Implantation of the Melody Transcatheter Pulmonary Valve - Miami ...

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JACC Vol. 54, No. 18, 2009October 27, 2009:1722–9Zahn et al.Early Results From the Transcatheter Pulmonary Valve Trial1727Figure 2adverse events were reported. With respect to the safetyoutcome criteria, 100% of patients were free fromprocedure- or device-related death, and 91% were free fromserious procedure- or device-related events.DiscussionKaplan-Meier Curve DepictingFreedom From Re-Intervention forStent Fracture and Associated RVOT ObstructionError bars shown are at the 95%confidence intervals. RVOT right ventricular outflow tract.To date, the only published series of Melody valveimplantation have been from the Bonhoeffer group anddemonstrate excellent short- and intermediate-term results(11,12). This study confirms that equally good acute andshort-term results can be achieved by trained, experiencedoperators at multiple other centers. Furthermore, it is thefirst prospective multicenter clinical trial of the Melodyvalve that uses defined entry criteria, standardized implantationand follow-up protocols, independent core laboratoriesfor assessment of outcomes, and cinefluoroscopy andCT pulmonary angiography to evaluate for stent fractureand pulmonary embolism.Procedural success and short-term effectiveness. Theprocedural success rate in this series was high (29 of 30attempts) and compared favorably with results published byexperienced operators (12,15). The current system designmakes Melody valve implantation simple and comparabletechnically to bare-metal stent implantation, a commonintervention performed in most congenital catheterizationlaboratories. There were no device malpositions or embolizationsin this series. The current delivery system, designedspecifically for this application, protects the stent andpreserves the balloon–stent relationship during advancementto the RVOT and may offer some advantages overconventional methods of stent implantation. The averagehospital stay of just over 1 day in this study comparesfavorably with both surgical conduit replacement and baremetalstenting.In the current study, a minimum sizing balloon waistof 14 mm was required to undergo valve implantation.Using this approach, only 1 patient had a postimplantationRV-PA gradient that was considered inadequateby pre-determined criteria. Pre-dilation of theconduit before sizing was a required component of theprotocol for conduits with an angiographic diameter 18mm, but pre-stenting was not allowed in this initialcohort (the protocol has since been modified to allowconcomitant procedures, including pre-stenting of the conduit).The rationale for pre-dilation was to optimize conduitdiameter before balloon sizing and Melody valve implantationand to assess compliance of the conduit and identify multipleor highly resistant stenoses. As Sugiyama et al. (16) confirmedin their series of bare-metal stenting for conduit obstruction,the smaller the achieved diameter of the conduit relative to thenormal pulmonary valve size for the patient, the higher thepost-intervention RVOT gradient. This may be more importantwith an implantable valve, in which the valve andvein segment add bulk to the implant site and may contributeto luminal narrowing and obstruction if the stent isunder-expanded.In the patient with a post-implantation peak RVOTgradient of 37 mm Hg, the obstruction was below theconduit and unrelated to the Melody valve itself. Four otherpatients developed Doppler mean gradients 30 mm Hg by6-month follow-up. These outcomes highlight the importanceof appropriate patient selection for the Melody valve.As more data become available, it will be important toevaluate patient-related and procedural data associated withearly recurrence of conduit obstruction to improve patientselection and execution of the procedure. It will also beimportant to determine the role of pre-dilation and/orpre-stenting in preventing recurrent RVOT obstruction.Consistent with prior reports, function of the Melodyvalve was excellent in short-term follow-up, with no ortrivial PR in almost all patients, and none with more thanmild regurgitation (11,12,15). RVOT gradients were significantlylower at 6 months than before implantation, andMRI demonstrated favorable RV volume remodeling. Amajority of patients improved in NYHA functional class,and none declined, consistent with prior reports (12).Although symptomatic improvement was typically noted 1month after implantation, some patients continued to improveas late as 6 months after implantation, raising thepossibility that cardiac remodeling and conditioning maycontinue beyond the acute restoration of pulmonary valvecompetence (21). In the current series, we did not observesignificant improvements in maximal VO 2 and anaerobicthreshold, although the preponderance of patients with PRas the primary indication for valve placement may be afactor in this finding. Coats et al. (22) reported that patientswith PR have minimal improvement in maximal VO 2 andanaerobic threshold after Melody valve implantation, in
