|Year : 2016 | Volume
| Issue : 3 | Page : 175-180
Polytetrafluoroethylene patch versus autologous pericardial patch for right ventricular outflow tract reconstruction
Sachin Talwar1, Murugan Sathiya Selvam1, Palleti Rajasekhar1, Sivasubramanian Ramakrishnan2, Shiv Kumar Choudhary1, Balram Airan1
1 Cardiothoracic and Vascular Surgery, All India Institute of Medical Sciences, New Delhi, India
2 Department of Cardiology, Cardiothoracic Center, All India Institute of Medical Sciences, New Delhi, India
|Date of Web Publication||2-Mar-2017|
Department of Cardiothoracic and Vascular Surgery, All India Institute of Medical Sciences, New Delhi - 110 029
Source of Support: None, Conflict of Interest: None
Objective: Reconstruction of right ventricular outflow tract (RVOT) during repair of Tetralogy of Fallot (TOF) often requires placement of a transannular patch (TAP). The purpose of the present study was to compare the outcomes following reconstruction of RVOT using polytetrafluoroethylene (PTFE) patch versus autologous glutaraldehyde-fixed pericardial patch. Materials and Methods: Fifty-three consecutive patients undergoing TAP repair for TOF in a single institute were randomized into two groups: Group I (pericardial patch), Group II (PTFE patch) and their postoperative outcomes in terms of postoperative rhythm, duration of mechanical ventilation, mediastinal and pleural drainage, stay in the Intensive Care Unit (ICU) and hospital, were assessed. The preoperative and postoperative gradients across the RVOT, pulmonary insufficiency, systolic right ventricular function were assessed echocardiographically by an independent cardiology team. Results: There was one death; there were no differences between the two groups regarding the postoperative duration of mechanical ventilation, ICU, and hospital stay. The requirement of inotropes was less in the PTFE patch group compared to the pericardial patch group (12.80 ± 8.04 vs. 17.30 ± 7.21, median 10 vs. 20, P = 0.025). The re-exploration rate in the PTFE group was higher than the other group (6 vs. 1). There was no difference in the RV systolic function between the two groups as assessed by echocardiogram before discharge. Conclusion: RVOT reconstruction during TOF repair can safely be performed using a PTFE patch with results similar to an autologous patch of glutaraldehyde-treated pericardium. Its results in the mid and long term need further evaluation.
Keywords: Patch materials, right ventricular outflow reconstruction, Tetralogy of Fallot, transannular patch
|How to cite this article:|
Talwar S, Selvam MS, Rajasekhar P, Ramakrishnan S, Choudhary SK, Airan B. Polytetrafluoroethylene patch versus autologous pericardial patch for right ventricular outflow tract reconstruction. J Pract Cardiovasc Sci 2016;2:175-80
|How to cite this URL:|
Talwar S, Selvam MS, Rajasekhar P, Ramakrishnan S, Choudhary SK, Airan B. Polytetrafluoroethylene patch versus autologous pericardial patch for right ventricular outflow tract reconstruction. J Pract Cardiovasc Sci [serial online] 2016 [cited 2022 Dec 9];2:175-80. Available from: https://www.j-pcs.org/text.asp?2016/2/3/175/201372
| Introduction|| |
Tetralogy of Fallot (TOF) is one of the common cyanotic congenital heart diseases. It has a wide spectrum of presentation from simple TOF with adequate right ventricular outflow tract (RVOT) and adequate pulmonary annulus to the extreme of pulmonary atresia. In between are patients with varying degrees of hypoplasia of RVOT and pulmonary annulus. In the initial days, when the repair of TOF was evolving, the ventricular septal defect (VSD) was closed through the right ventricle (RV) using a generous ventriculotomy, and a patch was used to augment the RVOT., Since then, surgery for TOF has evolved to the present era where intracardiac repair for TOF is commonly performed through a limited right ventriculotomy or through the right atrium (RA) with a reduction in perioperative morbidity and mortality.
Although in the current era, the attention of surgical correction of TOF has shifted to pulmonary valve-sparing procedures, it may not be feasible in all patients with TOF, and a significant number still require a transannular patch (TAP) for complete relief of RVOT obstruction after resection of the hypertrophic infundibular muscle bundles. The commonly used patch materials for RVOT augmentation (TAP) are unfixed autologous or bovine pericardium, autologous glutaraldehyde fixed pericardium, homograft with some valve, and various synthetic patches. The choice of these patch materials is empirical and based on surgeon preference, and except for a few studies comparing unfixed pericardium with glutaraldehyde-fixed pericardium,, there is a paucity of literature in this field. We, therefore, designed this study to compare the in-hospital clinical outcomes of TOF repair in those patients requiring TAP repair using glutaraldehyde-fixed autologous pericardial patch to that of a patch of expanded polytetrafluoroethylene (PTFE).
