Is There a Role for Mechanical Valved Conduits in the Pulmonary Position?

Transcription

1 CARDIOVASCULAR Is There a Role for Mechanical Valved Conduits in the Pulmonary Position? Felix Haas, MD, Christian Schreiber, MD, Jürgen Hörer, MD, Martin Kostolny, MD, Klaus Holper, MD, and Rüdiger Lange, MD Department of Pediatric Cardiothoracic Surgery, Wilhelmina Children s Hospital, Utrecht, The Netherlands, and Department of Cardiothoracic Surgery, German Heart Center at the Technical University Munich, Munich, Germany Background. The use of allografts or xenografts is the treatment of choice for pulmonary valve replacement. However, the limited durability is responsible for multiple reoperations associated with increased morbidity. In search of a definitive solution, the implantation of a mechanical valved conduit might be an option in highly selected patients. This study evaluated short-term results after pulmonary valve replacement with a mechanical valved conduit. Methods. Fourteen patients underwent pulmonary valve replacement with a mechanical valved conduit. All patients had a mean of previous operations. Seven patients were previously operated on for tetralogy of Fallot, 3 patients for pulmonary atresia, 3 patients for common arterial trunk, and 1 patient for subaortic stenosis. Results. All patients survived the operation and are currently well. At follow-up (11 to 63 months), all but 2 patients showed normal right ventricular function, with a mean gradient of 14 9 mm Hg (range, 4 to 30 mm Hg) across the pulmonary valve. At follow-up, there was no evidence of valve failure or tissue growth within the valve annulus. All patients are receiving anticoagulants to maintain an international normalized ratio of 3.0 to 4.5. Conclusions. In highly selected patients, the use of a mechanical valved conduit in the pulmonary position leads to satisfactory results. To avoid a predictable reoperation after multiple right ventricular outflow tract reconstruction, and therefore reoperation-related morbidity, the implantation of a mechanical prosthesis as a lifelong solution requires consideration. Selection criteria for this permanent solution should include older age, multiple previous operations, and patient compliance with anticoagulant therapy. (Ann Thorac Surg 2005;79:1662 8) 2005 by The Society of Thoracic Surgeons For many years, homografts or xenografts have been an important tool in reconstruction of the right ventricular (RV) outflow tract. Despite gradual deterioration of any implant, long-term follow-up data in large collectives have shown good results with regard to complication rate and durability [1, 2]. However, because of progressive degeneration with time, biologic valved conduits do not represent a permanent solution for children and adolescents with complex congenital heart defects. Repeat operations are characterized by specific technical problems, with increased morbidity and mortality in adults and in the pediatric population [3 5]. To avoid a predictable reoperation after RV outflow tract reconstruction with valved biologic conduits, implantation of a mechanical valved conduit as a lifelong solution might be an option in selected cases. We evaluated our short-term results after pulmonary valve replacement with a bileaflet mechanical valved conduit. Material and Methods From November 1998 to November 2003, a mechanical pulmonary valve replacement with a bileaflet valved conduit (St. Jude Medical, St. Paul, MN), was performed in 14 patients at the German Heart Center Munich. All patients have had previous reconstruction of the RV outflow tract, consisting of allograft or xenograft implantation in 11 patients and a transannular patch in 3. The underlying diagnoses of these 14 patients were tetralogy of Fallot in 7, pulmonary atresia with ventricular septal defect in 3, common arterial trunk in 3, and severe subaortic stenosis with subsequent Ross procedure in 1 patient. Four patients suffered from pulmonary hypertension before mechanical pulmonary valve replacement. Twelve patients showed decreased RV function, and 4 patients had reduced left ventricular function in cineangiography. Furthermore, 3 patients presented with severe tricuspid regurgitation, and additional severe aortic regurgitation was seen in 3 patients. Hemodynamic characteristics and preoperative and operative data are Accepted for publication Oct 28, Address reprint requests to Dr Haas, Wilhelmina Children s Hospital, UMC Utrecht, Department of Pediatric Cardiothoracic Surgery, Room KG , PO Box 85090, 3508 AB Utrecht, The Netherlands; f.haas@wkz.azu.nl. This article has been selected for the open discussion forum on the CTSNet Web Site: by The Society of Thoracic Surgeons /05/$30.00 Published by Elsevier Inc doi: /j.athoracsur

