Minimally Invasive Approaches to Diagnose and Monitor Eosinophilic GI Diseases.

PURPOSE OF REVIEW: This review seeks to understand novel avenues for eosinophilic GI disease management. Biomarkers offer a unique and non-invasive approach to tracking EoE disease progression. While no biomarkers have definitively met the diagnostic criteria for eosinophilic GI diseases, some biomarkers have been shown to be associated with disease activity. Here, we examine the potential of recently studied biomarkers. RECENT FINDINGS: Current research shows advancements in blood, luminal fluid, and breath testing. Particular areas of interest include mRNA analyses, protein fingerprinting, amplicon sequence variants (ASVs), T cells and IgE receptors, eosinophilic cationic proteins, cytokines, and nitric oxide exhalation. Preliminary results showed that mucosal biomarkers, directly captured from the esophagus, may reflect the best representation of biopsy-based results, in contrast to biomarkers obtained from indirect or peripheral (blood, breath) methods. However, this is based on limited clinical studies without sufficient numbers to evaluate true diagnostic accuracy. Large-scale randomized trials are needed to fully ascertain both the optimal sampling technique and the specific biomarkers that reflect diagnostic status of the disease.

Sulfonated Thermoresponsive Injectable Gel for Sequential Release of Therapeutic Proteins to Protect Cardiac Function after Myocardial Infarction.

Myocardial infarction causes cardiomyocyte death and persistent inflammatory responses, which generate adverse pathological remodeling. Delivering therapeutic proteins from injectable materials in a controlled-release manner may present an effective biomedical approach for treating this disease. A thermoresponsive injectable gel composed of chitosan, conjugated with poly(N-isopropylacrylamide) and sulfonate groups, was developed for spatiotemporal protein delivery to protect cardiac function after myocardial infarction. The thermoresponsive gel delivered vascular endothelial growth factor (VEGF), interleukin-10 (IL-10), and platelet-derived growth factor (PDGF) in a sequential and sustained manner in vitro. An acute myocardial infarction mouse model was used to evaluate polymer biocompatibility and to determine therapeutic effects from the delivery system on cardiac function. Immunohistochemistry showed biocompatibility of the hydrogel, while the controlled delivery of the proteins reduced macrophage infiltration and increased vascularization. Echocardiography showed an improvement in ejection fraction and fractional shortening after injecting the thermal gel and proteins. A factorial design of experimental study was implemented to optimize the delivery system for the best combination and doses of proteins for further increasing stable vascularization and reducing inflammation using a subcutaneous injection mouse model. The results showed that VEGF, IL-10, and FGF-2 demonstrated significant contributions toward promoting long-term vascularization, while PDGF's effect was minimal.

Injectable Polymeric Delivery System for Spatiotemporal and Sequential Release of Therapeutic Proteins To Promote Therapeutic Angiogenesis and Reduce Inflammation.

Myocardial infarction (MI) causes cardiac cell death, induces persistent inflammatory responses, and generates harmful pathological remodeling, which leads to heart failure. Biomedical approaches to restore blood supply to ischemic myocardium, via controlled delivery of angiogenic and immunoregulatory proteins, may present an efficient treatment option for coronary artery disease (CAD). Vascular endothelial growth factor (VEGF) is necessary to initiate neovessel formation, while platelet-derived growth factor (PDGF) is needed later to recruit pericytes, which stabilizes new vessels. Anti-inflammatory cytokines like interleukin-10 (IL-10) can help optimize cardiac repair and limit the damaging effects of inflammation following MI. To meet these angiogenic and anti-inflammatory needs, an injectable polymeric delivery system composed of encapsulating micelle nanoparticles embedded in a sulfonated reverse thermal gel was developed. The sulfonate groups on the thermal gel electrostatically bind to VEGF and IL-10, and their specific binding affinities control their release rates, while PDGF-loaded micelles are embedded in the gel to provide the sequential release of the growth factors. An in vitro release study was performed, which demonstrated the sequential release capabilities of the delivery system. The ability of the delivery system to induce new blood vessel formation was analyzed in vivo using a subcutaneous injection mouse model. Histological assessment was used to quantify blood vessel formation and an inflammatory response, which showed that the polymeric delivery system significantly increased functional and mature vessel formation while reducing inflammation. Overall, the results demonstrate the effective delivery of therapeutic proteins to promote angiogenesis and limit inflammatory responses.

Gold Nanoparticle-Functionalized Reverse Thermal Gel for Tissue Engineering Applications.

