- Email: [email protected]
Current Experience with Percutaneous Pulmonary Valve Implantation
Current Experience with Percutaneous Pulmonary Valve Implantation Johannes Nordmeyer, Louise Coats, MRCP, and Philipp Bonhoeffer, MD Transcatheter valve replacement has recently been introduced into clinical practice and has the potential to transform the management of valvular heart disease. To date, the largest human experience exists with percutaneous pulmonary valve implantation in patients with repaired congenital heart disease who require re-intervention to the right ventricular outflow tract. The application of this approach, however, is presently restricted to certain right ventricular outflow tract morphologies, because the device needs to be anchored safely to prevent device dislodgement. Early results of percutaneous pulmonary valve implantation show lower morbidity than surgery and significant early symptomatic improvement. In the future, the challenge will be to extend percutaneous pulmonary valve implantation to all patients with a clinical indication to delay or avoid repeat open-heart surgery. Semin Thorac Cardiovasc Surg 18:122-125 © 2006 Elsevier Inc. All rights reserved. KEYWORDS percutaneous valve replacement, pulmonary valve, congenital heart disease, catheterization
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cquired dysfunction of the pulmonary valve in the adult population is rare, whereas dysfunction of the right ventricular outflow tract (RVOT) can be commonly found in patients with repaired congenital heart disease. Conventionally, these patients now undergo repeat heart surgery in an attempt to restore pulmonary valvar competency and to protect from right ventricular dysfunction and arrhythmia. Unfortunately, various factors limit the longevity of biological valves and patients may require several reoperations during a lifetime. These factors include aneurysmal dilation, degeneration, calcification, and lack of growth.1-3 In 2000, a valved stent was implanted for the first time percutaneously into a degenerated right ventricular (RV) to pulmonary artery (PA) prosthetic conduit of a 12-year-old boy.4 This intervention has now been performed in over 120 patients with repaired congenital heart disease (age 7 to 59 years), with the initial series recently reported,5 and has the potential to reduce reoperations for this patient group.
Procedure Valved Stent The device is composed of a bovine jugular venous valve sutured to a balloon-expandable platinum iridium stent (Numed, The Cardiac Unit, Institute of Child Health and Great Ormond Street Hospital for Children, London, United Kingdom. This work was supported in part by the British Heart Foundation. Address reprint requests to Dr. Johannes Nordmeyer, Cardiothoracic Unit, Great Ormond Street Hospital for Children, Great Ormond Street, London WC1N 3JH, UK. E-mail: [email protected]
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Hopkinton, NY, Fig. 1A). It is mounted on a specially designed delivery system with a balloon-in-balloon catheter (Numed, Fig. 1B) available in diameters of 18 to 22 mm.6 The valved stent is delivered to the RVOT via the venous circulation, usually from a femoral approach, under general anesthesia with the guidance of biplane angiography (Fig. 2).
Indications There are clinical and morphological criteria that are applied to judge the suitability for percutaneous pulmonary valve implantation (PPVI). At our institution, every potential candidate for PPVI undergoes echocardiography, magnetic resonance imaging (MRI), electrocardiogram, and cardiopulmonary exercise testing to assess ventricular function and RVOT morphology. Clinical indications for PPVI mirror the conventional criteria for surgical re-intervention and include pulmonary regurgitation with increasing right ventricular size, substantial tricuspid regurgitation, arrhythmia, and/or impairment in exercise capacity or RVOT obstruction with right ventricular pressures greater than 2/3 systemic. The timing of re-intervention remains subject to debate as some investigators have found that right ventricular dysfunction may not be recoverable.7 Typically, this concern has had to be balanced against the limited longevity of biological valves and the need for reoperation in the future. The percutaneous approach now offers a less invasive treatment, without the need for cardiopulmonary bypass, which may potentially shift the indications toward earlier intervention.
Percutaneous pulmonary valve implantation
Figure 1 (A) Percutaneous pulmonary valve (Numed, Hopkinton, NY). (B) Device mounted on the delivery system (Numed).
