Concept of an expandable cardiac valve for surgical implantation in infants and children

In Vitro Proof of Concept of a First-Generation Growth-Accommodating Heart Valved Conduit for Pediatric Use

Currently available heart valve prostheses have no growth potential, requiring children with heart valve diseases to endure multiple valve replacement surgeries with compounding risks. This study demonstrates the in vitro proof of concept of a biostable polymeric trileaflet valved conduit designed for surgical implantation and subsequent expansion via transcatheter balloon dilation to accommodate the growth of pediatric patients and delay or avoid repeated open-heart surgeries. The valved conduit is formed via dip molding using a polydimethylsiloxane-based polyurethane, a biocompatible material shown here to be capable of permanent stretching under mechanical loading. The valve leaflets are designed with an increased coaptation area to preserve valve competence at expanded diameters. Four 22 mm diameter valved conduits are tested in vitro for hydrodynamics, balloon dilated to new permanent diameters of 23.26 ± 0.38 mm, and then tested again. Upon further dilation, two valved conduits sustain leaflet tears, while the two surviving devices reach final diameters of 24.38 ± 0.19 mm. After each successful dilation, the valved conduits show increased effective orifice areas and decreased transvalvular pressure differentials while maintaining low regurgitation. These results demonstrate concept feasibility and motivate further development of a polymeric balloon-expandable device to replace valves in children and avoid reoperations.

Pediatric pulmonary valve replacements: Clinical challenges and emerging technologies

Congenital heart diseases (CHDs) frequently impact the right ventricular outflow tract, resulting in a significant incidence of pulmonary valve replacement in the pediatric population. While contemporary pediatric pulmonary valve replacements (PPVRs) allow satisfactory patient survival, their biocompatibility and durability remain suboptimal and repeat operations are commonplace, especially for very young patients. This places enormous physical, financial, and psychological burdens on patients and their parents, highlighting an urgent clinical need for better PPVRs. An important reason for the clinical failure of PPVRs is biofouling, which instigates various adverse biological responses such as thrombosis and infection, promoting research into various antifouling chemistries that may find utility in PPVR materials. Another significant contributor is the inevitability of somatic growth in pediatric patients, causing structural discrepancies between the patient and PPVR, stimulating the development of various growth-accommodating heart valve prototypes. This review offers an interdisciplinary perspective on these challenges by exploring clinical experiences, physiological understandings, and bioengineering technologies that may contribute to device development. It thus aims to provide an insight into the design requirements of next-generation PPVRs to advance clinical outcomes and promote patient quality of life.

Transcatheter Heart Valves: A Biomaterials Perspective

Heart valve disease is prevalent throughout the world, and the number of heart valve replacements is expected to increase rapidly in the coming years. Transcatheter heart valve replacement (THVR) provides a safe and minimally invasive means for heart valve replacement in high-risk patients. The latest clinical data demonstrates that THVR is a practical solution for low-risk patients. Despite these promising results, there is no long-term (>20 years) durability data on transcatheter heart valves (THVs), raising concerns about material degeneration and long-term performance. This review presents a detailed account of the materials development for THVRs. It provides a brief overview of THVR, the native valve properties, the criteria for an ideal THV, and how these devices are tested. A comprehensive review of materials and their applications in THVR, including how these materials are fabricated, prepared, and assembled into THVs is presented, followed by a discussion of current and future THVR biomaterial trends. The field of THVR is proliferating, and this review serves as a guide for understanding the development of THVs from a materials science and engineering perspective.

Acute and Short-Term Outcomes of Percutaneous Transcatheter Mitral Valve Replacement in Children

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Expandable Valves, Annuloplasty Rings, Shunts, and Bands for Growing Children

In congenital heart surgery, the surgeon must constantly consider how a palliative or corrective procedure could be impacted by the child's somatic growth. Within pediatric valve surgery, existing valve repair techniques lack growth-accommodating prostheses. Valve replacement options are fixed in size and unable to grow with the child, thus subjecting children to repeated valve reoperations. When creating a systemic-to-pulmonary artery shunt, replacing a branch pulmonary artery or conduit, creating an extracardiac Fontan pathway, or banding the pulmonary artery, the implant size must factor in both the child's current size and his or her anticipated growth. A variety of growth-accommodating technologies have been developed to fill this unmet need. Some devices have reached the clinical arena, while several are in preclinical development. The purpose of this review is to characterize the clinical need for growing device technology, and then review established and developing technologies for growth accommodation in congenital heart surgery.

