Biological versus mechanical aortic valve replacement in children

Complexity and Outcome of Reoperations After the Ross Procedure in the Current Era

BACKGROUND

The Ross procedure has several advantages, but the need for reintervention is inevitable. The aim of this study was to examine the complexity and outcomes of reoperation after the Ross procedure.

METHODS

Retrospective chart review was performed of patients with a prior Ross procedure who underwent reoperation at our institution from September 1991 to January 2021. Demographic, echocardiographic, surgical, and perioperative data were collected. Descriptive statistical and regression analyses were performed.

RESULTS

A total of 105 patients underwent a reoperation at Mayo Clinic after the initial Ross procedure performed at our institution (n = 16; 16.2%) or elsewhere (n = 83; 83.8%). Mean age at the Ross procedure was 27 ± 17 years, and mean age at reoperation at our institution was 37 ± 19 years. Indications for surgical procedure varied, but 64% had autograft regurgitation as 1 of their indications for reoperation. Autograft interventions were performed in 78 patients (74.2%). Pulmonary valve or conduit replacement was performed in 56 patients (53.3%). Double root replacement was performed in 11 patients (10.5%). Aortic reconstruction was performed in 37 patients (38.4%). There were 5 early deaths (5%). During a median follow-up of 6.25 years (3 months-24 years), late deaths occurred in 14 patients (13.1%). Patients with ejection fraction <30% on preoperative echocardiography had shorter duration between the Ross procedure and subsequent reoperation (P = .03).

CONCLUSIONS

Reoperations after the Ross procedure are performed for a wide range of indications, with most due to autograft dysfunction. The number of early deaths is not low. Reoperation after the Ross procedure should be advised before left ventricular systolic dysfunction.

[Prosthetic repair of aortic valve cusps with autopericardium in children. State of the art and prospects]

According to the results of modern researchers, the main techniques used in congenital pathology of the aortic valve in children include balloon catheter dilatation of the aortic valve, surgical valvuloplasty, the Ross procedure and replacement of the aortic valve with a mechanical prosthesis. Many surgeons point out that these techniques in congenital pathology of the aortic valve yield suboptimal results. This is often due to the lack of a clear-cut definition between surgeons as to what operation should be performed in a particular age group. According to the reports of the majority of researchers, biological prostheses undergo early degeneration and structural changes in paediatric cardiac surgery and yield the worst results. Comparing the main techniques, optimal haemodynamics is observed after the Ross procedure. A disadvantage of this operation is the necessity of repeat intervention on the right ventricular outflow tract, which is required in 20 to 40%. Concomitant surgery of the mitral valve and/or aortic arch during the Ross procedure significantly increases the lethality and the risk of postoperative complications. Compared with an adult cohort of patients, children after prosthetic repair of the aortic valve using a mechanical prosthesis are more often found to have postoperative complications and a higher mortality rate. Yet another problem encountered in paediatric valve surgery is the unavailability of commercial prostheses sized ?19 mm. The duration of the intraoperative parameters for reconstructions of the aortic valve, the Ross procedure, and replacement of the aortic valve by the results of many studies averagely amounts to 74±34 min, 100±56 min, and 129±71 min, respectively. Yet another method which can be used for neocuspidization of the aortic valve in reconstructive surgery of the aortic root in paediatric patients is the use of glutaraldehyde-treated autologous pericardium. In our opinion, given the simplicity of the procedure, duration of the intraoperative parameters, and acceptable initial results reported by some researchers, the Ozaki procedure may be performed in children.

Postoperative morbidity and mortality from aortic valve replacements in 25 cases in Senegal

The purpose is to study the short- and medium-term morbidity and mortality linked to the implantation of an aortic prosthesis during cardiac surgery. This is a longitudinal, retrospective and descriptive study which takes place over a period from January 2017 to March 2020 (38 months) at the level of the thoracic and cardiovascular surgery clinic of the university Hospital Center of Fann in Dakar. All patients who underwent aortic valve replacement during this period were included in the study. A number of the series was 25 patients with a sex ratio of 2.66. The average age of the patients was 29.5 years (8-51 years). In the patients’ history, 19 patients (76%) had a notion of recurrent angina. Exercise dyspnea was the most common functional symptomatology present in 24 patients (96%). In the series, there were 22 cases (88%) of aortic insufficiency of various grades (2 to 4) with 7 cases (28%) associated with mitral insufficiency. We had 3 cases (12%) of aortic stenosis. All patients received surgical management under cardiopulmonary bypass. The average duration of cardiopulmonary bypass was 132 minutes ± 41.21 (53-226 minutes). The average duration of aortic clamping was 101 minutes ± 31.87 (53-164 minutes). The surgical procedures consisted in replacing the aortic valve with a biological prosthesis in one patient (4%) and a mechanical prosthesis in 24 patients (96%). The average length of hospital stay in intensive care was 5 days ± 4.03 (2-20 days). The average length of hospital stay was 20.76 days ± 13.19 (9 to 64 days). The average duration of follow-up was 8.2 months ± 4.57 (1 week - 32 months). During the follow-up, only one patient (4%) had developed infectious endocarditis on prosthesis and only one patient (4%) had a complication related to anticoagulant therapy (antivitamin K) such as gingivorrhagia and melena. We had recorded a single case of death at 6 months, a late mortality of 4%. Aortic valve replacement surgery, by median sternotomy gives satisfactory short- and medium-term results with negligible morbidity and negligible operative mortality.

Primary Aortic Root Replacement Outcomes and Risk Factors in Pediatric Patients

BACKGROUND

The study sought to identify the optimal aortic root replacement (ARR) strategy for pediatric patients, and a single-center experience was analyzed.

