Asian Cardiovasc Thorac Ann 2003;11:58-62
© 2003 Asia Publishing EXchange Ltd
Fate of Stentless Bioprostheses on Right Side of the Heart
Ersin Erek, MD,
Yusuf Kenan Yalcinbas, MD,
Ece Salihoglu, MD,
Nilufer Ozturk, MD,
Sevda Arat, MD1,
Ayse Sarioglu, MD2,
Umit Bilge Samanli, MD2,
Tayyar Sarioglu, MD
Department of Cardiovascular Surgery
1 Department of Anesthesiology
2 Department of Pediatric Cardiology, Istanbul Memorial Hospital, Istanbul, Turkey
For reprint information contact: Tayyar Sarioglu, MD Tel: 90 212 210 6666 Fax: 90 212 210 7152 email: tsarioglu{at}memorial.com.tr Department of Cardiovascular Surgery, Istanbul Memorial Hospital, Piyalepasa Bulvari, Okmeydani, Sisli, Istanbul 80270, Turkey.
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ABSTRACT
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Newly developed stentless bioprostheses have shown good midterm results in the aortic position, but few data are available on their use at the right side of the heart. Four types of stentless bioprosthesis were used for right-side reconstruction of congenital heart anomalies in 50 patients (3 Baxter-Edwards Prima, 27 Medtronic Freestyle, 14 Cryolife Ross, and 6 Medtronic Contegra). Mean age was 9.03 ± 6.25 years. Serial Doppler echocardiographic studies were performed to evaluate transvalvular pressure gradients. The hospital mortality was 6%. Reoperation was required in 3 patients in the early postoperative period because of left ventricular outflow tract obstruction, endocarditis, or tricuspid insufficiency. Measurements from 34 patients were available for statistical analysis. Clinical follow-up was complete in 43 of the 47 hospital survivors; the mean follow-up period was 16.6 ± 16 months. Four patients died during follow-up; 93% of the survivors have an unrestricted lifestyle. Although peak transvalvular conduit gradients increased in all types of conduit, no reoperation has yet been performed for conduit stenosis. The newly developed stentless bioprostheses may be a useful alternative for right-side reconstruction of congenital heart anomalies.
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INTRODUCTION
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Conduits are essential for correction of congenital discontinuity between the heart chambers and the pulmonary artery. Conduits represent one of the weakest facets of reconstructive surgery for congenital heart disease as they invariably need to be replaced because of growth of the patient or valve/conduit failure.1 Currently, homografts are considered the best choice, but they are scarce. Newly developed stentless bioprostheses provide further options as they resemble homografts morphologically and are readily available in all sizes.2 Midterm results with stentless bioprostheses in the aortic position are similar to those with homografts, but few data are available for the right side of the heart.3 The objectives of this study were to analyze early and mid-term results of 50 consecutive corrective operations for congenital heart disease, using a stentless bioprosthesis for reconstruction of the right side of the heart, and to evaluate the fate of these conduits echocardiographically.
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PATIENTS AND METHODS
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From January 1996 to August 2001, 50 patients underwent corrective operations using stentless bioprostheses for reconstruction of the right side of the heart. Thirty-one (62%) of the patients were male. The mean age was 9.03 ± 6.25 years (range, 1–31 years). Preoperative diagnoses and the operative procedures are listed in Table 1
. Eighteen patients had undergone a previous cardiac operation. In most cases, right-side reconstruction was performed after releasing the aortic crossclamp and while the heart was perfused. A small pericardial or Dacron extension was necessary for the proximal part of the conduit in many of the patients, except for those receiving a Medtronic Contegra conduit which has a long proximal part for onlay patching. Conduits were chosen on the basis of the best available substitute on the market in our country at the specific time. Baxter-Edwards Prima valves (Edwards Lifesciences Corp., Irvine, CA, USA) were used in 3 patients at the beginning of the series. The Medtronic Freestyle bioprosthesis (Medtronic Inc., Minneapolis, MN, USA) was our choice in the next 27 consecutive patients. The Cryolife Ross pulmonic heterograft (Cryolife Inc., Kennesaw, GA, USA) was placed in the next 14 patients, and the Medtronic Contegra bovine jugular vein conduit (Medtronic Inc., Minneapolis, MN, USA) was used in the last 6 patients. The largest possible conduit was chosen; most were 19 or 21 mm in diameter (Figure 1).
Doppler echocardiographic examinations were performed in the early postoperative period (before hospital discharge), 3 to 6 months after surgery, and annually thereafter. The flow velocity across the pulmonary valve was measured by continuous-wave Doppler in the left parasternal short-axis view, and the peak transvalvular pressure gradients of the pulmonary conduits were calculated by the modified Bernoulli equation.
Data were collected from hospital records. Patients were invited to the hospital for echocardiographic evaluation of the status of the conduits. Patients who lived in other parts of the country were contacted by telephone to assess their clinical status. Variables were expressed as mean ± standard deviation with the 95% confidence limits. The Kaplan-Meier method was used to estimate the cumulative survival. Patients were divided to 4 groups according to the type of conduit used. Early and late echocardiographic measurements were compared by the Wilcoxon matchedpairs signed-rank test. An increase in transvalvular gradients of more than 20 mm Hg was considered significant, and multiple logistic regression and Cox regression analyses were used to identify factors that influenced conduit function. The relevant variables tested for these analyses are shown in Table 3. Statistical analyses were performed with SPSS software version 5.0 for MS Windows (SPSS Inc., Chicago, IL, USA). Values of p < 0.05 were considered significant.
