Intercalated cushion cells within the cardiac outflow tract are derived from the myocardial troponin T type 2 (Tnnt2) Cre lineage.

BACKGROUND: The origin of the intercalated cushions that develop into the anterior cusp of the pulmonary valve (PV) and the noncoronary cusp of the aortic valve (AV) is not well understood. RESULTS: Cre transgenes in combination with the Rosa TdTomato-EGFP reporter were used to generate three-dimensional lineage mapping of AV and PV cusps during intercalated cushion development. Tie2-Cre;EGFP was used to mark endothelial-derived mesenchymal cells, Wnt1-Cre;EGFP for cardiac neural crest and cardiac Troponin T (Tnnt2)Cre;EGFP, for myocardial lineage. The highest percentage of intercalated cushion cells at embryonic day (E) 12.5 was Tnnt2-Cre; EGFP positive; 68.0% for the PV and 50.0% AV. Neither Tnnt2 mRNA nor Tnnt2-Cre protein was expressed in the intercalated cushions; and the Tnnt2-Cre lineage intercalated cushion cells were also positive for the mesenchymal markers Sox9 and versican. Tnnt2-Cre lineage was present within the forming intercalated cushions from E11.5 and was present in the intercalated cushion derived PV and AV cusps and localized to the fibrosa layer at postnatal day 0. CONCLUSIONS: Intercalated cushions of the developing outflow tract are populated with Tnnt2-Cre derived cells, a Cre reporter previously used for tracing and excision of myocardial cells and not previously associated with mesenchymal cells. Developmental Dynamics 247:1005-1017, 2018. © 2018 Wiley Periodicals, Inc.

Impact of Fetal Somatic Growth on Pulmonary Valve Annulus Z-Scores During Gestation and Through Birth in Patients with Tetralogy of Fallot.

Previous studies have suggested reduced pulmonary valve annulus (PVA) growth and progression of pulmonary outflow obstruction in fetuses with tetralogy of Fallot (TOF). The goals of this study were to (1) investigate the trajectory of PVA growth in utero, and (2) compare two methods of z-score determination for fetal and postnatal PVA size by echocardiography in order to improve prenatal counseling for patients with TOF. Fetal echocardiograms (FE) at a single institution with a diagnosis of TOF between 8/2008 and 12/2015 were retrospectively reviewed. Patients included had at least 2 FEs and 1 immediate postnatal echocardiogram (TTE). Fetal and postnatal demographic, clinical, and echocardiographic data were collected. Fetal body surface area (BSA) was calculated by estimating fetal weight and height; z-scores were determined based on fetal gestational age (GA) and BSA for both FEs and TTEs. Fetal PVA z-scores by GA or BSA were then compared to postnatal PVA z-scores by BSA. Twenty-two patients with 44 FEs and 22 TTEs were included. GA at the first FE was 23 weeks ± 3.4 and 32 weeks ± 3.1 at the second FE. There was no difference in PVA z-scores (by BSA) between the first and second FE (p = 0.34), but a decrease in PVA z-scores (by BSA) between the second FE and TTE (- 1.6 ± 0.5 vs. - 2.0 ± 0.7; p = 0.01). Repeat comparison with fetal PVA z-scores indexed to GA revealed no difference in z-scores between the first and second FE, but an increase in PVA z-scores between the second FE (by GA) and TTE (by BSA) (- 4.1 ± 1.0 vs. - 2.0 ± 0.7; p < 0.0001). The rate of PVA growth between the two FEs (23 µm/day ± 9.8) and between the second FE and TTE (28 µm/day ± 42) remained comparable (p = 0.57); however, the rate of BSA increase was greater in later gestation (9 cm2/day ± 3 vs. 20 cm2/day ± 11; p = 0.001). In patients with TOF, the rate of PVA growth appears to remain consistent through gestation; however, somatic growth rate increases in late gestation. Fetal PVA z-scores indexed to GA are thus inaccurate in predicting postnatal PVA z-scores typically indexed to BSA. This observation should be considered during prenatal consultation and delivery planning.