| Materials and Methods|| |
Fifty-three consecutive patients, aged 1–16 years undergoing intracardiac repair of TOF at the All India Institute of Medical Sciences, New Delhi, India, were included in the single-surgeon study. All the enrolled patients had a narrow pulmonary annulus needing a TAP as assessed preoperatively and confirmed intraoperatively (Z <−3). The study group was randomized into two groups based on withdrawal of lots, once the decision to perform a TAP repair had been confirmed in the operating room. The study protocol was duly approved by the Ethics Committee of the Institute, and informed consent was obtained from the parents of all the patients in the study. The study was designed, and the sample size was calculated to achieve a minimum statistical power of 0.9.
Surgery and anesthesia
Anesthesia was induced and maintained by weight-related doses of thiopental, fentanyl, midazolam, and relaxants such as rocuronium and vecuronium. All patients received cefotaxime as antibiotic prophylaxis after induction of anesthesia and during the next 48–72 h till the removal of all invasive lines and catheters. Cardiopulmonary bypass (CPB) was carried out using a nonpulsatile roller pump, membrane oxygenators, and standard (uncoated) extracorporeal circuits under mild hypothermia (32°C). The circuit was primed with appropriate amounts of Ringer's lactate solution, mannitol, and sodium bicarbonate. Blood was added or removed as per the desired hematocrit value. Del Nido solution was used for cardioplegia through the antegrade route in all the patients.
Intraoperative transesophageal echocardiography (TEE) was performed in all patients to confirm the diagnosis and to assess the pulmonary annulus and the need for placement of an outflow patch. Surgery was performed in a standard manner by a single surgeon through a midline sternotomy and aortic-bicaval cannulation for the institution of CPB. RA was opened after snugging venous cannulae, and left heart was vented through the interatrial septum. The VSD was closed with a Dacron patch, and infundibular resection was performed either trans through the RA through an adequate size right ventriculotomy that was extended across the pulmonary annulus taking care to preserve as much of the native pulmonary valve apparatus as possible.
If the patient had been randomized to the pericardial patch group (Group I), a patch of autologous pericardium harvested before commencing CPB was treated in 0.625% glutaraldehyde for 6 min was used for TAP reconstruction which was performed on an arrested heart using a continuous 6-0 polypropylene suture. The timing of fixation was limited to 6 min so that the pericardium would be just stiff enough to handle, as we realized that below 6 min handling is not good and previous studies have shown that prolonged fixation times may increase pericardial calcification. In the PTFE group (Group II), a 0.8 mm thick PTFE patch was cut out of an appropriate size Goretex graft (preferred over a 0.6 mm PTFE patch for better contouring) for appropriate contouring and was sutured in place using a continuous 6-0 PTFE suture to minimize needle hole bleeding.
All patients were started on low dose of dobutamine with or without low-dose dopamine at the time of rewarming, and CPB was weaned off gradually. The addition of a vasopressor depended on the systemic blood pressure. In many cases, a vasodilator in the form of nitroglycerin or sodium nitroprusside was added depending on the blood pressure, post-CPB postrepair RV (pRV)/left ventricular (LV), and intraoperative TEE. Intraoperative TEE was always performed for assessment of repair. pRV/LV was always measured, and a ratio of no more than 0.7 was accepted.
All patients were transferred to the Intensive Care Unit (ICU) after surgery and extubated after optimizing them. We followed a policy of early extubation unless signs of frank low cardiac output were present. Inotropic support was optimized as per requirement, and the dose and duration of the inotropic support were recorded.
Postoperative parameters that were assessed included rhythm, requirement of inotropic support, duration of mechanical ventilation, duration of ICU, and hospital stay. The inotropic requirement was assessed in terms of the standard inotropic score  that was calculated as follows:
Inotropic score = Dose in mcg/kg/min of (dopamine + dobutamine) × 1 + milrinone × 30 + (epinephrine + norepinephrine) ×100.
The postoperative echocardiographic assessment was performed by a separate team of cardiologists who were blinded to the nature of the patch material. The echocardiographic parameters included: tricuspid annular plane systolic excursion (TAPSE) in cm, RV fractional area change (FAC) as calculated from the systolic and diastolic dimensions of RV in the apical four chamber view, the pre- and post-operative gradient using continuous Doppler across RVOT, postoperative main pulmonary arterial dimension, and postoperative grade of pulmonary regurgitation (PR).
PR was graded as mild: Regurgitant jet below the pulmonary valve, moderate: Jet in the RVOT with the retrograde diastolic flow in the main pulmonary artery (MPA), and severe: Retrograde diastolic flow in both pulmonary artery branches.