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RESULTS
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The hospital mortality was 6%; 2 patients died from low cardiac output, and 1 from sepsis and multiorgan failure. The mean intensive care unit stay was 4.7 ± 5.8 days, and mean hospital stay was 13.1 ± 7.2 days. Three patients required reoperation in the early postoperative period because of left ventricular outflow tract obstruction, endocarditis, or tricuspid insufficiency. The major postoperative complications were prolonged intubation in 3 patients, permanent pacemaker implantation in 3, pericardial effusion in 4, reexploration for bleeding in 2, bacterial endocarditis in 2, and late sternal closure because of conduit compression in 1.
Clinical follow-up was complete in 43 of the 47 surviving patients (91.5%). The mean follow-up period was 16.6 ± 16 months. Four patients died during follow-up. Two of them died soon after reoperation for tricuspid (systemic atrioventricular valve) insufficiency and recurrent ventricular septal defect at 5 and 13 months postoperatively. One patient died of arrhythmia before a planned reoperation for a residual ventricular septal defect, tricuspid insufficiency, and conduit obstruction at 32 months postoperatively. The 4th patient died of congestive heart failure 4 years postoperatively. At the last follow-up examination, most (40/43, 93%) of the survivors enjoyed an unrestricted lifestyle. The probability of patient survival according to the Kaplan-Meier method was 83.9% at 1 and 3 years (Figure 2).
At the end of the study, echocardiographic measurements from 34 patients were available for statistical analysis (Table 2). Although the follow-up periods and number of patients were different, peak transvalvular conduit gradients increased in all groups. The differences in conduit gradients were statistically significant for the Cryolife Ross and Medtronic Freestyle and Contegra prostheses. Overall, there was no statistically significant factor associated with a gradient increase of more than 20 mm Hg (Table 3
).
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DISCUSSION
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Allografts and Dacron conduits with an integrated porcine bioprosthetic valve are the materials of choice for right-side reconstruction of congenital heart anomalies; allografts are regarded as the best option.4,5 However, several authors reported no significant differences in the mid- and long-term. In a long-term analysis of 173 patients, Bull and colleagues6 found no differences in the overall performance of homografts and heterografts in terms of late death or freedom from conduit obstruction. Ciaverella and colleagues7 reported that the reoperation rate for a group of patients with 516 extracardiac conduits (of which 333 were porcine-valved) was 18% after a mean follow-up of 3.6 years; only 0.8% of those with porcine-valved conduits required reoperation. Conduit obstruction may develop at any level in a porcine-valved Dacron conduit. Agarwal and colleagues8 noted that the site of major obstruction in 13 explanted porcine-valved conduits was the valve alone in 38%, the graft alone in 31%, and both the valve and the graft in 31%. Almeida and colleagues9 suggested that Dacron extension of homografts may increase the rate of conduit failure due to neointimal or fibrous peel formation on the Dacron section.
Calcification of the leaflets and/or the body is the most serious problem in conduit failure affecting both homografts and heterografts. Few data are available concerning the fate of the newly developed stentless bioprostheses for the right side of the heart, but midterm results in respect of the aortic position are similar to those obtained with homografts.3,10 Newly developed stentless bioprostheses contain no or a limited amount of foreign material, and are prepared by new methods such as zero-pressure glutaraldehyde fixation or anticalcification treatment. Clinical studies have demonstrated that new anticalcification treatments might be effective in reducing calcification of aortic valve leaflets.11 Moreover, Melina and colleagues12 showed that the Medtronic Freestyle valve had a lower calcification rate compared to homografts, in an 18-month follow-up period. It may be speculated that these properties will also decrease the incidence and rate of calcification, peel formation, and conduit failure in the right side of the heart. David and colleagues13 proposed that a lower content of elastic tissue and total calcium than in its aortic counterpart may render the pulmonary heterograft less prone to calcification.
The Medtronic Contegra bovine jugular vein conduit has some advantages. Its large proximal part for onlay patching, easy handling, tissue strength, and hemostatic properties make this conduit attractive. In this study, 2 of the 4 types of stentless bioprosthesis were of aortic origin (Medtronic Freestyle and Baxter-Edwards Prima). Although only the Cryolife Ross, and the Medtronic Freestyle and Contegra conduits had statistically significant increases in transvalvular gradients across the conduits, we observed a substantial increase in all groups (a relatively small number of patients received a Baxter-Edwards Prima prosthesis). No reoperation has been required so far for conduit failure. The patients with a mild to moderate gradient had an unrestricted lifestyle at the completion of the study.
Conduit type was not an independent factor for conduit stenosis in this study. Time after surgery might be a factor, but it was not statistically significant in this series. We observed conduit stenosis as early as 6 months after surgery; however, in some patients, conduit gradients remained stable and did not change with time. In view of these findings, we think that some unknown individual factors might have an important role in the development of conduit stenosis. Although conduit stenosis is still a problem, early and mid-term performance of the newly developed stentless bioprostheses are good and they may be a better alternative for right-side reconstruction of congenital heart anomalies. Evaluation of long-term results with a large series is necessary.
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ABSTRACT
INTRODUCTION