Development and maturation of the fibrous components of the arterial roots in the mouse heart.

The arterial roots are important transitional regions of the heart, connecting the intrapericardial components of the aortic and pulmonary trunks with their ventricular outlets. They house the arterial (semilunar) valves and, in the case of the aorta, are the points of coronary arterial attachment. Moreover, because of the semilunar attachments of the valve leaflets, the arterial roots span the anatomic ventriculo-arterial junction. By virtue of this arrangement, the interleaflet triangles, despite being fibrous, are found on the ventricular aspect of the root and located within the left ventricular cavity. Malformations and diseases of the aortic root are common and serious. Despite the mouse being the animal model of choice for studying cardiac development, few studies have examined the structure of their arterial roots. As a consequence, our understanding of their formation and maturation is incomplete. We set out to clarify the anatomical and histological features of the mouse arterial roots, particularly focusing on their walls and the points of attachment of the valve leaflets. We then sought to determine the embryonic lineage relationships between these tissues, as a forerunner to understanding how they form and mature over time. Using histological stains and immunohistochemistry, we show that the walls of the mouse arterial roots show a gradual transition, with smooth muscle cells (SMC) forming the bulk of wall at the most distal points of attachments of the valve leaflets, while being entirely fibrous at their base. Although the interleaflet triangles lie within the ventricular chambers, we show that they are histologically indistinguishable from the arterial sinus walls until the end of gestation. Differences become apparent after birth, and are only completed by postnatal day 21. Using Cre-lox-based lineage tracing technology to label progenitor populations, we show that the SMC and fibrous tissue within the walls of the mature arterial roots share a common origin from the second heart field (SHF) and exclude trans-differentiation of myocardium as a source for the interleaflet triangle fibrous tissues. Moreover, we show that the attachment points of the leaflets to the walls, like the leaflets themselves, are derived from the outflow cushions, having contributions from both SHF-derived endothelial cells and neural crest cells. Our data thus show that the arterial roots in the mouse heart are similar to the features described in the human heart. They provide a framework for understanding complex lesions and diseases affecting the aortic root.

In situ heart valve tissue engineering using a bioresorbable elastomeric implant - From material design to 12 months follow-up in sheep.

The creation of a living heart valve is a much-wanted alternative for current valve prostheses that suffer from limited durability and thromboembolic complications. Current strategies to create such valves, however, require the use of cells for in vitro culture, or decellularized human- or animal-derived donor tissue for in situ engineering. Here, we propose and demonstrate proof-of-concept of in situ heart valve tissue engineering using a synthetic approach, in which a cell-free, slow degrading elastomeric valvular implant is populated by endogenous cells to form new valvular tissue inside the heart. We designed a fibrous valvular scaffold, fabricated from a novel supramolecular elastomer, that enables endogenous cells to enter and produce matrix. Orthotopic implantations as pulmonary valve in sheep demonstrated sustained functionality up to 12 months, while the implant was gradually replaced by a layered collagen and elastic matrix in pace with cell-driven polymer resorption. Our results offer new perspectives for endogenous heart valve replacement starting from a readily-available synthetic graft that is compatible with surgical and transcatheter implantation procedures.

Systemic-Pulmonary Shunt Facilitates the Growth of the Pulmonary Valve Annulus in Patients With Tetralogy of Fallot.

