Replacement of obstructed extracardiac conduits with autogenous tissue reconstructions

Replacement of Obstructed Right Ventricle to Pulmonary Artery Conduits: The Modified Peel Operation

Reconstruction of the right outflow tract with extracardiac conduits has made complete repair of complex cardiac malformations possible. However, reoperation is usually required for a right ventricle-to-pulmonary artery conduit obstruction. We describe a modified peel operation, where the sides and posterior half of the previously placed conduit are preserved, and a prosthetic roof is placed over the conduit remnant. This has been our current technique to manage conduit obstructions. It is a safe operation and to teach residents. This review aims to convey the technical details of each step of this technique.

Branch pulmonary artery peel operation in a patient without a native intrapericardial pulmonary artery

A patient with pulmonary atresia with ventricular septal defect and major aortopulmonary collateral arteries without an intrapericardial pulmonary artery (PA) underwent a one-stage total correction, including both branch PA reconstructions, with a bovine pericardial roll at the age of 42 months. She was readmitted 54 months after the operation because of extracardiac conduit bacterial endocarditis and pulmonary infarction. The bovine pericardial roll between the right and left PAs was enucleated, and the surrounding fibrotic tissue (peel) was used as a new branch PA vascular conduit. A cardiac catheterization performed 86 months after the peel operation showed no aneurysmal dilatation, stenosis, or thrombotic occlusion.

Left Main Coronary Artery Compression by Right Ventricle-to-Pulmonary Artery Conduit Relieved by Anterior Translocation of the Right Pulmonary Artery

Pulmonary artery translocation has been described as an alternative surgical strategy to treat anomalous aortic origin of the coronary artery from the wrong sinus of Valsalva. We describe another application of this strategy in a patient who underwent complete repair of pulmonary atresia with ventricular septal defect and presented years later with ischemic symptoms due to compression of the left main coronary artery by the right ventricular-to-pulmonary artery conduit. To our knowledge, this is the first application of the pulmonary artery translocation technique to treat such a problem.

Right ventricular outflow tract reconstruction with a polytetrafluoroethylene monocusp valve: A twelve-year experience

OBJECTIVE

Transannular patching of the right ventricular outflow tract results in pulmonary insufficiency. Biologic monocusp valves prevent early pulmonary insufficiency but usually become nonfunctional in less than 1 year. Polytetrafluoroethylene monocusp leaflets demonstrated favorable characteristics in our animal studies and have been applied to a variety of right ventricular outflow tract reconstructions at our institution.

METHODS

From 1994 through 2006, 192 patients (mean age, 3.3 +/- 5.0 years) underwent right ventricular outflow tract reconstruction with a polytetrafluoroethylene monocusp valve (192 patients; 202 implants). Intraoperative, early postoperative, and late follow-up echocardiographic data (mean interval, 4.9 +/- 3.1 years; range, 6 months to 12 years) were retrospectively obtained to compare clinical outcomes among three preoperative diagnostic groups: patients undergoing initial repair of tetralogy of Fallot or pulmonary atresia/ventricular septal defect (group I), patients undergoing redo right ventricular outflow tract procedures (group II), and patients undergoing complex initial repairs (group III).

RESULTS

There were 4 early and 5 late deaths (9/192; 5%). The difference between the preoperative and postoperative peak right ventricular outflow tract gradients was significant (71.2 vs 23.1; P < .0001). Twenty-five (14%) patients had mild-to-moderate right ventricular outflow tract stenosis at one or more locations proximal and/or distal to the monocusp patch (mean gradient, 44.7 +/- 20.3 mm Hg). Freedom from increased pulmonary insufficiency greater than moderate was 86% at 1 year, 68% at 5 years, and 48% at 10 years. Twenty-five patients have undergone 35 reoperations 4.2 +/- 3.1 years (range, 3 months to 10 years after initial repair). Kaplan-Meier freedom from reoperation was 96%, 89%, and 82% at 1, 5, and 10 years. Freedom from reoperation in group II (69%) was significantly different from group I (88%; P = .01) and from group III (90%; P = .02), but there was no difference between groups I and III.

CONCLUSIONS

Use of a polytetrafluoroethylene monocusp valve prevents early and significantly reduces midterm pulmonary insufficiency. It is relatively inexpensive, easy to construct, and remains free from significant stenosis in the majority of patients. We have not witnessed significant calcification or pulmonary embolization, and the only antithrombic agent used has been low-dose aspirin.

Tissue engineering of viable pulmonary arteries for surgical correction of congenital heart defects

BACKGROUND

Tissue-engineered pulmonary arteries could overcome the drawbacks of homografts or prosthetic conduits used in the repair of many congenital cardiac defects. However, the ideal scaffold material for tissue-engineered conduits is still subject of intensive debate. In this study, we evaluated an acellularized allogeneic matrix scaffold for pulmonary artery tissue engineering with and without in-vitro reseeding with autologous endothelial cells in the pulmonary circulation in a growing sheep model.

