Article

PDF
Access to the PDF text
Advertising


Free Article !

Archives of cardiovascular diseases
Volume 106, n° 1
pages 19-26 (janvier 2013)
Doi : 10.1016/j.acvd.2012.09.005
Received : 20 June 2012 ;  accepted : 26 September 2012
Impact of right ventricular outflow tract size and substrate on outcomes of percutaneous pulmonary valve implantation
Impact du diamètre et du type de conduits utilisés pour reconstruire la voie d’éjection droite dans les résultats de la valvulation pulmonaire percutanée
 

Younes Boudjemline a, b, c, , Georgia Sarquella-Brugada a, Issam Kamache d, Mehul Patel a, Magalie Ladouceur a, b, Damien Bonnet a, c, Fazia-Marie Boughenou b, Alain Fraisse d, Laurence Iserin b
a Centre de Référence Malformations Cardiaques Congénitales Complexes M3C, Necker Hospital for Sick Children, Assistance Publique des Hôpitaux de Paris, Paediatric Cardiology, 75015 Paris, France 
b Centre de Référence Malformations Cardiaques Congénitales Complexes M3C, George Pompidou European Hospital, Assistance Publique des Hôpitaux de Paris, Unit for Adults with Congenital Heart Defects, 75015 Paris, France 
c Université Paris Descartes, Sorbonne Paris Cité, 75008 Paris, France 
d Timone Hospital, Assistance Publique des Hôpitaux de Marseille, Unit for Children and Adults with Congenital Heart Defects, 13385 Marseille, France 

Corresponding author. Hôpital Necker Enfants Malades, Cardiologie Pédiatrique, 149, rue de Sèvres, 75015 Paris cedex, France. Fax: +33 1 44 49 57 24.
Summary
Background

Owing to the wide variety of surgical substrates used for right ventricular outflow tract (RVOT) reconstruction, the predictors of successful outcomes in such patients are unclear.

Aims

To compare haemodynamic outcomes of percutaneous pulmonary valve implantation (PPVI) in patients with dysfunctional RVOT.

Methods

This was a multicentre prospective study on all consecutive patients who underwent PPVI from May 2008 to December 2009. All patients underwent prestenting using a bare-metal stent. The patients were divided into two groups based on the surgical substrate used for RVOT reconstruction.

Results

Baseline demographics, including right ventricle to pulmonary artery (RV-PA) pressure gradient and RV/aortic (Ao) pressure ratio, were similar in both groups. The mean RV-PA gradient and RV/Ao pressure ratio showed immediate and significant improvement after PPVI. At last follow-up, the RV-PA gradient and RV/Ao pressure ratio were significantly higher in patients with non-expandable conduits (P =0.002 and P =0.008, respectively). Patients with conduits greater than 20mm showed better immediate and midterm outcomes compared with other patients. Patients with non-expandable conduits less or equal to 20mm diameter showed good immediate outcomes but poor midterm haemodynamic outcomes compared with those with expandable conduits less or equal to 20mm diameter (P =0.03).

Conclusions

PPVI is successful with a wide variety of surgical substrates used for RVOT reconstruction; there was immediate haemodynamic improvement in all patients. However, patients with non-expandable conduits less or equal to 20mm had the worst outcomes. This information should be integrated into the decision-making process before selecting patients for PPVI.

The full text of this article is available in PDF format.
Résumé
Contexte

Il existe une grande variété de conduits chirurgicaux utilisés pour reconstruire la voie d’éjection droite. Lorsqu’ils sont potentiellement candidats à la mise en place d’une valve par voie percutanée, les facteurs prédictifs de succès ne sont aujourd’hui pas clairs.

Objectifs

Le but de l’étude est de comparer les résultats hémodynamiques après valvulation endovasculaire pulmonaire en fonction du type de conduits prothétiques.

Méthodes

Il s’agit d’une étude multicentrique, prospective regroupant tous les patients inclus consécutivement entre mai 2008 et décembre 2009. Tous les patients ont eu un pré-stenting avant la mise en place de la valve par voie percutanée. Les patients ont été divisés en deux groupes selon le type de conduit chirurgical mis en place pour reconstruire la voie d’éjection droite.