2 Ann Thorac Surg HAAS ET AL 2005;79: MECHANICAL VALVED CONDUITS FOR PULMONARY POSITION shown in Table 1. Mean age at operation was years (range, 10 to 38 years). All patients had a mean of previous operations by means of a median sternotomy (range, 2 to 5). Indications for operation were classified as, first, symptomatic patients with right heart failure and moderate to severe pulmonary valve dysfunction (n 6); second, asymptomatic patients with moderate to severe pulmonary valve dysfunction and evidence of significant RV dysfunction by cineangiography (n 4); and third, patients undergoing reoperation mainly for associated lesions such as tricuspid valve incompetence or aortic valve regurgitation in the presence of significant pulmonary valve dysfunction (n 4). In patients who had previously undergone RV pulmonary artery conduit placement, conduit exchange was indicated when the pressure gradient between the RV and the pulmonary artery exceeded 50 mm Hg, or when the RV exhibited signs of volume overload [6]. Selection criteria for prosthetic valve replacement were based on (1) older age, to avoid outgrowth of the prosthesis; (2) multiple previous operations with an increased reoperation-related morbidity; (3) current use of anticoagulants; and (4) patient compliance with anticoagulant therapy. Operative Details Ten of the 14 patients undergoing pulmonary valve replacement had other concomitant surgical procedures, such as pulmonary arterioplasty in 5, residual ventricular septal defect closure in 3, and tricuspid or aortic valve replacement with a mechanical prostheses in 3 (Table 1). All patients were operated on through a median sternotomy with cardiopulmonary bypass and moderate hypothermia (28 to 32 C). Aortic cross-clamping (92 31 minutes) was used in all but 4 patients to facilitate the intracardiac repair of associated lesions. The remaining patients underwent surgery on the beating heart. Total mean operative time was minutes. In all patients the distal part of the conduit was cut just above the valve level (Fig 1) and was sutured to the prosthetic ring proximally with 5-0 Prolene suture (Ethicon, Somerville, NJ). Then, an end-to-end anastomosis between the main pulmonary artery and the conduit was performed. The ventricular end of the tube was cut obliquely, thus creating a roof to cover the ventriculotomy (Fig 2). For an optimal bileaflet valve function, it was always attempted to place the prosthesis in a 90-degree position to the ventricular septum. The simplicity of the applied technique was the main reason for using a valved conduit in all patients. Follow-Up All patients were regularly followed up at 3-, 6-, or 12-month intervals at the outpatient Department of Pediatric Cardiology at the German Heart Center Munich, yielding a 100% complete follow-up. Follow-up time ranged from 11 to 63 months (mean, months). Clinical follow-up included patient examination with special attention to bleeding complications, electrocardiogram, roentgenogram, and two-dimensional echocardiography. Residual hemodynamic lesions, including mean gradients across the mechanical valved conduit, were assessed by Doppler flow studies in all patients. Results All patients survived the operation and were discharged in an improved clinical condition. Three patients had to be reoperated on for postoperative bleeding within the first 5 days, and 1 patient underwent thoracotomy for revision of a transatrial pacemaker lead after 22 days. The postoperative course in the remaining patients was uneventful. They are receiving anticoagulants (warfarin sodium, acenocoumarol) to maintain an international normalized ratio (INR) of 3.0 to 4.5. Self-management is performed in 8 patients. During follow-up, 3 patients were readmitted to the hospital because of atrial tachycardia, suspected endocarditis, and epistaxis in 1 patient each. No patient showed signs of thromboembolism or suffered from hemolytic anemia. The cardiac-to-thoracic ratio did not change significantly during follow-up. Echocardiography demonstrated normal RV function in all but 2 patients. Both patients had presented with severely depressed RV function preoperatively, and although