Modification of expanded polytetrafluoroethylene valved conduit using the thin-type leaflets

Handmade Bicuspid Valved Polytetrafluoroethylene Conduit for Right Ventricular Outflow Tract Reconstruction

Background: Excellent outcomes of right ventricle to pulmonary artery conduits with polytetrafluoroethylene (PTFE) valves have been reported. The purpose of this study was to analyze the short-term results of our handmade PTFE bicuspid valved conduit (VC) for right ventricular outflow tract reconstruction. Methods: Between September 2019 and May 2023, bicuspid PTFE-VC was implanted in 17 patients at a median age of 2.5 years (range, 3 months to 13.6 years). The PTFE-VC was fashioned from a commercially available PTFE tube graft (14 mm in three patients, 16 mm in three patients, 18 mm in one patient, 20 mm in three patients, and 22 mm in seven patients) and 0.1 mm thick PTFE membrane for the leaflet material. Valve function was assessed by echocardiogram after the implantation. The conduit reoperation and the conduit dysfunction were analyzed. There were no early deaths, but there was one late death. Results: There were no postoperative in-hospital deaths. Follow-up echocardiograms were available for 14 of 17 patients. The median follow-up was 21 months (range, 7-49 months). Conduit stenosis was none or trivial in 11 patients while it was mild in two and moderate in one patient and severe in 0 patients. Conduit insufficiency was mild or trivial in all 14 patients. By the end of the study period, freedom from reoperation/reintervention was 100%. There were no episodes of aneurysmal dilatation of the conduit or endocarditis. Conclusions: Handmade bicuspid PTFE VC shows good short-term outcome, with no significant valve dysfunction and no reintervention. A longer follow-up is necessary to evaluate the long-term advantages of using the handmade bicuspid PTFE VC.

Polymeric Heart Valves Will Displace Mechanical and Tissue Heart Valves: A New Era for the Medical Devices

The development of a novel artificial heart valve with outstanding durability and safety has remained a challenge since the first mechanical heart valve entered the market 65 years ago. Recent progress in high-molecular compounds opened new horizons in overcoming major drawbacks of mechanical and tissue heart valves (dysfunction and failure, tissue degradation, calcification, high immunogenic potential, and high risk of thrombosis), providing new insights into the development of an ideal artificial heart valve. Polymeric heart valves can best mimic the tissue-level mechanical behavior of the native valves. This review summarizes the evolution of polymeric heart valves and the state-of-the-art approaches to their development, fabrication, and manufacturing. The review discusses the biocompatibility and durability testing of previously investigated polymeric materials and presents the most recent developments, including the first human clinical trials of LifePolymer. New promising functional polymers, nanocomposite biomaterials, and valve designs are discussed in terms of their potential application in the development of an ideal polymeric heart valve. The superiority and inferiority of nanocomposite and hybrid materials to non-modified polymers are reported. The review proposes several concepts potentially suitable to address the above-mentioned challenges arising in the R&D of polymeric heart valves from the properties, structure, and surface of polymeric materials. Additive manufacturing, nanotechnology, anisotropy control, machine learning, and advanced modeling tools have given the green light to set new directions for polymeric heart valves.

Early Outcome of Simplified Standardized Trileaflet Polytetrafluoroethylene Valved Conduit Placement

Background

Use of the expanded polytetrafluoroethylene (ePTFE) valved conduit in the pulmonary position during the correction of congenital heart defects has significantly increased in popularity over the last decade due to its promising conduit longevity. We describe the standardized process to create and implant a trileaflet ePTFE pulmonary conduit along with the early outcomes of such procedures at our institute.

Methods

Records of 100 consecutive patients who underwent ePTFE valved conduit placement using our technique from April 2018 through February 2022 were retrospectively analyzed. The function of the conduit was evaluated by transthoracic echocardiography.

Results

The mean age of the patients was 28 ± 13.2 years old at the time of the operation. The conduit diameters ranged from 16 to 24 mm (mean 23.0 ± 1.9 mm). Conduit placement was utilized for pulmonary valve replacement in 68 patients, conduit change in 25 patients, and as a part of total repair in 7 patients. There were 2 in-hospital conduit-unrelated deaths from multi-organ dysfunction and pulmonary hypertensive crisis. From the postoperative echocardiography, the average peak pressure gradient across the conduit was 18.6 ± 9.0 mm Hg, and the conduit regurgitation was graded as none or trace in 81 patients, mild in 17 patients, and moderate in 2 patients. At 589 days of median follow-up, there was no conduit reoperation. Follow-up imaging of 60 available patients at a median time of 511 days did not show a significant change in conduit function.