Utilizing polymers in cardiac tissue engineering holds promise for restoring function to the heart following myocardial infarction, which is associated with grave morbidity and mortality. To properly mimic native cardiac tissue, materials must not only support cardiac cell growth but also have inherent conductive properties. Here, we present an injectable reverse thermal gel (RTG)-based cardiac cell scaffold system that is both biocompatible and conductive. Following the synthesis of a highly functionalizable, biomimetic RTG backbone, gold nanoparticles (AuNPs) were chemically conjugated to the backbone to enhance the system's conductivity. The resulting RTG-AuNP hydrogel supported targeted survival of neonatal rat ventricular myocytes (NRVMs) for up to 21 days when cocultured with cardiac fibroblasts, leading to an increase in connexin 43 (Cx43) relative to control cultures (NRVMs cultured on traditional gelatin-coated dishes and RTG hydrogel without AuNPs). This biomimetic and conductive RTG-AuNP hydrogel holds promise for future cardiac tissue engineering applications.

Structural and Biomechanical Adaptations of Right Ventricular Remodeling-In Pulmonary Arterial Hypertension-Reduces Left Ventricular Rotation During Contraction: A Computational Study.

Pulmonary hypertension (PH) is a degenerative disease characterized by progressively increased right ventricular (RV) afterload that leads to ultimate functional decline. Recent observational studies have documented a decrease in left ventricular (LV) torsion during ejection, with preserved LV ejection fraction (EF) in pediatric and adult PH patients. The objective of this study was to develop a computational model of the biventricular heart and use it to evaluate changes in LV torsion mechanics in response to mechanical, structural, and hemodynamic changes in the RV free wall. The heart model revealed that LV torsion and apical rotation were decreased when increasing RV mechanical rigidity and during re-orientation of RV myocardial fibers, both of which have been demonstrated in PH. Furthermore, structural changes to the RV appear to have a notable impact on RV EF, but little influence on LV EF. Finally, RV pressure overload exponentially increased LV myocardial stress. The computational results found in this study are consistent with clinical observations in adult and pediatric PH patients, which reveal a decrease in LV torsion with preserved LV EF. Furthermore, discovered causes of decreased LV torsion are consistent with RV structural adaptations seen in PH rodent studies, which might also explain suspected stress-induced changes in LV myocardial gene and protein expression.

An injectable sulfonated reversible thermal gel for therapeutic angiogenesis to protect cardiac function after a myocardial infarction.

BACKGROUND: Cardiovascular disease and myocardial infarction are associated with high mortality and morbidity and a more effective treatment remains a major clinical need. The intramyocardial injection of biomaterials has been investigated as a potential treatment for heart failure by providing mechanical support to the myocardium and reducing stress on cardiomyocytes. Another treatment approach that has been explored is therapeutic angiogenesis that requires careful spatiotemporal control of angiogenic drug delivery. An injectable sulfonated reversible thermal gel composed of a polyurea conjugated with poly(N-isopropylacrylamide) and sulfonate groups has been developed for intramyocardial injection with angiogenic factors for the protection of cardiac function after a myocardial infarction. RESULTS: The thermal gel allowed for the sustained, localized release of VEGF in vivo with intramyocardial injection after two weeks. A myocardial infarction reperfusion injury model was used to evaluate therapeutic benefits to cardiac function and vascularization. Echocardiography presented improved cardiac function, infarct size and ventricular wall thinning were reduced, and immunohistochemistry showed improved vascularization with thermal gel injections. The thermal gel alone showed cardioprotective and vascularization properties, and slightly improved further with the additional delivery of VEGF. An inflammatory response evaluation demonstrated the infiltration of macrophages due to the myocardial infarction was more significant compared to the foreign body inflammatory response to the thermal gel. Detecting DNA fragments of apoptotic cells also demonstrated potential anti-apoptotic effects of the thermal gel. CONCLUSION: The intramyocardial injection of the sulfonated reversible thermal gel has cardioprotective and vascularization properties for the treatment of myocardial infarction.

Microgrooves Encourage Endothelial Cell Adhesion and Organization on Shape-Memory Polymer Surfaces.

Cardiovascular stents have become the mainstay for treating coronary and other vascular diseases; however, the need for long-term anti-platelet therapies continues to drive research on novel materials and strategies to promote in situ endothelialization of these devices, which should decrease local thrombotic response. Shape-memory polymers (SMPs) have shown promise as polymer stents due to their self-deployment capabilities and vascular biocompatibility. We previously demonstrated isotropic endothelial cell adhesion on the unmodified surfaces of a family of SMPs previously developed by our group. Here, we evaluate whether endothelial cells align preferentially along microgrooved versus unpatterned surfaces of these SMPs. Results show that micropatterning SMP surfaces enhances natural surface hydrophobicity, which helps promote endothelial cell attachment and alignment along the grooves. With the addition of microgrooves to the SMP surface, this class of SMPs may provide an improved surface and material for next-generation blood-contacting devices.

A sulfonated reversible thermal gel for the spatiotemporal control of VEGF delivery to promote therapeutic angiogenesis.