BACKGROUND: Transannular patching (TAP) frequently accompanies primary repairs (PRs) in symptomatic neonates with tetralogy of Fallot (TOF). If a systemic-pulmonary shunt (SPS) facilitates the growth of the pulmonary valve annulus (PVA), patients with a marginally small PVA could benefit from a staged repair in terms of lowering the risk of TAP. METHODS: Among 216 infants with TOF who underwent surgical intervention between January 2004 and December 2013, 29 infants underwent SPS with a subsequent repair (SPS group), whereas 187 infants received a PR (PR group). Median age and the Z-score of the PVA (PVA [Z]) at SPS were 32 days and -3.5, respectively. There was one late death and one follow-up loss after SPS, and preservation of the PVA was achieved on repair in 16 patients (16 of 29; 55%). RESULTS: Multiple regression analysis showed that performance of SPS was the only indicator of the increase in the PVA (Z) in the entire cohort (n = 216). On mixed linear regression, the PVA (Z) increased significantly after the placement of an SPS (-3.6 + 0.2*duration in months, p = 0.001), whereas the prerepair changes in the PVA (Z) were not statistically significant in the PR group (p = 0.7), with a significant intergroup difference (p < 0.001). Receiver operating characteristic curve analysis showed that placement of TAP is expected when the preshunt PVA (Z) is smaller than -4.2 (area under the curve: 0.82; 95% confidence interval: 0.62 to 1.00; sensitivity, 100%; specificity, 73%). CONCLUSIONS: SPS facilitates outgrowth of the PVA over somatic growth in patients with TOF. However, preservation of the PVA may not be achieved on staged repair if the initial PVA is too small.

Effects of Balloon Pulmonary Valvuloplasty as Preoperative Palliation for Tetralogy of Fallot.

OBJECTIVES: We investigated the effect of balloon pulmonary valvuloplasty (BPV) as a palliative procedure for patients with tetralogy of Fallot (TOF). METHODS: This was a retrospective single-center study conducted between 2008 and 2014. We classified patients into three groups according to palliation: treatment with BPV (group I), with a Blalock-Taussig shunt (group II), and with infundibulectomy (group III). The growth of the pulmonary valve (PV) annulus and need for transannular patching (TAP) during total correction were compared between groups. RESULTS: Forty-eight patients were enrolled: 31, 10, and 7 in groups I, II, and III, respectively. The mean ages at palliation were 26.3 ± 23.6, 21.5 ± 16.4, and 15.2 ± 4.2 days in groups I, II, and III, respectively (P = .867). The success rate of BPV was 90.3%. The initial PV z-score before palliation did not differ between groups I, II, and III (-3.14 ± 1.44, -3.84 ± 1.47, and -3.71 ± 1.68; P = .494); the preoperative PV z-score before total correction was larger in group I than in group II (-1.19 ± 1.14 and -3.05 ± 1.19; P = .001), and also larger in group III than in group II (group III: -1.10 ± 0.90; P = .003). The change in pulse oxygen saturation differed significantly between the three groups (P = .031), particularly between groups I and II (P = .010), and the change in PV z-score was greater in groups I and III than in group II (P < .001). TAP during total correction was performed in 29.0%, 90.0%, and 16.7% of groups I, II, and III, respectively (P = .001; group I vs. II, P = .001; group II vs. III, P = .008). CONCLUSION: BPV was an effective and safe palliation that increased pulmonary blood flow and promoted growth of the PV annulus in selected symptomatic newborns with TOF.

Pediatric tubular pulmonary heart valve from decellularized engineered tissue tubes.

Pediatric patients account for a small portion of the heart valve replacements performed, but a pediatric pulmonary valve replacement with growth potential remains an unmet clinical need. Herein we report the first tubular heart valve made from two decellularized, engineered tissue tubes attached with absorbable sutures, which can meet this need, in principle. Engineered tissue tubes were fabricated by allowing ovine dermal fibroblasts to replace a sacrificial fibrin gel with an aligned, cell-produced collagenous matrix, which was subsequently decellularized. Previously, these engineered tubes became extensively recellularized following implantation into the sheep femoral artery. Thus, a tubular valve made from these tubes may be amenable to recellularization and, ideally, somatic growth. The suture line pattern generated three equi-spaced leaflets in the inner tube, which collapsed inward when exposed to back pressure, per tubular valve design. Valve testing was performed in a pulse duplicator system equipped with a secondary flow loop to allow for root distention. All tissue-engineered valves exhibited full leaflet opening and closing, minimal regurgitation (<5%), and low systolic pressure gradients (<2.5 mmHg) under pulmonary conditions. Valve performance was maintained under various trans-root pressure gradients and no tissue damage was evident after 2 million cycles of fatigue testing.

