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Ann Thorac Surg 2002;73:866-870
© 2002 The Society of Thoracic Surgeons

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Original article: cardiovascular

Extending the usable size range of homografts in the pulmonary circulation: outcome of bicuspid homografts

^a Division of Cardiac Surgery, The Hospital for Sick Children, University of Toronto, Toronto, Ontario, Canada
^b Division of Cardiology, The Hospital for Sick Children, University of Toronto, Toronto, Ontario, Canada

* Address reprint requests to Dr Van Arsdell, Division of Cardiac Surgery, The Hospital for Sick Children, 555 University Ave, Toronto, Ontario M5G 1X8, Canada

Presented at the Thirty-seventh Annual Meeting of The Society of Thoracic Surgeons, New Orleans, LA, Jan 29–31, 2001.

	Abstract

Top Abstract Introduction Patients and methods Results Comment Discussion References

 
Background. Small-sized homografts are often not available, making the use of surgically reduced cryopreserved homograft conduits appealing.

Methods. From January 1993 to January 2000, 21 large homografts were size-reduced by excising one leaflet and were implanted in the pulmonary circulation. Valve function was compared with 21 children—matched for weight, homograft size, and year of operation—who received a standard homograft.

Results. Implanted homograft size and patient weight were equivalent in both the bicuspid and standard groups. Median (range) in-hospital peak instantaneous echocardiographic gradient across the valve was 0 mm Hg (0 to 19) in the bicuspid group versus 0 mm Hg (0 to 17) in the standard group (p = 0.65). Median (range) in-hospital pulmonary insufficiency (scale of 0 to 4) was 2 (0 to 3) in the bicuspid group versus 1.5 (0 to 3) in the standard group (n = 10, p = 0.34). At a follow-up of 54 ± 29 months there was no significant difference in conduit reinterventions between the groups.

Conclusions. Surgical creation of a bicuspid valve in the pulmonary circulation results in a functionally equivalent conduit compared with standard homograft as measured by early and midterm valve function.

	Introduction

Top Abstract Introduction Patients and methods Results Comment Discussion References

 
Cryopreserved valved homograft conduits are extensively used in congenital heart surgery. Current data suggest that cryopreserved homografts are superior to other types of conduits in terms of handling characteristics, hemostasis, thrombogenicity, and function. However, the limited availability of small conduits is an important problem for neonatal surgery. The technique of surgical reduction of more readily available large size homograft conduits has been previously reported in the literature [1–3]. However, the number of patients reported has been very small and follow-up has been short. To the best of our knowledge, no study has compared the results of these surgically created "bicuspid" valve homografts and standard valve homograft conduits.

	Patients and methods

Top Abstract Introduction Patients and methods Results Comment Discussion References

 
Between January 1993 and January 2000, a total of 21 children had valved homograft conduits placed in the pulmonary circulation utilizing the technique of bicuspid size reduction (Fig 1). All operations were performed by three attending surgeons at the Hospital for Sick Children in Toronto. The decision to size reduce a larger homograft was made by the attending surgeon whenever an appropriate sized conduit was not available. A second group of children who had intracardiac repairs with standard homograft conduits—matched for body weight, homograft size, and year of operation (n = 21)—were identified from our cardiac surgery database. Comparisons of clinical, echocardiographic, and catheterization data were performed between the two groups during early and intermediate term postoperative follow-up.

View larger version (65K): [in this window] [in a new window]   Fig 1. Technique of size reduction of conduit. (A) Inside view of the conduit after excision of one cusp. (B) Reapproximation of the edges.

Implantation of all homografts—bicuspid and standard—was performed in a standard fashion. A hood was created over the ventriculotomy site with autologous pericardium, expanded polytetrafluoroethylene, or homograft. Pulmonary arterioplasty was performed when indicated. The remainder of the intracardiac repair was done according to the underlying pathology.

Patient follow-up
Intraoperative transesophageal echocardiography (TEE) was performed postcardiopulmonary bypass to assess valve function and the intracardiac repair. Transthoracic echocardiographic (TTE) assessment was done before hospital discharge in those patients who did not receive an intraoperative TEE (n = 18 bicuspid, 17 standard). Hospital survivors were followed up by regular clinical assessment, echocardiography, and when indicated, cardiac catheterization. Transthoracic echocardiography was performed at 3 months and 9 months and then yearly or whenever there was a change in clinical status of the patient. All children were reviewed between April 1999 and July 2000. It has been previously demonstrated that gradients measured by Doppler echocardiography in cryopreserved homografts correlate well with those obtained by cardiac catheterization [4]. The time interval between conduit implantation and first detection of functional deterioration of the conduit was recorded.