METHODS

Retrospective review of patients undergoing ARR from 1995 to 2018 was performed. Patients were stratified by surgical strategy (pulmonary autograft [Ross procedure], aortic homograft, mechanical valve conduit [Bentall procedure], or porcine xenograft [Freestyle bioprosthesis]) and aortic annulus size.

RESULTS

ARR was performed in 206 patients with a median follow-up of 5.0 (interquartile range, 1.4-11.4) years. Root replacements included Ross procedure (n = 98), homograft (n = 83), Bentall procedure (n = 18), and Freestyle bioprosthesis (n = 7). Overall survival was 92%, and freedom from reoperation or death was 81%. Reoperation-free survival was superior in the Ross group when compared with other groups. Because surgical options differ based on the size of the aortic annulus, the analysis was arbitrarily stratified. When the aortic annulus diameter was greater than 19 mm (n = 74), procedures included Ross procedure (n = 23), homograft (n = 29), Bentall procedure (n = 17), and Freestyle bioprosthesis (n = 5). Reoperation-free survival at median follow-up (5 years) was 86%, 58%, 100%, and 100%, respectively. The Bentall procedure offered the longest freedom from reoperation. In the subset with aortic annulus diameter less than 19 mm and a pulmonary valve suitable for a Ross procedure, patients underwent the Ross procedure (n = 75) or homograft ARR (n = 36). At median follow-up (3.8 years), reoperation-free survival was longer after the Ross procedure than after homograft ARR (88% vs 46%; P < .001).

CONCLUSIONS

In patients with a large aortic annulus, a Bentall ARR offers the longest reoperation-free survival. For patients with small aortic roots, a Ross procedure provides better a reoperation-free survival than does homograft ARR.

Current surgical strategies and techniques of aortic valve diseases in children

While the long-term outcome of surgical aortic valvotomy (SAV) appears to be better than that of balloon aortic valvuloplasty (BAV) as the primary procedure of aortic valve stenosis, the surgical strategies and techniques of treating aortic valve disease in children in other situations remain controversial. Valve repair should be first considered while replacement is still unavoidable in some cases, and new repair techniques developed by innovative surgeons are gradually becoming adopted. Some complex repair procedures such as cusp extension, leaflet replacement/reconstruction have provided satisfactory outcomes. The Ozaki technique replaces aortic valve leaflets with glutaraldehyde-treated autologous pericardium instead of replacing the valve entirely. Special instruments have been developed to make the Ozaki technique more reproducible and standardized. Neonates and infants undergoing aortic valve replacement (AVR) are a high-risk group, where repair should be the primary consideration rather than replacement. Several systematic reviews reveal that all currently available aortic valve substitutes such as pulmonary autograft, mechanical prosthesis, homograft and bioprosthesis are associated with suboptimal results in children, but pulmonary autograft appeared to be superior with high freedom from reintervention and better hemodynamic performance. The strategy for treatment of aortic valve disease should be specifically analyzed based on the brief of being beneficial for children.

Umbilical cord as human cell source for mitral valve tissue engineering - venous vs. arterial cells

Around 2% of the population in developed nations are affected by mitral valve disease and available valvular replacements are not designed for the atrioventricular position. Recently our group developed the first tissue-engineered heart valve (TEHV) specifically designed for the mitral position - the TexMi valve. The valve recapitulates the main components of the native valve, i.e. annulus, asymmetric leaflets and the crucial chordae tendineae. In the present study, we evaluated the human umbilical cord as a clinically applicable cell source for the TexMi valve. Valves produced with cells isolated from human umbilical cord veins (HUVs) and human umbilical cord arteries (HUAs) were conditioned for 21 days in custom-made bioreactors and evaluated in terms of extracellular matrix (ECM) composition and mechanical properties. In addition, static cell-laden fibrin discs were molded to investigate cell-mediated tissue contraction and differences in ECM production. HUA and HUV cells were able to deliver functional valves with a rich ECM composed mainly of collagen. Particularly noteworthy was the synthesis of elastin, which has been observed rarely in TEHV. The elastin synthesis was significantly higher in TexMi valves produced with HUV cells and therefore the HUV is considered to be the preferred cell source.

Surgery for Aortic Insufficiency Associated with Ventricular Septal Defect

Aortic valve repair in children is a challenge. We have adopted a technique of single aortic cusp extension with an autologous pericardial strip in patients diagnosed with severe aortic insufficiency (AI) associated with a ventricular septal defect (VSD). The purpose of this study was to report the short-term outcomes. Seven patients were operated on between January 2002 and December 2003. The mean age was 11.28 ± 2.1 years (range 8–14 years). The VSD was closed with a synthetic patch. Aortic cusp extension was performed at the right coronary cusp in 6 patients and the remainder had a non-coronary cusp extension. The mean diastolic arterial pressure increased from 35.71 ± 6.09 to 74.28 ± 7.31 mm Hg after the operation ( p < 0.001). The postoperative grade of AI was trivial in 4 patients, mild in 1 patient and non-existent in 2 patients. The mean follow-up period was 12.85 ± 6.12 months (range 2–20 months). This technique is very effective in patients with severe AI associated with a VSD. However, long-term durability will need to be carefully followed.

Systemic Semilunar Valve Replacement in Pediatric Patients Using a Porcine, Full-Root Bioprosthesis

BACKGROUND

Management of systemic semilunar valve disease in growing, young patients is challenging. When replacement is necessary, use of a pulmonary autograft is sometimes not possible for anatomic, pathologic, or technical reasons or due to parental or patient preference. We employed a stentless, porcine, full-root bioprosthesis in this setting and report our outcomes.