Statistical analysis was performed using SPSS 19 software (SPSS Inc., Chicago, Illinois, USA). Values are presented as mean or median ± standard deviation (SD) for quantitative variables and n (%) for qualitative variables. Comparisons between subgroups for continuous data were made with Student's t-test if normally distributed and Mann–Whitney U-test otherwise. Tests between subgroups for qualitative data were made with Pearson Chi-square test. Two-tailed P < 0.05 was considered statistically significant.
| Results|| |
Twenty-six patients underwent intracardiac repair of TOF with PTFE as the TAP material, and 27 patients underwent intracardiac repair with glutaraldehyde-fixed pericardial patch as the TAP material during the same period.
Preoperative baseline characteristics
These are summarized in [Table 1] and [Table 2] and were similar in both groups. Echocardiographically, there was only one patient in the PTFE group who had RV dysfunction as seen by TAPSE <−2 SD. The FAC was normal in this patient.
Intra- and post-operative immediate outcomes
Of the 53 patients operated [Table 3], there was one death in the PTFE patch group. This 5-year-old boy underwent surgery after coil embolization of significant collaterals with acceptable postoperative pRV/LV (0.6). He was extubated after 6 h and remained stable. He developed sudden pulmonary hemorrhage with aspiration and asphyxia. During resuscitation, he had cardiorespiratory arrest and required extracorporeal membrane oxygenation support. However, he developed disseminated intravascular coagulation and expired on postoperative day 3. For statistical analysis, this patient was excluded from the study.
The mean CPB time in the pericardial patch group was 96.15 ± 15.23 (median 92) min against 95.92 ± 13.03 (median 96) min in the PTFE group (P = 0.955). The mean aortic cross-clamp time in pericardial patch group was 59.67 ± 16.70 (median - 58) versus 64.12 ± 11.19 (median – 62) min (P = 0.268). No major arrhythmias occurred intraoperatively. Only two patients required cardioversion on releasing aortic cross-clamp. The mean duration of mechanical ventilation was 8.59 ± 2.57 (median – 8) h in pericardial patch group and 8.84 ± 4.1 (median – 8) h in the PTFE group (P = 0.819). The mean duration of ICU stay and hospital stay in the pericardial patch group was 51.78 ± 20.67 (median 51) h and 6.22 ± 1.34 days, respectively. In the PTFE group, the duration was 48.16 ± 23.20 (median 42) h and 6.44 ± 2.36 days, respectively (P > 0.05). The amount of mediastinal drainage also did not differ significantly in the two groups. There were seven re-explorations for increased mediastinal drainage, one in the pericardial patch group versus six in the PTFE patch group. The site of bleeding in these patients was in TAP in the pericardial patch. Of the six re-explorations in the PTFE group, four were from the patch site and two were from unrelated sites. The mean inotropic score in the pericardial patch group was 17.30 ± 7.21 (median – 20), and in the PTFE group was 12.80 ± 8.04 (median 10). This was statistically significant (P = 0.025).
Only two patients had RV dysfunction in the immediate postoperative period (both in PTFE patch group) [Table 4]. One had mild and one had severe PR. One patient was 3 years old with significant malnutrition (weight of 9 kg) and severe cyanosis and recurrent spells before surgery, and the other patient had pRV/LV ratio of 0.7 and postoperative RVOT gradient of 30 mmHg. The mean RVOT gradient after surgery was 17.48 ± 8.51 in the pericardial patch group as against 15.30 ± 7.30 in the PTFE patch group.
In the pericardial patch group, nine patients had mild PR, 15 had moderate PR, and two had severe PR, while in the PTFE patch, the values were 6, 17, and 2, respectively. These patients were not noted to have smaller MPA diameter or any other unfavorable anatomy before surgery.