Résultats

L’hémodynamique de base comprenant le gradient entre le ventricule droit et l’artère pulmonaire, le rapport pression ventriculaire droite sur pression aortique systolique, était similaire dans les deux groupes. Après valvulation, il y avait une amélioration immédiate de ces paramètres. Au dernier suivi, le gradient entre le ventricule droit et l’artère pulmonaire, le rapport pression ventriculaire droite sur pression aortique systolique étaient significativement plus élevés chez les patients ayant des conduits non dilatables (p =0,002 et p =0,008, respectivement). Les patients avec un conduit de diameter nominal supérieur à 20mm avaient un meilleur devenir à court et moyen terme par rapport aux autres. Les patients avec un conduit non expansible de moins de 20mm avaient un bon devenir à court terme mais un résultat hémodynamique médiocre à moyen terme lorsqu’ils étaient comparés aux patients avec des conduits expansibles de moins de 20mm (p =0,03).

Conclusions

Le remplacement valvulaire percutané est efficace chez des patients ayant eu une reconstruction de la voie d’éjection droite avec une grande variété de conduits chirurgicaux. Il était noté une amélioration de l’hémodynamique immédiate chez tous les patients quel que soit le type de conduit chirurgical en place. Cependant, les patients avec des conduits non expansibles de moins de 20mm avaient des résultats médiocres à moyen terme. Cette information doit être intégrée dans la prise de decision lors de la selection des patients pour une implantation percutanée d’une valve pulmonaire.

The full text of this article is available in PDF format.

Keywords : Transcatheter, Valve replacement, Congenital heart disease

Mots clés : Procédure percutanée, Remplacement valvulaire, Cardiopathies congénitales

Abbreviations : Ao, BMS, PA, PPVI, RV, RVOT, RV-PA, TR


Background

Percutaneous pulmonary valve replacement using the transcatheter technique has been widely accepted and practiced worldwide. The device (Melody® Transcatheter Pulmonary Valve; Medtronic Inc., Minneapolis, MN, USA) is available in a single diameter of 18mm, dilatable up to 22mm. The indications are currently limited to patients with dysfunctional right ventricular outflow tract (RVOT) homografts or prosthetic conduits with a diameter that does not exceed 22mm at the time of implantation [1, 2, 3, 4]. Surgical techniques to maintain right ventricle to pulmonary artery (RV-PA) continuity can be achieved by modification of RVOT or reconstruction using a variety of biological or synthetic tubes; these are available in various sizes as expandable or non-expandable conduits. Owing to wide variations in the surgical substrates used for RVOT reconstruction, the outcomes after percutaneous pulmonary valve insertion (PPVI) may vary and are presently unclear. We sought to evaluate the immediate and midterm haemodynamic outcomes of PPVI in patients with expandable versus non-expandable conduits.

Methods

This is a prospective multicentre non-randomized trial to evaluate outcomes after Melody® valve implantation in France (Y. B. principal investigator). The study received approval from the French Ministry of Health in May 2008. Patients with pulmonary regurgitation and/or stenosis were enrolled in four different centres across France (Paris, Massy, Marseille and Bordeaux). Patients with dysfunctional RVOT were identified and evaluated to assess suitability for PPVI. All patients were evaluated using a standard protocol to assess procedural success, complications, costs, safety and immediate and midterm outcomes. This is an ongoing study and the global results are still pending. We report outcomes on all patients who underwent PPVI from May 2008 to December 2009 in two centres (Centre de Reference Maladies Rares M3C, George Pompidou European Hospital [adult unit] and Necker Hospital [children unit], Paris, France, operator Y.B.; and Timone Hospital, Marseille, operator A.F.). The study is registered at the National Institute of Health website (www.clinicaltrials.gov) as identifier NCT01250327.

Preprocedure evaluation

All patients underwent a preinclusion clinical evaluation, including electrocardiography, echocardiography, exercise testing, computed tomography scan and magnetic resonance imaging. Qualifying patients had varying RVOT lesion characteristics, such as pulmonary obstruction, pulmonary regurgitation and mixed lesions [3]. Patients with obstruction or mixed lesions were included in this study. Medical charts were reviewed to assess the details of the RV-PA conduit. The study population was divided into two groups with respect to the expandable characteristics of the initial conduit: group I consisted of patients with expandable conduits; group II consisted of patients with non-expandable prosthetic conduits (Figure 1 and Table 1). The grouping was performed by two authors blinded to the outcome. The classification was made based on the intrinsic properties of the initial conduit and not on the properties after in vivo exposure; therefore, features such as calcifications, external compressions, etc. were not taken into account for classifications.



Figure 1


Figure 1. 

