Patient-specific 3D in vitro modeling and fluid dynamic analysis of primary pulmonary vein stenosis.

Introduction: Primary pulmonary vein stenosis (PVS) is a rare congenital heart disease that proves to be a clinical challenge due to the rapidly progressive disease course and high rates of treatment complications. PVS intervention is frequently faced with in-stent restenosis and persistent disease progression despite initial venous recanalization with balloon angioplasty or stenting. Alterations in wall shear stress (WSS) have been previously associated with neointimal hyperplasia and venous stenosis underlying PVS progression. Thus, the development of patient-specific three-dimensional (3D) in vitro models is needed to further investigate the biomechanical outcomes of endovascular and surgical interventions. Methods: In this study, deidentified computed tomography images from three patients were segmented to generate perfusable phantom models of pulmonary veins before and after catheterization. These 3D reconstructions were 3D printed using a clear resin ink and used in a benchtop experimental setup. Computational fluid dynamic (CFD) analysis was performed on models in silico utilizing Doppler echocardiography data to represent the in vivo flow conditions at the inlets. Particle image velocimetry was conducted using the benchtop perfusion setup to analyze WSS and velocity profiles and the results were compared with those predicted by the CFD model. Results: Our findings indicated areas of undesirable alterations in WSS before and after catheterization, in comparison with the published baseline levels in the healthy in vivo tissues that may lead to regional disease progression. Discussion: The established patient-specific 3D in vitro models and the developed in vitro-in silico platform demonstrate great promise to refine interventional approaches and mitigate complications in treating patients with primary PVS.

Targeted Rapamycin Delivery via Magnetic Nanoparticles to Address Stenosis in a 3D Bioprinted in Vitro Model of Pulmonary Veins.

Vascular cell overgrowth and lumen size reduction in pulmonary vein stenosis (PVS) can result in elevated PV pressure, pulmonary hypertension, cardiac failure, and death. Administration of chemotherapies such as rapamycin have shown promise by inhibiting the vascular cell proliferation; yet clinical success is limited due to complications such as restenosis and off-target effects. The lack of in vitro models to recapitulate the complex pathophysiology of PVS has hindered the identification of disease mechanisms and therapies. This study integrated 3D bioprinting, functional nanoparticles, and perfusion bioreactors to develop a novel in vitro model of PVS. Bioprinted bifurcated PV constructs are seeded with endothelial cells (ECs) and perfused, demonstrating the formation of a uniform and viable endothelium. Computational modeling identified the bifurcation point at high risk of EC overgrowth. Application of an external magnetic field enabled targeting of the rapamycin-loaded superparamagnetic iron oxide nanoparticles at the bifurcation site, leading to a significant reduction in EC proliferation with no adverse side effects. These results establish a 3D bioprinted in vitro model to study PV homeostasis and diseases, offering the potential for increased throughput, tunability, and patient specificity, to test new or more effective therapies for PVS and other vascular diseases.

Leveraging 3D Bioprinting and Photon-Counting Computed Tomography to Enable Noninvasive Quantitative Tracking of Multifunctional Tissue Engineered Constructs.

3D bioprinting is revolutionizing the fields of personalized and precision medicine by enabling the manufacturing of bioartificial implants that recapitulate the structural and functional characteristics of native tissues. However, the lack of quantitative and noninvasive techniques to longitudinally track the function of implants has hampered clinical applications of bioprinted scaffolds. In this study, multimaterial 3D bioprinting, engineered nanoparticles (NPs), and spectral photon-counting computed tomography (PCCT) technologies are integrated for the aim of developing a new precision medicine approach to custom-engineer scaffolds with traceability. Multiple CT-visible hydrogel-based bioinks, containing distinct molecular (iodine and gadolinium) and NP (iodine-loaded liposome, gold, methacrylated gold (AuMA), and Gd2 O3 ) contrast agents, are used to bioprint scaffolds with varying geometries at adequate fidelity levels. In vitro release studies, together with printing fidelity, mechanical, and biocompatibility tests identified AuMA and Gd2 O3 NPs as optimal reagents to track bioprinted constructs. Spectral PCCT imaging of scaffolds in vitro and subcutaneous implants in mice enabled noninvasive material discrimination and contrast agent quantification. Together, these results establish a novel theranostic platform with high precision, tunability, throughput, and reproducibility and open new prospects for a broad range of applications in the field of precision and personalized regenerative medicine.