Functional conduit deterioration was defined as any of the following: (1) a peak gradient across the valve or whole conduit of more than 30 mm Hg; (2) more than moderate pulmonary insufficiency ( 3 on a scale of 0 to 4, where 0 = none, 1 = trivial, 2 = mild, 3 = moderate, 4 = severe); (3) a catheter-based conduit intervention (dilation, stenting, or both); and (4) surgical conduit replacement.

Statistical analysis
Data are presented as frequencies, medians with ranges, and means with standard deviations as appropriate. Characteristics and outcomes of patients having a bicuspid versus a standard homograft conduit were compared in matched pair analysis using McNemar’s tests, paired t tests, and signed rank tests. Time-related survival, freedom from any conduit reintervention, and freedom from conduit replacement were calculated using Kaplan-Meier estimates, and the groups were compared using log rank tests. All statistical analyses were performed using SAS statistical software Version 7 (SAS Institute, Cary, NC) using default settings.

	Results

Top Abstract Introduction Patients and methods Results Comment Discussion References

 
Patient diagnoses, demographics, and intraoperative details are given in Tables 1 and 2. There are no statistically significant differences between the two groups of patients for any of the variables listed. Conduits that were surgically reduced were 21 ± 4 mm (mean ± SD) in diameter before reduction and 13 ± 3 mm after reduction. In-hospital echocardiography was performed in 18 patients in the bicuspid and in 17 patients in the standard group. The median (range) peak instantaneous echocardiographic gradient across the homograft valve was 0 mm Hg (0 to 19) in the bicuspid group patients versus 0 mm Hg (0 to 17) in the standard group (p = 0.65). The median (range) grade of pulmonary insufficiency, graded on a scale of 0 to 4, was 2 (mild [range 0 to 3]) in the bicuspid group (n = 10) versus 1.5 (trivial [range 0 to 3]) in the standard group (n = 10; p = 0.34).

Five children in the bicuspid group and 4 patients in the standard group had late catheter interventions (conduit balloon dilation or stent placement). Three children in the bicuspid group and 6 children in the standard group had replacement of the conduit. All children having their conduits replaced had right ventricle to pulmonary artery gradients of greater than 50 mm Hg (except in 1 who had a gradient of 42 but the right ventricular pressure was systemic). One child had a right ventricular outflow aneurysm. Branch pulmonary artery stenosis was known to be associated in 8 of 9 grafts replaced. Pathologic findings and surgical description of the explanted conduits were available in 5 patients. Findings were fibrosis (n = 5) and calcification (n = 3). No clear pathologic difference between the explanted bicuspid and standard grafts was identified.

Mean time to detection of functional deterioration of the valved conduit was 22 ± 17 months in the bicuspid group versus 12 ± 19 months in the standard group (p = 0.18). Overall Kaplan-Meier estimates of time-related freedom from interventional cardiac catheterization or surgical replacement of the conduit were 97% at 6 months, 85% at 1 year, 72% at 2 years, and 47% at 5 years. Kaplan-Meier estimates of time-related freedom from conduit catheter intervention or surgical conduit replacement were plotted for the two groups and are shown in Figure 2. There were no statistically significant differences between the two groups of patients (p = 0.87).

View larger version (16K): [in this window] [in a new window]   Fig 2. Time-related freedom from interventional cardiac catheterization or surgical conduit replacement.

	Comment

Top Abstract Introduction Patients and methods Results Comment Discussion References

Early valve function
Substantial changes to the geometry or possible damage to the cusps during the procedure of downsizing lead to concern about the possible loss of functional integrity of the size-reduced conduit valve. This concern was not substantiated by our data obtained from intraoperative or early postoperative echocardiography. There was no difference in the early valve function between these two groups as measured by the peak gradient across the conduit or severity of the insufficiency.