Melody valve to replace the mitral valve in small children: Lessons learned

Objective:

Infants requiring mitral valve replacement have few viable options. Recently, stented bovine jugular vein graft (Melody) has been surgically implanted in such cases. Herein, we report our experience, elaborating on evolution of implantation technique, pitfalls, as well as long-term outcome (including late dilatability).

Methods:

Seven Melody valves were implanted (2013–2019). The median patient age and weight were 6.7 (1.8–30.5) months and 5.8 (4.6–9.5) kg, respectively. The indications for implantation were mitral stenosis and/or regurgitation postatrioventricular septal defect (AVSD) repair (5), congenital mitral valve dysplasia (1), and Shone's complex (1). Operative technique involved shortening the valve and creating a neo-sewing ring at 2/3 (atrial)–1/3 (ventricular) junction. Implantation was followed by intraoperative balloon dilatation.

Results:

Five out of seven patients survived the perioperative period (one death due to technical failure and the other due to acute respiratory distress syndrome postcardiopulmonary bypass). Two out of five medium-term survivors got transplanted (1) or died due to acute myeloid leukemia (1). No valves were replaced. The mean echo gradient at discharge was a median 4 (2–6) mmHg. None of the patients showed left ventricular outflow tract or pulmonary venous obstruction. Two Melody valves were dilated late (5 months and 3 years postoperatively), resulting in decreasing mean gradients from 6 to 1 and from 17 to 4 mmHg. At last follow-up, surviving Melody had a mean gradient of 4 (1–9) mmHg.

Conclusions:

Mitral valve replacement with a Melody valve is feasible in infants, is reproducible, shows good immediate results, and offers the possibility of later dilatation. This technique offers a better solution compared to the existing alternatives for infants requiring a prosthetic mitral valve.

Replacement of the Mitral Valve Under One Year of Age: Size Matters

Surgical management of mitral valve disease in neonates and infants is challenging. When repair is no longer feasible, replacement may become inevitable, but should only be considered as an option of last resort due to the remarkably high rate of associated morbidity and mortality. Mechanical valves are the preferred choice in large annuli, while stented conduits seem promising in smaller ones. In patients with a preoperative mitral valve annulus equal or larger than 15-16 mm, an intra-annular placement of the smallest mechanical valve available should be attempted. In patients with smaller annuli, the placement of a stented valved conduit seems to display a lower mortality risk. Supra-annular implantation of prostheses should be reserved for exceptional cases and to those familiar with this technique because of the high rate of associated complications.

Experience and Outcomes of Surgically Implanted Melody Valve in the Pulmonary Position

BACKGROUND

Multiple congenital cardiac malformations require pulmonary valve replacement and/or right ventricular outflow (RVOT) reconstruction. Pulmonary valve replacement remains challenging in children owing to the limited growth potential of prosthetic valves. We evaluated outcomes in patients undergoing surgical implantation of a Melody valve in the RVOT.

METHODS

Data were retrospectively collected for 23 patients undergoing surgical Melody valve implantation at Boston Children's Hospital between 2009 and 2019. We assessed postoperative valve function, reintervention rates, and mortality.

RESULTS

Median age was 1.7 years (range, 2 months to 6 years); 12 patients were aged greater than 2 years (52%). Diagnosis was tetralogy of Fallot in 15 patients (65%); 15 had a prior RVOT operation (65%). The Melody valve was dilated before surgery to a median diameter of 14 mm (range, 10-20 mm). No patients had acute pulmonary regurgitation. One required transcatheter RVOT reintervention before discharge. Median follow-up was 3.7 years (range, 0.02-8.7 years) with moderate or greater pulmonary regurgitation in 2 patients. Catheter-based interventions (mean, 0.83 ± 1.07/patient) occurred at a median of 1 year (range, 16 days to 5.4 years) and included valve expansion for somatic growth (n = 10) and subsequent valve-in-valve replacement (n = 3). Three patients (13%) required surgical valve explant or replacement at a median of 1.0 year (range, 0.6-3.7 years) for Melody-specific indications. One-, 3-, and 5-year freedom from Melody-driven reoperation was 90%, 90%, and 83%, respectively.

