll Cardiol. 2009;53(20):1859-1863.

30. Schievano S, Taylor AM, Capelli C, Coats L, Walker F, Lurz P, Nordmeyer J, Wright S, Khambadkone S, Tsang V, Carminati M, Bonhoeffer P. First-in-man implantation of a novel percutaneous valve: a new approach to medical device development. EuroIntervention.5(6):745-750.

31. Bacha EA, Marshall AC, McElhinney DB, del Nido PJ. Expanding the hybrid concept in congenital heart surgery. Semin Thorac Cardiovasc Surg Pediatr Card Surg Annu. 2007:146-150.

32. Robb JD, Harris MA, Minakawa M, Rodriguez E, Koomalsingh KJ, Shuto T, Shin DC, Dori Y, Glatz AC, Rome JJ, Gorman RC, Gorman JH, 3rd, Gillespie MJ. Melody valve implantation into the branch pulmonary arteries for treatment of pulmonary insufficiency in an ovine model of right ventricular outflow tract dysfunction following tetralogy of Fallot repair. Circ Cardiovasc Interv.4(1):80-87.

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