1728 Zahn et al. JACC Vol. 54, No. 18, 2009Early Results From the Transcatheter Pulmonary Valve Trial October 27, 2009:1722–9contrast to patients who receive a Melody valve primarily forstenosis (22). Further examination of the physiologic mechanismsunderlying changes in exercise performance andsymptomatic improvement is warranted.Stent fracture. Stent fracture, well described after bothbare-metal stenting of RVOT conduits and Melody valveimplantation, was an important finding in this study(19,23). Peng et al. (19) described 221 patients treated forconduit obstruction with bare-metal stenting and found a43% incidence of stent fracture, with external compressionand a substernal conduit location identified as importantrisk factors. In a series of 123 patients who underwentMelody valve placement, Nordmeyer et al. (23) reported a75% freedom from Melody stent fracture at 2 years, withimplantation in the native RVOT, no calcification along theRVOT, and greater recoil after balloon deflation associatedwith a higher risk of fracture. It is logical to postulate fromthese 2 studies that when excessive external loading forcesare applied to stents in the RVOT, either from dynamiccompression or other cyclic stresses, there is an importantrisk of stent fracture. The current series includes too fewpatients to provide robust insight into this issue, but thefrequency of stent fracture appears consistent with theseearlier reports. Nordmeyer et al. (24) recently reported aseries of patients who underwent successful treatment ofre-stenosis after Melody stent fracture, with bare-metalstenting followed by implantation of a second Melody valve.The same approach was used in 3 patients in this series,with good acute results. Further attention is needed tobetter understand the risk factors for, prevention of, andtreatment of stent fracture in patients undergoing transcatheterpulmonary valve placement.Safety. The procedural adverse event rate of 9% in thiscohort is acceptable for a new procedure of this magnitudeand compares favorably with previously published reportsinvolving catheter or surgical intervention for conduit dysfunction(1–3,16–20). The large profile of the deliverysystem did not result in any obvious vascular damage orprohibit delivery of the device in any patient, includingchildren as young as 10 years. Importantly, none of theadverse events in this study resulted in death or long-termsequelae. Aside from stent fractures and re-interventions, asdiscussed above, there were no device- or procedure-relatedadverse events reported during follow-up.Protocol. There are challenges to developing a standardized,rigorous protocol for percutaneous pulmonary valveplacement in individuals with dysfunctional RVOT conduitsand a spectrum of hemodynamic disease that includesvariable degrees of PR and obstruction. There are limiteddata from which to define rigorous, outcome-based indicationsfor valve implantation. Moreover, the indications forimplantation and metrics of success will necessarily differ forpatients at different points on this disease spectrum, andthere is no simple means of capturing the complexities ofmixed disease. The inclusion criteria for this protocol weredesigned to reflect general practice on the basis of thepublished literature and the experience of the participatingcenters and were graduated according to symptomatic status.To address the question of clinical equipoise, 2 independentphysicians, 1 congenital cardiac surgeon and 1pediatric cardiologist, reviewed prospective patients andprovided written support for the decision to implant aMelody valve. Nevertheless, individuals varied within thecohort, and our population may have differed in compositionfrom that of previously reported series (12,21). Echocardiographicassessment of hemodynamic entry criteriamay be considered a limitation of the study protocol and waschosen for logistical reasons. The catheterization protocolused in this study was successful in identifying 2 patients atrisk for coronary compression, a potentially fatal complication.Pre-implantation balloon inflation with simultaneouscoronary angiography should be used in any case of conduitstenting or transcatheter valve implantation when coronaryartery compression is suspected. Further, the protocol specifiedcinefluoroscopy at the 6-month follow-up visit toassess for stent fracture. The decision to use cinefluoroscopywas based on its anticipated high sensitivity for detectingeven minor stent fractures.ConclusionsThis is the first multicenter prospective trial of an implantabletranscatheter pulmonary valve in a population ofpatients with congenital heart disease and RVOT conduitdysfunction. The implantation success rate was high, thefrequency of adverse events was acceptable, and short-termoutcomes were encouraging, supporting the conclusion thatthis technology can be translated effectively to experienced,properly trained interventional cardiologists and is nothighly operator dependent. Longer follow-up and a largerpatient experience are needed to determine the ultimate roleof this therapy in the treatment of conduit dysfunction.Reprint requests and correspondence: Dr. Doff B. McElhinney,Department of Cardiology, Children’s Hospital, 300 LongwoodAvenue, Boston, Massachusetts 02115. E-mail: doff.mcelhinney@cardio.chboston.org.REFERENCES1. Stark J, Bull C, Stajevic M, Jothi M, Elliott M, de Leval M. Fate ofsubpulmonary homograft conduits: determinants of late homograftfailure. J Thorac Cardiovasc Surg 1998;115:506–16.2. Bielefeld M, Bishop D, Campbell D, Mitchell M, Grover F, ClarkeD. Reoperative homograft right ventricular outflow tract reconstruction.Ann Thorac Surg 2001;71:482–7.3. Gerestein C, Takkenberg J, Oei F, et al. Right ventricular outflow tractreconstruction with an allograft conduit. Ann Thorac Surg 2001;71:911–7.4. Wells WJ, Arroyo H Jr., Bremner RM, Wood J, Starnes VA.Homograft conduit failure in infants is not due to somatic outgrowth.J Thorac Cardiovasc Surg 2002;124:88–96.5. Powell A, Lock J, Keane J, Perry S. Prolongation of RV-PA conduitlife span by percutaneous stent implantation: intermediate long-termresults. Circulation 1995;92:3282–8.6. Ovaert C, Caldarone CA, McCrindle BW, et al. Endovascular stentimplantation for the management of postoperative right ventricular
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