Mechanical and microstructural analysis of a radially expandable vascular conduit for neonatal and pediatric cardiovascular surgery

Monitoring cardiovascular disease severity using near-infrared mechanoluminescent materials as a built-in indicator

Artificial vascular grafts (AVGs) are widely used to treat cardiovascular diseases (CVDs). But none of the reported AVGs can also monitor the CVD severity. Because CVDs affect the blood pressure, we proposed to employ a force-sensing material that emits near-infrared (NIR) light upon force loading, a NIR mechanoluminescent (ML) material (CaZnOS:Nd³⁺), as an indicator in AVGs to tackle this challenge. Specifically, we used a polydimethylsiloxane AVG modified with this ML material, termed ML-AVG, to achieve the rapid and convenient monitoring of two CVD models (vascular occlusion and hypertension) in real time. The NIR ML material showed good blood and tissue compatibility without causing an inflammatory response. By implanting the ML-AVGs into the common carotid artery (CCA) of rats, we observed the NIR ML signals emitted from the AVGs by a thermal camera, a NIR spectrometer, and a NIR camera. The NIR ML signal was linearly correlated with the degree of vascular opening (in the vascular occlusion model) or the degree of hypertension (in the hypertension model). Our work suggests that NIR ML materials can monitor the severity of diseases with force or pressure as biomarkers.

Tunable Blood Shunt for Neonates With Complex Congenital Heart Defects

Despite advancements in procedures and patient care, mortality rates for neonatal recipients of the Norwood procedure, a palliation for single ventricle congenital malformations, remain high due to the use of a fixed-diameter blood shunt. In this study, a new geometrically tunable blood shunt was investigated to address limitations of the current treatment paradigm (e.g., Modified Blalock-Taussig Shunt) by allowing for controlled modulation of blood flow through the shunt to accommodate physiological changes due to the patient’s growth. First, mathematical and computational cardiovascular models were established to investigate the hemodynamic requirements of growing neonatal patients with shunts and to inform design criteria for shunt diameter changes. Then, two stages of prototyping were performed to design, build and test responsive hydrogel systems that facilitate tuning of the shunt diameter by adjusting the hydrogel’s degree of crosslinking. We examined two mechanisms to drive crosslinking: infusion of chemical crosslinking agents and near-UV photoinitiation. The growth model showed that 15–18% increases in shunt diameter were required to accommodate growing patients’ increasing blood flow; similarly, the computational models demonstrated that blood flow magnitudes were in agreement with previous reports. These target levels of diameter increases were achieved experimentally with model hydrogel systems. We also verified that the photocrosslinkable hydrogel, composed of methacrylated dextran, was contact-nonhemolytic. These results demonstrate proof-of-concept feasibility and reflect the first steps in the development of this novel blood shunt. A tunable shunt design offers a new methodology to rebalance blood flow in this vulnerable patient population during growth and development.

Case Report: "Smart Palliation" and "Clepsydra Shape": A new approach in complex congenital heart disease

A limiting factor in using vascular conduits in the pediatric/newborn population is their inability to grow. Many complex congenital heart diseases require palliative surgery, but using rigid and nonexpandable conduits does not allow the structures to grow and anticipates the need for redo surgery. In newborns, a way to increase the palliation time according to the patient's growth is desirable. In recent years, expandable shunts (exGraft™ PECA) have been developed. According to recent material studies, a shunt could increase diameter after endovascular balloon dilatation. In this case report, we describe the first case of endovascular Blalock-Thomas-Taussig shunt (mBT) shunt expansion in a Tetralogy of Fallot / atrial-ventricular Septal Defect complete (TOFAVSDc) patient with trisomy 21 who went to palliative treatment for tracheomalacia (noncardiac lesion association), severe pulmonary arteries hypoplasia, and low weight. This case introduces the "Smart Palliation concept" in the clinical scenario of selected growing patients where the lifetime of the Blalock-Thomas-Taussig (BT) shunt, anatomic substrates, and complexity of clinical status may require an additional palliation time. The limitation of endovascular conduit expansion is the fragility of the anastomosis site. The anastomosis site is a lesser strength structure of the conduit, and dilatation could develop procedure complications. For this reason, in this paper, we introduced our project design: a new technique (Clepsydra Shape) that consists, before surgical implantation, of pre-expansion of the proximal and distal anastomotic parts of the shunt to obtain an increase of 30% in size of both anastomotic sides, preventing stress- and stretch-related lesion of future balloon dilatation.

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

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

Early Infant Symptomatic Patients With Tetralogy of Fallot With Absent Pulmonary Valve: Pulmonary Artery Management and Airway Stabilization

BACKGROUND

Tracheobronchomalacia and airway obstruction from severely dilated pulmonary arteries in tetralogy of Fallot with absent pulmonary valve (TOF-APV) has been associated with high rates of respiratory failure and mortality (15% to 25%). It is not known whether aggressive pulmonary artery (PA) or direct airway intervention during early definitive cardiac repair improves outcomes.

METHODS

A retrospective observational study was made of all patients undergoing surgical repair for TOF-APV at our center between 2006 and 2018.

RESULTS

Twenty patients underwent repair at a median age of 51 days and PA Z-scores of 8.1. Twelve patients had a valve implanted, 6 of whom required reoperation for valve replacement at a median of 9 months (range, 3 to 28) compared with 8 who had initial transannular patch, and only 1 patient required subsequent valve replacement (P < .05). Seven patients had central PAs replaced with thin-walled Gore-Tex (WL Gore, Flagstaff, AZ) grafts; none of these required PA reoperation during a median follow-up of 26.5 months, whereas 3 of 13 patients who did not have PA replacement with Gore-Tex required subsequent PA reoperation (P < .05). Concomitant airway interventions (eg, tracheobronchopexy/plasty) were performed in 4 patients and none required subsequent airway interventions, whereas 2 patients not having initial airway intervention required subsequent tracheopexy (P < .05). Three patients in the cohort eventually required tracheostomy (15%), and 2 patients died (10%; on postoperative days 30 and 326); none had received initial airway intervention.

CONCLUSIONS

Pulmonary artery replacement and aggressive direct airway management at initial definitive repair of cardiac TOF-APV can be performed safely with acceptable survival outcomes and low rates of airway and PA reintervention.

Use of a Dilatable exGraft Conduit in Single-Ventricle Palliation

Surgically paced prosthetic conduits are commonly used in the treatment of congenital heart disease. A major limitation of available prosthetic grafts is that they do not grow with the patient. We describe a human case of percutaneous balloon dilation of a surgically placed exGraft conduit (PECA Labs, Inc, Pittsburgh, PA) in a neonate with single-ventricle disease. The use of dilatable conduits could change the management of many congenital heart defects and greatly reduce both the morbidity of repeat cardiac reoperations and the deleterious effects of prolonged conduit dysfunction that accrue between surgical conduit revisions.