METHODS

Over 9 years (2005 to 2013), 24 patients of mean age 13.1 years (range, 3 months to 20.3 years) underwent operation for mixed stenosis and insufficiency in 16 of 24 (67%), pure insufficiency in 7 of 24 (29%), and pure stenosis in 1 of 24 (4%). Twenty patients had previous interventions of repair or replacement, valvuloplasty, or multiple operations. Survival, follow-up echocardiographic findings, and outcomes were documented. All patients were maintained on daily aspirin.

RESULTS

There were no hospital deaths and no early or late deaths over a mean follow-up for 23 patients of 46.1 months (range, 14 months to 9.2 years). One patient moved abroad and was lost to follow-up. Echocardiographic follow-up (mean 34.0 months) demonstrated that no patient developed more than mild insufficiency or moderate stenosis. In total, 20 of 24 (83%) showed no insufficiency and 11 of 24 patients (46%) showed no stenosis. Near or complete normalization of left ventricular mass and dimension was demonstrated. There were no explants and no thromboembolic or bleeding events.

CONCLUSIONS

When use of a pulmonary autograft is not an option, the porcine full-root bioprosthesis appears favorable for systemic semilunar valve replacement in the pediatric and young adult population. Of note, when prosthetic degeneration does occur, stenosis predominates rather than insufficiency. Longer term studies are warranted.

The Ross Operation in Children and Young Adults

Objectives:

To determine UK national trends and results of the Ross operation in relation to all aortic valve interventions.

Methods:

Examination of the UK Congenital Central Cardiac Audit Database for all aortic valve procedures performed between 2000 and 2011 in children (0-16 years) and young adults (16-30 years).

Results:

A total of 2,206 aortic valve procedures were performed in children and 1,824 in young adults, the proportions in the two groups being: Ross operation (19% vs 15%, respectively), surgical valvoplasty (9.5% vs 4%), surgical valvotomy (9.5% vs 1%), aortic valve replacement (AVR; 11% vs 55%), aortic root replacement (4% vs 18%), and balloon valvoplasty (47% vs 7%). The 30-day and 1-year survival after Ross is 99.3% and 98.7%, respectively, in the last four years achieving 100%. In children, the proportion of balloon valvoplasty increased from an average of 43% in 2000 to 2006 to 53% in 2007 to 2011, whereas the Ross operation decreased from 22% to 16% ( P < .001). In young adults, the figures are an increase from 49% to 58% for AVR compared to a decrease from 23% to 9% for Ross ( P < .001). Our own single-center series of 91 patients also shows standard results for early- and long-term survival and freedom from reoperation, but gradually fewer Ross operations performed. The year-on-year changes show a significant decreasing trend locally and nationally.

Conclusions:

Despite an excellent track record, the Ross operation is performed less frequently in the United Kingdom. This report is a first step in comparing treatment modalities at national level.

In vitro generation of atrioventricular heart valve neoscaffolds

Tissue engineering of cardiovascular structures represents a novel approach to improve clinical strategies in heart valve disease treatment. The aim of this study was to engineer decellularized atrioventricular heart valve neoscaffolds with an intact ultrastructure and to reseed them with umbilical cord-derived endothelial cells under physiological conditions in a bioreactor environment. Mitral (n=38) and tricuspid (n=36) valves were harvested from 40 hearts of German Landrace swine from a selected abattoir. Decellularization of atrioventricular heart valves was achieved by a detergent-based cell extraction protocol. Evaluation of the decellularization method was conducted with light microscopy and quantitative analysis of collagen and elastin content. The presence of residual DNA within the decellularized atrioventricular heart valves was determined with spectrophotometric quantification. The described decellularization regime produced full removal of native cells while maintaining the mechanical stability and the quantitative composition of the atrioventricular heart valve neoscaffolds. The surface of the xenogeneic matrix could be successfully reseeded with in vitro-expanded human umbilical cord-derived endothelial cells under physiological flow conditions. After complete decellularization with the detergent-based protocol described here, physiological reseeding of the xenogeneic neoscaffolds resulted in the formation of a confluent layer of human umbilical cord-derived endothelial cells. These results warrant further research toward the generation of atrioventricular heart valve neoscaffolds on the basis of decellularized xenogeneic tissue.

A modification of the pulmonary autograft procedure to prevent late autograft dilatation

Although the pulmonary autograft procedure for aortic valve replacement is a commonly utilized option for children, its use is diminishing in adult-aged patients. One commonly cited concern is the tendency for the pulmonary autograft to dilate in the aortic position. This article reviews a technique we have used in 36 patients since October, 2004 that stabilizes the autograft so that it cannot dilate. There have been no operative or late deaths and the autograft has continued to function in 34 patients. Two patients have undergone autograft replacement because of early failure, which we believe was likely related to technical considerations in our early technique (first reported in the 2005 STCVS Pediatric Cardiac Surgery Annual). The technical modifications described in this article have produced a more reliable and reproducible technique and have not resulted in any autograft failures in our experience. One patient with Marfan's syndrome and a bicuspid aortic valve is symptom- and dilation-free 8 years post op, with no autograft or pulmonary homograft insufficiency, normal activity and a stable aortic root by serial echocardiography. Our results suggest that this technique might be applicable for selected adult patients in whom autograft growth is not necessary and for whom the risk of autograft dilatation would provide a reason to avoid a pulmonary autograft procedure.

The fate of the neoaortic valve and root after the modified Ross-Konno procedure

OBJECTIVES

In children with aortic valve disease associated with annular hypoplasia or complex multilevel left ventricular outflow tract obstruction, the Ross procedure, combined with a modified Konno-type aortoventriculoplasty, is advocated. We aim to examine the fate of the neoaortic apparatus and assess neoaortic valve function after the modified Ross-Konno procedure.

