Ann Thorac Surg 2000;69:1920-1924
© 2000 The Society of Thoracic Surgeons
Original articles: Cardiovascular
Hemashield implantation in young patients with congenital cardiovascular lesions
Ryo Aeba, MDa,
Toshiyuki Katogi, MDa,
Shiaki Kawada, MDa
a Division of Cardiovascular Surgery, Keio University, Tokyo, Japan
Address reprint requests to Dr Aeba, Division of Cardiovascular Surgery, Keio University, 35 Shinanomachi, Shinjuku, Tokyo 160-8582, Japan
e-mail: aeba{at}mc.med.keio.ac.jp
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Abstract
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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.
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Introduction
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Prosthetic material plays an important role in surgery for congenital cardiovascular lesions, because biomaterials including xenogeneic pericardium can exhibit accelerated calcification and there is limited availability of aortic and pulmonary arterial allograft and autologous pericardium. Collagen-impregnated vascular prostheses have gained widespread acceptance in adult cardiovascular surgery because preclotting is not required (thereby minimizing operative time), there is minimal or no blood leakage even with full heparinization, and hemostasis is excellent at the stitch holes. These advantages can be also realized in young patients. In addition, there are several potential advantages specific to young patients including a high compliance (pliability) that matches thin and fragile vascular walls, and an expected low incidence of long-term complications resulting from the dense adherence of the pseudoneointima to the material. On the other hand, a sterile inflammatory reaction has been reported early after implantation, which has been attributed to the impregnated collagen [1–3]. These potential advantages appear to outweigh the risks. The experience in adults, however, may not be directly extrapolated to young patients. In this report, our experience with Hemashield prostheses in patients younger than 20 years of age is reviewed.
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Patients and methods
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Between May 1993 and April 1999, 21 consecutive patients younger than 20 years of age underwent cardiovascular surgery at the Keio University Hospital using a collagen-impregnated woven Dacron graft (Hemashield Microvel double-velour graft, Meadox Medicals, Oakland, NJ). They were followed for 3 months to 6 years (mean follow-up: 2.8 ± 1.8 years). Demographic and perioperative data are detailed in Table 1. The cardiac diagnoses varied. Sixteen patients (76%) had left ventricular outflow tract obstruction at subvalvular (n = 3), valvular (n = 6), supravalvular (n = 1), and aortic arch (n = 8) levels. The other lesions included a double-outlet right ventricle (n = 3), tetralogy of Fallot (n = 2), d-transposition of the great arteries (n = 1), and truncus arteriosus (n = 1). Pulmonary arterial hypertension (systolic pressure: > 30 mm Hg) was found in only 2 patients (10%). Cardiopulmonary bypass and cardioplegic heart arrest were used in 95% and 71% of patients, respectively. Preoperatively, there were no patients with a high fever, increased white cell count, or high plasma C-reactive protein concentration.
Table 2 summarizes surgical procedures. In 8 patients, Hemashield was used exclusively for aortic reconstruction. Four patients who had a residual or recurrent stenosis after aortoplasty for aortic arch interruption (n = 2) or coarctation (n = 2) underwent extraanatomic bypass grafting from the ascending to the descending thoracic or supraceliac abdominal aorta [4]. Two patients with either aortic coarctation or an ascending aortic aneurysm with aortic valve stenosis underwent aortic replacement with a Hemashield tube graft. One patient with aortic coarctation underwent a patch plasty. A patient with supravalvular aortic stenosis underwent symmetric aortoplasty using three individual Hemashield patches.
Ventriculoaortoplasty was performed in 8 patients using a Hemashield patch for augmentation of the left ventricular outflow tract between the ventricular septum and the ascending aorta. Of these, 6 patients with normal ventriculoarterial alignment underwent the Konno operation [5]. In the remaining two patients with d-transposition of the great arteries or a double-outlet right ventricle, the longitudinal aortic incision on the anterior aspect was extended into the right ventricular free wall toward the previous interventricular patch. The resultant ventriculoaortic incision was augmented with a single Hemashield patch after mechanical valve insertion. In 2 patients with a double-outlet right ventricle and a subaortic or noncommitted ventricular septal defect, a biventricular repair with intraventricular rerouting of the left ventricular outflow tract was performed using a Hemashield baffle.