Intermediate valve function
Concern has also been raised about the long-term function of the bicuspid valve. We found similar intervals between conduit implantation and detection of valve function deterioration for both groups. There are slightly more conduit changes in the standard group (6 in the standard versus 3 in the bicuspid group); however, the difference was not statistically significant. All children in the current study were small (weight < 13.5 kg; age < 5 years) and received small conduits (< 18 mm) at the time of their original implantation. Consequently we expected to find relatively short intervals between conduit implantation and reintervention or replacement. We were encouraged to find that bicuspid size reduction did not result in an increased need for conduit intervention or replacement. There are several reports of intermediate- and long-term follow-up of standard homograft conduits in the literature [5–11]. Perron and associates [6] from Boston reported a high incidence of homograft failure in young infants. Fifty-five percent of infants had homograft failure at a median interval of 2.3 years (mean 3.6) and 47% had a conduit reoperation at a median interval of 3.1 years (mean 4.6). Age at implantation [5, 7] and size of the implanted conduit [5, 12, 13] seem to be the most important predictors of early conduit failure and need for reoperation. This association is thought to be primarily due to growth of the young child over time, but may also be related to a decrease in the functional lumen of the conduit [14], likely secondary to calcification or immune related. Another potential risk factor for early graft failure, as described by Yankah and associates [7], is anatomic type of conduit, ie, aortic versus pulmonary. A previous study from our institution [5] also pointed out the difference in long term outcome between the pulmonary and aortic conduits, especially in younger children. In the current study we had a similar distribution of aortic and pulmonary homografts in the two groups of patients. Because the total number of aortic homografts was small, we did not analyze our results according to anatomic type of conduit. It is unlikely, however, that such an analysis would have affected our conclusions.

Survival and event-free survival
There was no significant difference in survival or event-free survival between the two groups of patients. Mortality was substantially higher than occurs in the present era—likely related to institutional learning during the transition to early primary repairs. We do not believe the apparent (but not statistically significant) increased mortality of the bicuspid group to be related to the conduit size reduction, particularly in view of the good conduit valve function in the immediate postoperative period.

Conclusions
The intermediate-term functional outcome of surgically reduced bicuspid homograft conduits in the pulmonary circulation are equivalent to that of standard homografts. Size reduction of larger homografts is a feasible and effective method of improving the availability of small conduits. We believe that bicuspid size reduction is an important surgical technique for congenital cardiac surgeons and that the continued use of these conduits is justified.

	Discussion

Top Abstract Introduction Patients and methods Results Comment Discussion References

 
Dr. JAMES L. MONRO (Southampton, UK): It is a very useful trick and I first used it in 1986 on a 3.5 kg child with truncus arteriosus and it got me out of trouble when we did not have a small enough homograft. I had to replace that aortic homograft 14 years later. I have used it on two other occasions, both in 1987. One was replaced 10 years later and the other is still working now, 13 years later. The results I obtained with this small group reflect my own experience with truncus using aortic valves. Do you think they are doing better than the pulmonary valves you had, or is it that we are perhaps waiting longer before replacing them? We tend to wait until they are symptomatic or if the RV pressure is two thirds of systemic. Were you replacing these values when there was a 30 mm gradient?

DR WILLIAMS: The valves that were replaced were replaced because of progressive stenosis.

DR MONRO: But was that when they had a 30-mm gradient across the valve or did you leave it later? It just seems to me you are replacing these valves rather early. It is disappointing they have not lasted longer.

DR. WILLIAMS: I am sorry, I missed your question. Why were the valves replaced?

DR MONRO: What was your indication for replacing them?

DR WILLIAMS: An increasing RV pressure because of stenosis.

DR MONRO: In your presentation you mentioned a 30-mm gradient. Was that the indication or was it more severe than that by the time you replaced the valve?

DR WILLIAMS: I am not certain of the details but I think the RV/LV ratio exceeded two thirds, so in a young child we would probably not wait in that situation because it is only going to go higher.

DR LUDWIG K. VON SEGESSER (Lausanne, Switzerland): I would like to congratulate you for this nice presentation. As an alternative solution to shortage in small homografts, we now use bovine jugular veins that are valved and that are about 10 or 15 cm long so that you have enough material for the heart reconstruction. We have used these devices for similar indications as well as Ross procedures with good early results in about two dozen implants. Do you consider this type of alternative?