METHODS

Forty-three patients, with a median age of 6 years, underwent the modified Ross-Konno procedure with a myectomy but without the use of a ventricular septal patch. Serial postoperative echocardiograms (n = 187) were analyzed, and regression models adjusted for repeated measures were used to model the longitudinal growth of the neoaortic annulus and root.

RESULTS

There were 2 operative deaths (5%) and 1 late mortality. At 8 years, survival was 93% and freedom from autograft, homograft, and all-cause reoperation was 100%, 81%, and 72%, respectively. The median postprocedure diameter and z score were 14 mm (7-21 mm) and +1.3 (-3.0 to +6.1) for the neoaortic annulus and 21 mm (9-30 mm) and +1.6 (-1.3 to +4.1) for the neoaortic root, respectively. Serial echocardiograms showed a progressive increase in annular (+0.56 mm/year, P < .001) and root (+0.89 mm/year, P < .001) diameters but little change in annular (-0.07/year, P = .08) and root (-0.002/year, P = .96) z scores. Autograft regurgitation developed in 9 patients; however, the degree and progression of regurgitation over time were not significant (P = .22).

CONCLUSIONS

After the modified Ross-Konno procedure, the neoaortic annulus and root increased in size proportionately to somatic growth. Autograft regurgitation, usually mild and stable, developed in few patients, and none required autograft reoperation. Our findings support the use of the modified Ross-Konno as the procedure of choice in children with aortic valve disease and complex left ventricular outflow tract obstruction.

Antithrombotic therapy in neonates and children: Antithrombotic Therapy and Prevention of Thrombosis, 9th ed: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines

BACKGROUND

Neonates and children differ from adults in physiology, pharmacologic responses to drugs, epidemiology, and long-term consequences of thrombosis. This guideline addresses optimal strategies for the management of thrombosis in neonates and children.

METHODS

The methods of this guideline follow those described in the Methodology for the Development of Antithrombotic Therapy and Prevention of Thrombosis Guidelines: Antithrombotic Therapy and Prevention of Thrombosis, 9th ed: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines.

RESULTS

We suggest that where possible, pediatric hematologists with experience in thromboembolism manage pediatric patients with thromboembolism (Grade 2C). When this is not possible, we suggest a combination of a neonatologist/pediatrician and adult hematologist supported by consultation with an experienced pediatric hematologist (Grade 2C). We suggest that therapeutic unfractionated heparin in children is titrated to achieve a target anti-Xa range of 0.35 to 0.7 units/mL or an activated partial thromboplastin time range that correlates to this anti-Xa range or to a protamine titration range of 0.2 to 0.4 units/mL (Grade 2C). For neonates and children receiving either daily or bid therapeutic low-molecular-weight heparin, we suggest that the drug be monitored to a target range of 0.5 to 1.0 units/mL in a sample taken 4 to 6 h after subcutaneous injection or, alternatively, 0.5 to 0.8 units/mL in a sample taken 2 to 6 h after subcutaneous injection (Grade 2C).

CONCLUSIONS

The evidence supporting most recommendations for antithrombotic therapy in neonates and children remains weak. Studies addressing appropriate drug target ranges and monitoring requirements are urgently required in addition to site- and clinical situation-specific thrombosis management strategies.

Single-centre experience of 101 paediatric and adult Ross procedures: mid-term results

We aimed to determine outcomes for the Ross procedure in paediatric and adult patients, with particular emphasis on survival, complication and reintervention rates. A retrospective review of 101 patients who had the Ross procedure in a congenital cardiac surgical centre serving a population of approximately 2.5 million was performed. There were 69 adults and 32 children with a mean age of 24.8 ± 13.9 years. Indications for surgery were aortic stenosis (48), regurgitation (10), mixed disease (35) and complex left outflow tract obstruction (8). The mean follow-up duration was 4.7 ± 3.7 years. The mini-inclusion technique was used to incorporate the autograft, and in all cases, pulmonary homografts were placed in the right ventricular outflow tract. Sub-aortic resection was also performed in six and Ross-Konno operations in eight patients. There were no early deaths and there was one late death secondary to endocarditis. Freedom from reintervention was 92% at 5 years and 77% at 10 years. Children were significantly more likely to require reintervention (16%, 5 of 32 versus 4%, 3 of 69, P = 0.05). The Ross procedure carries low early and mid-term mortality, and reintervention rates appear acceptable. The Ross procedure should be considered a feasible alternative to prosthetic valves in patients who require aortic valve replacement.

Comparative evaluation of left ventricular mass regression after aortic valve replacement: a prospective randomized analysis

BACKGROUND

We assessed the hemodynamic performance of various prostheses and the clinical outcomes after aortic valve replacement, in different age groups.

METHODS

One-hundred-and-twenty patients with isolated aortic valve stenosis were included in this prospective randomized randomised trial and allocated in three age-groups to receive either pulmonary autograft (PA, n = 20) or mechanical prosthesis (MP, Edwards Mira n = 20) in group 1 (age < 55 years), either stentless bioprosthesis (CE Prima Plus n = 20) or MP (Edwards Mira n = 20) in group 2 (age 55-75 years) and either stentless (CE Prima Plus n = 20) or stented bioprosthesis (CE Perimount n = 20) in group 3 (age > 75). Clinical outcomes and hemodynamic performance were evaluated at discharge, six months and one year.