Schematic representation of the study design. BMS: bare-metal stent; PPVI: percutaneous pulmonary valve insertion.

Zoom

Cardiac catheterization and sizing of the RVOT

All patients underwent cardiac catheterization using general anaesthesia or deep sedation with or without endotracheal ventilation. A preprocedure detailed haemodynamic assessment was done in all patients, with assessment of mean right atrial, RV (systolic, early and end-diastolic), PA and aortic (Ao) pressures (systolic, diastolic and mean). The peak-to-peak RV-PA gradient was calculated as the difference in systolic pressure between the RV chamber and the main PA. If the RV/Ao systolic pressure ratio was greater than 0.66, stenosis was the primary indication. If the RV/Ao systolic pressure ratio was less than 0.25 in the presence of pulmonary regurgitation, pulmonary regurgitation was considered the primary lesion. The remainder were categorized as mixed lesions. Patients with regurgitation as the primary lesion were excluded from this study. RVOT and aortic root angiograms were performed in two views (lateral and four-chamber) in all patients. Ao angiography was performed to assess the proximity of the Melody® valve landing zone to the coronary arteries.

Preparation for Melody® valve insertion

All patients had prestenting of the RVOT using single or multiple bare-metal stents (BMSs) (CP, [NuMED, Hopkinton, NY, USA] or Max LD [EV3, Plymouth, MN, USA]).

Melody® valve insertion

The Melody® valve (Model PB10) was inserted using the 22-mm Ensemble® transcatheter valve delivery system (NU10) (Medtronic Inc., Minneapolis, MN, USA). All patients underwent RVOT predilatation with a balloon of appropriate diameter (ATLAS® or Mullins PTA Dilatation Balloon; Bard Peripheral Vascular, Inc., Tempe, AZ, USA) before Melody® valve implantation. The diameter of the balloon was equal to the nominal conduit size (maximum diameter 22mm). Balloons were inflated to the burst pressure indicated on the manufacturer’s label, regardless of the grouping. In patients with no circumferential conduit (patch enlargement), a PTA Dilatation Balloon 22mm in diameter was used. Postdilatation was achieved using a high-pressure balloon in all patients, with the aim of decreasing the RVOT gradient as much as possible. Therefore, overexpansion above the nominal conduit size was performed when needed. Haemodynamic and angiographic assessments were repeated after PPVI in all patients. All patients received heparin and antibiotic prophylaxis during and after the procedure, according to institutional protocol, and were discharged on aspirin 100mg/day orally.

Follow-up

All patients were scheduled for an office visit at 1, 3, 6, 12 and 24 months following valve implantation. A repeat transthoracic echocardiogram was performed during every follow-up. All events were recorded in a large institutional review board-approved database.

Statistical analysis

PASW Statistics version 17.0 (SPSS, Inc., Chicago, IL, USA) was used for statistical analysis. Nominal variables are expressed as numbers and percentages and were compared using Fisher’s exact test or the chi-square test, as appropriate. Ordinal variables are presented as means±standard deviations and were compared using the Wilcoxon rank sum test. Continuous variables are expressed as means±standard deviations and were compared using the independent variables t test. All tests were two-sided and a P value<0.05 was considered statistically significant.

Results

Fifty-two consecutive patients who underwent Melody® valve implantation at two centres (Necker/George Pompidou [n =44]; Marseille [n =8]) from May 2008 to December 2009 were included in this study. There were 20 children (i.e. aged below 18 years) and 32 adults (mean age, 22.7±9.18 years; median age, 22.2 years [10.6–54.8 years]). Forty-one patients were aged above 15 years. There were 33 patients in group I (expandable) and 19 patients in group II (non-expandable). Angiographic views in each group are given in Figure 2, Figure 3, Figure 4.



Figure 2


Figure 2. 

Angiographic views showing a patient with a non-expandable conduit following insertion of a Melody® valve. A. Still frame without dye showing the Melody® valve securely fixed by the existence of a metallic ring around the right ventricular outflow tract conduit, limiting its expansion. B. Excellent function of the inserted valve: no leak on angiography. Note the space between the ring and the stent related to the fabric of the prosthetic conduit.

Zoom



Figure 3


Figure 3. 

Angiographic views showing a patient with a non-expandable conduit at various stages of a Melody® valve implantation. A. Angiographic view at the beginning of the procedure showing a stenotic extra-anatomic right ventricular outflow tract Gore-Tex conduit. B and C. Angiographic views showing the results after opening with multiple bare-metal stents and insertion of the Melody® valve. The expansion of the stents remains limited.