Use of oversized injectable valves in growing children for total repair of right ventricular outflow tract anomalies (preliminary results).

Right ventricular outflow tract surgery was originally confined to transannular patching, in the belief that pulmonary regurgitation was well tolerated. Because follow-up evaluations revealed the deleterious effects of pulmonary regurgitation, surgery today aims to spare or replace the valve. Available replacement devices have short lifetimes, considering growth mismatch in children. We hypothesize that oversizing the right infundibulum anticipates growth and that a squeezed prosthesis can complete the expansion process. The No-React® Injectable BioPulmonic Valve is designed for right infundibular surgery in adults, and hundreds of implants have shown promising results. We used this device for surgery in babies, with the addition of an innovative oversizing technique. This study evaluates our preliminary results and investigates whether such a technique might reduce growth mismatch. From September 2010 through July 2012, we implanted 11 injectable pulmonic valves. The median age of our patients was 23 months. After opening the right infundibulum, we enlarged it as much as possible with a wide patch. Before completing the patch suture, we injected an oversized valve. No problems occurred during surgery. No major insufficiency or leak was observed. We conclude that prostheses can be quite oversized and perform well even when not completely expanded. Oversized injectable pulmonic valves, shrunken to a smaller diameter, enabled the implantation of a device wider than otherwise possible, without affecting performance. Moreover, the prosthesis tended to return to its original size following growth, thereby reducing growth mismatch. Longer follow-up and larger numbers of patients are needed for verification.

Pulmonary annulus growth after the modified Blalock-Taussig shunt in tetralogy of Fallot.

BACKGROUND: In tetralogy of Fallot (TOF), it is well known that postoperative pulmonary regurgitation reduces right ventricular function during long-term follow-up. Complete repair without a transannular patch should help avoid pulmonary regurgitation. Recently, primary complete repair has been preferred to the staged repair with use of a Blalock-Taussig shunt (BTS) even in neonates or small infants; however, little has been reported about the influence of a BTS on pulmonary annular growth. METHODS: We examined 40 patients with TOF or double-outlet right ventricle with pulmonary stenosis. Twenty-one patients received a BTS before complete repair, whereas 19 patients underwent primary complete repair. Pulmonary annular size was measured by echocardiography before BTS, complete repair, or both, and ventricular volume was measured by cardiac catheterization. RESULTS: There were no significant differences in complete repair age or body size between the groups. Pulmonary annulus sizes in the BTS group were smaller than those in the primary repair group (Z score, -5.1 ± 2.5 vs -3.7 ± 1.8). After the BTS, significant annular growth (Z score, -2.8 ± 2.1) was observed (p = 0.0028), with a significant increase in left ventricular end-diastolic volume (p = 0.015). When patients with severe pulmonary stenosis (Z score > -7.0) were excluded, pulmonary annular preservation at complete repair was achieved in 64.7% (11/17) of the BTS group and 36.8% (7/19) of the primary repair group (p = 0.088). CONCLUSIONS: The BTS increased the pulmonary annular size and the left ventricular volume during the 6 months before complete repair, resulting in preservation of the pulmonary valve function.

Development and characterization of acellular porcine pulmonary valve scaffolds for tissue engineering.