RESULTS

In group 1, patients with PA had significantly lower mean gradients than the MP (2.6 vs. 10.9 mmHg, p = 0.0005) with comparable left ventricular mass regression (LVMR). Morbidity included 1 stroke in the PA population and 1 gastrointestinal bleeding in the MP subgroup. In group 2, mean gradients did not differ significantly between both populations (7.0 vs. 8.9 mmHg, p = 0.81). The rate of LVMR and EF were comparable at 12 months; each group with one mortality. Morbidity included 1 stroke and 1 gastrointestinal bleeding in the stentless and 3 bleeding complications in the MP group. In group 3, mean gradients did not differ significantly (7.8 vs 6.5 mmHg, p = 0.06). Postoperative EF and LVMR were comparable. There were 3 deaths in the stented group and no mortality in the stentless group. Morbidity included 1 endocarditis and 1 stroke in the stentless compared to 1 endocarditis, 1 stroke and one pulmonary embolism in the stented group.

CONCLUSIONS

Clinical outcomes justify valve replacement with either valve substitute in the respective age groups. The PA hemodynamically outperformed the MPs. Stentless valves however, did not demonstrate significantly superior hemodynamics or outcomes in comparison to stented bioprosthesis or MPs.

A single center's experience with the Ross procedure in pediatrics

The use of a pulmonary autograft for aortic valve replacement (AVR) has become more prevalent than other forms of AVR in the pediatric population. We reviewed the data on pediatric patients who underwent the Ross procedure at our institution from 1993 to 2005. Sixty patients <18 years old who underwent a Ross procedure had available clinical and echocardiographic data collected and statistical analysis performed. Mortality rate was 3.3%, while overall survival and freedom from reoperation of either the homograft or the autograft were 96.7% and 66.2%, respectively, at 10 years. Freedom from reoperation of the left ventricular outflow tract was 60.5% at 10 years. Echocardiographic data showed aortic regurgitation to be mild or less in 76% of patients by last follow-up, while dilation of the sinuses of Valsalva had occurred in 52%. Compared to other AVR options, the Ross procedure in eligible pediatric patients demonstrates good intermediate survival rates and continued growth potential, yet a time-dependent need for reoperation.

Intermediate-term results after the aortic valve replacement using bileaflet mechanical prosthetic valve in children

OBJECTIVE

Intermediate/long-term results after aortic valve replacement using bileaflet mechanical valve in children should be clarified as a standard of treatment of aortic valve disease in children.

METHODS

Forty-five patients aged under 15 years underwent 46 aortic valve replacements using bileaflet mechanical prosthetic valve. Patients' ages ranged from 1 to 15 years (9 years as a median value), and follow-up period was 9.2 years as a median value (maximum 19 years).

RESULTS

In situ valve replacement was performed in 21 procedures, while annular enlargement was required in 25 procedures (Nicks 10, Yamaguchi 3, Manouguian 2, Konno 10). All patients except two received prosthesis 19mm or larger in size. There was one operative death and two late deaths. Two episodes of cerebral infarction, two valve thrombosis, two re-operations, one infective endocarditis, and one sudden death were recognized as valve-related complications in five patients. The reasons for re-operation were prosthesis-patient mismatch in one (Ross procedure) and valve thrombosis in one (re-replacement). At 15 years after the operation, re-replacement free rate, valve-related event free rate and actuarial survival rate were 94+/-4%, 86+/-6% and 92+/-4%, respectively. The transprosthetic flow velocity estimated by Doppler echocardiography at the final follow-up was well correlated with manufactured valve area index (cm(2)/body surface area).

CONCLUSIONS

Although aortic annular enlargement was required in more than half of the cases, intermediate-term results after aortic valve replacement using bileaflet mechanical prosthetic valve in children was satisfactory. Indications for alternative treatment such as Ross procedure might be considered in limited cases.

The use of acellular matrices for the tissue engineering of cardiac valves

Tissue-engineering approaches to cardiac valve replacement have made considerable advances over recent years and it is likely that this application will realize clinical success in the near future. Research in this area has been driven by the inadequacy of the currently available cardiac valve prostheses for younger patients who require multiple reoperations as they grow and develop. Tissue engineering has the potential to provide a valve capable of the same growth, repair, and regeneration as a natural valve and could improve outcomes for patients of all ages. Owing to the function and physical environment of the cardiac valve, the development of tissue-engineered replacements is unusual in that the biomechanical properties of the construct must dominate the biological properties in order for the valve to be functional at the time of implantation. As a result of this, conventional tissue-engineering scaffolds based on biodegradable polymers or collagen may not at present be suitable in this situation because of their initial limited strength. Research into the use of acellular xenogeneic and allogeneic matrices for tissue-engineered heart valves has consequently become extremely popular since the biomechanical properties of the valve can potentially be preserved with an optimal decellularization technique that removes the cells without damaging the matrix. A number of acellular scaffolds have already been tested clinically both unseeded and preseeded with cells and these have met with variable results. This article reviews the concepts involved and the advantages and disadvantages of the different approaches to tissue engineering a living cardiac valve.

Valvular endothelial cells and the mechanoregulation of valvular pathology

Endothelial cells are critical mediators of haemodynamic forces and as such are important foci for initiation of vascular pathology. Valvular leaflets are also lined with endothelial cells, though a similar role in mechanosensing has not been demonstrated. Recent evidence has shown that valvular endothelial cells respond morphologically to shear stress, and several studies have implicated valvular endothelial dysfunction in the pathogenesis of disease. This review seeks to combine what is known about vascular and valvular haemodynamics, endothelial response to mechanical stimuli and the pathogenesis of valvular diseases to form a hypothesis as to how mechanical stimuli can initiate valvular endothelial dysfunction and disease progression. From this analysis, it appears that inflow surface-related bacterial/thrombotic vegetative endocarditis is a high shear-driven endothelial denudation phenomenon, while the outflow surface with its related calcific/atherosclerotic degeneration is a low/oscillatory shear-driven endothelial activation phenomenon. Further understanding of these mechanisms may help lead to earlier diagnostic tools and therapeutic strategies.