a marked clinical improvement was obvious, complete recovery of RV function was not achieved. At follow-up, 7 patients were asymptomatic, 5 patients were categorized to New York Heart Association functional class II, and only 1 patient to class III. Although 10 patients reported a marked physical improvement, 2 patients reported minor improvement, and only 1 patient could not detect any subjective change. Doppler flow studies demonstrated only mild pressure gradients across the bileaflet mechanical conduit, with a mean of 14 9mm Hg (range, 4 to 30 mm Hg). There was no evidence of valve failure, or neointimal growth within the valve annulus or the conduit itself. Comment 1663 The increasing population of grown-up congenital heart patients with multiple previous operations has stimulated us to provide a more definitive surgical repair. This retrospective analysis of our experience with a mechanical valved conduit in the pulmonary position confirms that this procedure can be considered as a safe alternative to the well-established allograft or xenograft implantation. Implantation of a mechanical valved conduit comprises only approximately 3% from a total of more than 400 allograft or xenograft implantations at our institution [1]. This small percentage emphasizes the highly selected nature of this particular group of patients. Although early mortality for isolated RV pulmonary artery conduit replacement decreased during recent years [7], severe cardiac laceration and air embolism were recently reported in 5.2% of patients, who had undergone one to three reoperations [5]. Unpublished data from our institution have shown an incidence of 9.7% for severe cardiac or pulmonary laceration in patients operated on from four to nine times, although careful surgical technique and judicious use of elective CARDIOVASCULAR

3 CARDIOVASCULAR 1664 HAAS ET AL Ann Thorac Surg MECHANICAL VALVED CONDUITS FOR PULMONARY POSITION 2005;79: femorofemoral bypass had been used. The reduction of the potential risk at reoperation, and an improved quality of life associated with a more definitive surgical repair, give reasons for the consideration of a mechanical valved conduit in the pulmonary position. In this study, pulmonary valve replacement was performed successfully without any early and late mortality. Most patients reported a marked physical improvement at last follow-up, and RV function had improved to normal on echocardiography in all but 2 patients. The high proportion of patients exhibiting a normal RV function on postoperative echocardiography can be explained by the fact that pulmonary valve replacement had been performed before severe RV dysfunction developed, thus maintaining adequate RV contractility postoperatively. A competent prosthetic valve, with a low pressure gradient, without progressive deterioration, as reported for homografts or xenografts [1, 2], may additionally account for a maintained normal RV function. The incomplete improvement of New York Heart Association functional class during follow-up in 6 of our patients is at least partially caused by additional comorbidity, such as severe atrioventricular valve insufficiency, aortic valve insufficiency, impaired left ventricular function, or the occurrence of pulmonary hypertension. Four main criteria were used in the decision-making process for a mechanical valved conduit. First, older age to avoid outgrowth of the prosthesis; second, multiple previous operations with an increased reoperation-related morbidity; third, current use of anticoagulants; and fourth, patient compliance with anticoagulant therapy. Older age represented one criterion, although, a mechanical valved conduit was also implanted in 2 patients aged 10 and 12 years. The high number of previous operations in one and a chest deformity with a suspected high risk of reoperation in the other resulted in the choice for a mechanical prosthesis, although somatic growth has not yet been completed. Whether these patients eventually develop a patient-prosthesis mismatch later in life Fig 1. Preparation of the bileaflet valved conduit. The distal part of the conduit was cut just above the valve level and was then sutured to the prosthetic ring, proximally (arrow). This new proximal part was cut obliquely, thus creating a roof to cover the ventriculotomy. Fig 2. Ideal positioning of the valved conduit. The prosthesis was always attempted to be placed in a 90-degree position relative to the ventricular septum.