Currently available replacement heart valves all have limitations. This study aimed to produce and characterize an acellular, biocompatible porcine pulmonary root conduit for reconstruction of the right ventricular outflow tract e.g., during Ross procedure. A process for the decellularization of porcine pulmonary roots was developed incorporating trypsin treatment of the adventitial surface of the scraped pulmonary artery and sequential treatment with hypotonic Tris buffer (HTB; 10 mM Tris pH 8.0, 0.1% (w/v) EDTA, and 10 KIU aprotinin), 0.1% (w/v) sodium dodecyl sulfate in HTB, two cycles of DNase and RNase, and sterilization with 0.1% (v/v) peracetic acid. Histology confirmed an absence of cells and retention of the gross histoarchitecture. Immunohistochemistry further confirmed cell removal and partial retention of the extracellular matrix, but a loss of collagen type IV. DNA levels were reduced by more than 96% throughout all regions of the acellular tissue and no functional genes were detected using polymerase chain reaction. Total collagen levels were retained but there was a significant loss of glycosaminoglycans following decellularization. The biomechanical, hydrodynamic, and leaflet kinematics properties were minimally affected by the process. Both immunohistochemical labeling and antibody absorption assay confirmed a lack of α-gal epitopes in the acellular porcine pulmonary roots and in vitro biocompatibility studies indicated that acellular leaflets and pulmonary arteries were not cytotoxic. Overall the acellular porcine pulmonary roots have excellent potential for development of a tissue substitute for right ventricular outflow tract reconstruction e.g., during the Ross procedure.

Pulmonary artery conduit in vivo dimensional requirements in a growing ovine model: comparisons with the ascending aorta.

BACKGROUND AND AIM OF THE STUDY: The pulmonary trunk (PT) structure and function are abnormal in multiple congenital cardiovascular diseases. Existing surgical treatments of congenital malformations of the right ventricular outflow tract and PT do not provide a long-term replacement that can adapt to normal growth. Although there is strong interest in developing tissue-engineered approaches for PT conduit replacement, there remains an absence of any complete investigation of the native geometric growth patterns of the PT to serve as a necessary benchmark. METHODS: Eleven Dorset sheep (aged 4-12 months) underwent a single cardiac magnetic resonance imaging study, from which luminal arterial surface points were obtained using a novel semi-automated segmentation technique. The three-dimensional shapes of the PT and ascending aorta (AA) were measured over the same time period to gain insight into differences in the geometric changes between these two great vessels. RESULTS: The volumetric growth of the PT appeared to be a linear function of age, whereas its surface geometry demonstrated non-uniform growth patterns. While tortuosity was maintained with age, the cross-sectional shape of the main pulmonary artery (MPA) evolved from circular in young animals to elliptical at 12 months. In addition, the distal MPA near the pulmonary artery bifurcation tapered with age. CONCLUSION: It can be concluded that postnatal growth of the PT is not a simple proportionate (i.e. isotropic) size increase, but rather exhibits complex three-dimensional geometric features during somatic growth.

Technical modification enabling pulmonary valve-sparing repair of a severely hypoplastic pulmonary annulus in patients with tetralogy of Fallot.

OBJECTIVES: Although pulmonary valve-sparing repair is preferable for patients with tetralogy of Fallot, the repair of very small pulmonary valves is challenging. The present study evaluates our modification for preserving severely hypoplastic pulmonary valves in patients with tetralogy of Fallot. METHODS: Sixty-eight consecutive patients who underwent complete repair of a tetralogy of Fallot between 2005 and 2011 were retrospectively reviewed. Patients with pulmonary atresia, absence of a pulmonary valve, atrioventricular septal defect and/or subarterial ventricular septal defect were excluded. There were 19 (28%) patients with a severely hypoplastic pulmonary annulus determined by preoperative echocardiography (z-score <-4). For these patients, we collected echocardiographic data and information about their postoperative course. RESULTS: Valve preserving was successful in 11 of 19 (58%) of the z < -4 group, compared with 48 of 49 (98%) of the z > -4 group. In the z < -4 valve-sparing subgroup (n = 11), the preoperative pulmonary valve diameter z-score was -4.9 (range -6.3 to -4.3), and an approach involving ventriculotomy with no transannular patch was employed at a mean age of 6.9 (range 2.2-16.1) months. In this subgroup, residual right ventricular outflow tract velocity was 2.4 ± 0.6 m/s at discharge from the hospital. During a mean follow-up of 2.6 ± 2.4 years, no reintervention was necessary. Late right ventricular outflow tract velocity was 2.2 ± 0.6 m/s, and there was no severe pulmonary regurgitation. The pulmonary valve annulus grew in relation to the patient's body surface area (z = -0.51, range -4.2-0.24) without any aneurysmal changes in the right ventricular outflow tract. CONCLUSIONS: Although our modification of valve-sparing repair for severely hypoplastic pulmonary valves in patients with tetralogy of Fallot could not be applied in all patients, this strategy enabled acceptable growth of the valve annulus, with only mild stenosis during the early to mid-term follow-up. This modification seems to be an option, even for a very small pulmonary valve.

