Ann Thorac Surg 2008;85:195-198. doi:10.1016/j.athoracsur.2007.08.018
© 2008 The Society of Thoracic Surgeons
Original Articles: Cardiovascular
Novel Approach to Right Ventricular Outflow Tract Reconstruction Using a Stentless Porcine Valve
Michael D. Black, MDa,*,
S. Jill Ley, RNa,
Anne-Marie Regal, MDa,
Richard E. Shaw, PhDb
a Department of Cardiac Surgery, California Pacific Medical Center, San Francisco, California
b Department of Clinical Research, California Pacific Medical Center, San Francisco, California
Accepted for publication August 9, 2007.
* Address correspondence to Dr Black, Pediatric Cardiac Surgery, California Pacific Medical Center, 2100 Webster St, Suite 511, San Francisco, CA 94115 (Email: blackm{at}sutterhealth.org).
Presented at the Poster Session of the Forty-second Annual Meeting of The Society of Thoracic Surgeons, Chicago, IL, Jan 30–Feb 1, 2006.
 |
Abstract
|
|---|
Background: The use of a stentless aortic bioprosthesis offers the advantages of a larger effective valve orifice size, reduced transvalvular gradients, and improved hemodynamics versus stented valves. We hypothesized that these features would make the Toronto stentless porcine valve a preferred choice for patients with congenital abnormalities of the right ventricular outflow tract.
Methods: We retrospectively reviewed medical records of 21 patients with tetralogy of Fallot who subsequently underwent right ventricular outflow tract reconstruction during a 6-year period.
Results: The majority of patients received a 29-mm valve (n = 13), 5 received a 27-mm valve, with 1 each additional implant of a 19-, 22-, and 23-mm prosthesis. The mean age and weight were 24.5 years (range, 7 to 54 years) and 55.6 kg (range, 13.9 to 98.0 kg), respectively. Preoperatively, all patients had severe pulmonary insufficiency, mixed with mild to moderate stenosis in 2. The duration of postoperative echocardiographic follow-up ranged from 10 to 70 months (mean, 37.7 months). At the time of most recent follow-up, pulmonary insufficiency was graded as zero to trace in 47.4% (9 of 19 patients), mild in 42.1% (8 of 19 patients), and moderate in 10.5%, with 6 patients (31.6%) having concomitant pulmonary stenosis. The most recent mean and peak transvalvular gradients averaged 17.4 mm Hg (range, 11 to 24 mm Hg) and 26 mm Hg (range, 13 to 42 mm Hg), respectively. There have been no valve-related complications or explants, with one late death as a result of a noncardiac cause.
Conclusions: The stentless porcine valve is well suited for valve replacement in children, adolescents, and adults with congenital abnormalities of the right ventricular outflow tract, regardless of patient or valve size, particularly when significant downstream hemodynamic abnormalities exist.
|
Introduction
|
|---|
Pulmonary valve integrity remains a critical determinant of both short-term and long-term outcomes in lesions requiring right ventricular outflow tract (RVOT) reconstruction [1]. Prosthetic valve insertion into the RVOT of children, in particular, presents a unique challenge to congenital heart surgeons trying to balance early hemodynamic performance with freedom from repeat interventions. Although bioprosthetic valves avoid anticoagulation concerns, children are at increased risk for accelerated calcification with subsequent valvular stenosis. Homografts offer excellent hemodynamic performance, but are also subject to early calcification with associated conduit obstruction and may not be readily available, and desired sizes are often limited. Valve deterioration in these patients can result in the rapid progression of free pulmonary insufficiency or obstruction of the RVOT that remains poorly tolerated long-term.
The Toronto stentless porcine valve (SPV; St. Jude Medical, St. Paul, MN) is a low-pressure, glutaraldehyde-fixed xenograft supported by polyethylene terephthalate fiber (Dacron) cloth with lack of an accompanying aortic wall, thus minimizing the risk of calcification, an important advantage for implantation within the pediatric population. The use of a stentless bioprosthetic valve design reportedly allows for dissipation of mechanical stress on the valve leaflets, contributing to reduced structural failure and enhanced durability versus stented valves [2]. The effective valve orifice size is 2 to 4 mm larger than a stented valve of the same size through elimination of the stent and accompanying sewing ring [3]. These features contribute to reduced transvalvular gradients and improved hemodynamic performance, which are of particular importance with the rapid heart rates seen in children. Continued regression of left ventricular mass has been demonstrated up to 3 years after valve implantation in the aortic position [4]. Since their introduction into clinical practice less than a decade ago, favorable results and proven durability are reported, albeit exclusively in the systemic circulation.