4 Table 1. Preoperative Hemodynamic Data and Operative Characteristics of the 14 Patients Diagnosis Previous Operations NYHA Class RVEF CTR RVedP (mm Hg) Syst RVP (mm Hg) Syst PAP (mm Hg) PVS PVR TVI Age (y) BSA (m 2 ) SJM Conduit Size (mm) Additional Procedures Symptomatic patients Fallot 2 II III Pacemaker replacement Fallot 2 II IV III I none Fallot 4 IV III III TVR (SJM 33 mm) PA VSD 5 II III I LP and RP arterioplasty, re-vsd closure PA VSD 4 II III III II RP arterioplasty, AVR (SJM 25 mm) Fallot MAPCAs 2 II III LP arterioplasty, Lig. Ap-collaterals Asymptomatic patients CAT 3 I IV none Fallot 2 I III RP arterioplasty, re- VSD closure Fallot 2 I IV III II none PA VSD, MAPCAs 3 I III III II Re-VSD closure Patients with residual defects Fallot 2 III II IV TVR (SJM 33 mm) CAT 2 I II II AVR (SJM 31 mm) CAT 4 I III II RP arterioplasty, AVR (SJM 29 mm) AVS, LVOTO, MVI, TVI 5 I II IV TVR (SJM 29 mm) Ap-collaterals aortopulmonary-collaterals; AVR aortic valve replacement; AVS aortic valve stenosis; BSA body surface area; CAT common arterial trunk; CTR cardio-thoracic ratio; Fallot tetralogy of Fallot; Lig ligature; LP left pulmonary; LVOTO left ventricular outflow tract obstruction; MAPCAs multiple aortopulmonary collaterals; MVI mitral valve insufficiency; NYHA New York Heart Association; PA pulmonary atresia; PAP pulmonary artery pressure; PVR pulmonary valve regurgitation; PVS pulmonary valve stenosis; RP right pulmonary; RVedP right ventricular end-diastolic pressure; RVEF right ventricular ejection fraction; 2 RVEF 0.50; 22 RVEF 0.40; 222 RVEF 0.30; RVP right ventricular pressure; SJM St. Jude Medical; Syst systolic; TVI tricuspid valve insufficiency. Ann Thorac Surg HAAS ET AL 2005;79: MECHANICAL VALVED CONDUITS FOR PULMONARY POSITION 1665 CARDIOVASCULAR

5 CARDIOVASCULAR 1666 HAAS ET AL Ann Thorac Surg MECHANICAL VALVED CONDUITS FOR PULMONARY POSITION 2005;79: has to be determined. The criterion of multiple reoperations alone is probably not sufficient for the selection process in some patients. Those patients who underwent only two previous operations were either currently treated with anticoagulants owing to a mechanical valve in the aortic position or they had to undergo mechanical valve replacement as an additional procedure. Specific anatomic conditions such as chest deformities, occlusion of the femoral vessels, or the extensive attachment of the heart or the great vessels to the sternum contributed to the decision for the use of a mechanical valve in the pulmonary position. Women of childbearing age for whom anticoagulants would create difficulty and noncompliant patients should be excluded. Up to now, the placement of a mechanical valve in the pulmonary position has not gained widespread acceptance. This is mainly the result of anecdotal reports of severe thromboembolic complications and severe bleeding complications [8 12], which date back to the late 1980s. However, at that time both mechanical valve types and, more importantly, anticoagulation regimen were different or were not even applied [8, 10, 13]. Although a mechanical valve in the pulmonary position may occasionally function long-term without anticoagulation [14], the reported high incidence of valve thrombosis without anticoagulation underlines the need for adequate anticoagulation. Well-known criteria for anticoagulation for all mechanical valves in all other positions than the pulmonary one exist [15]. Although to date no evidenced-based recommendations on the therapeutic range of INR are provided, we currently favor an INR of 3.0 to 4.5. One theory for the need of a more aggressive anticoagulation regimen in right-sided mechanical valve replacement is the low-pressure and relatively slow-flow situation. This justifies a high level of anticoagulation. Additionally, all patients of the present study had intracardiac conditions that favor thrombus formation, ie, enlargement of the right or left atrium, atrial fibrillation, impaired left ventricular or RV function, and congestive heart failure, which exclude a lower intensity target. With our regimen, only 1 patient experienced epistaxis during follow-up. A recently performed randomized study has also shown that the rate of major bleeding is not statistically different between a targeted INR of 2.0 to 3.0 and a targeted INR of 3.0 to 4.5 [16]. In our opinion, patients are not at higher risk for major bleeding with the INR kept within this target range. Systematic patient education and monitoring as well as self-management of anticoagulation therapy reduces the variation in the INR, thereby leading to a possibly lower frequency of bleeding complications and thromboembolism. In the present study, 3 of 14 patients underwent reoperations within the