Midterm outcomes and predictors of reintervention after the Ross procedure in infants, children, and young adults

OBJECTIVES

This study assessed the type, time course, and risk factors for right and left ventricular outflow tract reinterventions after the Ross procedure in a population of infants, children, and young adults.

METHODS

Patients who underwent the Ross procedure between January 1995 and June 2004 were included (n = 121 consecutive patients). Kaplan-Meier and hazard analyses of right and left ventricular outflow tract reinterventions were performed, and predictors of reintervention were identified through multivariate analysis.

RESULTS

The median age at the Ross procedure was 8.2 years (4 days to 34 years); 20% were aged less than 1 year. Half of the patients had isolated aortic valve disease; the other half had complex left-sided heart disease. Early mortality (<30 days) was 2.5% (n = 3). There were 2 late deaths (1.7%). Follow-up (median 6.5 years [2.5 months to 10.4 years]) was available for 96% of survivors (n = 111). Right ventricular outflow tract reintervention (n = 22 in 15 patients) was performed 2.0 years (2.0 weeks to 9.8 years) after the Ross procedure because of stenosis in 19 of 22 cases. Freedom from right ventricular outflow tract reintervention at 8 years was 81%. Smaller homograft size was the strongest predictor (P < .001) of right ventricular outflow tract reintervention. Left ventricular outflow tract reintervention (n = 15 in 15 patients) was performed 2.8 years (1.0 months to 11.6 years) after the Ross procedure because of severe neoaortic insufficiency in 10 of 15 patients. Freedom from left ventricular outflow tract reintervention at 8 years was 83%. Native pulmonary valve abnormalities (P < .01), original diagnosis of aortic insufficiency (P < .01), prior aortic valve replacement (P = .01), and prior ventricular septal defect repair (P = .04) predicted left ventricular outflow tract reintervention.

CONCLUSIONS

At midterm follow-up after the Ross procedure, interim mortality is rare. Neoaortic insufficiency and right ventricle to pulmonary artery conduit obstruction are common postoperative sequelae, requiring reintervention in one quarter of patients.

Redo Aortic Valve Replacement in Children

BACKGROUND

Some children who have had an aortic valve replacement (AVR) will need valve re-replacement (redo-AVR). We analyzed our results with 38 redo-AVRs in 30 children.

METHODS

Thirty children, aged 2 months to 20 years (mean, 11.5 +/- 5.4 years), underwent 38 redo-AVRs 1 month to 14 years (mean, 4.6 +/- 4.5 years) after previous AVR. Seven children had a second redo-AVR and one had a third redo-AVR (his fourth AVR). Reoperation indication was primarily stenosis in 19, regurgitation in 12, endocarditis in 3, valve thrombosis-emboli in 3, and ruptured aortic aneurysm in 1. The initial valve was mechanical in 26, homograft in 7, xenograft in 4, or a Ross procedure in 1. Sixteen patients (42%) had a previous Konno procedure.

RESULTS

The new valve was mechanical (28), homograft (5), xenograft (4), or a Ross procedure (1). Twenty-five valves were upsized on re-replacement. The median valve size was 23 mm (median size increase 4 mm). Twenty-seven operations (71%) included annulus enlargement (16 redo-Konno, 8 new Konno, and 3 Manougian). Twelve children (32%) had concomitant operations including mitral valve repair-replacement (4) and right ventricular outflow tract procedure (5). Three of the 4 hospital deaths were with second or third time redo-AVR. The only death in patients with first time redo-AVR was a patient in cardiogenic shock at the time of operation.

CONCLUSIONS

Redo-AVR in children can be performed with reasonable morbidity and mortality. A larger prosthesis can often be placed in these children. Second or third time redo-AVR appears to be riskier. Earlier referral before onset of ventricular dysfunction is warranted.

Is the Ross procedure as good as we thought it would be?

For patients requiring intervention because of progressive disease of the aortic valve, the perfect palliation will provide a valve that produces normal dynamics of flow, will not require anti-coagulation, will grow with the patient, and have long term durability. Current surgical interventions include aortic valvoplasty, or replacement with either a mechanical or tissue prosthesis. Options for tissue valves include insertion of a pulmonary autograft in the Ross procedure, a cadaveric homograft, or porcine or bovine xenograft valves. The optimal option is still debated.

Valvular endothelial cells regulate the phenotype of interstitial cells in co-culture: effects of steady shear stress

Valvular endothelial cells interact with interstitial cells in a complex hemodynamic and mechanical environment to maintain leaflet tissue integrity. The precise roles of each cell type are difficult to ascertain in a controlled manner in vivo. The objective of this study was to develop a three-dimensional aortic valve leaflet model, comprised of valvular endothelium and interstitial cells, and determine the cellular responses to imposed lumenal fluid flow. Two leaflet models were created using type I collagen hydrogels. Model 1 contained 1 million/mL porcine aortic valve interstitial cells (PAVICs). Model 2 added a seeding of the lumenal surface of Model 1 with approximately 50,000/cm(2) porcine aortic valve endothelial cells (PAVECs). Both leaflet models were exposed to 20 dynes/cm(2) steady shear for up to 96 h, with static constructs serving as controls. Endothelial cell alignment, matrix production, and cell phenotype were monitored. The results indicate that PAVECs align perpendicularly to flow similar to 2D culture. We report that PAVICs in model 1 express vimentin strongly and alpha-smooth-muscle actin (SMA) to a lesser extent, but SMA expression is increased by shear stress, particularly near the lumenal surface. Model 1 constructs increase in cell number, maintain protein levels, but lose glycosaminoglycans in response to shear. Co-culture with PAVECs (Model 2) modulates these responses in both static and flow environments, resulting in PAVIC phenotype that is more similar to the native condition. PAVECs stimulated a decrease in PAVIC proliferation, an increase in protein synthesis with shear stress, and reduced the loss of glycosaminoglycans with flow. Additionally, PAVECs stimulated PAVIC differentiation to a more quiescent phenotype, defined by reduced expression of SMA. These results suggest that valvular endothelial cells are necessary to properly regulate interstitial cell phenotype and matrix synthesis. Additionally, we show that tissue-engineered models can be used to discover and understand complex biomechanical relationships between cells that interact in vivo.