We hypothesized that the above features would contribute to excellent event-free survival with optimal hemodynamics after insertion of the Toronto SPV in the RVOT for congenital lesions. The purpose of this review was to evaluate the short-term and intermediate results of a stentless aortic bioprosthesis in the pulmonary circulation after congenital cardiac surgical repair with RVOT reconstruction, across a wide range of patient ages and sizes.
|
Material and Methods
|
|---|
Population
A total of 21 patients previously operated on for tetralogy of Fallot who underwent subsequent reconstruction of the RVOT using a Toronto SPV by a single surgeon were identified through our clinical database. A retrospective review of these medical records was undertaken after the study was approved by the institutional review board at the investigating center, and written patient consent was waived. Two early patients operated on in Canada were lost to follow-up and were therefore excluded from further analysis. Follow-up intervals for the remaining patients (n = 19), ranged from 10 to 70 months (mean, 37.7 months; median, 34.0 months) after valve implantation.
Operative Techniques
The technique of SPV implantation was performed as previously described by Vricella and coworkers [5]. The SPV was sized using the largest RVOT orifice, frequently found proximal to the native pulmonary valve annulus and within the iatrogenic RVOT aneurysm. Valve implantation is simplified by using a running proximal suture of polypropylene, with three separate strategic sutures placed in each of the positioned valve struts. Orientation of the valve is critical, and must be determined before suture placement to optimize flow within the branch pulmonary arteries. Any preexisting patch material was removed before sizing the valve. Concomitant procedures included closure of residual ventricular septal defects (n = 4), repair of right ventricular aneurysms (n = 4), tricuspid valve repair (n = 4), aortic valve repair (n = 2), and modified Maze procedure (n = 1), with additional limited patches to reconstruct the RVOT (thus roofing the newly implanted pulmonary valve) in 11 patients.
Hemodynamic Assessment
Hemodynamic evaluation of right ventricular function poses technical challenges, regardless of assessment modality, because of the unique geometry and dynamic features of the right-sided versus left-sided circulation. Echocardiographic follow-up was used, despite its limitations, owing to its wide availability at referral centers and study completeness in all 19 patients. Assessment findings included mean (n = 14) or peak (n = 15) gradients across the pulmonary valve, as well as noting the presence and degree of pulmonary valve insufficiency, stenosis, or structural deterioration. A majority of patients had serial echocardiographic findings available, with the most recent used for analysis of pulmonary valve function. Valve gradients were evaluated serially and compared with the duration of follow-up to assess valve function with time. Finally, the general clinical status of the patient was obtained from the referring cardiologist at the time of follow-up.
Statistical Analysis
Continuous data are presented as mean and median, and categorical data presented as percentage. The Excel software package (Microsoft Corporation, Redmond, WA) was used to store data and to provide descriptive statistics for data presentation. Categorical variables were analyzed using 
2 analysis. A probability value of 0.05 was used to determine statistical significance.