METHODS

Ovine pulmonary arteries (n = 10) were acellularized by trypsin/ethylenediamine tetraacetic acid incubation. Autologous endothelial cells were harvested from carotid arteries, and the pulmonary conduits were seeded with endothelial cells. We implanted in-vitro, autologous, reendothelialized (group A, n = 5) and acellularized pulmonary conduits (group B, n = 5) in the pulmonary circulation. The animals were sacrificed 6 months after the operation. Explanted valves were examined histologically and by immunohistochemistry.

RESULTS

The conduit diameter increased in both groups (group A, 44% +/- 11%; group B, 87% +/- 18%; p < 0.05). In group A, however, a proportional increase in diameter was present, whereas in group B, a disproportionate increase resulting in aneurysm formation was observed. Histologically, the conduit wall integrity was destroyed in group B and preserved in group A. In group B, the extracellularmatrix degenerated with a reduced amount of collagens and proteoglycanes. Furthermore, no elastic fibers were detectable. In contrast, the extracellularmatrix in group A was close to native ovine tissue.

CONCLUSIONS

Tissue-engineered pulmonary conduits (autologous endothelial cells and allogeneic matrix scaffolds) functioned well in the pulmonary circulation. They demonstrated an increase in diameter and an extracellular matrix comparable to that of native ovine tissue.

Intermediate Results of the Double-Switch Operations for Atrioventricular Discordance

BACKGROUND

Since 1987, anatomic biventricular repair using the double-switch operations has been our principal choice for patients with atrioventricular discordance. These alternative procedures have the theoretical advantage of using the anatomic left ventricle to support the systemic circulation.

METHODS

A total of 45 patients underwent the double-switch operation. Their ages ranged from 6 months to 21 years. Associated malformations included pulmonary atresia in 27, pulmonary stenosis in 11, and Ebstein's malformation in 5. An atrial switch plus an arterial switch procedure was performed in 7, and an atrial switch plus a Rastelli-type ventriculoarterial switch procedure in 38. Follow-up ranged from 6 months to 15 years.

RESULTS

Early mortality was 8.9% (n = 4). In the latter half of the series (n = 23, since 1994), there was no early death. Six patients died late. Actuarial survival at 5 and 10 years was 83.6% and 77.6%, respectively. Six patients required conduit replacement, and 2 required revision of an intraatrial baffle for pulmonary venous channel obstruction and infection, respectively. Freedom from reoperation was 95.3% at 5 years and 76.2% at 10 years. Freedom from arrhythmia was 88.8% at 5 years and 78.4% at 10 years. The systemic ventricular ejection fraction was 0.568 +/- 0.103 at 1 year (n = 39), 0.555 +/- 0.105 at 5 years (n = 17), and 0.539 +/- 0.098 at 10 years (n = 12).

CONCLUSIONS

The surgical results of the double-switch operations have been improving. Intermediate follow-up suggests that these alternative procedures are a reasonable option for patients with atrioventricular discordance.

The tissue-engineered vascular graft using bone marrow without culture

OBJECTIVE

To overcome the shortcomings of current vascular grafts, tissue-engineering methods have been applied to cardiovascular regions. We previously reported the creation of a tissue-engineered vascular graft by using vascular mixed cells. However, the cost and manpower for harvesting and culturing the cells was too burdensome. To overcome these drawbacks, we have developed a new method for creating a tissue-engineered vascular graft by using bone marrow cells, which can be obtained easily and used immediately, without cell culture.

METHODS

Biodegradable polymers seeded with different types of cells (group V, cultured venous cells; group B, bone marrow cells without culture; and group C, non-cell-seeded graft [as control]) were implanted into the inferior venae cavae of dogs. The grafts were explanted at 4 weeks and assessed histologically and biochemically.

RESULTS

In the histologic examination, a regular layer of Masson-staining collagen fiber and a layer of factor VII-stained endothelial and ant-alpha-smooth muscle cell antigen-immunoreactive cells stained in groups V and B like native vascular tissue, whereas no such stained regular lining was detected in group C. A 4-hydroxyproline assay in group C showed significantly lower levels than in groups V and B or native tissue ( P < .05). The DNA content of the tissue-engineered vascular graft tended to be higher in group C than in groups V and B or in native tissue.

CONCLUSIONS

In the creation of tissue-engineered vascular grafts, the method of using bone marrow cells seems to be useful and superior to that of using vascular cells because bone marrow cells can be used directly, without culture.

Late results of the peel operation for replacement of failing extracardiac conduits

BACKGROUND

Pulmonary ventricle to pulmonary artery conduits have made repairing many complex congenital cardiac anomalies possible. Late patient outcome is adversely affected by the hemodynamic consequences of conduit failure and the need for reoperation for conduit replacement.