first 5 days for postoperative bleeding. This high incidence is likely to be caused by the well-known association between length of operation, multiple reoperations, and postoperative bleeding complications. The mean operative time was minutes, and the patients underwent a mean of previous operations. Owing to the fact that anticoagulation with warfarin or acenocoumarol was started after the patient s chest tubes were removed, the possible association between oral anticoagulation treatment and postoperative bleeding can be ruled out. Recently, it has been reported that tilting-disc valves in the pulmonary position may perform better than bileaflet valves [17]. This has led these authors to hypothesize about the possible advantages of structural features of monodisc valves. However, an attempt to categorize prostheses by design seems inappropriate [18]. Reviewing the current literature, the reported thromboses of bileaflet valves were frequently accompanied with an insufficient anticoagulation regimen, rather than owing to any clinical or structural drawback [8, 10, 13]. Still, anticoagulation carries a risk for thromboembolic events, which is reported to be approximately 3% to 4% in adults and children [19, 20]. However, because of the high lytic activity of the lung, minor thromboembolism may not cause clinical significance. All these anticoagulation-related drawbacks should be taken into account when considering a more definitive solution in patients with multiple inevitable reoperations. Study Limitations This study comprises a highly selected small series of patients with heterogeneous causes, in whom a mechanical valved conduit was placed in the pulmonary position. Although the patient cohort is small and reliable statistics cannot be drawn, it is the largest series ever published. With the increasing population of grown-up congenital heart patients who have often had previous operations by means of a median sternotomy, the option of a mechanical valved conduit in the pulmonary position may gain greater importance in the future. This study shows the applicability of mechanical prosthesis with encouraging results. Whether or not lifelong anticoagulation carries a lower risk than the surgical morbidity and mortality of multiple allograft and xenograft replacements will only be determined by long-term follow-up. However, the reduction of the potential risk of further reoperations and improvement of cost effectiveness may justify the consideration of a mechanical prosthesis in highly selected patients. Conclusions To avoid a predictable reoperation after RV outflow tract reconstruction with allografts or xenografts, and therefore reoperation-related morbidity, the implantation of a mechanical valved conduit as a possible lifelong solution might be an option in selected patients. Although this retrospective analysis comprises only a small number of patients, the results are encouraging. At our institution, selection criteria for a mechanical valved conduit in the pulmonary position are based on, first, older age, to avoid outgrowth of the prosthesis; second, multiple previous operations with an increased reoperation-related morbidity; third, current use of anticoagulants; and fourth, patient compliance with anticoagulant therapy.

6 Ann Thorac Surg HAAS ET AL 2005;79: MECHANICAL VALVED CONDUITS FOR PULMONARY POSITION References 1. Lange R, Weipert J, Homann M, et al. Performance of allografts and xenografts for right ventricular outflow tract reconstruction. Ann Thorac Surg 2001;71(Suppl):S Stark J, Bull C, Stajevic M, et al. Fate of subpulmonary homograft conduits: determinants of late homograft failure. J Thorac Cardiovasc Surg 1998;115: Pansini S, Ottino G, Forsennati PG, et al. Reoperations on heart valve prostheses: an analysis of operative risk and late results. Ann Thorac Surg 1990;50: Cohn LH, Aranki SF, Rizzo RJ, et al. Decrease in operative risk of reoperative valve surgery. Ann Thorac Surg 1993;56: Russell JL, LeBlanc JG, Sett SS, Potts JE. Risk of repeat sternotomy in pediatric cardiac operations. Ann Thorac Surg 1998;66: Weipert J, Meisner H, Mendler N, et al. Allograft implantation in pediatric cardiac surgery: surgical experience from 1982 to Ann Thorac Surg 1995;60(Suppl):S Dearani JA, Danielson GK, Puga FJ, et al. Late follow-up of 1095 patients undergoing operation for complex congenital heart disease utilizing pulmonary ventricle to pulmonary artery conduits. Ann Thorac Surg 2003;75: Ilbawi MN, Lockhart CG, Idriss FS, et al. Experience with St. Jude Medical valve prosthesis in children. J Thorac Cardiovasc Surg 1987;93: Miyamura H, Kanazawa H, Hayashi J, Eguchi S. Thrombosed St. Jude Medical valve prosthesis in the right side of the heart in patients