Pulmonary root translocation in malposition of great arteries repair allows right ventricular outflow tract growth.

OBJECTIVE: Optimal surgical treatment of patients with transposition of the great arteries (TGA), ventricular septal defect (VSD), and pulmonary stenosis (PS) remains a matter of debate. This study evaluated the clinical outcome and right ventricle outflow tract performance in the long-term follow-up of patients subjected to pulmonary root translocation (PRT) as part of their surgical repair. METHODS: From April 1994 to December 2010, we operated on 44 consecutive patients (median age, 11 months). All had malposition of the great arteries as follows: TGA with VSD and PS (n = 33); double-outlet right ventricle with subpulmonary VSD (n = 7); double-outlet right ventricle with atrioventricular septal defect (n = 1); and congenitally corrected TGA with VSD and PS (n = 3). The surgical technique consisted of PRT from the left ventricle to the right ventricle after construction of an intraventricular tunnel that diverted blood flow from the left ventricle to the aorta. RESULTS: The mean follow-up time was 72 ± 52.1 months. There were 3 (6.8%) early deaths and 1 (2.3%) late death. Kaplan-Meier survival was 92.8% and reintervention-free survival was 82.9% at 12 years. Repeat echocardiographic data showed nonlinear growth of the pulmonary root and good performance of the valve at 10 years. Only 4 patients required reinterventions owing to right ventricular outflow tract problems. CONCLUSIONS: PRT is a good surgical alternative for treatment of patients with TGA complexes, VSD, and PS, with acceptable operative risk, high long-term survivals, and few reinterventions. Most patients had adequate pulmonary root growth and performance.

The evolving role of intraoperative balloon pulmonary valvuloplasty in valve-sparing repair of tetralogy of Fallot.

OBJECTIVE: The late morbidity of pulmonary regurgitation has intensified the interest in valve-sparing repair of tetralogy of Fallot. This study reviewed a single institution's experience with valve-sparing repair and investigated the role of intraoperative balloon valvuloplasty. METHODS: A retrospective chart review identified 238 patients who underwent complete primary repair of tetralogy of Fallot at less than 180 days of age. Patients were divided into 4 groups on the basis of the type of right ventricular outflow tract repair: transannular patch (n = 111), commissurotomy or standard rigid dilation (n = 71), intraoperative balloon pulmonary valvuloplasty (n = 32), or no valvar intervention (n = 24). RESULTS: Baseline demographic and anatomic factors differed among the 4 procedural groups with substantial overlap. Among 142 patients with pulmonary valve hypoplasia (z score, -2 to -4), 37% had valve-sparing repair. These patients had significant annular growth over time: z score increased 0.67 and 1.00 per year in the intraoperative balloon valvuloplasty (P < .001) and traditional valve-sparing (P < .001) groups, respectively. Rates of valve growth did not differ across groups, but z scores were 0.58 lower for the balloon valvuloplasty group across all time points (P = .001). Freedom from reintervention and surgery was shorter for the balloon valvuloplasty group than for the other groups (P < .001). CONCLUSIONS: Patients with tetralogy of Fallot and pulmonary valve hypoplasia who undergo valve-sparing repair with intraoperative balloon valvuloplasty have significant longitudinal annular growth, with normalization of annular size over time. Despite application in patients with more hypoplastic valves, balloon valvuloplasty resulted in similar valve growth and pulmonary regurgitation as traditional methods, but higher rates of reintervention. Although the precise role of this technique needs further refinement, it is likely to be most useful in patients with moderate pulmonary stenosis and moderate pulmonary valve dysplasia.