In view of the large delivery system, the procedure is restricted to patients older than 5 years and over 20 kg in weight. A safe anchoring site for the valved stent is essential; in our experience dysfunctional homografts or other RVto-PA conduits provide the best environment. With current technology, there are limitations in terms of outflow tract size. RVOT dimensions greater than 22 mm with dynamic outflow tract aneurysms, seen commonly following transannular patch repair of the RVOT, are currently not suitable for PPVI.
Results In our patient population (⬎120 patients) the commonest primary diagnoses were variants of Tetralogy of Fallot (57.5%) with most patients in New York Heart Association (NYHA) functional class 2 (maximum 4). The majority of patients had a homograft placement (76.6%) and had had two previous sternotomies (1 to 6).
123 The implantation of a percutaneous pulmonary valve was attempted in 121 patients and was successful in 120 patients with a mean procedure time of 102 minutes. It resulted in a rapid improvement in symptoms and objective exercise capacity (VO2max from 24.1 ⫾ 7.5 to 25.7 ⫾ 7.2 mL/kg/min, P ⬍ 0.01, in patients who were able to undergo formal exercise testing). The patients benefited from relief of RVOT obstruction reflected by a decrease in RV systolic pressure (62.6 ⫾ 18.2 to 46.6 ⫾ 13.9 mm Hg, P ⬍ 0.001) and RVOT pressure gradient (37.3 ⫾ 21.4 to 17.7 ⫾ 10.7 mm Hg, P ⬍ 0.001, Fig. 3A) and also benefited from a competent pulmonary valve. MRI was performed in most patients before and after the procedure showed reduction in pulmonary regurgitant fraction (24.4 ⫾ 15.0 versus 3.3 ⫾ 4.6%, P ⬍ 0.001, Fig. 3B) and RV end-diastolic volume (158.0 ⫾ 59.6 versus 144.5 ⫾ 73.4 mL/beat, P ⬍ 0.001). The median hospital stay was 2 days (2 to 22 days). This was significantly shorter than after surgical pulmonary valve implantation (median 7, 4 to 114 days) when we retrospectively compared our results following surgical or percutaneous re-intervention to the RVOT.8 We also saw that the predominant indication for re-intervention in the surgical group was mainly pulmonary regurgitation (64.9%), whereas in the percutaneous group it was mainly homograft/conduit stenosis or a mixed lesion (68.6%), which reflected the need to anchor the valved stent safely. The occurrence of procedural complications necessitating urgent surgery was comparable in the surgical and the percutaneous group (9.6% versus 4.2%), whereas important early morbidity was 8.5% in the surgical group and 5.8% in the percutaneous group. Currently, freedom from explantation is 75.3% at 5 years (Fig. 4).
Complications As with any new procedure, there is a learning curve, which shapes device design, patient selection, and procedural technique. In five patients, procedural complications occurred which required early conversion to surgery. Two patients
Figure 2 (A) Lateral angiogram showing significant pulmonary regurgitation. (B) The delivery system is placed at the site of implantation and uncovered. (C) Result after percutaneous implantation of a pulmonary valve showing the competency of the valved stent with no residual pulmonary regurgitation.
J. Nordmeyer, L. Coats, and P. Bonhoeffer
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Figure 3 (A) RVOT gradient fell significantly after PPVI (37.3 ⫾ 21.4 to 17.7 ⫾ 10.7 mm Hg, P ⬍ 0.001). (B) Pulmonary regurgitant fraction fell significantly after PPVI (24.4 ⫾ 15.0 versus 3.3 ⫾ 4.6%, P ⬍ 0.001).