Hemashield was used in the low-pressure pulmonary artery or right ventricular free wall in 6 patients. One patient with tetralogy of Fallot and pulmonary atresia who had previously undergone a Rastelli repair using an extracardiac conduit between the right ventricle and pulmonary trunk [6] developed progressive conduit obstruction. This patient underwent total excision of the conduit followed by placement of a Hemashield patch in the autologous conduit bed [7]. The second patient, who had truncus arteriosus, underwent a Rastelli repair using a Hemashield Y-shaped tube graft as an extracardiac conduit between the right ventricle and the right and left branch pulmonary arteries. The third patient, who had tetralogy of Fallot, pulmonary atresia, major aortopulmonary collateral arteries, and a nonconfluent left branch pulmonary artery, underwent bypass from the pulmonary trunk to the left branch pulmonary artery as well as the Blalock-Taussig shunting and obliteration of the major aortopulmonary collateral arteries. The two patients who underwent biventricular repair of the double-outlet right ventricle, and the patient who underwent the Konno operation had a Hemashield patch implanted in the right ventricular free wall as well as in the high-pressure side of the heart.
Hemashield was implanted in the high-pressure aortic walls (n = 16), in interventricular septation (n = 10), and in the low-pressure pulmonary circulation (n = 6). According to the configuration of the graft, Hemashield was used as a tube conduit (n = 9, 43%), and as a baffle or patch created by excision from a tube graft (n = 12, 57%).
Data collected for analysis included gender, age at operation (years), body weight at operation (kg), body surface area (m2), preoperative systolic pulmonary arterial pressure (mm Hg), total cardiopulmonary bypass time (minutes), myocardial ischemic time (minutes), size of Hemashield graft implanted (cm2), location of Hemashield graft, use of a Hemashield tube graft, presence of cyanosis before operation, history of previous operations, history of homologous blood transfusion, current homologous blood transfusion, and concomitant procedures performed in the operation (Table 1). Statistical analysis was performed using the SPSS program for Windows (SPSS Inc, Chicago, IL). Quantitative variables were expressed as the mean ± the standard deviation of the mean. Two-way analysis of variance with repeated measures with group as a between-subjects factor and time as a within-subjects factor was used to identify determinants of peak body temperature, white cell count, and plasma C-reactive protein concentration between the first and fourth postoperative weeks. Univariable analysis was performed and variables with a p value less than 0.1 were included in the multivariable analysis. The level of significance was set at a p value less than 0.05.
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Results
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Hemashield implantation was performed without technical problems. There were no patients in whom establishment of hemostasis was difficult (hemostasis time > 1 hour). There was no intraoperative kinking of the grafts. Reexploration was not required for any reason including postoperative bleeding or hemodynamic deterioration. Postoperatively, systemic inflammation was observed between the first and fourth weeks. This was characterized by high fever, increased white cell counts, and C-reactive protein concentrations (Table 3). The peak body temperature and white cell count did not significantly decrease until the third week (p > 0.1). Four weeks after implantation the C-reactive protein concentration failed to normalize (< 0.5 mg/mL) in 12 patients (57%). The white cell count failed to normalize (< 12,000) in 3 patients (14%). None of these patients had a documented bacterial or fungal infection despite meticulous culture examination of the blood, urine, and sputum. In 1 patient with truncus arteriosus who underwent Y-shaped extraanatomic conduit reconstruction of the right ventricular outflow tract, a left pleural effusion persisted for 4 weeks after surgery. All patients were followed with a comprehensive evaluation, which included chest radiography, echocardiography, computed tomography, and cardiac catheterization. There were no midterm complications including hematoma formation, seroma, juxtaprosthetic aneurysmal formation, pyrexia, configuration change, thrombosis, infection, or restenosis of the graft. None of the patients was symptomatic or required medications except anticoagulation in those with a mechanical valve.
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Table 3. Change in Peak Body Temperature, White Cell Count, and Plasma C-Reactive Protein Concentration During the First 4 Weeks After Implantation of a Hemashield
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Multivariable analysis identified the use of Hemashield for pulmonary arterial reconstruction as an independent incremental risk factor for elevated C-reactive protein concentration in the plasma (F = 12.3, p = 0.002). This group difference was significant during the first and third postoperative weeks (Fig 1). None of the determinants reached the statistically significant level as independent factors for increased body temperature or white cell count.
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Fig 1. Peak plasma C-reactive protein (CRP) concentrations. Concentrations in patients whom Hemashield implanted in the pulmonary artery (PA) or right ventricular free wall (RVFW) were significantly higher than in those implanted in others. (p = 0.002 by analysis of variance). Bars represent the standard deviation of the mean.