Aortic valve repair for congenital abnormalities of the aortic valve

BACKGROUND

Due to shortcomings of any valve replacement, repairing and retaining the native valve may be beneficial for congenital aortic valve disease.

METHODS

Retrospective review of data and follow-up of aortic valve repair from a single institution.

RESULTS

From 1993 to 2001, 56 patients underwent aortic valve repair [median age 13.4 years (range 1 day to 45 years)]. The predominant aortic valve lesion was mixed aortic stenosis/aortic insufficiency 25 (45%), aortic insufficiency 24 (43%) and aortic stenosis 7 (13%). Repair techniques included sub-commissural plication 36 (64%), commissurotomy 24 (43%), cusp plication 15 (27%), pericardial patch cusp extension 8 (14%) and resuspension of commissures 4 (7%). Most patients (88%) required a combination of techniques; 61% required additional procedures. Hospital survival was 55/56 [98%; (95% CI 91-100%)] no patient was discharged on anticoagulation for aortic valve pathology. Fifty-three patients [95%; (95% CI 85-98%)] remain alive after a median follow-up of 37 months; four survivors required aortic valve replacement and two required repeat aortic valve repair [84%; (95% CI 72-91%) reintervention-free survival].

CONCLUSIONS

(1) In this study, aortic valve repair for congenital abnormalities avoided reoperation in the majority of patients, avoided anticoagulation and retained growth potential of the valve. (2) Repeat aortic valve repair or replacement was used to treat subsequent valve deterioration.

Systemic mechanical heart valve replacement in children under 16 years of age

We report the early and late outcome following left-sided mechanical heart valve replacement in children. Between 10/1981 and 02/2001, 27 children (13 male, mean age 7.2 +/- 5.2 years, range 0.53-15.7 years) underwent mechanical mitral (MVR 16), aortic (AVR 9) or double valve replacement (DVR 2) with St. Jude Medical valves. Eighteen children (66.7%) had undergone previous cardiac surgery. Valve disease was congenital in 23, due to endocarditis in 2 and rheumatic in 2 patients. Concomitant cardiac surgery was performed in 12 patients (44.4%). Operative mortality was 3.7% (1/27). Perioperative complications were complete heart block (5) and myocardial infarction (1). Mean follow-up was 6.5+/-5.9 years (range 0.4-19 years, total 169.9 patient-years). There was one valve-related late death due to mitral valve thrombosis without phenprocoumon. Actuarial survival after 1, 5 and 10 years was 93, 93 and 93%. Late complications included endocarditis (2), minor hemorrhagic event (1) and stroke (1). Overall 10-year freedom from any anticoagulation-related adverse event under phenprocoumon was 91% (1.3%/patient year). Eight patients required reoperations: re-MVR (5; outgrowth of the prostheses (3), pannus overgrowth (2)), closure of paravalvular leak after AVR (2), and re- DVR (1; endocarditis). Actuarial freedom from reoperation after 1, 5 and 10 years was 96, 88 and 76%.

CONCLUSION

Mechanical valve prostheses are a valuable option for left-sided heart valve replacement in pediatric patients with good results. Operative mortality and the incidence of any valve-related events as endocarditis, reoperation, thromboembolism or anticoagulation related bleeding is acceptable.

Do pulmonary autografts provide better outcomes than mechanical valves? A prospective randomized trial

BACKGROUND

The objective of this study was to compare the performance of pulmonary autografts with mechanical aortic valves, in the treatment of aortic valve stenosis.

METHODS

Forty patients with aortic valve stenoses, and below the age of 55 years, were randomly assigned to receive either pulmonary autografts (n = 20) or mechanical valve (Edwards MIRA; Edwards Lifesciences, Irvine, CA) prostheses (n = 20). Clinical outcomes, left ventricular mass regression, effective orifice area, ejection fraction, and mean gradients were evaluated at discharge, 6 months, and one year after surgery. Follow-up was complete for all patients.

RESULTS

Hemodynamic performance was significantly better in the Ross group (mean gradient 2.6 mm Hg vs 10.9 mm Hg, p = 0.0005). Overall, a significant decrease in left ventricular mass was found one year postoperatively. However, there was no significant difference in the rate and extent of regression between the groups. There was one stroke in the Ross group and one major bleeding complication in the mechanical valve group. Both patients recovered fully.

CONCLUSIONS

In our randomized cohort of young patients with aortic valve stenoses, the Ross procedure was superior to the mechanical prostheses with regard to hemodynamic performance. However, this did not result in an accelerated left ventricular mass regression. Clinical advantages like reduced valve-related complications and lesser myocardial strain will have to be proven in the long term.

Outcomes and Associated Risk Factors for Aortic Valve Replacement in 160 Children

Background— We sought to define patient characteristics, outcomes, and associated risk factors after aortic valve replacement (AVR) in children.