Retrograde Pulmonary Vein Recanalization Using Transcatheter Electrosurgery.

Transcatheter electrosurgery is a wire-based technique used to traverse or cut tissue within blood-filled spaces using alternating current delivered by guidewires or catheters. The use of transcatheter electrosurgical techniques in the pediatric population has been limited. We are reporting the first case of retrograde pulmonary vein recanalization using transcatheter electrosurgery. (Level of Difficulty: Advanced.).

Factors Influencing Reintervention Following Ductal Artery Stent Implantation for Ductal-Dependent Pulmonary Blood Flow: Results From the Congenital Cardiac Research Collaborative.

BACKGROUND: Stenting of the patent ductus arteriosus (PDA) is an established palliative option for infants with ductal-dependent pulmonary blood flow. Following initial palliation, reintervention on the PDA stent is common, but risk factors have not been characterized. METHODS: Infants with ductal-dependent pulmonary blood flow palliated with PDA stent between 2008 and 2015 were reviewed within the Congenital Cardiac Research Collaborative. Rates and risk factors for reintervention were analyzed. RESULTS: Among 105 infants who underwent successful PDA stenting, 41 patients (39%) underwent a total of 53 reinterventions on the PDA stent, with all but one occurring within 6 months of the initial intervention. Stent redilation constituted the majority of reintervention (n=35; 66%) followed by additional stent placement (n=11; 21%) and surgical shunt placement (n=7; 13%). The majority of reintervention was nonurgent, and there were no deaths during the reintervention procedure. All but one reintervention occurred within 6 months of the initial procedure. On univariate analysis, risk factors for reintervention included anticipated single-ventricle physiology, lack of prior balloon pulmonary valvuloplasty, use of drug-eluting stent, and increased ductal tortuosity. CONCLUSIONS: In infants with ductal-dependent pulmonary blood flow palliated with PDA stent implantation, reintervention is common, can be performed safely, and is associated with both anatomic/procedural factors and anticipated final physiology.

Patient-Specific 3D Bioprinted Models of Developing Human Heart.

The heart is the first organ to develop in the human embryo through a series of complex chronological processes, many of which critically rely on the interplay between cells and the dynamic microenvironment. Tight spatiotemporal regulation of these interactions is key in heart development and diseases. Due to suboptimal experimental models, however, little is known about the role of microenvironmental cues in the heart development. This study investigates the use of 3D bioprinting and perfusion bioreactor technologies to create bioartificial constructs that can serve as high-fidelity models of the developing human heart. Bioprinted hydrogel-based, anatomically accurate models of the human embryonic heart tube (e-HT, day 22) and fetal left ventricle (f-LV, week 33) are perfused and analyzed both computationally and experimentally using ultrasound and magnetic resonance imaging. Results demonstrate comparable flow hemodynamic patterns within the 3D space. We demonstrate endothelial cell growth and function within the bioprinted e-HT and f-LV constructs, which varied significantly in varying cardiac geometries and flow. This study introduces the first generation of anatomically accurate, 3D functional models of developing human heart. This platform enables precise tuning of microenvironmental factors, such as flow and geometry, thus allowing the study of normal developmental processes and underlying diseases.

Risk Factors for Red Blood Cell Transfusions in Children Undergoing Cardiac Catheterization.