METHODS

We retrospectively reviewed 102 patients (65 males, 37 females) who underwent operation with autologous tissue reconstruction ("peel operation") between May 1983 and November 2001, in which a prosthetic roof was placed over the fibrous bed of the explanted conduit. Ages ranged from 5 to 58 years old (median age 19 years old). Explanted conduits were Hancock (n = 54), homograft (n = 21), Tascon (n = 11), and other (n = 16). The conduit roof was constructed with pericardium (n = 91) and other (n = 11). A prosthetic pulmonary valve was utilized in 68 patients: porcine in 65 patients and mechanical in 3 patients. A nonvalved reconstruction was performed in 34 patients. Concomitant cardiac procedures were performed in 66 patients.

RESULTS

Early mortality overall was 2% (n = 2) and was 0% for patients who underwent isolated conduit replacement (n = 36). Mean follow-up was 7.6 years (maximum, 19 years). Overall survival at 10 and 15 years was 91% (84.7, 97.2) and 76% (62.8, 91.7), respectively. Nine patients required reoperation related to the peel operation: regurgitation in nonvalved conduit (n = 7); moderate pulmonary bioprosthesis stenosis and regurgitation with atrial arrhythmia (n = 1); and pulmonary bioprosthesis endocarditis (n = 1). Overall survivorship free of reoperation for peel reconstruction failure at 10 and 15 years was 90.7% (82.6, 99.6) and 82% (69.4, 97.0), respectively. Survivorship free of reoperation for patients with a prosthetic valve was 93.7%, and for those with no prosthetic valve was 80.0% at 15 years (p = 0.57). At late follow-up, 89% of patients were in New York Heart Association functional class I or II.

CONCLUSIONS

The peel operation simplifies conduit replacement, can be performed with low risk, and provides a generous-sized flow pathway. In our experience late results demonstrate a lower freedom from reoperation than conventional prosthetic or homograft conduits.

Late follow-up of 1095 patients undergoing operation for complex congenital heart disease utilizing pulmonary ventricle to pulmonary artery conduits

BACKGROUND

Pulmonary ventricle (PV) to pulmonary artery (PA) conduits have made possible the correction of many complex congenital cardiac anomalies.

METHODS

Between April 1964 and January 2001, 1270 patients underwent operation with conduit placement from the PV to PA. The present study evaluates late outcome of 1095 patients (612 males, 483 females) having an operation before July 1992. Mean age was 9.6 +/- 8.2 years old. Diagnoses included pulmonary atresia/tetralogy of Fallot (459), transposition of the great arteries (TGA) (232), truncus arteriosus (193), double outlet right ventricle (DORV) (121), corrected TGA (49), septated univentricular heart (36), and other (5). A porcine-valved Dacron conduit was used in 730, homograft in 239, and non-valved conduit in 126.

RESULTS

Early mortality decreased from 23.5% prior to 1980 to 3.7% for the most recent decade. Mean follow-up was 10.9 years (maximum, 29 years). Actuarial survival for early survivors at 10 and 20 years was 77.0% +/- 1.5% and 59.5% +/- 2.6%. On univariate analysis, clinical and hemodynamic factors associated with late mortality were male gender, older age at operation, higher post-repair PV/systemic ventricle (SV) pressure ratio, higher distal PA pressure, and longer bypass time (p < or = 0.01 for all). On multivariate analysis, independent risk factors for late mortality were male gender, older age at operation, diagnosis of TGA, corrected TGA, truncus, or univentricular heart, and PV/SV pressure ratio > or = 0.72 (p < or = 0.03 for all). Freedom from reoperation for conduit failure at 10 and 20 years was 55.5% +/- 2.0% and 31.9% +/- 2.7%. On multivariate analysis, independent risk factors for conduit failure were homograft conduit, diagnosis of TGA, younger age at operation, and smaller conduit size (p < or = 0.007 for all). Reoperation for one conduit replacement was performed in 306 patients, two conduit replacements in 55 patients, three in 6 patients, and four in 3 patients. Overall early mortality for conduit replacement in this series was 4.9%; it was 1.7% for patients operated on from 1989 through 1992. At follow-up, 84% of survivors were in NYHA class I or II.

CONCLUSIONS

Operations that include conduit placement and replacement can be performed with low early mortality. Younger age at operation was associated with improved late survival. The diagnosis of TGA was associated with increased risk for conduit failure, and the durability of the homograft, in this series, was inferior to the porcine-valved Dacron conduit. Quality of life was excellent for most patients despite the need for reoperation.

