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Ann Thorac Surg 2001;71:S356-S360
© 2001 The Society of Thoracic Surgeons
a Section of Cardiothoracic Surgery, James W. Riley Hospital for Children, and Indiana University School of Medicine, Indianapolis, Indiana, USA
Address reprint requests to Dr Turrentine, Section of Cardiothoracic Surgery, Indiana University School of Medicine, 545 Barnhill Dr, EH 215, Indianapolis, IN 46202-5123
e-mail: mturren{at}iupui.edu
Presented at the VIII International Symposium on Cardiac Bioprostheses, Cancun, Mexico, Nov 3–5, 2000.
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Abstract |
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Methods. Ninety-nine patients who underwent aortic valve replacement (January 1973 through September 2000) were included in this study. Procedures included implantation of pulmonary autograft (PA) (n = 42), aortic homograft (AH) (n = 3), mechanical valves (MV) (n = 41), and xenograft tissue valves (XG) (n = 13).
Results. The mean follow-up times were: 3.8 ± 1.3 years for PA, 3.5 ± 1.5 years for AH, 7.7 ± 4.7 years for MV, and 8.4 ± 4.8 years for XG. There were no significant differences in perioperative outcomes among the groups (p 
0.05) or early deaths (2 each in the MV, AH, and PA groups). The incidence of valve-related complications and reoperations was high in the MV (n = 5), XG (n = 7), and AH (n = 1) groups as compared with the PA group (n = 3, p < 0.01). Early and late mortality for the series was 8.6% (n = 8). Overall, the reoperation rate was 20.7% (n = 18): 15.2% (5 of 33) MV, 70% (7 of 10) XG, 50% (1 of 2) AH, and 11.9% (5 of 42) for PA. The actuarial survival rate was 87.8% and 100% at 10 years for MV and XG, and 95.2% and 6.6% at 7 years for PA and AH.
Conclusions. Aortic valve replacement in children can be performed with acceptable mortality and good long-term results. The Ross procedure, although more complicated, has the advantage of not requiring anticoagulation therapy, can be performed in all age groups, possesses inherent growth potential, and exhibits the most normal left ventricular outflow tract hemodynamics.
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Introduction |
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Initially, aortic valve replacement (AVR) in children used caged-ball mechanical prostheses that were used exclusively in the 1960s and early 1970s. The xenograft (XG) valve was introduced in the early to mid-1970s and was initially considered better suited for children because it had a lower profile than the then-popular caged-ball prosthesis, but unfortunately these valves demonstrated early failure [3]. The new generation mechanical valves exhibit minimal structural degeneration, but continue to be prone to valve-related complications, including hemolysis, infection, and thromboembolism. In addition, patient size limits their utilization and the smallest available valves carry significant rest- and exercise-related valve gradients. The use of anticoagulation strategies in children with these valves is challenging and possibly carries a high mortality compared with adults [4]. The difficulties presented by mechanical and bioprosthetic valves in pediatric patients have motivated a number of institutions to use human valve substitutes. Recent results from human valve use for AVR in children have been highly favorable [5, 6]. Availability of allograft aortic valves allows AVR in small children, but results have shown they are also susceptible to early degeneration [5, 6]. These challenges make the use of a pulmonary valve autograft, or Ross procedure, possibly the preferred approach to AVR for all patients in the pediatric age range.
We have reviewed our experience at the Indiana University School of Medicine and present our current strategy of valve replacement choice(s) in various age groups.
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Material and methods |
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TopAbstractIntroductionMaterial and methodsResultsCommentReferences |
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0.05). Starr–Edwards ball-valve prostheses (Baxter Healthcare Corp, Santa Ana, CA; n = 3) were used in the period from 1973 to 1976. The Bjork–Shiley aortic valve (Shiley Laboratories, Irvine, CA; n = 6) was used from 1975 to 1983. CarboMedics valves (CarboMedics Inc, Austin, TX) were implanted in 2 patients with small aortic annuli in which the 16-mm valve was chosen, and 1 patient received a Medtronic–Hall (Medtronic Inc, Minneapolis, MN) valve in 1994. The St. Jude Medical aortic prosthesis (St. Jude Medical Inc, St. Paul, MN; n = 29) was first implanted in 1982 and has been our choice of MV when size permits.
Xenograft valves (Hancock porcine valve, Hancock Extracorporeal, Inc, Anaheim, CA and Carpentier-Edwards porcine valve, Baxter Healthcare Corp, Irvine, CA) were implanted during the period from 1975 to 1990. The three AH valves (CryoLife Inc, Kennesaw, GA) were inserted in 1993. Beginning in 1993, 42 consecutive operations were performed with pulmonary autograft (Ross procedure). All 42 patients undergoing the Ross procedure had right ventricular outflow tract (RVOT) reconstruction performed with a pulmonary homograft (PH, CryoLife Inc).