Zoom



Figure 4


Figure 4. 

Angiographic views showing a patient with an expandable conduit (homograft) at various stages of a ®Melody valve implantation. A. Angiographic view at the beginning of the procedure showing a stenotic homograft. B and C. Angiographic views showing the results after prestenting and insertion of the Melody® valve. The stents are fully expanded and valve function is excellent.

Zoom

Basal haemodynamic characteristics, such as RV-PA gradient and RV/Ao pressure ratio, were similar in both groups. The mean RV-PA gradient and RV/Ao pressure ratio showed immediate and significant improvement after PPVI, regardless of the substrate or size. The improvement was, however, more pronounced in patients with expandable compared with non-expandable conduits (12.9±6.6mmHg vs 19.7±7.9mmHg [P =0.002]; and 0.4±0.1 vs 0.5±0.1 [P =0.008]) (Table 2).

The mean follow-up duration was similar in both the groups (511.8±288.6 days vs 491.32±229 days; P =0.7). Group I showed better outcomes until the last follow-up. No stent fracture was observed in any group.

Further stratification of each group based on the prePPVI diameter of the RVOT conduit showed varying outcomes. A cutoff of 20mm was found and used for subdividing each group. Group II subgroups (group IIA: less or equal to 20mm [n =9]; group IIB: greater than 20mm [n =10]) showed the following results: both subgroups showed similar basal characteristics and immediate haemodynamic improvement (Table 3). However, at last follow-up, RV systolic pressure measured by tricuspid regurgitation jet showed poor haemodynamic outcomes in subgroup IIB compared with subgroup IIA (75.8±36.9mmHg vs 41.5±8.5mmHg; P =0.006).

Group I subgroups (group IA: less or equal to 20mm [n =15]; group IB: greater than 20mm [n =18]) showed the following results: both subgroups showed similar basal characteristics and immediate haemodynamic improvement (Table 4). However, at last follow-up, RV systolic pressure showed poor haemodynamic outcomes in subgroup IB compared with subgroup IA (47.9±21.9mmHg vs 36.8±4.5mmHg; P =0.005).

Comparative haemodynamic outcomes after PPVI in patients with pre-existing expandable and non-expandable RVOT conduits20mm in diameter showed poor outcomes for non-expandable conduits compared with expandable conduits (Table 5).

Discussion

Percutaneous pulmonary valve replacement using the transcatheter technique for approved indications is becoming standard practice worldwide. The technique using the Melody® valve is presently limited to patients with dysfunctional prosthetic conduits or homografts with a diameter that does not exceed 22mm at the time of implantation [1, 2, 3, 4]. RV-PA continuity can be achieved surgically by using various tubes: expandable conduits and non-expandable synthetic conduits. As such, candidates for percutaneous pulmonary valve replacement are heterogeneous with respect to the type of surgical RVOT reconstruction and the results may thus differ accordingly. Outcomes after PPVI in patients with homografts may not be the same as in patients with prosthetic conduits. In our centre, the availability of homografts is low, making prosthetic conduits the first choice in most instances. Our goal, therefore, was to compare the haemodynamic results of PPVI in patients with expandable versus non-expandable conduits.

The results of the current study show the universal efficacy of PPVI in all types of RVOT reconstruction, at least up to midterm. The diameter of the conduits did not play a role in RVOT obstruction relief as long as the surgical substrates were homografts or patch enlargement. These surgical substrates can be expanded and possibly overexpanded at or above their nominal diameter, with resultant loss of RV-PA gradient. However, results are worst in patients with non-expandable prosthetic conduits, especially when size is taken into account. Many factors can be implicated to explain these results. Firstly, by definition, conduits with armatures or non-expandable material such as Dacron have lower distensibility than homografts; this is compounded by exuberant pannus formation on the prosthetic conduit over time. Prestenting with a BMS has been recommended to limit the risk of stent fractures [5, 6]. However, this was suggested and demonstrated in a cohort of patients with homografts as RVOT substitutes. In patients with non-expandable conduits, the BMS struts would encroach the RVOT lumen, causing further narrowing; this may explain the poor haemodynamic outcomes in such patients. Prestenting is likely to be very useful in patients with dynamic RVOT motion and/or extracardiac compression from neighbouring structures–factors that may lead to Melody® valve stent fracture and poor outcomes. The BMS struts form a good platform for scaffolding of tissue in the preparation of a stable landing zone for the Melody® valve.