Conclusions

Our standardized ePTFE valved conduit creation and placement demonstrated satisfactory clinical and echocardiographic outcomes.

Midterm Outcomes for Polytetrafluoroethylene Valved Conduits

BACKGROUND

Various conduits for right ventricular outflow tract reconstruction have been reported, but most of them are not available in China. The study investigators developed a simple handsewn valved conduit using expanded polytetrafluoroethylene (ePTFE). This study evaluated the midterm outcomes for this conduit.

METHODS

This retrospective study included a total of 72 patients who underwent right ventricular outflow tract reconstruction with ePTFE valved conduits between January 2014 and June 2020. During follow-up, echocardiograms were performed for all patients, and magnetic resonance imaging was performed for patients with repaired tetralogy of Fallot.

RESULTS

Patients had a median age of 69 months (interquartile range, 28-127 months) and a median follow-up period of 33 months (interquartile range, 9-51 months). There was no early death, but 2 late deaths (2.78%) occurred. The median conduit size was 18 mm (interquartile range, 18-20 mm) and the z score was +1.3 (interquartile range, +0.6-+2). Peak velocity across the ePTFE valve was 2.38 m/s (95% CI, 2.11-2.63 m/s). Pulmonary valve regurgitation was none or trivial in 27 (38.5%) patients, mild in 42 (60.0%) patients, and moderate in 1 (1.4%) patient. Conduit dysfunction occurred in 5 patients: 4 had moderate conduit stenosis, and 1 had moderate regurgitation. The right ventricular end-diastolic volume index in repaired tetralogy of Fallot was significantly decreased after surgery (171 mL/m2 vs 130 mL/m2; P < .001). No reintervention or conduit replacement was needed.

CONCLUSIONS

This handsewn ePTFE valved conduit was associated with appreciable hemodynamic outcomes during the midterm follow-up period. Long-term follow-up studies are needed to corroborate these findings.

Decellularized bovine jugular vein and hand-sewn ePTFE valved conduit for right ventricular outflow tract reconstruction in children undergoing Ross procedure

Background

The Ross procedure is recommended as an optimal aortic valve replacement (AVR) in children and young adults due to several advantages. Nevertheless, multiple reconstructions of the right ventricular outflow tract (RVOT) with new valve conduits have caused some concern regarding the durability of the Ross AVR. Decellularized bovine jugular vein conduit (BJVC) (DP-BJVC) and hand-sewn expanded polytetrafluoroethylene valved conduits (ePTFE VC) are widely employed to reconstruct the RVOT with satisfactory long-term outcomes. However, few studies have compared the safety and efficacy between the two valve conduits. We aimed to evaluate the early outcomes and report our single center experience in the application of these conduits.

Methods

Twenty-two pediatric patients (aged &lt; 18 years) who underwent Ross procedures with DP-BJVC and ePTFE VC in our center between 1 June, 2017 and 31 January, 2022 were enrolled. The Kaplan–Meier method was used to evaluate survival, freedom from RVOT reintervention, and freedom from RVOT graft dysfunction. Mixed-effects analysis with the Geisser–Greenhouse correction and Sidak's multiple comparisons test for post-hoc analysis was employed to compare the peak gradient across the conduit at varying follow-ups.

Results

All patients were followed up in full. The total early survival rate was 90.9%; two patients in the DP-BJVC group died. There was no significant difference in early mortality, cross-clamp time (p = 0.212), in-hospital stay (p = 0.469), and RVOT graft thrombosis or endocarditis between the two groups. There was similarly no significant difference between Kaplan–Meier freedom from RVOT graft dysfunction curve (P = 0.131). The transprosthetic gradient gradually increased over time in both groups and was significantly higher in the DP-BJVC group at follow-up (P &lt; 0.05).

Conclusions

Both conduits show excellent early and midterm outcomes for RVOT reconstruction in the Ross procedure. We suggest that DP-BJVC is more suitable for infants, and ePTFE conduit is more suitable for older children who require larger conduits.

Handmade tri-leaflet ePTFE conduits versus homografts for right ventricular outflow tract reconstruction

BACKGROUND

This study aimed to investigate the performance of handmade tri-leaflet expanded polytetrafluoroethylene (ePTFE) conduits in the absence of a suitable homograft.

METHODS

Patients who underwent right ventricular outflow tract reconstruction with tri-leaflet ePTFE conduits or homografts between December 2016 and August 2020 were included. The primary endpoint was the incidence of moderate or severe conduit stenosis (≥ 36 mmHg) and/or moderate or severe insufficiency. The secondary endpoint was the incidence of severe conduit stenosis (≥ 64 mmHg) and/or severe insufficiency.