needed surgery due to device instability, one due to coronary artery compression, one due to homograft rupture, and in one patient the valved stent covered the right pulmonary artery (Fig. 5). To reduce the risk of procedural complications, careful patient selection is essential; useful investigations include three-dimensional imaging, balloon sizing of the RVOT, and performing an aortogram and/or selective coronary angiogram in combination with an inflated balloon in the RVOT to judge the course of the coronary arteries. Follow-up complications included stent fractures, which occurred in about 18% of our patient population, usually with no clinical consequence. In four patients widespread stent fractures occurred with device dysfunction and required subsequent treatment, three with an implantation of a second PPV, one with surgery. The occurrence of endocarditis and intravascular hemolysis have been documented in a few cases, though it is still too early to compare the prevalence with that of surgically implanted valves. As with other biological valves, we anticipate that the longevity of the valves will be limited. It is likely that calcification and degeneration will occur with time but to date we have not seen this complication. In our overall experience of more than 120 patients, early mortality unrelated to procedural complications occurred in two patients who presented in extreme clinical condition and were treated with an emergency percutaneous procedure.
tion rate. The PPVI device would have to cost more than $33,678.22 before this approach became more expensive than surgery, while mortality would need to reach 25% at 25 years before PPVI lost incremental effectiveness. Furthermore, assuming all late complications (⬎5 years) could be treated percutaneously with a second PPV, the repeat PPVI rate could reach 17% per year before this approach becomes less cost-effective than surgery. Based on this information, longevity of the percutaneous valve does not need to match that of surgically implanted valves to retain cost-effectiveness.9
Future Developments Development of new devices to address larger RVOTs is under investigation in animal models. A hybrid method combining minimally invasive surgery and transcatheter pulmonary valve implantation may provide one approach.10 With this technique the main pulmonary artery is banded using two radiopaque rings with a diameter of 18 mm. This allows reduction in the diameter of the RVOT and subsequent placement of a valved stent. Although this is more invasive than
Cost-Effectiveness Based on our experience together with long-term projections from literature and assumptions, we compared models of cost and cost-effectiveness over 25 years for PPVI, based on data of 84 patients, against known costs and outcomes for PVR in 94 contemporary patients.9 Costs included the initial procedure, subsequent complications, and reoperations. Outcome was measured by life expectancy. One-way sensitivity analysis was applied to determine the implications of varying valve price, re-intervention rate, and mortality in the PPVI group. As we found in earlier studies PPVI had a shorter hospital stay (2 versus 7 days), fewer complications, and lower mortality. This meant that PPVI was more cost-effective at all time points than surgery, despite a higher interven-
Figure 4 Freedom from explantation is 75.3% at 5 years following PPVI.
Percutaneous pulmonary valve implantation
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Figure 5 (A) Anteroposterior angiogram performed before PPVI. (B) Angiogram following PPVI complicated by obstruction of the right pulmonary artery.
transcatheter valve implantation, it can be performed via a lateral thoracotomy without the need for cardiopulmonary bypass. Another approach is to develop new devices that contain a bovine valve, but permit “downsizing” of large RVOTs.11 These procedures at present are limited to the experimental setting. There are also limitations for patients at the other end of the spectrum of RVOT size. In patients with small conduits, there is particular risk of homograft rupture at the time of device implantation and stent fracture during follow-up. Furthermore, children with small conduits may outgrow these, despite restoration of valve function, and require surgical replacement of the conduit in adulthood.
Conclusions Percutaneous pulmonary valve implantation provides an additional and complementary approach to conventional surgery. To date, it also represents the most successful and clinically applicable experience of transcatheter valve technology. Until now, surgical re-intervention has been the only option for many children and adults with repaired congenital heart disease. This novel technique now offers a less traumatic approach, without cardiopulmonary bypass, and a shorter hospital stay. With time, we will understand whether these encouraging early results are sustained in the long term. It is likely, however, that a significant shift away from the strategy of reoperation towards transcatheter procedures will occur in this patient population. The use of 3D imaging provides important information to judge the suitability for PPVI. Future technical developments in the field of transcatheter pulmonary valve implantation in combination with advances in imaging (eg, MRI-cathlab) will allow us to extend the indications for this novel technique with high standards of safety. Attractively, PPVI could also offer greater cost-effectiveness in the setting of repeat interventions. It is evident though, that a close cooperation between surgeons and interventional cardiologists is essential to develop the best long-
term treatment strategy for patients. Percutaneous pulmonary valve implantation will become an important treatment option for patients with dysfunction of the RVOT.
