De Novo Valve Tissue Morphology Following Bioscaffold Mitral Valve Replacement in a Juvenile Non-Human Primate Model.

The utility of implanting a bioscaffold mitral valve consisting of porcine small intestinal submucosa (PSIS) in a juvenile baboon model (12 to 14 months old at the time of implant; n = 3) to assess their in vivo tissue remodeling responses was investigated. Our findings demonstrated that the PSIS mitral valve exhibited the robust presence of de novo extracellular matrix (ECM) at all explantation time points (at 3-, 11-, and 20-months). Apart from a significantly lower level of proteoglycans in the implanted valve's annulus region (p < 0.05) at 3 months compared to the 11- and 20-month explants, there were no other significant differences (p > 0.05) found between any of the other principal valve ECM components (collagen and elastin) at the leaflet, annulus, or chordae tendinea locations, across these time points. In particular, neochordae tissue had formed, which seamlessly integrated with the native papillary muscles. However, additional processing will be required to trigger accelerated, uniform and complete valve ECM formation in the recipient. Regardless of the specific processing done to the bioscaffold valve, in this proof-of-concept study, we estimate that a 3-month window following bioscaffold valve replacement is the timeline in which complete regeneration of the valve and integration with the host needs to occur.

Scavenging right atrial Bretschneider histidine-tryptophan-ketoglutarate cardioplegia: Impact on hyponatremia and seizures in pediatric cardiac surgery patients.

OBJECTIVE: Custodiol-HTK cardioplegia (Custodiol-HTK Koheler Chemie, GmbH, Bensheim, Germany) causes fluctuations in serum sodium levels, hyponatremia, and is associated with postoperative seizures. We investigated the influence of scavenging right atrial effluent during delivery on intraoperative serum sodium levels and postoperative seizure incidence in pediatric cardiac surgery patients. METHODS: A total of 204 patients younger than age 18 years undergoing congenital heart surgery between January 2016 and March 2018 were analyzed retrospectively. Serum sodium levels after administration of Custodiol-HTK cardioplegia were compared between the scavenge and nonscavenge groups and then in the propensity score-matched cohort (n = 96). Postoperative seizures were documented clinically and with electroencephalogram findings. Logistic regression models were used to identify the independent predictors of serum sodium level after aortic crossclamp. RESULTS: Of 204 patients, 156 (76.5%) were in the nonscavenge, and 48 (23.5%) in the scavenge groups. A serum sodium level <130 mEq/L after crossclamp and administration of Custodiol-HTK cardioplegia in the nonscavenge group were 70% versus 21% in the scavenge group (odds ratio, 8.8; 95% confidence interval, 4.1-18.3; P < .0001) in the entire cohort, and 77% versus 21% (odds ratio, 12.8; 95% confidence interval, 4.8-33.1; P < .0001) in the propensity score-matched cohort. Of 16 patients experiencing a postoperative seizure, 14 (87.5%) had a sodium level <130 mEq/L and 2 (12.5%) had a sodium level ≥130 mEq/L (odds ratio, 5.1; 95% confidence interval, 1.3-22.8; P = .021) after crossclamp. Postoperative seizures occurred in the nonscavenge group but not the scavenge group in the entire cohort (P = .02) and in the propensity score-matched patients (P = .041). Multivariable analysis of the entire cohort showed that scavenge intervention was an independent factor associated with significantly decreased risk of sodium level <130 mEq/L (odds ratio, 0.17; 95% confidence interval, 0.08-0.36; P = .000). CONCLUSIONS: Right atrial effluent scavenging was protective against fluctuations in serum sodium levels after crossclamp and Custodiol-HTK cardioplegia administration independently in both entire and matched cohort, and was also associated with decreased incidence of postoperative seizures.

Porcine Small Intestinal Submucosa Mitral Valve Material Responses Support Acute Somatic Growth.

Background: Conceptually, a tissue engineered heart valve would be especially appealing in the pediatric setting since small size and somatic growth constraints would be alleviated. In this study, we utilized porcine small intestinal submucosa (PSIS) for valve replacement. Of note, we evaluated the material responses of PSIS and subsequently its acute function and somatic growth potential in the mitral position. Methods and Results: Material and mechanical assessment demonstrated that both fatigued 2ply (∼65 µm) and 4ply (∼110 µm) PSIS specimens exhibited similar failure mechanisms, but at an accelerated rate in the former. Specifically, the fatigued 2ply PSIS samples underwent noticeable fiber pullout and recruitment on the bioscaffold surface, leading to higher yield strength (p < 0.05) and yield strain (p < 0.05) compared to its fatigued 4ply counterparts. Consequently, 2ply PSIS mitral valve constructs were subsequently implanted in juvenile baboons (n = 3). Valve function was longitudinally monitored for 90 days postvalve implantation and was found to be robust in all animals. Histology at 90 days in one of the animals revealed the presence of residual porcine cells, fibrin matrix, and host baboon immune cells but an absence of tissue regeneration. Conclusions: Our findings suggest that the altered structural responses of PSIS, postfatigue, rather than de novo tissue formation, are primarily responsible for the valve's ability to accommodate somatic growth during the acute phase (90 days) following mitral valve replacement. Impact Statement Tissue engineered heart valves (TEHVs) offer the potential of supporting somatic growth. In this study, we investigated a porcine small intestinal submucosa bioscaffold for pediatric mitral heart valve replacement. The novelty of the study lies in identifying material responses under mechanical loading conditions and its effectiveness in being able to function as a TEHV. In addition, the ability of the scaffold valve to support acute somatic growth was evaluated in the Baboon model. The current study contributes toward finding a solution for critical valve diseases in children, whose current prognosis for survival is poor.

