Use of a Dilatable exGraft Conduit in Single-Ventricle Palliation

Reintervention for Superior Vena Cava Obstruction After Heart Transplant

BACKGROUND

Children undergoing orthotopic heart transplant (OHT) may require complex reconstruction of superior vena cava (SVC) anomalies. SVC anatomy and mode of reconstruction are potential risk factors for SVC obstruction.

METHODS

A retrospective single-center review was conducted of patients undergoing initial OHT between January 1, 1990, and July 1, 2021. Simple SVC anatomy included a single right SVC to the right atrium or bilateral SVCs with a left SVC to an intact coronary sinus, without prior superior cavopulmonary connection. Presence of anomalous SVC anatomy, superior cavopulmonary connection, or previous atrial switch operation defined complex anatomy. Reconstructive strategies included atrial anastomosis; direct SVC-to-SVC anastomosis; and augmented SVC anastomosis using innominate vein, patch, cavopulmonary connection, or interposition graft. The primary outcome was reintervention for SVC obstruction.

RESULTS

Of 288 patients, pretransplant diagnoses included congenital heart disease (n = 155 [54%]), cardiomyopathy (n = 125 [43%]), and other (n = 8 [3%]). Most (n = 208 [72%]) had simple SVC anatomy compared with complex SVC anatomy (80 [28%]). Reintervention for SVC obstruction occurred in 15 of 80 (19%) with complex anatomy and 1 of 208 (0.5%) with simple anatomy (P = .0001). Reintervention was more common when innominate vein or a patch was used (9/25 [36%]) compared with an interposition graft (1/7 [14%]) or direct anastomosis (6/82 [7%]; χ2 = 13.1; P = .001). Most reinterventions occurred within 30 days of OHT (14/16 [88%]).

CONCLUSIONS

Patients with complex SVC anatomy have a higher rate of reintervention for SVC obstruction after OHT compared with those with simple SVC anatomy. In cases of complex SVC anatomy, interposition grafts may be associated with less reintervention compared with complex reconstructions using donor tissue.

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.