|
Results
|
|---|
The majority of patients regardless of size (including the smallest at 13.9 kg) received a 29-mm valve (n = 13), 5 patients received a 27-mm valve, and 1 each received implantation of a 19-, 22-, and 23-mm prosthesis. The smallest valve sizes were implanted in Canada early in our experience. The mean and median values for patient age were 24.5 and 16 years, respectively (range, 7 to 54 years), and mean patient weight was 55.6 kg (median, 53.6 kg; range, 13.9 to 98.0 kg). Echocardiography before SPV implant revealed severe pulmonary insufficiency in all 21 patients, as well as mild to moderate stenosis in 2. Two additional patients had acquired absence of the left branch pulmonary artery with associated elevation of pulmonary artery pressures. Postoperative echocardiographic follow-up was available for 19 of 21 patients, ranging from 10 to 70 months (mean, 37.7 months; median, 34.0 months). At the time of most recent follow-up, pulmonary insufficiency was graded as zero to trace in 47.4% of patients (9 of 19 patients), mild in 42.1% (8 of 19 patients), and moderate in 10.5% (2 of 19 patients; 1 patient was known to have sustained valve injury during a subsequent endovascular procedure). Six patients (31.6%) were reported to have concomitant pulmonary stenosis, graded as mild in 5 and moderate in 1. The most recent mean and peak transvalvular gradients averaged 17.4 mm Hg (median, 18 mm Hg; range, 11 to 24 mm Hg) and 26.0 mm Hg (median, 25.5 mm Hg; range, 13 to 42 mm Hg), respectively. There was no significant relationship identified between mean pressure gradients and valve size, as shown in Figure 1. Owing to the pliability of the valve and the iatrogenic deformation of the RVOT, 27- and 29-mm valves were the most frequent valve sizes implanted regardless of the patient’s size. The latter is illustrated in Figure 2; there was a poor correlation between the size of the implanted valve and the size of the patient (correlation coefficient, 0.30). Throughout the follow-up period, both mean and peak gradients remained acceptably low and remarkably stable for the entire sample, both averaging less than 30 mm Hg during the follow-up interval (Table 1). To date, there have been no valve-related complications, valve explants, or repeat interventions, with 1 patient death as a result of a noncardiac cause (sepsis in a chronic renal dialysis patient approximately 2 years after valve implantation). In addition, no patient was recognized as having new-onset pulmonary arterial branch stenosis.
|
Comment
|
|---|
The long-term survival of children with tetralogy of Fallot continues to improve with time, with increasing numbers of patients presenting for subsequent pulmonary valve intervention in adolescence or adulthood. Recent trends toward early primary repair of tetralogy of Fallot with preservation of the native pulmonary valve may ultimately reduce the need for pulmonary valve replacement in later years [6, 7]. Although less-invasive percutaneous valve replacement shows promise, current methods are limited by the quality of the implanted valve, size limitations, and risks of bleeding and infection [8]. Surgical replacement of the insufficient pulmonary valve in patients with tetralogy of Fallot has been shown to significantly improve right ventricular function and reduce arrhythmias, and carries a low risk of mortality, leading to earlier intervention in recent years [9–11].
Pulmonary valve integrity is critical to prevent chronic right ventricular volume overload and dilation of the patched infundibulum (which can contribute to RVOT aneurysm formation). A combination of mild stenosis and regurgitation intuitively seems optimal to balance flow across the RVOT and avoid both volume and pressure overload of the right ventricle, thus preserving the life of the valve and avoiding or delaying pulmonary valve replacement. Chronic pulmonary insufficiency culminates in poor exercise tolerance, shortness of breath on exertion, tricuspid valve regurgitation, atrial dysrhythmias, widened QRS patterns, and an increased incidence of sudden death [12, 13]. Valve choice may have a profound impact on the avoidance of pulmonary insufficiency and these sequelae. The Toronto SPV appears to be well suited for congenital abnormalities in the RVOT, even with elevated pulmonary resistance. This is a common finding in these patients as a result of long-standing systemic-to-pulmonary shunts and permanent changes in the pulmonary vasculature (which may be underappreciated at the time of catheterization) or the loss of branch pulmonary arteries, particularly those that originate from either the ductus arteriosus or the thoracic aorta.
The SPV is malleable and thus easily placed in nonanatomic positions, a tremendous advantage in congenital repairs with atypical anatomy. The pulmonary confluence is frequently distorted by a large, overriding aorta and previous pulmonary arterioplasties. The valve’s length is approximately 19 mm, and thus is short enough to accommodate the most peculiar anatomic arrangements, even in infants and small children. Importantly, proximal placement of the valve within the RVOT is possible without endangering the origin of the branch pulmonary arteries, but requires carefully planned positioning of the three valve struts to optimize flow into these vessels.
The valve’s excellent durability in the pulmonary circulation, to date, would at least seem to parallel previously published outcomes in the systemic circulation. In fact, we believe that increased longevity can be anticipated because of the large implant size and reduced hemodynamic stressors within the right-sided circulation. We suspect that valve failure will most likely occur from stenosis as a result of dystrophic calcification of the porcine valve, perhaps amenable to catheter-based palliation with either balloon dilation or stent implantation. Fortunately, pressure loading of the right ventricle lacks the significant morbidities seen with volume loading of the right ventricle. In addition, lack of an integral conduit prevents complex, long-segment stenosis and its associated morbidities, as has been reported with homografts. We concur with other published works demonstrating the benefits of early intervention to maximize right ventricular remodeling, preventing irreversible right ventricular fibrosis [14].