with tetralogy of Fallot. J Thorac Cardiovasc Surg 1987;94: Fyfe DA, Taylor AB, Kline CH, et al. Doppler echocardiographic evaluation of streptokinase lysis of thrombosed right-sided St. Jude Medical valves in patients with congenital heart defects. Am Heart J 1991;121: Fleming WH, Sarafian LB, Moulton AL, et al. Valve replacement in the right side of the heart in children: long-term follow-up. Ann Thorac Surg 1989;48: Okita Y, Miki S, Kusuhara K, et al. Replacement of a thrombosed St. Jude Medical prosthesis in pulmonary position after repeated thrombolytic therapy. Thorac Cardiovasc Surg 1992;40: Pass HI, Sade RM, Crawford FA, Hohn AR. Cardiac valve prostheses in children without anticoagulation. J Thorac Cardiovasc Surg 1984;87: Nurozler F, Bradley SM. St. Jude Medical valve in pulmonary position: anticoagulation and thrombosis. Asian Cardiovasc Thorac Ann 2002;10: Bonow RO, Carabello B, de Leon AC Jr, et al. ACC/AHA guidelines for the management of patients with valvular heart disease: executive summary: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (Committee on Management of Patients with Valvular Heart Disease). Circulation 1998;98: Acar J, Iung B, Boissel JP, et al. AREVA: multicenter randomized comparison of low dose versus standard dose anticoagulation in patients with mechanical prosthetic heart valves. Circulation 1996;94: Rosti L, Murzi B, Colli AM, et al. Mechanical valves in the pulmonary position: a reappraisal. J Thorac Cardiovasc Surg 1998;115: Butchart EG. Prosthesis-specific and patient-specific anticoagulation. In: Butchard EG, Bodnar E, eds. Current issues in heart valve disease: thrombosis, embolism and bleeding. London: ICR, 1992; Levine MN, Rascob G, Kearon C. Hemorrhagic complications of anticoagulant treatment. Chest 1998;114(Suppl): 511S 23S. 20. Bradley SM, Sade RM, Crawford FA, Stroud MR. Anticoagulation in children with mechanical valve prostheses. Ann Thorac Surg 1997;64:30 6. CARDIOVASCULAR INVITED COMMENTARY The search for the ideal pulmonary valve substitute continues to challenge surgeons, and the choice of prosthesis remains an important decision in clinical practice. Although bioprostheses and homografts are most commonly used for pulmonary valve replacement (PVR), limited durability necessitates reoperation for most patients. Late results of mechanical valves in the pulmonary position are conflicting. Indeed, in the few available reports, mechanical valve thrombosis occurred in 25% to 56% of patients [1 3]. However, it is important to note that inadequate anticoagulation or no anticoagulation was documented in many patients who had thrombotic complications develop in many of these retrospective reviews. Haas and colleagues report their results of 14 patients (average age 24.8 yr) who after several prior operations underwent PVR with a mechanical valved conduit. There were no valve-related complications during short-term follow-up (mean age, 2.9 yr), and all patients were anticoagulated with warfarin with a target international normalized ratio of 3.0 to 4.5. The important point of this report in contrast to prior studies is the absence of valve thrombosis. Their technique of valve implantation employs a Dacron conduit, and a limitation of this report is the lack of truly late results with the use of a conduit as a part of their reconstruction. In most older patients, an adequate sized pulmonary prosthesis can be inserted with no prosthetic material or by using only an anterior patch of pericardium to augment the valve annulus. The potential disadvantage of preferential use of valved conduits is late development of obstructive intimal fibrocalcific peels within the right-sided Dacron conduits [4]. We have utilized a mechanical prosthesis in 17 adult patients who required PVR (0.7% of all PVR performed at our clinic), and in late follow-up of the first 10 patients (mean follow-up, 8.3 yr; maximum follow-up, 25 yr) there was no instance of valve thrombosis. Our implantation technique differs in that we prefer to perform an isolated PVR with patch reconstruction of the previous conduit bed or native pulmonary artery using autologous or bovine pericardium. Currently we consider mechanical PVR for patients who have had multiple prior operations, or who are on warfarin for another reason. In general, we have not advised mechanical PVR in children, but would give consideration to mechanical PVR if anticoagulation is required for a mechanical prosthesis on the left side of the heart. In addition to adequate anticoagulation with warfarin (target international normalized ratio, 3.0 to 4.0), antiplatelet therapy should be considered [5]. These mea by The Society of Thoracic Surgeons /05/$30.00 Published by Elsevier Inc doi: /j.athoracsur