Acknowledgments Louise Coats and Philipp Bonhoeffer are supported by the British Heart Foundation. Philipp Bonhoeffer is a consultant for NuMed and Medtronic.
References 1. Tweddell JS, Pelech AN, Frommelt PC, et al: Factors affecting longevity of homograft valves used in right ventricular outflow tract reconstruction for congenital heart disease. Circulation 102:III130-III135, 2000 (19 suppl 3) 2. Breymann T, Boethig D, Goerg R, et al: The Contegra bovine valved jugular vein conduit for pediatric RVOT reconstruction: 4 years experience with 108 patients. J Card Surg 19(5):426-431, 2004 3. Wells WJ, Arroyo H Jr, Bremner RM, et al: Homograft conduit failure in infants is not due to somatic outgrowth. J Thorac Cardiovasc Surg 124(1):88-96, 2002 4. Bonhoeffer P, Boudjemline Y, Saliba Z, et al: Percutaneous replacement of pulmonary valve in a right-ventricle to pulmonary-artery prosthetic conduit with valve dysfunction. Lancet 356(9239):1403-1405, 2000 5. Khambadkone S, Coats L, Taylor A, et al: Percutaneous pulmonary valve implantation in humans: results in 59 consecutive patients. Circulation 112(8):1189-1197, 2005 6. Khambadkone S, Bonhoeffer P: Percutaneous implantation of pulmonary valves. Exp Rev Cardiovasc Ther 1(4):541-548, 2003 7. Therrien J, Siu SC, McLaughlin PR, et al: Pulmonary valve replacement in adults late after repair of tetralogy of fallot: are we operating too late? J Am Coll Cardiol 36(5):1670-1675, 2000 8. Coats L, Tsang V, Khambadkone S, et al: The potential impact of percutaneous pulmonary valve stent implantation on right ventricular outflow tract re-intervention. Eur J Cardiothorac 27(4):536-543, 2005 9. Coats L, Fengu S, Deanfield J, et al: Right ventricular outflow tract dysfunction percutaneous pulmonary valve implantation: a cost-effective strategy for management of right ventricular outflow tract dysfunction. JACC supplement, ACC abstract 945-114, 2006 (abstr) 10. Boudjemline Y, Schievano S, Bonnet C, et al: Off-pump replacement of the pulmonary valve in large right ventricular outflow tracts: a hybrid approach. J Thorac Cardiovasc Surg 129(4):831-837, 2005 11. Boudjemline Y, Agnoletti G, Bonnet D, et al: Percutaneous pulmonary valve replacement in a large right ventricular outflow tract: an experimental study. J Am Coll Cardiol 43(6):1082-1087, 2004
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cquired dysfunction of the pulmonary valve in the adult population is rare, whereas dysfunction of the right ventricular outflow tract (RVOT) can be commonly found in patients with repaired congenital heart disease. Conventionally, these patients now undergo repeat heart surgery in an attempt to restore pulmonary valvar competency and to protect from right ventricular dysfunction and arrhythmia. Unfortunately, various factors limit the longevity of biological valves and patients may require several reoperations during a lifetime. These factors include aneurysmal dilation, degeneration, calcification, and lack of growth.1-3 In 2000, a valved stent was implanted for the first time percutaneously into a degenerated right ventricular (RV) to pulmonary artery (PA) prosthetic conduit of a 12-year-old boy.4 This intervention has now been performed in over 120 patients with repaired congenital heart disease (age 7 to 59 years), with the initial series recently reported,5 and has the potential to reduce reoperations for this patient group.
Procedure Valved Stent The device is composed of a bovine jugular venous valve sutured to a balloon-expandable platinum iridium stent (Numed, The Cardiac Unit, Institute of Child Health and Great Ormond Street Hospital for Children, London, United Kingdom. This work was supported in part by the British Heart Foundation. Address reprint requests to Dr. Johannes Nordmeyer, Cardiothoracic Unit, Great Ormond Street Hospital for Children, Great Ormond Street, London WC1N 3JH, UK. E-mail: [email protected]
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Hopkinton, NY, Fig. 1A). It is mounted on a specially designed delivery system with a balloon-in-balloon catheter (Numed, Fig. 1B) available in diameters of 18 to 22 mm.6 The valved stent is delivered to the RVOT via the venous circulation, usually from a femoral approach, under general anesthesia with the guidance of biplane angiography (Fig. 2).