OBJECTIVE: To identify risk factors associated with risk of red blood cell transfusions (RBCTs) following pediatric cardiac catheterizations. STUDY DESIGN: We performed a review of all pediatric cardiac catheterizations from 2012 to 2017. The primary endpoint was RBCT within 72 hours of pediatric cardiac catheterization. Patient and procedural factors were reviewed. Generalized linear modelling was performed to describe interactions among relevant risk factors. RESULTS: In total, 831 RBCTs occurred within 72 hours of 6028 pediatric cardiac catheterizations (13.8%). Univariate analysis revealed that the prevalence of RBCT was highest among infants (37.6% incidence of RBCT) and among those with higher estimated blood loss as a percent of blood volume (P = .03). Among infants, multivariate analysis revealed that weight (OR 0.72; 95% CI 0.63-0.81), complex 2-ventricle (OR 3.14, 95% CI 2.18-4.57), and single ventricle status (OR 5.21, 95% CI 3.42-8.01) were associated with risk of RBCT. Inpatient infants from intensive care (OR 4.74; 95% CI 3.49-6.49) or stepdown units (OR 2.33; 95% CI 1.58-3.46) were at higher risk. Length of procedure (OR 2.57; 95% CI 2.03-3.26) and oxygen saturation (OR 0.98; 95% CI 0.97-0.99; P < .01) were also associated with RBCTs. CONCLUSIONS: Hospitalized infants with single ventricle or complex 2-ventricle anatomy are at highest risk of RBCT. Length of procedure, blood loss, and oxygen saturations are additional risk factors associated with RBCT. Operators should consider these factors when planning pediatric cardiac catheterizations, particularly when exposure to RBCT is undesirable.

Engineering Functional Cardiac Tissues for Regenerative Medicine Applications.

PURPOSE OF REVIEW: Tissue engineering has expanded into a highly versatile manufacturing landscape that holds great promise for advancing cardiovascular regenerative medicine. In this review, we provide a summary of the current state-of-the-art bioengineering technologies used to create functional cardiac tissues for a variety of applications in vitro and in vivo. RECENT FINDINGS: Studies over the past few years have made a strong case that tissue engineering is one of the major driving forces behind the accelerating fields of patient-specific regenerative medicine, precision medicine, compound screening, and disease modeling. To date, a variety of approaches have been used to bioengineer functional cardiac constructs, including biomaterial-based, cell-based, and hybrid (using cells and biomaterials) approaches. While some major progress has been made using cellular approaches, with multiple ongoing clinical trials, cell-free cardiac tissue engineering approaches have also accomplished multiple breakthroughs, although drawbacks remain. This review summarizes the most promising methods that have been employed to generate cardiovascular tissue constructs for basic science or clinical applications. Further, we outline the strengths and challenges that are inherent to this field as a whole and for each highlighted technology.

Thromboprophylaxis strategies for children with single-ventricle circulations (superior or total cavo-pulmonary connections) after stent implantation.

OBJECTIVE: To define optimal thromboprophylaxis strategy after stent implantation in superior or total cavopulmonary connections. BACKGROUND: Stent thrombosis is a rare complication of intravascular stenting, with a perceived higher risk in single-ventricle patients. METHODS: All patients who underwent stent implantation within superior or total cavopulmonary connections (caval vein, innominate vein, Fontan, or branch pulmonary arteries) were included. Cohort was divided into aspirin therapy alone versus advanced anticoagulation, including warfarin, enoxaparin, heparin, or clopidogrel. Primary endpoint was in-stent or downstream thrombus, and secondary endpoints included bleeding complications. RESULTS: A total of 58 patients with single-ventricle circulation underwent 72 stent implantations. Of them 14 stents (19%) were implanted post-superior cavopulmonary connection and 58 (81%) post-total cavopulmonary connection. Indications for stenting included vessel/conduit stenosis (67%), external compression (18%), and thrombotic occlusion (15%). Advanced anticoagulation was prescribed for 32 (44%) patients and aspirin for 40 (56%) patients. Median follow up was 1.1 (25th-75th percentile, 0.5-2.6) years. Echocardiograms were available in 71 patients (99%), and advanced imaging in 44 patients (61%). Thrombosis was present in two patients on advanced anticoagulation (6.3%) and none noted in patients on aspirin (p = 0.187). Both patients with in-stent thrombus underwent initial stenting due to occlusive left pulmonary artery thrombus acutely post-superior cavopulmonary connection. There were seven (22%) significant bleeding complications for advanced anticoagulation and none for aspirin (p < 0.001). CONCLUSIONS: Antithrombotic strategy does not appear to affect rates of in-stent thrombus in single-ventricle circulations. Aspirin alone may be sufficient for most patients undergoing stent implantation, while pre-existing thrombus may warrant advanced anticoagulation.

Radiation Risk Categories in Cardiac Catheterization for Congenital Heart Disease: A Tool to Aid in the Evaluation of Radiation Outcomes.