DR WILLIAMS: We have considered it but have no experience with it. I think clearly there is a need for a better valve conduit and I am interested in all the options that are coming along. But I think the way to solve whether there is a better conduit or not is to stick to this very small age group. If you do a test in a 5-year-old or a 10-year-old, it will be 15 years before we know whether there is an improvement. If you do a series of neonates, then we will know within 2 years whether A is better than B.

	References

Top Abstract Introduction Patients and methods Results Comment Discussion References

 

1. Michler R.E., Chen J.M., Quaegebeur J.M. Novel technique for extending the use of allograft in cardiac operations. Ann Thorac Surg 1994;57:83-87.[Abstract]
2. Santini F., Mazzucco A. Bicuspid homograft reconstruction of the right ventricular outflow tract in infants. Ann Thorac Surg 1995;60:S624-S625.
3. Kitamura S., Kawachi K., Niwaya K., et al. Size-reduced cryopreserved pulmonary valve allograft for an RV-PA conduit: technical modification and functional evaluation. J Card Surg 1995;10:14-20.[Medline]
4. Chan K.C., Fyfe D.A., McKay C.A., Sade R.M., Crawford F.A. Right ventricular outflow reconstruction with cryopreserved homografts in pediatric patients: intermediate term follow-up with serial echocardiographic assessment. J Am Coll Cardiol 1994;24:483-489.[Abstract]
5. Caldarone C.A., Van Arsdell G.S., Coles J.G., Webb G., Freedom R.M., Williams W.G. Independent factors associated with longevity of prosthetic pulmonary valves and valved conduits. J Thorac Cadiovasc Surg 2000;120:1002-1031.
6. Perron J., Moran A.M., Gauvreau K., Del Nido P.J., Mayer J.E., Jonas R.A. Valved-homograft conduit repair of the right heart in early infancy. Ann Thorac Surg 1999;68:542-548.[Abstract/Free Full Text]
7. Yankah A.C., Alexi-Meskhishvili V., Weng Y., Schorn K., Lange P.E., Hetzer R. Accelerated degeneration of allografts in the first two years of life. Ann Thorac Surg 1995;60:S71-S77.
8. Cleveland D.C., Williams W.G., Razzouk A.J., et al. Failure of cryopreserved homograft valved conduits in the pulmonary circulation. Circulation 1992;86:SII150-SII153.
9. Razzouk A.J., Williams W.G., Cleveland D.C., et al. Surgical connections from ventricle to pulmonary artery: comparison of four types of valved implants. Circulation 1992;86:SII154-SII158.
10. Sharma S., Cobanoglu A., Dobbs J., Rice M. Clinical results of cryopreserved valved conduits in the pulmonary ventricle to pulmonary artery position. Am J Surg 1993;165:587-591.[Medline]
11. Hawkins J.A., Bailey W.W., Dillon T., Schwartz D.C. Midterm results with cryopreserved allograft valved conduits from the right ventricle to the pulmonary arteries. J Thorac Cardiovasc Surg 1992;104:910-916.[Abstract]
12. LeBlanc J.G., Russel J.L., Sett S.S., Potts J.E. Intermediate follow up of right ventricular outflow tract reconstruction with allograft conduits. Ann Thorac Surg 1998;66:S174-S178.
13. Rajasinghe H.A., McElhinney D.B., Reddy V.M., Mora B.N., Hanley F.L. Longterm follow-up of truncus arteriosus repaired in infancy: a twenty-year experience. J Thorac Cardiovasc Surg 1997;113:869-878.[Abstract/Free Full Text]
14. Salim M.A., DiSessa T.G., Alpert B.S., Arheart K.L., Novick W.M., Watson D.C. The fate of homograft conduits in children with congenital heart disease: an angiographic study. Ann Thorac Surg 1995;59:67-73.[Abstract/Free Full Text]

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This Article Abstract Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Add to Personal Folders Download to citation manager Author home page(s): Bhagawan Koirala Glen S. Van Arsdell Michael A. Borger Christopher A. Caldarone John G. Coles William G. Williams Permission Requests Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Koirala, B. Articles by Williams, W. G. Search for Related Content PubMed PubMed Citation Articles by Koirala, B. Articles by Williams, W. G.