Tetralogy of Fallot without the infundibular septum-restricted growth of the pulmonary valve annulus after annulus preservation may render the right ventricular outflow tract obstructive.

OBJECTIVE: Tetralogy of Fallot (ToF) with infundibular septal deficiency (ISD) is commonly associated with postoperative right ventricular outflow tract obstruction (RVOTO), presumably caused by subpulmonary extension of ventricular septal defect (VSD) and restricted growth of the pulmonary valve annulus (PVA). We sought to determine the postoperative growth of the PVA after annulus preservation according to the presence or absence of the infundibular septum. METHODS: A retrospective review of 90 patients who underwent surgical repair of ToF between June 1997 and August 2008 was performed. Median age at operation was 9.5 months. Infundibular septum was absent in 15 (15/90, 17%). PVA was preserved in 71 patients (71/90, 79%), including 13 patients with ISD (13/15, 87%). RESULTS: Median follow-up duration was 39 months (2 months to 13 years). There was no early mortality and one late noncardiac death. Among the patients with PVA preservation, reoperation for RVOTO was performed in 4 patients (4/71, 6%), including 3 patients without the infundibular septum. ISD was identified as the only risk factor in reoperation for RVOTO after PVA preservation (RR: 21.85, P = .007). Among the patients who underwent repair with PVA preservation during infancy (n = 43), PVA (Z-score) increased postoperatively in patients with the infundibular septum (+ 0.021/month, P = .009), whereas the changes in PVA (Z-score) were nonsignificant in patients with ISD (-0.021/month, P = .306), with a marginal intergroup difference (P = .056). CONCLUSIONS: PVA preservation in ToF with ISD may be associated with a higher risk for postoperative RVOTO, which can be attributed to the restricted growth of the PVA.

Extracellular matrix remodeling and cell phenotypic changes in dysplastic and hemodynamically altered semilunar human cardiac valves.

INTRODUCTION: Congenital cardiac valve disease is common, affecting ∼1% of the population, with substantial morbidity and mortality, but suboptimal treatment options. Characterization of the specific matrix and valve cell phenotypic abnormalities in these valves could lend insight into disease pathogenesis and potentially pave the way for novel therapies. METHODS: Thirty-five human aortic and pulmonic valves were categorized based on gross and microscopic assessment into control valves (n=21); dysplastic valves, all except one also displaying hemodynamic changes (HEMO/DYSP, n=6); and hemodynamically altered valves (HEMO, n=8). Immunohistochemistry was performed on valve sections and flow cytometry on valvular interstitial cells. RESULTS: While both hemodynamically altered aortic and pulmonic valves demonstrated increased collagen turnover and cell activation, prolyl 4-hydroxylase and hyaluronan increased in hemodynamically altered aortic valves but decreased in hemodynamically altered pulmonic valves relative to control valves (P<.001). HEMO/DYSP aortic valves demonstrated decreased collagen and elastic fiber synthesis and turnover compared to both hemodynamically altered aortic valves and control aortic valves (each P<.006). Valvular interstitial cells from both hemodynamically altered and HEMO/DYSP pulmonic valves showed altered cell phenotype compared to control valves (each P<.032), especially increased non-muscle myosin. Furthermore, valvular interstitial cells from hemodynamically altered pulmonic valves and HEMO/DYSP aortic and pulmonic valves each demonstrated greater size and complexity compared to control valves (each P<.05). CONCLUSIONS: Dysplastic semilunar valves displayed alterations in collagen and elastic fiber turnover that were distinct from valves similarly exposed to altered hemodynamics as well as to control valves. These results demonstrate that dysplastic valves are not simply valves with gross changes or loss of leaflet layers, but contain complex matrix and cell phenotype changes that, with future study, could potentially be targets for novel nonsurgical treatments.

Balloon pulmonary valvuloplasty in tetralogy of Fallot: effects on growth of pulmonary annulus and transannular patch.