To stratify diverse procedure types into categories with similar radiation exposure in cardiac catheterization for congenital heart disease. Radiation exposures for a comprehensive list of specific procedure types and stratification of outcomes based on radiation risk are not currently available. Data between January 2014 and December 2015 were collected on all cases performed at sites participating in C3PO-QI (Congenital Cardiac Catheterization Outcomes Project-Quality Improvement Initiative) and 9 centers were included. Using expert consensus, 40 unique procedure types were defined by diagnostic characteristics or the intervention(s) performed, and dose area product (DAP) per kilogram of body weight (µGy × m2/kg) was summarized. Using empiric and consensus methods, three radiation risk categories were created. A total of 11,735 cases were included for analysis. Thirteen (n = 7918) procedure types with median DAP/kg < 100 were categorized in the low radiation exposure category (median DAP/kg 39). The medium exposure category (n = 1807) consisted of 16 procedure types with median DAP/kg values ranging 100 to < 200 (overall median DAP/kg 131). Finally, the high radiation exposure category (n = 1073) consisted of 11 procedure types with median DAP/kg ≥ 200 (overall median DAP/kg of 231). The radiation exposure risk categories created in this multi-center dataset are a critical step towards the development of a robust risk adjustment methodology for radiation exposure in catheterization for congenital heart disease.

Angiographic follow-up of infants and children undergoing percutaneous carotid artery interventions.

OBJECTIVE: The purpose of this study was to review the outcomes following the percutaneous carotid arterial (PCA) approach in infants and children with congenital heart disease. BACKGROUND: PCA access is becoming more commonly adopted following reports demonstrating it is a safe alternative to surgical carotid cutdown and even the femoral arterial route. However, follow-up outcomes after PCA remain unreported. METHODS: We reviewed all cases with PCA access and follow-up catheterizations which included carotid artery (CA) angiography between May 2012 until December 2016. We examined for evidence of CA stenosis at follow-up angiography and assessed any other CA complications associated with vascular access. RESULTS: There were 61 PCA catheterizations performed in 55 unique patients. Follow-up CA imaging with angiography was available in 43 patients (78%, 43/55). There was no vessel stenosis nor lumen irregularity in 28 (65%) patients. In 15 cases (35%), there was a mild degree of irregularity or narrowing by angiography (median 4.1%, range 2.3%-12.5%). Nine patients underwent repeat PCA catheterizations. Seven of these had no visible vascular stenosis on follow-up angiographic imaging, including a patient who was accessed three separate times from the CA. No statistically significant risk factors for developing mild CA stenosis were identified. CONCLUSIONS: PCA access for pediatric interventional catheterization appears to be safe with a very low rate of mild stenosis, and very few complications. Follow-up outcomes in our series are excellent, with a CA patency rate of 100%, even after multiple procedures. Mild CA stenosis was not associated with patient size or sheath introducer caliber. While the acute results from percutaneous CA catheterization have proven safe in recent literature, longer-term outcomes remain unreported. At our institution, the outcomes following percutaneous carotid access are associated with an excellent patency rate of 100%, even after multiple procedures on the same vessel. A low incidence of mild vessel stenosis can be appreciated on follow-up angiography.

Surgical Repair of Pulmonary Atresia With Ventricular Septal Defect and Major Aortopulmonary Collaterals With Absent Intrapericardial Pulmonary Arteries.

BACKGROUND: One anatomic variant of pulmonary atresia with ventricular septal defect and major aortopulmonary collaterals (PA/VSD/MAPCAs) is characterized by the absence of intrapericardial pulmonary arteries. This anatomy obviates the possibility of incorporating the pulmonary arteries for reconstruction or palliative procedures. The purpose of this study was to evaluate the surgical results in patients undergoing repair of PA/VSD/MAPCAs with absent pulmonary arteries. METHODS: This was a retrospective review of 35 patients who underwent surgical repair of PA/VSD/MAPCAs with absent pulmonary arteries between 2007 and 2014. The median age at the time of surgery was 3.4 months, and the median weight was 4.9 kg. All patients underwent unifocalization of MAPCAs, with an average of 3.5 ± 1.4 MAPCAs per patient. RESULTS: Twenty-eight of the 35 patients (80%) underwent complete single-stage surgical repair, including unifocalization of MAPCAs, VSD closure, and right ventricle to pulmonary artery conduit. After complete repair, the average right ventricular to aortic pressure ratio was 0.33 ± 0.07. There were no deaths in this subgroup. Seven patients (20%) were not deemed suitable candidates for VSD closure after their unifocalization procedure, and therefore underwent palliation with a central shunt. There was 1 operative death and 1 interim death. Three patients have subsequently undergone complete repair, and 2 are awaiting further evaluation and treatment. CONCLUSIONS: The majority of patients with PA/VSD/MAPCAs and absent pulmonary arteries can undergo complete single-stage repair with satisfactory postoperative hemodynamics. These results suggest that unifocalization of MAPCAs can provide a reasonable pulmonary vascular bed in the absence of intrapericardial pulmonary arteries.