Indications There are clinical and morphological criteria that are applied to judge the suitability for percutaneous pulmonary valve implantation (PPVI). At our institution, every potential candidate for PPVI undergoes echocardiography, magnetic resonance imaging (MRI), electrocardiogram, and cardiopulmonary exercise testing to assess ventricular function and RVOT morphology. Clinical indications for PPVI mirror the conventional criteria for surgical re-intervention and include pulmonary regurgitation with increasing right ventricular size, substantial tricuspid regurgitation, arrhythmia, and/or impairment in exercise capacity or RVOT obstruction with right ventricular pressures greater than 2/3 systemic. The timing of re-intervention remains subject to debate as some investigators have found that right ventricular dysfunction may not be recoverable.7 Typically, this concern has had to be balanced against the limited longevity of biological valves and the need for reoperation in the future. The percutaneous approach now offers a less invasive treatment, without the need for cardiopulmonary bypass, which may potentially shift the indications toward earlier intervention.
Percutaneous pulmonary valve implantation
Figure 1 (A) Percutaneous pulmonary valve (Numed, Hopkinton, NY). (B) Device mounted on the delivery system (Numed).
In view of the large delivery system, the procedure is restricted to patients older than 5 years and over 20 kg in weight. A safe anchoring site for the valved stent is essential; in our experience dysfunctional homografts or other RVto-PA conduits provide the best environment. With current technology, there are limitations in terms of outflow tract size. RVOT dimensions greater than 22 mm with dynamic outflow tract aneurysms, seen commonly following transannular patch repair of the RVOT, are currently not suitable for PPVI.
Results In our patient population (⬎120 patients) the commonest primary diagnoses were variants of Tetralogy of Fallot (57.5%) with most patients in New York Heart Association (NYHA) functional class 2 (maximum 4). The majority of patients had a homograft placement (76.6%) and had had two previous sternotomies (1 to 6).
123 The implantation of a percutaneous pulmonary valve was attempted in 121 patients and was successful in 120 patients with a mean procedure time of 102 minutes. It resulted in a rapid improvement in symptoms and objective exercise capacity (VO2max from 24.1 ⫾ 7.5 to 25.7 ⫾ 7.2 mL/kg/min, P ⬍ 0.01, in patients who were able to undergo formal exercise testing). The patients benefited from relief of RVOT obstruction reflected by a decrease in RV systolic pressure (62.6 ⫾ 18.2 to 46.6 ⫾ 13.9 mm Hg, P ⬍ 0.001) and RVOT pressure gradient (37.3 ⫾ 21.4 to 17.7 ⫾ 10.7 mm Hg, P ⬍ 0.001, Fig. 3A) and also benefited from a competent pulmonary valve. MRI was performed in most patients before and after the procedure showed reduction in pulmonary regurgitant fraction (24.4 ⫾ 15.0 versus 3.3 ⫾ 4.6%, P ⬍ 0.001, Fig. 3B) and RV end-diastolic volume (158.0 ⫾ 59.6 versus 144.5 ⫾ 73.4 mL/beat, P ⬍ 0.001). The median hospital stay was 2 days (2 to 22 days). This was significantly shorter than after surgical pulmonary valve implantation (median 7, 4 to 114 days) when we retrospectively compared our results following surgical or percutaneous re-intervention to the RVOT.8 We also saw that the predominant indication for re-intervention in the surgical group was mainly pulmonary regurgitation (64.9%), whereas in the percutaneous group it was mainly homograft/conduit stenosis or a mixed lesion (68.6%), which reflected the need to anchor the valved stent safely. The occurrence of procedural complications necessitating urgent surgery was comparable in the surgical and the percutaneous group (9.6% versus 4.2%), whereas important early morbidity was 8.5% in the surgical group and 5.8% in the percutaneous group. Currently, freedom from explantation is 75.3% at 5 years (Fig. 4).