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Comment
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The Hemashield provides a number of advantages over other prosthetics to young patients undergoing reconstruction of cardiovascular lesions. The greater compliance (pliability) of Hemashield compared with uncoated Dacron fabric with low porosity was crucial, especially in the reconstruction of the ventricular outflow tract, which almost always has three-dimensionally complex configurations. In the Konno operation [5], Hemashield was used for the ventriculoaortoplasty patch. Because the long axis of the incision in the ventricular septum and the ascending aorta was curved, patch placement using stiff material would have been a potential source of bleeding, left-to-right shunting, or kinking of the coronary arterial ostium. In the rerouting of the left ventricular outflow tract for the double-outlet right ventricle, the optimal intraventricular baffle should have a convex shape and a curved configuration. Again, the use of baffle material with a low compliance may have a deleterious effect on the dynamic morphology of the aortic valve leaflets or annulus. Hemashield can be used as an aortic patch or an aorto–aortic bypass graft for obstructive lesions. The aortic wall in these children is often thin and fragile. In such cases, the hemostatic properties of Hemashield help to minimize operative time and blood loss. Additionally, there are several long-term advantages in the use of high-porosity prostheses with sealant. After the sealant protein is absorbed and replaced by endothelial and fibrous tissue, a high-porosity fiber matrix should promote more dense anchoring of the pseudoneointima, which has a smooth and homogenous inner surface. Endothelialization on the inner surface should prevent infectious complications of the graft, and thrombus formation during the longer follow-up period in young patients.
Expanded polytetrafluoroethylene (ePTFE), which is widely used in arterial reconstruction, may be an alternative option to Hemashield. The advantages may include excellent healing properties and the impervious barrier to blood and fluid. Some technical difficulties may be encountered in the reconstruction of large-caliber vessels, because ePTFE is somewhat rubbery and stiff, which can result in kinking. Poor hemostasis at the stitch holes is another source of concern, although the use of ePTFE suture may ameliorate the problem.
In several clinical reports with adult patients, heterogeneic protein-coated vascular prostheses have been noted to cause inflammatory or allergic reactions without evidence of infection up to several weeks after implantation [1–3]. A statistically meaningful comparison between these adult patients and the young patients in the present study is impossible because of differences in the implantation locations, the diagnoses, and the surgical procedures. This phenomenon, however, appears to occur in the same time frame in young and older patients. One important finding is that the degree of systemic inflammation is independent of the size of the Hemashield graft implanted.
There is some controversy surrounding the use of Hemashield for pulmonary arterial reconstruction. A low incidence of Hemashield tube graft obstruction due to detached intraluminal pseudoneointima may be expected because of strong anchoring to the fiber matrix, although no clinical or laboratory studies have proved this advantage. On the contrary, there is a great concern regarding early obstruction. Molina and coworkers [8] experimented with a growing lamb model using several different types of vascular prostheses for the pulmonary artery. Both albumin-coated and uncoated knitted Dacron tube conduits demonstrated similarly suboptimal behavior. Two independent researchers [9, 10] reported a total of 7 clinical recipients of a knitted Hemashield tube conduit in the pulmonary position who developed a scar contracture of, or neointimal overproliferation on, the inner surface of the graft, which led to obstruction. A similar phenomenon has been observed with Tascon collagen-impregnated and knitted Dacron fabric (Tascon Medical Technologies, Irvine, CA) [11]. In our series, none of the 6 patients in whom woven Hemashield was placed in the pulmonary artery showed clinical evidence of graft obstruction, although the mean length of follow-up was only 2.8 years. It may be important to note that this group had a more intense systemic inflammation reaction than the patients in whom Hemashield was implanted in a higher pressure position. It is also interesting that the use of Hemashield in the ventricular septum, in which one aspect of the patch was exposed to the low-pressure right ventricle, did not result in systemic inflammation. It may be that stretch of the Hemashield graft may play a role in prevention of the inflammatory reaction. Whether coated protein results in an intense inflammatory reaction, which can lead to graft obstruction, requires further clinical and experimental investigation.
In summary, Hemashield can be used in a variety of unique situations for reconstructing congenital cardiovascular lesions in young patients. Impregnated collagen prostheses can induce a systemic inflammatory reaction that may persist for several weeks following implantation, especially when used in the low-pressure pulmonary arterial system. All vascular prostheses have their unique limitations. We believe that Hemashield is particularly well suited for reconstruction of high-pressure, left-sided congenital abnormalities and in selected cases of low-pressure, right-sided lesions in young patients.
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References
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Angelini G.D., Witsenburg M., Ten Kate F.J.W., Hiddema P.A.E., Quaegebeur J.M. Severe stenotic scar contracture of the Microvel Hemashield right-sided extracardiac conduit. Ann Thorac Surg 1989;48:714-716.[Abstract/Free Full Text]
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Accepted for publication December 29, 1999.
Related Article
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Invited commentary
- Carl L. Backer and Constantine Mavroudis
Ann. Thorac. Surg. 2000 69: 1924-1925.
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Abstract
Introduction