CONCLUSIONS

The Melody valve can be surgically implanted in the RVOT of young patients with acceptable early results. These valves can be successfully dilated through transcatheter reintervention to accommodate growth.

Surgical Atrioventricular Valve Replacement With Melody Valve in Infants and Children

Background Pediatric patients with atrioventricular valve disease have limited options for prosthetic valve replacement in sizes <15 mm. Based on successful experience with the stented bovine jugular vein graft (Melody valve) in the right ventricular outflow tract, the prosthesis has been modified for surgical valve replacement in pediatric patients with atrioventricular dysfunction with the intention of subsequent valve expansion in the catheterization laboratory as the child grows. Methods and Results A multicenter, retrospective cohort study was performed among patients who underwent atrioventricular valve replacement with Melody valve at 17 participating sites from North America and Europe, including 68 patients with either mitral (n=59) or tricuspid (n=9) replacement at a median age of 8 months (range, 3 days to 13 years). The median size at implantation was 14 mm (range, 9-24 mm). Immediately postoperatively, the valve was competent with low gradients in all patients. Fifteen patients died; 3 patients underwent transplantation. Nineteen patients required reoperation for adverse outcomes, including valve explantation (n=16), left ventricular outflow tract obstruction (n=1), permanent pacemaker implantation (n=1), and paravalvular leak repair (n=1). Twenty-five patients underwent 41 episodes of catheter-based balloon expansion, exhibiting a significant decrease in median gradient ( P<0.001) with no significant increase in grade of regurgitation. Twelve months after implantation, cumulative incidence analysis indicated that 55% of the patients would be expected to be free from death, heart transplantation, structural valve deterioration, or valve replacement. Conclusions The Melody valve is a feasible option for surgical atrioventricular valve replacement in patients with hypoplastic annuli. The prosthesis shows acceptable short-term function and is amenable to catheter-based enlargement as the child grows. However, patients remain at risk for mortality and structural valve deterioration, despite adequate early valvular function. Device design and implantation techniques must be refined to reduce complications and extend durability. Clinical Trial Registration URL: https://www.clinicaltrials.gov. Unique identifier: NCT02505074.

Handmade trileaflet valve design and validation for patch-valved conduit reconstruction using generalized regression machine learning model

Pulmonary valve diseases include the different degrees of aortic stenosis or congenital defects in children or adults. Valve repair or replacement surgery is commonly performed to relieve valvular dysfunction and improve the significant flow regurgitation in the aortic valve and the pulmonary valve. However, commercial valve stents and valved conduits are sometimes not available for children or patients with special conditions. The handmade trileaflet valve design has been used with different range of diameters for patch-valved conduit reconstruction. Thus, we propose a multiple regression model, as a generalized regression neural network (GRNN), to determine the optimal trileaflet parameters, including the width, length, and upper lower curved structure. Through computed tomography pulmonary angiography, while the diameter of the main pulmonary artery is determined, a leaflet template can be rapidly sketched and made. Using an experimental pulmonary circulation loop system, the efficacy of the valved conduit can be validated using the regurgitation fraction method. In contrast to commercial valve stents, experimental results indicate that the handmade trileaflet valve can also improve severe pulmonary regurgitations.

First Surgical Melody Valve-In-Valve Implantation for Early Degeneration in Mitral Position

Congenital mitral valve disease is a real challenge in infants and small children. The implantation of expandable stented valves in mitral position has become one of the options of choice in consideration of their acceptable short-term expandable durability and subsequent feasibility of balloon expansion of these devices. We report the first case of a surgical Melody valve-in-valve procedure for early Melody valve degeneration in the mitral position. The result was good, and the procedure safe, rapid, and without an increased risk when a mechanical valve implantation will be necessary.

Insufficiency of a Damus-Kaye-Stansel anastomosis in a Fontan patient: Transfemoral implantation of an Edwards Sapien 3 valve

We present a 22-year-old patient with a univentricular heart who had already undergone five open heart surgeries including a Damus-Kaye-Stansel procedure, Fontan completion and tricuspid valve replacement. In addition, epimyocardial pacemaker implantation and repeated revisions had been necessary. He developed symptomatic free regurgitation of the pulmonary portion of his DKS anastomosis. To avoid additional high-risk open-heart surgery, we successfully implanted an Edwards Sapien 3 valve transfemorally in the pulmonary portion of the DKS anastomosis relieving insufficiency.