The results of this study compel the interventionalist to strongly consider the type and size of surgical substrate used for RVOT modification or reconstruction. According to our study results, the patient subsets that derive the highest benefit from PPVI are, in descending order: patients with expandable conduits regardless of conduit size; patients with non-expandable conduits of diameter greater than 20mm at time of insertion; patients with non-expandable conduits less or equal to 20mm at time of insertion. In the second and third subsets, the decision about prestenting should be weighed against potential late lumen loss and worsening RV haemodynamics with time.

The quest for a better substrate for PPVI continues as we adapt to current technology. What is an ideal substrate? In our opinion there is no clear answer. Both types of substrates have drawbacks and advantages. We believe that non-expandable conduits offer a safer landing zone for Melody® valve insertion, with less risk of stent fractures. However, their use limits the capability of stent expansion, especially when the inner diameter is less than 20mm. In comparison, expandable conduits have greater expansion capabilities but an increased risk of stent movement and fracture. It is important to understand the natural history of homografts and prosthetic conduits and their degeneration with time, to answer this question. If calcific process is implicated, the replacement conduit should be as large as possible to reduce the RVOT gradient and improve long-term outcomes. The option of PPVI by the transcatheter technique is always available, even in such cases. A smaller conduit is probably indicated to offer the possibility of transcatheter valve implantation but we do not recommend this approach as technology is rapidly evolving. What is true today may not be true tomorrow with new devices with larger diameters.

Conclusion

PPVI is feasible, safe and successful in patients with the wide variety of surgical substrates used for RVOT reconstruction. There was immediate haemodynamic improvement in all patients. Patients with expandable RVOT conduits showed better haemodynamic outcomes then those with non-expandable prosthetic conduits, regardless of conduit diameter. Patients with non-expandable RVOT prosthetic conduits20mm diameter showed poor midterm results. This information needs to be integrated into the decision-making process before selecting patients for PPVI.

Disclosure of interest

The authors declare that they have no conflicts of interest concerning this article.


Acknowledgements

The authors thank the French Ministry of Health, STIC 2008 (REVALV), for financial support and the ‘URC’ of Georges Pompidou Hospital.

References

Eicken A., Ewert P., Hager A., and al. Percutaneous pulmonary valve implantation: two-centre experience with more than 100 patients Eur Heart J 2011 ;  32 : 1260-1265 [cross-ref]
Lurz P., Coats L., Khambadkone S., and al. Percutaneous pulmonary valve implantation: impact of evolving technology and learning curve on clinical outcome Circulation 2008 ;  117 : 1964-1972 [cross-ref]
McElhinney D.B., Hellenbrand W.E., Zahn E.M., and al. Short- and medium-term outcomes after transcatheter pulmonary valve placement in the expanded multicenter US melody valve trial Circulation 2010 ;  122 : 507-516 [cross-ref]
Zahn E.M., Hellenbrand W.E., Lock J.E., and al. Implantation of the melody transcatheter pulmonary valve in patients with a dysfunctional right ventricular outflow tract conduit early results from the u.s. Clinical trial J Am Coll Cardiol 2009 ;  54 : 1722-1729 [cross-ref]
Demkow M., Biernacka E.K., Spiewak M., and al. Percutaneous pulmonary valve implantation preceded by routine prestenting with a bare metal stent Catheter Cardiovasc Interv 2011 ;  77 : 381-389 [cross-ref]
Nordmeyer J., Lurz P., Khambadkone S., and al. Pre-stenting with a bare metal stent before percutaneous pulmonary valve implantation: acute and 1-year outcomes Heart 2011 ;  97 : 118-123 [cross-ref]



© 2012  Elsevier Masson SAS. All Rights Reserved.
EM-CONSULTE.COM is registrered at the CNIL, déclaration n° 1286925.
As per the Law relating to information storage and personal integrity, you have the right to oppose (art 26 of that law), access (art 34 of that law) and rectify (art 36 of that law) your personal data. You may thus request that your data, should it be inaccurate, incomplete, unclear, outdated, not be used or stored, be corrected, clarified, updated or deleted.
Personal information regarding our website's visitors, including their identity, is confidential.
The owners of this website hereby guarantee to respect the legal confidentiality conditions, applicable in France, and not to disclose this data to third parties.
Close
Article Outline