Polytetrafluoroethylene monocusp valve technique for right ventricular outflow tract reconstruction

Nonvalve transannular patch repair of right ventricular outflow tract obstructive (RVOTO) defects results in pulmonary insufficiency, which can contribute to early postoperative right ventricular dysfunction. In both animal and clinical studies, monocusp valves provide perioperative RVOT competence and improved right ventricular functional characteristics. In these reports, monocusp leaflet construction with 0.1-mm polytetrafluoroethylene (PTFE) appeared equal, or superior, to biologic monocusp valves. Construction of the polytetrafluoroethylene monocusp valve is an inexpensive and straightforward way to create a competent RVOT in a variety of RVOTO anomalies. Based on our clinical experience, it effectively prevents short-term and significantly reduces midterm pulmonary insufficiency without evidence of stenosis.

PTFE monocusp valve reconstruction of the right ventricular outflow tract

BACKGROUND

Transannular patching of right ventricular outflow tract obstructive (RVOTO) defects results in pulmonary insufficiency (PI). Biologic monocusp valves (MO) can prevent acute PI but are prone to early degeneration and progressive regurgitation. Polytetrafluoroethylene (PTFE, 0.1 mm) MO leaflets demonstrated favorable characteristics in animal studies, and the technique was applied to a variety of RVOTO anomalies.

METHODS

From June 1990 through June 1999, 158 patients underwent either PTFE MO RVOT reconstruction (n = 115 patients; 120 implants) or nonvalved transannular repair (TA) repairs (n = 43 patients; 5 subsequent MO implants) at our institution. Standard MO construction techniques and TA repairs were utilized. Intraoperative, postoperative, and echocardiographic data with a mean interval of 2.6 years (range 6 months to 8 years) were used in retrospective fashion to compare clinical outcomes. In addition, PTFE monocusp valves beyond 6 months postimplant underwent echocardiographic analysis of MO function and durability.

RESULTS

There were 4 early (MO-3, TA-1) and no late deaths. Overall, perioperative complications were not significantly different between MO and TA groups, nor were total hospitalization days (9.1 versus 10.7, p = 0.24). However, a significant difference in intensive care unit (ICU) utilization (3.6 versus 5.8 days, p = 0.03) favored MO patients. Patients with tetralogy of Fallot (TOF) and ventricular septal defect/pulmonary atresia (VSD/PA) undergoing the MO implant demonstrated a trend toward improved survival (p = 0.08) when compared to TA repairs. Intraoperative PI was graded mild in the MO group and moderate-severe in the TA group (p = 0.003). Progressive MO regurgitation occurred (mild-moderate) but remained significantly less than the transannular patch repairs (p < 0.05).

CONCLUSIONS

Utilization of a PTFE MO valve prevents short-term and significantly reduces midterm PI. It is inexpensive, easy to construct, and demonstrates no evidence of stenosis, calcification, or embolization. Despite longer cardiopulmonary bypass and ischemic times, it reduces ICU stay and, in both TOF and VSD/PA patients, decreases operative morbidity and mortality.

Early results of right ventricular-pulmonary artery conduits in patients under 1 year of age

OBJECTIVES

Management strategies for the repair of many complex heart defects require the implantation of a valved conduit between the right ventricle (RV) and the pulmonary artery (PA), often using aortic or pulmonary homograft valves. Their limited availability, however, has led to the development and use of new conduits. We retrospectively compared our experience with small homografts in patients of less than 1 year of age with the TissueMed bioprosthetic valved conduit.

METHODS

From March 1994 to November 1997 29 patients in their first year of life underwent conduit implantation for complex heart defects. These were retrospectively reviewed in order to determine the incidence of death or conduit stenosis. Seventeen patients received homografts and 12 TissueMed conduits.

RESULTS

Diagnoses and operative details including conduit size were similar in the two groups and in all cases complete repair of the underlying defect was carried out. Early post-operative mortality was 4/17 (23.5%) in the homograft group and 3/12 (25%) in the TissueMed group. Echo Doppler evaluation within 1 month of operation showed no right ventricular outflow tract (RVOT) obstruction in any of the survivors. In the TissueMed group 8/9 (77%) survivors have gone on to develop significant RVOT obstruction within 12 months of operation. There have been three late deaths in this group all related to severe RVOT obstruction. Two patients died during an attempt at balloon dilatation and one patient died of progressive right heart failure. Five patients had successful replacement of the TissueMed conduit. One child remains well with no evidence of RVOT obstruction. At operation to replace conduit, or at autopsy, the stenoses were related to the deposition of fibrous tissue at the anastomotic suture lines. In the homograft group none of the survivors developed RVOT obstruction during the first 12 months post-operatively. There was one late death (non-cardiac in origin) and one child is awaiting conduit replacement 40 months after initial implantation for obstruction.