Methods and Results— Clinical records from children undergoing AVR from 1974 to 2004 at our institution were reviewed. Competing-risks methodology determined the time-related prevalence of 3 mutually exclusive end states: death, repeated replacement, and survival without subsequent AVR and their associated risk factors. Longitudinal echocardiographic data were analyzed by mixed linear-regression models. Children (n=160) underwent 198 AVRs, with 33 having >1. Competing-risks analysis predicted that 10 years from the initial AVR, 19% had died without subsequent AVR, 34% underwent a second AVR, and 47% remained alive without replacement. Risk factors for death without a second AVR included lower weight ( P <0.001) and younger age at AVR ( P =0.04), performance of aortic arch reconstruction together with AVR ( P =0.03), and nonautograft use ( P =0.03). Risk factors for a second AVR included earlier operation year ( P =0.04) and implantation of a bioprosthetic or homograft valve ( P =0.004). Analysis of serial echocardiographic measurements showed that pulmonary autograft use was associated with slower progression of peak aortic gradient ( P =0.002), smaller left ventricular dimension ( P =0.04), and decreased prevalence of aortic regurgitation ( P =0.04).

Conclusions— Mortality and repeated valve replacement are common after initial AVR in children, especially in younger patients and those with bioprosthetic or homograft valves. Pulmonary autograft use is associated with decreased mortality, slower gradient progression, and smaller left ventricular dimension.

The Ross procedure performed in the setting of congenitally bifoliate aortic valve with anomalous right coronary artery

We treated successfully using the Ross procedure a 14-year old with a congenitally stenotic bifoliate aortic valve associated with anomalous origin of the right coronary artery. The anomalous artery arose from the same aortic sinus that gave rise to the main stem of the left coronary artery, and reached the right atrioventricular groove by traversing the tissue plane between the aortic root and the subpulmonary infundibulum. Both coronary arteries were reimplanted using a single arterial button.

Aortic valve repair

Aortic valve replacement options are limited in children, and all of them have disadvantages. Aortic valve repair techniques have evolved slowly and have not gained wide acceptance; however, large series using a variety of techniques demonstrate that valve repair is possible with excellent early hemodynamics and satisfactory intermediate durability. The results of aortic valve repair at the Children's Hospital of Wisconsin are presented. Simple repairs (blunt valvotomy, commissurotomy, or commissurotomy with leaflet thinning) directed at congenital aortic stenosis resulted in 86% +/- 5% freedom from reintervention at 10 years. Repair of aortic insufficiency with ventricular septal defect (VSD) resulted in 93.3% +/- 6% freedom from reoperation at 10 years. Complex repairs included a combination of techniques and yielded 5-year freedom from reintervention of 83% +/- 7% compared with 73% +/- 11% for patients undergoing aortic valve replacement (P = .62). Aortic valve repair provides an alternative to aortic valve replacement in selected patients. The utility of aortic valve repair and aortic valve replacement must be measured not only in freedom from reintervention but also in regression of left ventricular mass and exercise testing. Improvement in outcome depends on better patient selection and suitable bioprosthetic materials.

The Ross procedure is an ideal aortic valve replacement operation for the teen patient

The Ross procedure is an ideal aortic valve replacement for the teenage patient because the pulmonary autograft is durable, is nonthrombogenic, has excellent hemodynamics, and grows. Since 1992, our center has performed 194 Ross procedures, and 53 of these were in teenagers (10 to 21 years of age). In this group, there have been no perioperative deaths, hospital length of stay was 4 days, and re-operation for autograft failure was only 2% at mean follow-up of 69 months. All patients are in NYHA heart failure class I. Because of its proven efficacy, the Ross operation is our preferred aortic valve replacement for the teenage patient.

Human umbilical cord cells: a new cell source for cardiovascular tissue engineering

BACKGROUND

Tissue engineering of viable, autologous cardiovascular constructs with the potential to grow, repair, and remodel represents a promising new concept for cardiac surgery, especially for pediatric patients. Currently, vascular myofibroblast cells (VC) represent an established cell source for cardiovascular tissue engineering. Cell isolation requires the invasive harvesting of venous or arterial vessel segments before scaffold seeding, a technique that may not be preferable, particularly in pediatric patients. In this study, we investigated the feasibility of using umbilical cord cells (UCC) as an alternative autologous cell source for cardiovascular tissue engineering.

METHODS

Human UCC were isolated from umbilical cord segments and expanded in culture. The cells were sequentially seeded on bioabsorbable copolymer patches (n = 5) and grown in vitro in laminar flow for 14 days. The UCC were characterized by flow cytometry (FACS), histology, immunohistochemistry, and proliferation assays and were compared to saphenous vein-derived VC. Morphologic analysis of the UCC-seeded copolymer patches included histology and both transmission and scanning electron microscopy. Characterization of the extracellular matrix was performed by immunohistochemistry and quantitative extracellular matrix protein assays. The tissue-engineered UCC patches were biomechanically evaluated using uniaxial stress testing and were compared to native tissue.

RESULTS

We found that isolated UCC show a fibroblast-like morphology and superior cell growth compared to VC. Phenotype analysis revealed positive signals for alpha-smooth muscle actin (ASMA), desmin, and vimentin. Histology and immunohistochemistry of seeded polymers showed layered tissue formation containing collagen I, III, and glycoaminoglycans. Transmission electron microscopy showed viable myofibroblasts and the deposition of collagen fibrils. A confluent tissue surface was observed during scanning electron microscopy. Glycoaminoglycan content did not reach values of native tissue, whereas cell content was increased. The biomechanical properties of the tissue-engineered constructs approached native tissue values.

CONCLUSIONS

Tissue engineering of cardiovascular constructs using UCC is feasible in an in vitro environment. The UCC demonstrated excellent growth properties and tissue formation with mechanical properties approaching native tissue. It appears that UCC represent a promising alternative autologous cell source for cardiovascular tissue engineering, offering the additional benefits of using juvenile cells and avoiding the invasive harvesting of intact vascular structures.