Per-Ventricular Insertion of Melody Valve-in-Valve in the Neoaortic Position in a Single-Ventricle Patient

Percutaneous therapies for congenital heart disease have been evolving rapidly despite limited investment from industry. The Melody transcatheter pulmonary valve (Medtronic, Inc, Minneapolis, MN USA) replacement therapy represents an important advancement in this arena. It has been approved in the United States for use in the pulmonary position, on a Humanitarian Device Exemption status. Off-label use of the Melody transcatheter pulmonary valve has extended to the mitral, pulmonary, and aortic valves, especially in previously implanted valves with prosthetic valve degeneration. The single-ventricle patient poses additional challenges. However, there exists one report in the English literature of a patient undergoing Melody transcatheter neoaortic valve replacement after the patient developed severe neoaortic regurgitation after Fontan palliation. Here, we describe a patient with hypoplastic left heart syndrome, palliated with a Norwood modified Blalock-Taussig shunt, with a progressively regurgitant quadricusp neoaortic valve who underwent bioprosthetic valve replacement. There was early prosthetic valve degeneration after a year of bioprosthesis implantation. As he was declined for transplantation, he underwent successful perventricular Melody valve-in-valve replacement.

The ordeal of left atrioventricular valve replacement in children under 1 year of age

OBJECTIVES

This study reviews the outcomes of children under 1 year of age who had left atrioventricular valve (LAVV) replacement (LAVVR) in one centre and explores the benefits of an innovative approach for LAVVR in very small patients.

METHODS

Thirteen consecutive patients operated for LAVV replacement between 1997 and 2016 were reviewed retrospectively. Indication for surgery was regurgitation in 7, stenosis in 5 and both stenosis and regurgitation in 1. Nine patients (69%) had previous LAVV repair. Median age at surgery was 126 days (39-327 days). In the primary surgery, 7 mechanical valves and 1 mitral homograft were implanted. Five inverted semilunar valve conduits were implanted consisting of a Contegra valve in 4 and a pulmonary homograft in 1.

RESULTS

Hospital mortality was 31% (4 of 13). Two patients required postoperative extracorporeal membrane oxygenation. Six patients developed complete atrioventricular block, with 2 survivors requiring a pacemaker. Late mortality was 31% (4 of 13). Two of the 4 patients who received an inverted Contegra conduit died. Median follow-up of the 5 survivors was 4 years (2-16 years). Four patients had 10 further replacements consisting of 6 redo conventional mechanical valves replacement, 3 supra-annular valve implantation, and 1 modified Ross II. The 5 inverted semilunar valve conduits implanted lasted for 1, 5, 6, 22 and 37 months.

CONCLUSIONS

LAVVR below 1 year of age is associated with a considerable operative and late mortality. LAVVR with an inverted conduit bearing semilunar valves may be an alternative strategy for patients with the smallest annuli.

Transcatheter pulmonary valve implantation: valve technology and procedural outcome

PURPOSE OF REVIEW

Procedural technique and short-term outcomes of transcatheter pulmonary valve implantation (TPVI) have been widely described. The purpose of this article is to provide an update on current valve technology, and to focus on recent data surrounding TPVI in the dilated right ventricular outflow tract (RVOT), hybrid interventions, significant outcomes, and procedural costs.

RECENT FINDINGS

Transcatheter valve technology has expanded with current trials evaluating self-expandable valves that can be implanted in dilated RVOTs. Until those valves are widely available, hybrid techniques have been shown to offer a potential alternative in these patients, as well as in patients of small size. Although medium-term results of TPVI have shown 5-year freedom from reintervention or replacement of 76%, new data have underlined some concerns relating to bacterial endocarditis after the procedure. Procedural costs remain a concern, but vary greatly between institutions and healthcare systems.

SUMMARY

TPVI has emerged as one of the most innovative procedures in the treatment of patients with dysfunctional RVOT and pulmonary valves. Further device development is likely to expand the procedure to patients of smaller size and with complex, dilated RVOTs.