CONCLUSIONS

The homograft is a satisfactory conduit for re-establishment of RV-PA continuity in infancy. Further work needs to be undertaken in order to elucidate the mechanisms of early graft failure in bioprosthetic conduits if these are to be a suitable alternative for RV outflow reconstruction in infants.

Hemashield implantation in young patients with congenital cardiovascular lesions

BACKGROUND

There is substantial controversy regarding the use of Hemashield in young patients.

METHODS

Twenty-one consecutive patients younger than 20 years of age with a variety of congenital cardiovascular lesions underwent surgical procedures using a Hemashield woven graft. Hemashield was used for reconstruction of the aortic wall (n = 16), ventricular septum (n = 10), and right ventricular free wall or pulmonary artery (n = 6).

RESULTS

A sterile inflammatory reaction was observed including high fever, increased white cell count, and elevated plasma C-reactive protein concentration for up to 4 weeks after implantation. Multivariable analysis identified the use of Hemashield in the right ventricular free wall or pulmonary artery as an incremental risk factor for elevation of plasma C-reactive protein concentration during the first 3 weeks after implantation (p = 0.002). There were no midterm complications including restenosis of the grafts in the right ventricular outflow tract.

CONCLUSIONS

Hemashield can be used in a variety of situations for reconstruction of congenital cardiovascular lesions in young patients. Impregnated collagen can cause a significant systemic inflammatory reaction for several weeks after implantation, especially when used in the low-pressure right heart.

Direct neonatal ventriculo-arterial connections (REV): early results and future implications

BACKGROUND

Is the time-honored supposition correct that insertion of a competent prosthetic conduit or homograft is necessary to achieve right ventricular (RV) to pulmonary artery continuity in neonates? A direct ventriculo-arterial connection, or réparation à l'étage ventriculaire (REV), has been successfully used to achieve RV to pulmonary artery continuity in neonates without mortality or major morbidity. Acute RV function is preserved even in the face of free pulmonary insufficiency, but scrupulous preservation of pulmonary artery patency (unobstructed pathway) must be achieved.

METHODS

We retrospectively reviewed the cases of 6 neonates who underwent direct ventriculo-arterial connection to achieve RV to pulmonary artery continuity during open heart procedures in the last 3 years.

RESULTS

The 6 neonates had a mean age of 12.3 days (range, 2 days to 6 weeks) and a mean weight of 3.2 kg (range, 2.7 to 3.6 kg) at operation. Two of them had a diagnosis of aortic atresia + ventricular septal defect and successfully achieved an in-series circulation. Two had pulmonary atresia + ventricular septal defect and 2, double-outlet right ventricle + transposition of the great arteries + ventricular septal defect + pulmonary atresia. Follow-up is a mean of 16 months (range, 6 to 22 months). Surgical reintervention was required in 3 neonates and resulted in excellent hemodynamics in 2 of them. In the other patient, who had bilateral long-segment branch pulmonary artery hypoplasia, stents were placed without hemodynamic benefit. All children are currently alive with preserved RV function even in the presence of free pulmonary insufficiency.

CONCLUSIONS

Although the creation of a direct ventriculo-arterial connection has routinely been used for children older than 1 year with satisfactory initial results, its application in neonate is very limited. Why have neonates been denied this viable alternative? Perhaps the answer involves legitimate concerns about the consequent free pulmonary insufficiency and the presumed acute RV diastolic dysfunction.

Fate of subpulmonary homograft conduits: determinants of late homograft failure

PATIENTS AND METHODS

Between 1971 and 1993, 656 conduits were placed in the subpulmonary position. Patients receiving heterografts or valveless conduits and patients dying within 90 days of insertion were excluded; thus 405 homograft conduits were studied. There were 293 aortic homografts, 94 pulmonary, and 18 of unknown type. The end point of conduit failure was defined by conduit replacement for whatever reason, balloon dilation of the conduit, or death of the patient with the conduit in place. The following factors were analyzed: aortic versus pulmonary homograft, antibiotic preservation versus cryopreservation, ABO and Rh compatibility, type of material used for conduit extension, age at operation, size of the conduit, diagnosis, and reoperations. Conduit number (1 to 405) in the series was included in the multivariable model.

RESULTS

First conduits and conduits inserted earlier in the series appeared to last longer than second and subsequent conduits and those inserted later in the series (p = 0.001 and 0.003, respectively). Overall survival of conduits at 5, 10, and 15 years was 84% (95% CL, 80% to 88%), 58% (95% CL, 50% to 66%), and 31% (95% CL, 19% to 43%). Corresponding figures for the first conduits were 88% (95% CL, 84% to 92%), 65% (95% CL, 56% to 73%), and 34% (95% CL, 20% to 47%). The longest surviving homograft conduit in our series lasted 22.7 years. Regarded univariately, reoperation (redo worse), order number (recent worse), type of conduit (pulmonary worse than aortic), preservation (cryopreserved worse than antibiotic preserved), and age at operation (older patients worse) were statistically significant. However, in multivariable analysis, including all the above in the model, only reoperation and order number had significant predictive power. When patient survival was considered, patients operated on more recently survived longer despite the fact that their conduits were being replaced earlier. Overall, survival of patients at 5 and 15 years was 95% (95% CL, 93% to 98%) and 85% (95% CL, 77% to 92%), respectively.