RESULTS

There were 102 patients in the ePTFE group and 52 patients in the homograft group. The median age was younger [34.5 (interquartile range: 20.8-62.8) vs. 60.0 (interquartile range: 39.3-81.0) months, P = 0.001] and the median weight was lower [13.5 (10.0-19.0) vs. 17.8 (13.6-25.8) kg, P = 0.003] in the ePTFE group. The conduit size was smaller (17.9 ± 2.2 vs. 20.5 ± 3.0 mm, P < 0.001) and the conduit Z score was lower (1.48 ± 1.04 vs. 1.83 ± 1.05, P = 0.048) in the ePTFE group. There was no significant difference in the primary endpoints (log rank, P = 0.33) and secondary endpoints (log rank, P = 0.35). Multivariate analysis identified lower weight at surgery [P = 0.01; hazard ratio: 0.75; 95% confidence interval (CI) 0.59-0.94] and homograft conduit use (P = 0.04; hazard ratio: 8.43; 95% CI 1.14-62.29) to be risk factors for moderate or severe conduit insufficiency. No risk factors were found for moderate or severe conduit stenosis or conduit dysfunction on multivariate analysis.

CONCLUSION

Handmade tri-leaflet ePTFE conduits showed acceptable early and midterm outcomes in the absence of a suitable homograft, but a longer follow-up is needed.

Conduits for Right Ventricular Outflow Tract Reconstruction in Infants and Young Children

Purpose of Review: Right ventricular outflow tract (RVOT) reconstruction remains a challenge due to the lack of an ideal conduit. Data and experience are accumulating with each passing day. Therefore, it is necessary to review this topic from time to time. This is a 2021 update review focused on the history, evolution, and current situation of small-sized conduits (≤ 16 mm) for RVOT reconstruction in infants and young children.

Recent Findings: Currently, the available small-sized (≤16 mm) conduits can meet most clinical needs. Homograft is still a reliable choice for infants and young children validated by a half-century clinical experience. As an alternative material, bovine jugular vein conduit (BJVC) has at least comparable durability with that of homograft. The performance of expanded polytetrafluoroethylene (ePTFE) is amazing in RVOT position according to limited published data. The past century has witnessed much progress in the materials for RVOT reconstruction. However, lack of growth potential is the dilemma for small-sized conduits. Tissue-engineering based on cell-free scaffolds is the most promising technology to obtain the ideal conduit.

Summary: No conduit has proved to have lifelong durability in RVOT position. We are far from the ideal, but we are not in a state of emergency. In-depth clinical research as well as innovation in material science are needed to help improve the durability of the conduits used in infants and young children.

Evolution of pulmonary valve reconstruction with focused review of expanded polytetrafluoroethylene handmade valves

OBJECTIVES

Many surgeons develop unique techniques for unmet needs for right ventricular outflow reconstruction to resolve pulmonary regurgitation after corrective surgery for congenital heart diseases. Expanded polytetrafluoroethylene (ePTFE) stands out as a reliable synthetic material, and clinical results with handmade ePTFE valves have been promising. This review focuses on the historical evolution of the use of ePTFE in pulmonary valve replacement and in the techniques for pioneering the translation of the handmade ePTFE trileaflet design for the transcatheter approach.

METHODS

We searched for and reviewed publications from 1990 to 2020 in the Pubmed database. Nineteen clinical studies from 2005 to 2019 that focused on ePTFE-based valves were summarized. The evolution of the ePTFE-based valve over 3 decades and recent relevant in vitro studies were investigated.

RESULTS

The average freedom from reintervention or surgery in the recorded ePTFE-based valve population was 90.2% at 5 years, and the survival rate was 96.7% at 3 years.

CONCLUSIONS

Non-inferior clinical results of this ePTFE handmade valve were revealed compared to allograft or xenograft options for pulmonary valve replacement. Future investigations on transferring ePTFE trileaflet design to transcatheter devices should be considered.

Right Ventricle to Pulmonary Artery Conduit With Tricuspid Expanded Polytetrafluoroethylene Valves

BACKGROUND

Excellent outcomes of right ventricle to pulmonary artery conduits with expanded polytetrafluoroethylene (ePTFE) valves have been reported. The purpose of this study was to evaluate the outcomes of the different material conduits with tricuspid ePTFE valves.