Complications As with any new procedure, there is a learning curve, which shapes device design, patient selection, and procedural technique. In five patients, procedural complications occurred which required early conversion to surgery. Two patients
Figure 2 (A) Lateral angiogram showing significant pulmonary regurgitation. (B) The delivery system is placed at the site of implantation and uncovered. (C) Result after percutaneous implantation of a pulmonary valve showing the competency of the valved stent with no residual pulmonary regurgitation.
J. Nordmeyer, L. Coats, and P. Bonhoeffer
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Figure 3 (A) RVOT gradient fell significantly after PPVI (37.3 ⫾ 21.4 to 17.7 ⫾ 10.7 mm Hg, P ⬍ 0.001). (B) Pulmonary regurgitant fraction fell significantly after PPVI (24.4 ⫾ 15.0 versus 3.3 ⫾ 4.6%, P ⬍ 0.001).
needed surgery due to device instability, one due to coronary artery compression, one due to homograft rupture, and in one patient the valved stent covered the right pulmonary artery (Fig. 5). To reduce the risk of procedural complications, careful patient selection is essential; useful investigations include three-dimensional imaging, balloon sizing of the RVOT, and performing an aortogram and/or selective coronary angiogram in combination with an inflated balloon in the RVOT to judge the course of the coronary arteries. Follow-up complications included stent fractures, which occurred in about 18% of our patient population, usually with no clinical consequence. In four patients widespread stent fractures occurred with device dysfunction and required subsequent treatment, three with an implantation of a second PPV, one with surgery. The occurrence of endocarditis and intravascular hemolysis have been documented in a few cases, though it is still too early to compare the prevalence with that of surgically implanted valves. As with other biological valves, we anticipate that the longevity of the valves will be limited. It is likely that calcification and degeneration will occur with time but to date we have not seen this complication. In our overall experience of more than 120 patients, early mortality unrelated to procedural complications occurred in two patients who presented in extreme clinical condition and were treated with an emergency percutaneous procedure.
tion rate. The PPVI device would have to cost more than $33,678.22 before this approach became more expensive than surgery, while mortality would need to reach 25% at 25 years before PPVI lost incremental effectiveness. Furthermore, assuming all late complications (⬎5 years) could be treated percutaneously with a second PPV, the repeat PPVI rate could reach 17% per year before this approach becomes less cost-effective than surgery. Based on this information, longevity of the percutaneous valve does not need to match that of surgically implanted valves to retain cost-effectiveness.9
Future Developments Development of new devices to address larger RVOTs is under investigation in animal models. A hybrid method combining minimally invasive surgery and transcatheter pulmonary valve implantation may provide one approach.10 With this technique the main pulmonary artery is banded using two radiopaque rings with a diameter of 18 mm. This allows reduction in the diameter of the RVOT and subsequent placement of a valved stent. Although this is more invasive than
Cost-Effectiveness Based on our experience together with long-term projections from literature and assumptions, we compared models of cost and cost-effectiveness over 25 years for PPVI, based on data of 84 patients, against known costs and outcomes for PVR in 94 contemporary patients.9 Costs included the initial procedure, subsequent complications, and reoperations. Outcome was measured by life expectancy. One-way sensitivity analysis was applied to determine the implications of varying valve price, re-intervention rate, and mortality in the PPVI group. As we found in earlier studies PPVI had a shorter hospital stay (2 versus 7 days), fewer complications, and lower mortality. This meant that PPVI was more cost-effective at all time points than surgery, despite a higher interven-
Figure 4 Freedom from explantation is 75.3% at 5 years following PPVI.
Percutaneous pulmonary valve implantation
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Figure 5 (A) Anteroposterior angiogram performed before PPVI. (B) Angiogram following PPVI complicated by obstruction of the right pulmonary artery.
transcatheter valve implantation, it can be performed via a lateral thoracotomy without the need for cardiopulmonary bypass. Another approach is to develop new devices that contain a bovine valve, but permit “downsizing” of large RVOTs.11 These procedures at present are limited to the experimental setting. There are also limitations for patients at the other end of the spectrum of RVOT size. In patients with small conduits, there is particular risk of homograft rupture at the time of device implantation and stent fracture during follow-up. Furthermore, children with small conduits may outgrow these, despite restoration of valve function, and require surgical replacement of the conduit in adulthood.