CONCLUSIONS

Pulmonary and aortic homografts, both cryopreserved and preserved in nutrient antibiotic solution, give similar results. All conduits will probably have to be replaced during the lifetime of the patient. In view of the worse performance of replacement conduits, techniques of repair that avoid the use of conduits should be further explored. Despite gradual deterioration of homograft conduits, they remain an important tool in the correction of many complex lesions with excellent 15-year patient survival.

Creation of viable pulmonary artery autografts through tissue engineering

BACKGROUND

"Repair" of many congenital cardiac defects requires the use of conduits to establish right ventricle to pulmonary artery continuity. At present, available homografts or prosthetic conduits lack growth potential and can become obstructed by tissue ingrowth or calcification leading to the need for multiple conduit replacements. Tissue engineering is an approach by which cells are grown in vitro onto biodegradable polymers to construct "tissues" for implantation. A tissue engineering approach has recently been used to construct living cardiac valve leaflets from autologous cells in our laboratory. This study assesses the feasibility of a tissue engineering approach to constructing tissue-engineered "living" pulmonary artery conduits.

MATERIALS AND METHODS

Ovine artery (group A, n = 4) or vein (group V, n = 3) segments were harvested, separated into individual cells, expanded in tissue culture, and seeded onto synthetic biodegradable (polyglactin/polyglycolic acid) tubular scaffolds (20 mm long x 15 mm diameter). After 7 days of in vitro culture, the autologous cell/polymer vascular constructs were used to replace a 2 cm segment of pulmonary artery in lambs (age 68.4 +/- 15.5 days, weight 18.7 +/- 2.0 kg). One other control animal received an acellular polymer tube sealed with fibrin glue without autologous cells. Animals were sacrificed at intervals of 11 to 24 weeks (mean follow-up 130.3 +/- 30.8 days, mean weight 38.9 +/- 13.0 kg) after echocardiographic and angiographic studies. Explanted tissue-engineered conduits were assayed for collagen (4-hydroxyproline) and calcium content, and a tissue deoxyribonucleic acid assay (bis-benzimide dye) was used to estimate number of cell nuclei as an index of tissue maturity.

RESULTS

The acellular control graft developed progressive obstruction and thrombosis. All seven tissue-engineered grafts were patent and demonstrated a nonaneurysmal increase in diameter (group A = 18.3 +/- 1.3 mm = 95.3% of native pulmonary artery; group V = 17.1 +/- 1.2 mm = 86.8% of native pulmonary artery). Histologically, none of the biodegradable polymer scaffold remained in any tissue-engineered graft by 11 weeks. Collagen content in tissue-engineered grafts was 73.9% +/- 8.0% of adjacent native pulmonary artery. Histologically, elastic fibers were present in the media layer of tissue-engineered vessel wall and endothelial specific factor VIII was identified on the luminal surface. Deoxyribonucleic acid assay showed a progressive decrease in numbers of cell nuclei over 11 and 24 weeks, suggesting an ongoing tissue remodeling. Calcium content of tissue-engineered grafts was elevated (group A = 7.95 +/- 5.09; group V = 13.2 +/- 5.48; native pulmonary artery = 1.2 +/- 0.8 mg/gm dry weight), but no macroscopic calcification was found.

CONCLUSIONS

Living vascular grafts engineered from autologous cells and biodegradable polymers functioned well in the pulmonary circulation as a pulmonary artery replacement. They demonstrated an increase in diameter suggesting growth and development of endothelial lining and extracellular matrix, including collagen and elastic fibers. This tissue-engineering approach may ultimately allow the development of viable autologous vascular grafts for clinical use.

Extending the concept of the autograft for complete repair of transposition of the great arteries with ventricular septal defect and left ventricular outflow tract obstruction: a report of ten cases of a modified procedure

BACKGROUND

In most cases of transposition of the great arteries with ventricular septal defect and left ventricular outflow tract obstruction, a Lecompte procedure (réparation à l'étage ventriculaire) is possible without interposition of a conduit between the right ventricle and pulmonary artery. However, the anterior location of the pulmonary arteries after the Lecompte maneuver may be a potential cause for right ventricular outflow obstruction, which continues to be reported in 5% to 25% of cases. We have used a tubular segment of aortic autograft to connect the pulmonary artery, left in the orthotopic posterior position (without the Lecompte maneuver), to the right ventricle in 10 consecutive patients with transposition, ventricular septal defect, and left ventricular outflow tract obstruction.