METHODS

Forty-one consecutive patients who received right ventricle to pulmonary artery conduit with tricuspid ePTFE valves for biventricular repair between April 2004 and December 2016 were studied. The conduits made of autologous pericardial roll or xenograft roll were used in 22 patients (group P) and the conduits made of ePTFE tube were used in 19 patients (group G). The conduit reoperation and the conduit dysfunction were analyzed.

RESULTS

During the median follow-up of 5.8 years, no death related to the conduit was observed. There were four reoperations (three in group P and one in group G). Freedom from conduit reoperation at 5 years was 100% in both groups (P = .30). Freedom from more than moderate conduit stenosis at 5 years after operation was not significantly different between groups (46.9% in group P vs 76.3% in group G, P = .23) even though the group G conduits were significantly smaller and freedom from more than moderate conduit regurgitation at 5 years was significantly better in group G (63.3% in group P vs 94.1% in group G, P = .04).

CONCLUSIONS

The conduit with ePTFE valves in the ePTFE tubes had better conduit function compared with the conduit with autologous pericardial or xenograft roll, especially in terms of conduit regurgitation.

In vitro Assessment of the Impacts of Leaflet Design on the Hemodynamic Characteristics of ePTFE Pulmonary Prosthetic Valves

Prosthetic pulmonary valves are widely used in the management procedures of various congenital heart diseases, including the surgical pulmonary valve replacement (PVR) and right ventricular outflow tract reconstruction (RVOT). The discouraging long-term outcomes of standard prostheses, including homografts and bioprosthetic, constrained their indications. Recent developments in the expanded-polytetrafluoroethylene (ePTFE) pulmonary prosthetic valves provide promising alternatives. In this study, the hemodynamic characteristics of bileaflet and trileaflet ePTFE valve designs were experimentally evaluated. The in vitro tests were performed under the right ventricle (RV) flow conditions by using an in vitro RV circulatory system and particle image velocimetry (PIV). The leaflet kinetics, trans-valvular pressure gradients, effective orifice areas, regurgitant fractions, energy losses, velocity fields, and Reynolds shear stress (RSS) in both prostheses were evaluated. The opening of the bileaflet and trileaflet valve takes 0.060 and 0.088 s, respectively. The closing of the former takes 0.140 s, in contrast to 0.176 s of the latter. The trans-valvular pressure is 6.8 mmHg in the bileaflet valve vs. 7.9 mmHg in the trileaflet valve. The effective orifice area is 1.83 cm2 in the bileaflet valve and 1.72 cm2 in the trileaflet valve. The regurgitant fraction and energy loss of bileaflet are 7.13% and 82 mJ, which are 7.84% and 101.64 mJ in its bileaflet counterpart. The maximum RSS of 48.0 and 49.2 Pa occur at the systole peak in the bileaflet and trileaflet valve, respectively. A higher average RSS level is found in the bileaflet valve. The results from this preliminary study indicate that the current bileaflet prosthetic valve design is capable of providing a better overall hemodynamic performance than the trileaflet design.

Histopathologic Analysis of Explanted Polytetrafluoroethylene-Valved Pulmonary Conduits

The expanded polytetrafluoroethylene (ePTFE)-valved conduits as alternative material for right ventricular outflow reconstruction provides satisfactory long-term outcomes. The purpose of this study was to investigate degenerative changes in failed conduits through histopathologic analysis of the explanted specimens. All leaflets of explanted conduits were observed macroscopically, and their longitudinal sections were examined microscopically. Three typical findings, that is, calcification of the leaflet, neointimal proliferation, and proteinaceous infiltration into the leaflet, were evaluated quantitatively by measuring their degree and appearance probability. A total of 15 leaflets from 5 failed conduits (group F) and 12 leaflets from 5 nonfailed conduits (group non-F) were included. The median duration of implantation was 7.6 years (5.3-10.9 years) in group F and 1.3 years (0.7-3.9 years) in group non-F (P = 0.003). In group F, calcification tended to occur in the middle and upper third of the leaflet, causing stiffening, distortion, and exophytic concretion of the leaflet, and mean neointimal thickness on inflow and outflow surfaces were 0.33 ± 0.02 mm and 0.22 ± 0.01 mm, respectively. There was a moderately strong correlation between appearance probability of calcification in group F and that of proteinaceous infiltration in group non-F (correlation coefficient 0.67, P < 0.001). Proteinaceous infiltration into the leaflet was presumed be responsible for future calcification of the leaflet and subsequent stenotic conduit failure. Modification of the ePTFE material to prevent proteinaceous infiltration may contribute to improving the durability of ePTFE-valved conduit.