| Discussion|| |
Autologous pericardium either fixed or unfixed is harvested during cardiovascular procedures and has been used in the surgical reconstruction of many different areas. Using autologous pericardium as a patch material has multiple advantages such as ready availability, conformability, nonporosity, and lack of bleeding through needle holes. It may also be less likely to cause thrombosis or hemolysis. The unfixed autologous pericardium is a low-cost biomaterial that is free of donor-derived pathogens, does not provoke an immune response, and is easy to access. However, it has poor handling characteristics, and the clinical use of fresh autologous pericardium in cardiovascular surgery is limited because of uncertain factors such as the onset of tissue shrinkage or stretching several years after implantation. The implants may become fibrotic and retracted, exhibiting progressive thinning with dilatation and aneurysm. Retraction and fibrosis were observed when fresh pericardium was used as a patch or artificial chordae in heart valve reconstruction. The closure of large ventricular defects or patch reconstruction of the RVOT was reported to result in aneurysmal changes. In addition, pediatric patients often have to undergo multiple reconstructive surgical procedures so that the application of autologous pericardium for repair or reconstruction of congenital defects is also limited. Because of these limitations, reconstruction of RVOT using glutaraldehyde-fixed pericardial patch was advocated. The advantages of using a glutaraldehyde-fixed pericardial patch are good handling characteristics, limited stretching postoperatively, and less immunogenicity. However, it increases the risk of calcification ,,, and hence may potentially cause residual RVOTO and because of tissue destruction increase in PR on the long term. Messina et al. compared glutaraldehyde-fixed pericardial patch to conventional autologous unfixed pericardium for reconstruction of RVOT. At 6 months follow-up, the unfixed pericardial patch cohort showed dilatation of RVOT by independent observers. Other studies have also demonstrated the propensity of unfixed pericardial patch to dilate and also cause RVOT aneurysms in the late postoperative period. This may contribute to the increase in the severity of PR progression after TAP repair.,, Studies have also reported that the efficacy of TAP depends on an optimal size of the patch: too large a patch will cause regurgitation, and too small a patch will result in stenosis.
Tissue patches have the disadvantages of immunogenicity. However, at reoperation like pericardium, the tissue patches are known to become aneurysmal, calcify heavily, and become strongly adherent to the surrounding structures. In light of the above problems, a nonimmunologic, nondegenerating, and relatively durable material such as PTFE can be used for TAP repair. Vascular grafts made of PTFE are used for the construction of arterial shunts in neonates with complex cyanotic heart defects, for palliative reconstruction of interrupted aortic arch, for the construction of extra-anatomic aortic bypass and total cavopulmonary connection. The PTFE patches are suitable for closure of septal defects, plastic reconstruction of the right and the LV outflow tracts, correction of coarctation of the aorta, and plastic repair of stenoses on the MPA and its branches. PTFE membranes represent very good pericardial substitutes after complex surgeries with valve replacement or the use of a valved conduit, where reoperation is anticipated. It is expected that at reoperation, these patches would not be aneurysmal because of their rigid nature and the peel formed around the patch would prevent the development of dense adhesions with the surrounding structures. However, there was a need to validate and compare the early results of the use of the PTFE patch when compared to the time-tested pericardial patch. Hence in this study, we tried to compare the in-hospital outcome of TAP repair using PTFE patch and glutaraldehyde-fixed pericardial patch.
PTFE is chemically composed of carbon chains saturated with fluorine. Its medical use began with its application in artificial heart valves in the early 1960s. The PTFE molecule is biostable, and the implant made from it does not undergo biological deterioration within the body. The surface of PTFE is electronegative, which minimizes its reaction with blood components. These physical aspects of PTFE correlate with some of the biological properties, such as low thrombogenicity. The advantages of PTFE are surface modification, tissue ingrowth into the prostheses, good surgical handling, low porosity rate 85%–95%, and low immunogenicity. Disadvantages are pseudointimal hyperplasia at the anastomotic site, and uncommonly, calcification.,
In the present study, we were able to find a weak difference in the inotropic score between the usage of glutaraldehyde-fixed pericardial patch and PTFE patch for reconstruction of RVOT. Other than this finding, there was no significant difference between the two groups. This may be because of the favorable mechanical property of the PTFE patch and the early recovery of the myocardial function because of these properties. However, the re-exploration rate following placement of a PTFE patch was more than that of the pericardial patch (6 against 1). This may be due to the issue of needle hole bleeding in PTFE patch. This problem can be tackled with using a smaller size needle or PTFE suture.
In the present study, only two patients had postoperative right ventricular dysfunction as given by a TAPSE Z score <−2 SD and also reduced FAC of RV. Both these patients had intense preoperative cyanosis as the additional risk factor. One of them had a postoperative gradient of 30 mm Hg across RVOT, and the other had a gradient of 18 mm Hg. Both of them had moderate only PR. As we could not show an association between any anatomic or physiological variable and progression of PR, we assume that progression of PR is an inexorable process, mainly related to the RVOT dynamics, such as an increase in RVOT diameter with time. However, the PTFE patch may be advantageous in the long term because it is expected to provide a more rigid anterior wall resistant to dilatation and thus could theoretically limit PR progression and deterioration of RV function.
The sample size was limited and conclusions regarding predictors of adverse outcome cannot be reliably drawn from this small study group. We did not have any follow-up of the progression of PR in these patients. We plan to continue this study over the mid and long term to elucidate these issues further.
| Conclusion|| |
RVOT reconstruction during TOF repair can safely be performed using a PTFE patch with results similar to an autologous patch of glutaraldehyde treated pericardium. Its results in the mid and long term need further evaluation.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Table 1], [Table 2], [Table 3], [Table 4]
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