Isolated AVR was performed in 53 (53.5%) patients. Forty-six children (46.5%) underwent 55 additional concomitant cardiac procedures during the valve implantation. In 8 patients, combined AVR and mitral valve replacement was performed. Three additional patients had concomitant mitral valve repair and 4 children underwent combined AVR and replacement of the ascending aorta. Follow-up consisted of a retrospective analysis including chart review and available echocardiographic evaluation. Complications were reported as a percentage of the patients in the specific group available for follow-up and not of the group, or series total.
Statistical analysis
SPSS statistical program (SPSS Inc, Chicago, IL) was used to perform data analysis. Data are expressed as mean and range. The Kaplan–Meier product limit method and Cox proportional hazards regression methods were used for actuarial survival analysis and analysis of freedom from reoperation. Multiple regression analysis was performed as conditional backward stepwise proportional hazards regression. Significant p values were considered to be less than or equal to 0.05.
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Results |
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There were 4 late deaths (MV, n = 3; PA, n = 1) occurring at a mean of 1.7 years after AVR (range 3 months to 5 years), with 3 deaths (75%) occurring in the first postoperative year. Two deaths (50%) were in children undergoing double valve replacement with MV and occurred 6 months and 5 years after operation. Their deaths were the result of endocarditis and hepatitis. The third late MV death occurred in a patient 6 months postoperatively secondary to endocarditis. The PA late death occurred from aspiration pneumonia 7 months after a Ross–Konno procedure and 2 months after PH revision.
Complications and morbidity
Postoperative valve-related complications occurred in 18 of the 87 patients (20.7%) seen during follow-up: 7 of 10 XG (70%), 5 of 33 MV (15.2%), 1 of 2 AH (50%), and 5 of 42 PH (11.9%). Furthermore, the mean time interval between AVR and replacement of human tissue prosthesis was 3 years, whereas replacement of an MV occurred after a mean time interval of 7.6 years. Causes of reoperation included pannus formation (n = 3), endocarditis (n = 5), structural valve deterioration (n = 3), nonvalve-related subaortic obstruction (n = 1), AH valve insufficiency (n = 2), severe left ventricular dysfunction resulting in conversion to heart transplant (n = 1), PA group RVOT stenosis (n = 2), and homograft valve degeneration (n = 1). The actuarial curve for freedom from reoperation after AVR is summarized in Figure 3.
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Xenograft group
Follow-up on 10 patients (10 of 13, 77%) of this group ranged from 6 months to 16 years (mean 8.4 ± 4.8 years). The mean age of the patients at follow-up was 20.6 ± 8.4 years. Postoperative echocardiographic examination was performed 6 to 60 months after operation. Late complications occurred in 7 patients (70%). Three of these patients demonstrated calcific biological valve stenosis and underwent reoperation with a PA (n = 2) and MV (n = 1). Three cases of XG structural valve deterioration have been replaced with MV. One patient with nonvalve-related subaortic obstruction had conversion to an apical aortic conduit. In the XG group, there were no cases of hemolysis or thromboembolism.
Pulmonary autograft group
Follow-up was 100% complete (42 of 42) in this group ranged from 3 months to 7 years (mean 3.8 ± 1.3 years). The mean age of the patients was 7.9 ± 5.3 years. There was one early and four late complications in this group (5 of 42, 11.9%). The first case occurred in a 6-week-old neonate with severe AI and an aortic valve mass. It was thought that this pathology resulted from an anticardiolipin antibody problem with calcified vegetation of the aortic valve. This patient could not be weaned from bypass after a Ross procedure and was placed on extracorporeal membrane oxygenation support. No recovery of ventricular function occurred over the next 4 days and an orthotopic cardiac transplantation was performed on the fifth day. The child continues to do well 4 years after transplantation. The second complication occurred in a patient who had undergone a Ross–Konno procedure 5 months earlier. The patient’s PH became severely insufficient and developed tricuspid regurgitation. The patient underwent replacement of the PH with a bovine pericardial valve and a tricuspid valvuloplasty. The patient died from aspiration pneumonia 2 months after PH revision. The third patient had AI, ascending aortic dilation, and mild RVOT homograft obstruction 3 years after a Ross procedure. This patient underwent reoperation with aortic annuloplasty and ascending aortoplasty. The fourth late complication occurred in a patient who had previously undergone AH AVR with calcification of the AH and conversion to a Ross procedure. The patient developed aortic, mitral, and pulmonary insufficiency and underwent an aortic annuloplasty, DeVega mitral valvuloplasty, and Gore-Tex (W.L. Gore and Assoc, Flagstaff, AZ) monocusp RVOT repair. The resultant postoperative AI was trivial in both patients after aortic annuloplasty. In the PA group, there were no cases of endocarditis, hemolysis, or thromboembolism.