Custodiol cardioplegia solution compared to cold blood cardioplegia in pediatric cardiac surgery: a single-institution experience.

OBJECTIVE: Custodiol is an intracellular, crystalloid cardioplegia solution that is a single-dose alternative to multi-dose cold blood cardioplegia; however, there is scarce data regarding its use in infants and children. The objective of this study was to compare its impact on myocardial function in infants. METHODS: Single-center retrospective review including 132 patients <12 months old undergoing biventricular repair. There were 106 patients who received single-dose Custodiol and 27 patients who received multi-dose blood cardioplegia. Demographic and echocardiographic data were compared between the two groups. RESULTS: Patients receiving Custodiol were slightly younger (100 ± 62 days) and lower weight (4.7 ± 1.3 kg) compared to 152 ± 86 days and 5.2 ± 1.3 kg for blood cardioplegia (p < 0.05). The Society of Thoracic Surgeons/European Association for Cardio-Thoracic Surgery Congenital Heart Surgery score was similar between both groups. Average cardiopulmonary bypass time was similar between both groups (Custodiol 93 ± 54 minutes vs. blood 81 ± 44 minutes, p = 0.46) as was aortic cross-clamp time (Custodiol 58 ± 33 minutes vs. cold blood 53 ± 33 minutes, p = 0.62). Pre-operative left ventricular ejection fraction was similar for blood 73 ± 8% versus Custodiol 70 ± 9%, p = 0.21. There was also no intergroup difference in left ventricular ejection fraction 24 hours post op (blood 64 ± 9% vs. Custodiol 65 ± 12%, p = 0.53) or at discharge (blood 66 ± 10% vs. Custodiol 66 ± 11%, p = 0.95). The pre-operative right ventricle function by fractional area change was also similar in blood cardioplegia (46 ± 13%) versus Custodiol (48 ± 9%, p = 0.38) and showed similar drops in parameters in the two groups 24 hours after surgery and at discharge. CONCLUSION: Single-dose Custodiol is as safe as blood cardioplegia for myocardial protection in congenital cardiac surgery for the cross-clamp times evaluated in this study. Evaluation at longer cross-clamp times would be helpful to determine if there is a greater benefit to single-dose Custodiol versus more repeated doses of blood cardioplegia for longer cross-clamp times.

Mitral valve replacement using a handmade construct in an infant.

We recently reported the feasibility of a handmade left atrioventricular valve using decellularized extracellular matrix for 3 months in a failed repair of AV canal defect. We present the use of an extracellular matrix mitral valve for 9 months in an infant with an un-repairable congenitally malformed valve. The valve functioned perfectly without anticoagulation until the patient expired from non-cardiac complications of their fibrillin gene defect. This report adds further experience using valves made from extracellular matrix in the systemic ventricle both in terms of application and in terms of short-term durability of the construct.

Hydrodynamic Assessment of Aortic Valves Prepared from Porcine Small Intestinal Submucosa.

Infants and children born with severe cardiac valve lesions have no effective long term treatment options since currently available tissue or mechanical prosthetic valves have sizing limitations and no avenue to accommodate the growth of the pediatric patient. Tissue engineered heart valves (TEHVs) which could provide for growth, self-repair, infection resistance, and long-term replacement could be an ideal solution. Porcine small intestinal submucosa (PSIS) has recently emerged as a potentially attractive bioscaffold for TEHVs. PSIS may possess the ability to recruit endogenous cardiovascular cells, leading to phenotypically-matched replacement tissue when the scaffold has completely degraded. Our group has successfully implanted custom-made PSIS valves in 4 infants with critical valve defects in whom standard bioprosthetic or mechanical valves were not an option. Short term clinical follow-up has been promising. However, no hydrodynamic data has been reported to date on these valves. The purpose of this study was to assess the functional effectiveness of tri-leaflet PSIS bioscaffolds in the aortic position compared to standard tri-leaflet porcine bioprosthetic valves. Hydrodynamic evaluation of acute PSIS function was conducted using a left heart simulator in our laboratory. Our results demonstrated similar flow and pressure profiles (p > 0.05) between the PSIS valves and the control valves. However, forward flow energy losses were found to be significantly greater (p < 0.05) in the PSIS valves compared to the controls possibly as a result of stiffer material properties of PSIS relative to glutaraldehyde-fixed porcine valve tissue. Our findings suggest that optimization of valve dimensions and shape may be important in accelerating de novo valve tissue growth and avoidance of long-term complications associated with higher energy losses (e.g. left ventricular hypertrophy). Furthermore, long term animal and clinical studies will be needed in order to conclusively address somatic growth potential of PSIS valves.