Conclusions Percutaneous pulmonary valve implantation provides an additional and complementary approach to conventional surgery. To date, it also represents the most successful and clinically applicable experience of transcatheter valve technology. Until now, surgical re-intervention has been the only option for many children and adults with repaired congenital heart disease. This novel technique now offers a less traumatic approach, without cardiopulmonary bypass, and a shorter hospital stay. With time, we will understand whether these encouraging early results are sustained in the long term. It is likely, however, that a significant shift away from the strategy of reoperation towards transcatheter procedures will occur in this patient population. The use of 3D imaging provides important information to judge the suitability for PPVI. Future technical developments in the field of transcatheter pulmonary valve implantation in combination with advances in imaging (eg, MRI-cathlab) will allow us to extend the indications for this novel technique with high standards of safety. Attractively, PPVI could also offer greater cost-effectiveness in the setting of repeat interventions. It is evident though, that a close cooperation between surgeons and interventional cardiologists is essential to develop the best long-
term treatment strategy for patients. Percutaneous pulmonary valve implantation will become an important treatment option for patients with dysfunction of the RVOT.
Acknowledgments Louise Coats and Philipp Bonhoeffer are supported by the British Heart Foundation. Philipp Bonhoeffer is a consultant for NuMed and Medtronic.
References 1. Tweddell JS, Pelech AN, Frommelt PC, et al: Factors affecting longevity of homograft valves used in right ventricular outflow tract reconstruction for congenital heart disease. Circulation 102:III130-III135, 2000 (19 suppl 3) 2. Breymann T, Boethig D, Goerg R, et al: The Contegra bovine valved jugular vein conduit for pediatric RVOT reconstruction: 4 years experience with 108 patients. J Card Surg 19(5):426-431, 2004 3. Wells WJ, Arroyo H Jr, Bremner RM, et al: Homograft conduit failure in infants is not due to somatic outgrowth. J Thorac Cardiovasc Surg 124(1):88-96, 2002 4. Bonhoeffer P, Boudjemline Y, Saliba Z, et al: Percutaneous replacement of pulmonary valve in a right-ventricle to pulmonary-artery prosthetic conduit with valve dysfunction. Lancet 356(9239):1403-1405, 2000 5. Khambadkone S, Coats L, Taylor A, et al: Percutaneous pulmonary valve implantation in humans: results in 59 consecutive patients. Circulation 112(8):1189-1197, 2005 6. Khambadkone S, Bonhoeffer P: Percutaneous implantation of pulmonary valves. Exp Rev Cardiovasc Ther 1(4):541-548, 2003 7. Therrien J, Siu SC, McLaughlin PR, et al: Pulmonary valve replacement in adults late after repair of tetralogy of fallot: are we operating too late? J Am Coll Cardiol 36(5):1670-1675, 2000 8. Coats L, Tsang V, Khambadkone S, et al: The potential impact of percutaneous pulmonary valve stent implantation on right ventricular outflow tract re-intervention. Eur J Cardiothorac 27(4):536-543, 2005 9. Coats L, Fengu S, Deanfield J, et al: Right ventricular outflow tract dysfunction percutaneous pulmonary valve implantation: a cost-effective strategy for management of right ventricular outflow tract dysfunction. JACC supplement, ACC abstract 945-114, 2006 (abstr) 10. Boudjemline Y, Schievano S, Bonnet C, et al: Off-pump replacement of the pulmonary valve in large right ventricular outflow tracts: a hybrid approach. J Thorac Cardiovasc Surg 129(4):831-837, 2005 11. Boudjemline Y, Agnoletti G, Bonnet D, et al: Percutaneous pulmonary valve replacement in a large right ventricular outflow tract: an experimental study. J Am Coll Cardiol 43(6):1082-1087, 2004