Cerebral microvascular nNOS responds to lowered oxygen tension through a bumetanide-sensitive cotransporter and sodium-calcium exchanger.

Na(+) cotransporters have a substantial role in neuronal damage during brain hypoxia. We proposed these cotransporters have beneficial roles in oxygen-sensing mechanisms that increase periarteriolar nitric oxide (NO) concentration ([NO]) during mild to moderate oxygen deprivation. Our prior studies have shown that cerebral neuronal NO synthase (nNOS) is essential for [NO] responses to decreased oxygen tension and that endothelial NO synthase (eNOS) is of little consequence. In this study, we explored the mechanisms of three specific cotransporters known to play a role in the hypoxic state: KB-R7943 for blockade of the Na(+)/Ca(2+) exchanger, bumetanide for the Na(+)-K(+)-2Cl(-) cotransporter, and amiloride for Na(+)/H(+) cotransporters. In vivo measurements of arteriolar diameter and [NO] at normal and locally reduced oxygen tension in the rat parietal cortex provided the functional analysis. As previously found for intestinal arterioles, bumetanide-sensitive cotransporters are primarily responsible for sensing reduced oxygen because the increased [NO] and dilation were suppressed. The Na(+)/Ca(2+) exchanger facilitated increased NO formation because blockade also suppressed [NO] and dilatory responses to decreased oxygen. Amiloride-sensitive Na(+)/H(+) cotransporters did not significantly contribute to the microvascular regulation. To confirm that nNOS rather than eNOS was primarily responsible for NO generation, eNOS was suppressed with the fusion protein cavtratin for the caveolae domain of eNOS. Although the resting [NO] decreased and arterioles constricted as eNOS was suppressed, most of the increased NO and dilatory response to oxygen were preserved because nNOS was functional. Therefore, nNOS activation secondary to Na(+)-K(+)-2Cl(-) cotransporter and Na(+)/Ca(2+) exchanger functions are key to cerebral vascular oxygen responses.

Cerebral microvascular dilation during hypotension and decreased oxygen tension: a role for nNOS.

Endothelial (eNOS) and neuronal nitric oxide synthase (nNOS) are implicated as important contributors to cerebral vascular regulation through nitric oxide (NO). However, direct in vivo measurements of NO in the brain have not been used to dissect their relative roles, particularly as related to oxygenation of brain tissue. We found that, in vivo, rat cerebral arterioles had increased NO concentration ([NO]) and diameter at reduced periarteriolar oxygen tension (Po(2)) when either bath oxygen tension or arterial pressure was decreased. Using these protocols with highly selective blockade of nNOS, we tested the hypothesis that brain tissue nNOS could donate NO to the arterioles at rest and during periods of reduced perivascular oxygen tension, such as during hypotension or reduced local availability of oxygen. The decline in periarteriolar Po(2) by bath manipulation increased [NO] and vessel diameter comparable with responses at similarly decreased Po(2) during hypotension. To determine whether the nNOS provided much of the vascular wall NO, nNOS was locally suppressed with the highly selective inhibitor N-(4S)-(4-amino-5-[aminoethyl]aminopentyl)-N'-nitroguanidine. After blockade, resting [NO], Po(2), and diameters decreased, and the increase in [NO] during reduced Po(2) or hypotension was completely absent. However, flow-mediated dilation during occlusion of a collateral arteriole did remain intact after nNOS blockade and the vessel wall [NO] increased to approximately 80% of normal. Therefore, nNOS predominantly increased NO during decreased periarteriolar oxygen tension, such as that during hypotension, but eNOS was the dominant source of NO for flow shear mechanisms.