METHODS

Ten consecutive patients aged 2 months to 11 years (mean 32 months) have undergone a modified Lecompte operation. Eight had severe pulmonary stenosis, two had pulmonary atresia, and four had a restrictive ventricular septal defect at the time of the operation. Two had multiple ventricular septal defects. Seven had undergone one (n = 5) or two (n = 2) previous modified Blalock-Taussig shunts. All patients underwent a total correction with left ventricular-aortic intraventricular connection (four needed a ventricular septal defect enlargement), connection between the right ventricle and pulmonary arteries with a tubular segment of autograft aorta, without the Lecompte maneuver (anterior location of the bifurcation of the pulmonary arteries) on the right (n = 6) or the left (n = 4) of the aorta. No valvular device was used for the right ventricular outflow repair.

RESULTS

No early or late deaths occurred. One patient with multiple ventricular septal defects needed an early (2 weeks) reoperation for a residual muscular ventricular septal defect. All patients are currently in New York Heart. Association class I, without medications, in sinus rhythm, at a mean follow-up of 30 months. Late results up to 3.6 years show no calcification on the chest roentgenogram, and at the most recent echocardiogram, right ventricular pressures were low (25 to 40 mm Hg, mean 33 mm Hg) and no significant gradient (over 10 mm Hg) was found between the right ventricle and pulmonary arteries. Left and right ventricular function was satisfactory.

CONCLUSION

This modification of the Lecompte operation using a segment of autograft allows an excellent early and late result, with no danger of compression of anteriorly placed pulmonary arteries, no significant right ventricular outflow obstruction, and normal appearance of the tubular autograft. In view of laboratory and clinical evidence, normal growth of the autograft can be anticipated. It allows an elective correction of transposition, ventricular septal defect, and left ventricular outflow tract obstruction without a previous Blalock-Taussig shunt (three patients) and correction at a young age (three patients younger than 1 year).

Pulmonary artery augmentation with autologous aortic tissue

OBJECTIVE

To assess durability and viability of autologous aortic tissue used to augment severe branch pulmonary artery stenosis with a novice surgical technique.

PATIENTS AND METHODS

Seven patients underwent corrective surgery for complex cyanotic congenital heart disease. Their age ranged from 3-6 years, and their weight 11-17.4 kg. All had concomitant branch pulmonary artery stenosis repaired utilizing an autologous patch, harvested from the patient's own aorta by excising a ring and opening it to form the patch. The aorta is reconstructed directly by end to end anastomosis.

RESULTS

One patient died in hospital. Another patient died at 18 months at home. The surviving five patients have remained well in the follow up period of mean 31 months (range 10-52). All patients were restudied by follow up echocardiography and remain with no evidence of the aortic autograft tissue calcification or stenosis. The reconstructed aorta showed no stenosis at the site of anastomosis.

CONCLUSION

The intermediate term results of this novice surgical technique appear encouraging and justify the technique. However, longer follow up will be required to confirm the continued growth of this patch material.

Lay-open pulmonary arterioplasty for postoperative hilar pulmonary artery stenosis

OBJECTIVE

Lay-open pulmonary arterioplasty, a novel surgical technique to enlarge postoperative stenosis at the hilar pulmonary artery, was evaluated.

METHODS

Lay-open arterioplasty, in which the enlarged hilar stenotic pulmonary artery is partially made up of previous surgical scar tissue instead of being covered by a patch, was performed on 10 patients whose ages ranged from 2.2 to 15.7 years. Surgical results were assessed by angiography.

RESULTS

All patients tolerated the procedure without bleeding or embolic complications associated with pulmonary arterioplasty. Nine patients underwent concomitant procedures including total repair (n = 5), central interposing shunt (n = 3), and right ventricular outflow tract reconstruction (n = 1). No deaths or life-threatening events occurred during the total follow-up period of 18 patient-years. The stenotic segment was significantly enlarged from the preoperative diameter of 0.9 +/- 1.1 mm (mean +/- standard deviation) to the postoperative diameter of 8.0 +/- 1.3 mm, values which correspond to 7.0% +/- 8.8% and 68.4% +/- 11.5% of the normative values, respectively. A follow-up angiogram (n = 5) revealed an increase in the pulmonary artery diameter balanced with somatic growth (initial value, 65.2% +/- 9.0% of normal; second value, 69.1% +/- 7.7% of normal). No aneurysms or clinically significant restenoses were seen on the angiograms.

CONCLUSIONS

Our initial midterm results with this method were promising. The pulmonary arteries subjected to this procedure grew in proportion to somatic growth.