This review demonstrates that the SPV is well suited for pulmonary valve replacement in patients of all ages and sizes. Excellent hemodynamics, the avoidance of anticoagulation, the lack of artificial valve sounds, low risk of endocarditis, and the malleability of the SPV are features that optimize its significance in the pulmonary position.
|
References
|
|---|
- Borowski A, Ghodsizad A, Litmathe J, Lawrenz W, Schmidt KG, Gams E. Severe pulmonary regurgitation late after total repair of tetralogy of Fallot: surgical considerations Pediatr Cardiol 2004;25:466-471.[Medline]
- Park SZ, Reardon MJ. Current status of stentless aortic xenografts Curr Opin Cardiol 2000;15:74-81.[Medline]
- Reardon MJ, David TE. Stentless xenograft aortic valves Curr Opin Cardiol 1999;14:84-89.[Medline]
- Bach DS, Goldman B, Verrier E, et al. Eight-year hemodynamic follow-up after aortic valve replacement with the Toronto SPV stentless aortic valve Semin Thorac Cardiovasc Surg 2001;13(Suppl 1):173-179.[Medline]
- Vricella LA, Coady MA, Black, MD. Initial experience with a stentless porcine bioprosthesis for right ventricular outflow tract reconstruction in children J Thorac Cardiovasc Surg 2003;125:727-728.[Free Full Text]
- Rao V, Kadletz M, Hornberger L, Freedom RM, Black, MD. Preservation of the pulmonary valve during repair of tetralogy of Fallot Ann Thorac Surg 2000;69:176-179.[Abstract/Free Full Text]
- Black MD, Ley SJ, Tede N, et al. Improved results with intraoperative extubation and minimally invasive techniques in infants with tetralogy of Fallot. 2005Presented at the 3rd Annual Bay Area Clinical Research Symposium, October 14, San Francisco, CA.
- Khambadkone S, Bonhoeffer P. Nonsurgical pulmonary valve replacement: why, when, and how? Catheter Cardiovasc Interv 2004;62:401-408.[Medline]
- Discigil B, Dearani JA, Puga FJ, et al. Late pulmonary valve replacement after repair of tetralogy of Fallot J Thorac Cardiovasc Surg 2001;121:344-351.[Medline]
- Bando K, Danielson GK, Schaff HV, Mair DD, Julsrud PR, Puga FJ. Outcome of pulmonary and aortic homografts for right ventricular outflow tract reconstruction J Thorac Cardiovasc Surg 1995;109:509-517.[Abstract/Free Full Text]
- Kanter KR, Budde JM, Parks WJ, et al. One hundred pulmonary valve replacements in children after relief of right ventricular outflow tract obstruction Ann Thorac Surg 2002;73:1801-1806.[Abstract/Free Full Text]
- Carvalho JS, Shinebourne EA, Busst C, Rigby ML, Redington AN. Exercise capacity after complete repair of tetralogy of Fallot: deleterious effects of residual pulmonary regurgitation Br Heart J 1992;67;:470-473.[Abstract/Free Full Text]
- Marie PY, Marcon F, Brunotte F, et al. Right ventricular overload and induced sustained ventricular tachycardia in operatively "repaired" tetralogy of Fallot Am J Cardiol 1992;69:785-789.[Medline]
- Dave HH, Buechel ERV, Dodge-Khatami A, et al. Early insertion of a pulmonary valve for chronic regurgitation helps restoration of ventricular dimensions Ann Thorac Surg 2005;80:1615-1620.[Abstract/Free Full Text]
This article has been cited by other articles:
|
|
|
|
 
J. A. Hawkins, C. T. Sower, L. M. Lambert, P. C. Kouretas, P. T. Burch, A. K. Kaza, M. D. Puchalski, and A. T. Yetman
Stentless porcine valves in the right ventricular outflow tract: improved durability?
Eur. J. Cardiothorac. Surg.,
April 1, 2009;
35(4):
600 - 605.
[Abstract]
[Full Text]
[PDF]
|
|
|
Top
Abstract
Introduction