Aortic homograft group
Follow-up of the 2 surviving patients (100%) in this group ranged from 2 to 6 years (mean 3.5 ± 1.5 years). Late complications occurred in 1 patient (50%). This patient had AH degeneration and underwent a Ross procedure 4 years after the primary AVR.
Echocardiography
Echocardiography was performed in the immediate postoperative period (range 1 to 9 days after operation; mean 4 days) in all 43 surviving patients in the PA and AH groups. Subsequent postoperative echocardiography was performed 1 to 44 months after operation (mean 14.6 months). At the early postoperative study, insufficiency of the neoaortic valve was graded as 0 or trivial in 28 patients, 1+ in 14 patients, and 2+ in 1 patient. At the recent postoperative study, insufficiency of the neoaortic valve was graded as 0 or trivial in 25 patients, 1+ in 16 patients, and 2+ in 2 patients. Chi-square analysis demonstrated no significant differences in the early and later echocardiographic grading of valve insufficiency.
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Comment |
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TopAbstractIntroductionMaterial and methodsResultsCommentReferences |
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Young patients requiring AVR pose a difficult problem for the surgeon in terms of available, and suitable, valves for a variety of patients’ sizes and defects [8–10]. There are four general types that can be chosen for AVR: mechanical and bioprosthetic valves, homografts, and the PAs. Mechanical prostheses represent for most surgeons the easiest and safest alternative for AVR in children and good results have been reported [11]. However, the potential risk of thromboembolic complications, the fixed diameter of the prosthesis in the growing child, and the need for lifelong anticoagulation in active children and attendant risk of hemorrhage, represents important drawbacks to mechanical AVR. The need for anticoagulation therapy in children has recently received adequate consideration [4, 6, 12]. We recommend full anticoagulation therapy with warfarin for all patients with MV although, in compliant patients, tight control of the international normalized ratio at a slightly lower level (ie, 1.8 to 2.2) with the addition of low-dose enteric-coated aspirin is a favored alternative with theoretically broader anticoagulation efficacy.
The initial enthusiasm for XG valves faded, as the follow-up reports showed early degeneration, calcification, and structural failure of these valves in pediatric patients [5]. These complications led to a high incidence of reoperations for these valves, particularly in younger patients. Although new types of XG valves (eg, pericardial, new generation stented porcine, and porcine stentless valves) seem to offer better hemodynamic performance and anticalcification characteristics, long-term results are needed to confirm their suitability and increased durability in children. We believe the implantation of an XG valve in children should be avoided, or limited to special cases. Such cases would include the older female pediatric patient in whom a Ross procedure cannot be performed because of an unsuitable pulmonary valve or other mitigating circumstances.
The first report by Ross [13] describing the use of an AH to perform AVR 35 years ago stimulated significant interest in this technique. Unfortunately, homografts do not seem to offer a definitive solution to the problem of AVR in children. The reported reoperation rate is lower than for XG but higher than MV AVR patients. Furthermore, the availability of homografts, in particular the smaller diameters, is limited and they have no growth potential. Our experience with AH AVR is limited to 3 patients (1993 to 1995). Our experience was nothing but dismal, with 1 early death and 1 reoperation (conversion to a Ross procedure for early calcified homograft LVOTO). We would favor the use of a homograft only in instances in which a Ross procedure was not feasible and the annulus was too small to accommodate another type of replacement valve.
In the last 10 years, there has been a growing interest in AVR with PA [13]. Theoretically, the PA is the ideal prosthesis for AVR, as no anticoagulation is required and the autograft should not exhibit leaflet degeneration (although there is the potential of developing AI as a result of annular dilatation or mechanical distortion). In addition, the PA possesses excellent hemodynamic characteristics and has the potential to grow with the child [7]. We began our Ross series in June 1993 and, since then, 42 children have undergone AVR with the PA. We use the Ross–Konno operation for septal enlargement in cases of combined complex tunnel LVOTO and associated aortic valve pathology. The survivors (38 of 42, 90.5%) at midterm follow-up demonstrate acceptable function of both the PA and homograft.
The Ross procedure represents our current procedure of choice for infants and children requiring AVR. One of the most convincing advantages of the PA is its growth capacity in the aortic root [7, 8]. The lack of growth in the PH can be compensated by oversizing it 5 to 15 mm and thereby improving its durability. Bileaflet MV are a good second-tier choice in children who do not possess an adequate, or functional, pulmonary valve for use in a Ross procedure and who are large enough to accommodate an adult-sized mechanical prosthesis. Long-term durability of new generation XG valves and AH is unproved, but provide a secondary choice for young female patients, particularly during childbearing years.
This review demonstrates that AVR can be accomplished in children with low operative and long-term mortality and with a low complication rate. We feel the Ross AVR improves the quality of life for children by eliminating the need for lifelong anticoagulation. In addition, the Ross has the potential to decrease the need for reoperation as a result of growth of the patient. Today, we prefer the Ross procedure in all pediatric patients in which it is technically feasible.
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