Results of an autologous tissue reconstruction for replacement of obstructed extracardiac conduits

Between May 1983 and March 1, 1995, 50 patients had replacement of an obstructed pulmonary ventricle-pulmonary artery conduit with an autologous tissue reconstruction in which a prosthetic roof was placed over the fibrous tissue bed of the explanted conduit. The roof was constructed with xenograft pericardium (most recently) (n = 42), homograft dura mater (n = 5), or Dacron fabric (n = 3). Patient ages ranged from 5 to 34 years (median 16 years). The explanted conduits were Hancock conduits (n = 33), Tascon conduits (n = 6), homograft (n = 4), Dacron tube (n = 3), and others (n = 4). Preoperative maximum systolic gradients ranged from 44 to 144 mm Hg (median 78 mm Hg). Thirty-seven concomitant cardiac procedures were done in 29 patients. When a valve was necessary (n = 15), it was possible to place a large-sized valve in the autologous tissue reconstructions (range 22 to 29 mm, median 26 mm). Cardiopulmonary bypass times ranged from 34 to 223 minutes (median 84 minutes), and aortic crossclamp times ranged from 0 (in 32 patients) to 109 minutes (median 0 minutes). Intraoperative postrepair peak systolic gradients from pulmonary ventricle to pulmonary artery ranged from 0 to 33 mm Hg (median 13 mm Hg). There was one early death (2%) in a patient who had additional cardiac procedures. Follow-up was complete in all patients and ranged from 1 month to 11.8 years (median 7.5 years). There were two sudden late deaths: conduits in both were known to be free from obstruction. Forty-four of the 47 surviving patients had evaluation of the gradient by echocardiography or cardiac catheterization 1 month to 11 years (median 7 years) after operation. The gradients ranged from 5 to 45 mm Hg (median 20 mm Hg). None of the conduits developed an obstructive peel, valve obstruction, or valve incompetence. At 10 years, the freedom from reoperation for conduit obstruction was 100%, and freedom from reoperation for any cause was 81%. This technique simplifies conduit replacement, allows for a generous-sized outflow tract, has a low risk, and yields late results that appear superior to those of cryopreserved homografts or other types of extracardiac conduits.

Autologous reconstruction of pulmonary trunk at reoperation after extracardiac conduit repair

Between 1991 and 1993, 5 patients underwent reoperation for critical stenosis of extracardiac conduit. Indication for extracardiac conduit repair was pulmonary truncal atresia in 3 patients and coronary anomaly including single left coronary artery and left anterior descending artery from right coronary artery in 2 patients. Age at reoperation ranged from 8 to 23 years (mean, 16.2 years). Preoperative systolic pressure ratio of right to left ventricles ranged from 0.83 to 1.05 (mean, 0.93), with the pressure gradient across the conduit ranging from 52 to 100 mm Hg (mean, 74.4 mm Hg). At reoperation, stenotic conduit was completely removed and central pulmonary artery was extensively mobilized. In 4 patients who had a relatively short distance (15 to 25 mm) between the pulmonary arterial stump and the right ventriculotomy incision, the distal pulmonary arterial stump was anastomosed directly to the cranial margin of the right ventriculotomy incision to serve as a floor mode of autologous tissue. In 1 patient with a long distance (40 mm), right ventricular-pulmonary arterial continuity was restored with a tailored autologous pericardial tube. There were no early or late deaths. Postoperative catheterization study revealed a satisfactory reduction of right ventricular pressure with the systolic pressure ratio ranging from 0.42 to 0.51 (mean, 0.47) and the pressure gradient across the right ventricular outflow tract ranged within 13 mm Hg (mean, 5 mm Hg). Restoration of right ventricular-pulmonary arterial continuity was successfully achieved by introducing the concept of autologous tissue repair even at reoperation instead of the insertion of new extracardiac conduit in patients with tetralogy of Fallot after extracardiac conduit repair.

Comparative study of lyophilized human dura mater and lyophilized bovine pericardium as dural substitutes in neurosurgery

In a prospective, controlled randomized study either lyophilized bovine pericardium or lyophilized human dura mater have been used as a patch for the closure of the dura in 102 patients. The aim of this investigation was to compare both materials in terms of immunogenic response of the patients. The rate of post-operative complications was comparably low in both groups (wound infection in 1/51 patients each). In regard of workability, thickness of the material and flexibility the pericardium patches were judged to be by far superior. Neither signs of a cellular nor of an intesified humoral response could be detected in patients who received the pericardium implants. Thus, lyophilized bovine pericardium seems to be a superior alternative for the surgical repair of dural defects.

Extended use of a pulmonary homograft for right ventricular outflow tract reconstruction

When a pulmonary homograft is used for reconstruction of the right ventricular outflow tract a patch or tube extension is usually required to close the gap in the right ventriculotomy. We describe here a simple method by which a large patch can be tailored from the homograft using the distal main pulmonary artery and its branches.