BACKGROUND: Balloon pulmonary valvuloplasty and its benefit on the growth of pulmonary annulus and pulmonary artery in tetralogy of Fallot (TOF) patients remains controversial. The purpose ofthe present study was to determine the growth of pulmonary valve annulus and pulmonary artery and to evaluate the need of transannular patch during total surgical correction in patients with tetralogy of Fallot (TOF) after balloon pulmonary valvuloplasty. MATERIAL AND METHOD: Fifty-one severely hypoxic TOF patients, who underwent balloon dilatation ofpulmonary valve, were included in the present study. The clinical outcomes, oxygen saturation, and echocardiographic parameters before and after balloon dilatation were analyzed. RESULTS: There were 33 males and 18females. The mean age was 3 years 5 months old (range, I month-15 years 8 months old). The mean oxygen saturation increasedfrom 73.9 +/- 9.1 to 84.8 +/- 6.7% immediately after the procedure (p-value < 0.05). There was no serious procedural-related complication. At the mean follow-up period of 2 years and 4 months, the mean Z-score of pulmonary annulus size increased from -2.56 SD to -1.87 SD (p-value < 0.05) and the right pulmonary artery size from -0.29 SD to + 0.46 SD (p-value < 0.05). Thirty-seven patients (66.1%) underwent corrective surgery. Pulmonary transannular patch was performed in 11 of37 patients (29.7%). CONCLUSION: Pulmonary valve dilatation in patients with TOF is safe. It promotes the growth ofthe pulmonary valve annulus and pulmonary artery and may decrease the need of transannular patch at the time of surgical correction.

Differential changes in the molecular stability of collagen from the pulmonary and aortic valves during the fetal-to-neonatal transition.

During the fetal-to-neonatal transition, transvalvular pressures (TVPs) on the aortic and pulmonary valves change dramatically-but differently for each valve. We have examined changes in the molecular stability and crosslinking of collagen during this transition. Aortic and pulmonary valves were harvested from fetal and neonatal cattle. Using differential scanning calorimetry (DSC), denaturation of valvular collagen was examined and, using HPLC, the types and quantities of enzymatic crosslinks were examined. No difference in hydrothermal stability was found between the collagens in the fetal aortic and pulmonary valves; this was expected since the TVP is approximately the same across both valves before birth. Only in the neonatal samples was the collagen from aortic valves (higher TVP) less stable than that from pulmonary valves (lower TVP). Surprisingly, the enthalpy of denaturation did not differ either between valve type or with age, suggesting an entropic mechanism of altered molecular stability. A significant difference in immature-to-mature crosslink ratio was found between neonatal aortic and pulmonary valves: a difference absent in fetal valves. This ratio-indicative of remodeling rate-parallels (and may be a function of) the changing in vivo load. This study highlights the relationship between in vivo load and both (i) molecular stability and (ii) collagen remodeling in heart valves.

Biointegration and growth of porcine valved pulmonary conduits in a sheep model.

As there is currently no suitable valved pulmonary conduit for small children, porcine conduits treated by the L-Hydro process were implanted into 9 newborn lambs to investigate growth potential. Of the 8 survivors, 7 were kept alive for 12 months after implantation. The diameter of the conduit and gradient across the valve were evaluated at surgery and at 3 and 9 months postoperatively using bidirectional echocardiographic and angiographic methods. After sacrifice, histological and radiological analyses were performed. The mean weight of the animals was 4.2 +/- 1.1 kg at implantation and 43.1 +/- 6.2 kg at sacrifice. There was a significant increase in mean valve area from 139.9 +/- 18.0 mm2 at implantation to 443.5 +/- 89.2 mm2 at 12 months. Pre-sacrifice angiography showed no transvalvular gradient, and radiographic analysis did not reveal significant conduit wall or leaflet calcification in any of the animals. Histological examination of the grafts demonstrated total integration, with native-like intact valve leaflets. Thus functional evaluation, echocardiography, and histology demonstrated growth of the grafts with completely endothelialized and apparently normal pulmonary valve leaflets without calcification.