Despite medical and surgical advancements for the treatment of cardiovascular disease, mortality and morbidity remain high. Therapeutic angiogenesis has been one approach to address the major clinical need for a more effective treatment to restoring blood flow in ischemic organs and tissues, but current progress in angiogenic drug delivery is inadequate at providing sufficient bioavailability without causing safety concerns. An injectable sulfonated reversible thermal gel composed of a polyurea conjugated with poly(N-isopropylacrylamide) and sulfonate groups has been developed for the delivery of angiogenic factors. The thermal gel allowed for the spatiotemporal control of vascular endothelial growth factor release with a decreased initial burst release and reduced release rate in vitro. A subcutaneous injection mouse model was used to evaluate efficacious vascularization and assess the inflammatory response due to a foreign body. Thermal gel injections showed substantial vascularization properties by inducing vessel formation, recruitment and differentiation of vascular endothelial cells, and vessel stabilization by perivascular cells, while infiltrating macrophages due to the thermal gel injections decreased over time. These results demonstrated effective localization and delivery of angiogenic factors for therapeutic angiogenesis. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 3053-3064, 2018.

Left ventricular torsion rate and the relation to right ventricular function in pediatric pulmonary arterial hypertension.

The right ventricle and left ventricle are physically coupled through the interventricular septum. Therefore, changes in the geometry and mechanics of one ventricle can directly affect the function of the other. In treatment of pediatric pulmonary arterial hypertension, the left ventricle is often overlooked, with clinical focus primarily on improving right ventricular function. Pediatric pulmonary arterial hypertension represents a disease distinct from adult pulmonary arterial hypertension based on etiology and survival rates. We aimed to assess left ventricular torsion rate in pediatric pulmonary arterial hypertension and its role in right ventricular dysfunction. Cardiac magnetic resonance images with tissue tagging were prospectively acquired for 18 pediatric pulmonary arterial hypertension (WHO class I) patients and 17 control subjects with no known cardiopulmonary disease. The pulmonary arterial hypertension cohort underwent cardiac magnetic resonance within 48 hours of clinically indicated right heart catheterization. Using right heart catheterization data, we computed single beat estimation of right ventricular end-systolic elastance (as a measure of right ventricular contractility) and ventricular vascular coupling ratio (end-systolic elastance/arterial afterload). Left ventricular torsion rate was quantified from harmonic phase analysis of tagged cardiac magnetic resonance images. Ventricular and pulmonary pressures and pulmonary vascular resistance were derived from right heart catheterization data. Right ventricular ejection fraction and interventricular septum curvature were derived from cardiac magnetic resonance. Left ventricular torsion rate was significantly reduced in pulmonary arterial hypertension patients compared to control subjects (1.40 ± 0.61° vs. 3.02 ± 1.47°, P < 0.001). A decrease in left ventricular torsion rate was significantly correlated with a decrease in right ventricular contractility (end-systolic elastance) ( r = 0.61, P = 0.007), and an increase in right ventricular systolic pressure in pulmonary arterial hypertension kids ( r = -0.54, P = 0.021). In both pulmonary arterial hypertension and control subjects, left ventricular torsion rate correlated with right ventricular ejection fraction (controls r = 0.45, P = 0.034) (pulmonary arterial hypertension r = 0.57, P = 0.032). In the pulmonary arterial hypertension group, interventricular septum curvature demonstrated a strong direct relationship with right ventricular systolic pressure ( r = 0.7, P = 0.001) and inversely with left ventricular torsion rate ( r = -0.57, P = 0.013). Left ventricular torsion rate showed a direct relationship with ventricular vascular coupling ratio ( r = 0.54, P = 0.021), and an inverse relationship with mean pulmonary arterial pressure ( r = -0.60, P = 0.008), and pulmonary vascular resistance ( r = -0.47, P = 0.049). We conclude that in pediatric pulmonary arterial hypertension, reduced right ventricular contractility is associated with decreased left ventricular torsion rate.

Measurement of Wall Shear Stress Exerted by Flowing Blood in the Human Carotid Artery: Ultrasound Doppler Velocimetry and Echo Particle Image Velocimetry.

Vascular endothelial cells lining the arteries are sensitive to wall shear stress (WSS) exerted by flowing blood. An important component of the pathophysiology of vascular diseases, WSS is commonly estimated by centerline ultrasound Doppler velocimetry (UDV). However, the accuracy of this method is uncertain. We have previously validated the use of a novel, ultrasound-based, particle image velocimetry technique (echo PIV) to compute 2-D velocity vector fields, which can easily be converted into WSS data. We compared WSS data derived from UDV and echo PIV in the common carotid artery of 27 healthy participants. Compared with echo PIV, time-averaged WSS was lower using UDV (28 ± 35%). Echo PIV revealed that this was due to considerable spatiotemporal variation in the flow velocity profile, contrary to the assumption that flow is steady and the velocity profile is parabolic throughout the cardiac cycle. The largest WSS underestimation by UDV was found during peak systole (118 ± 16%) and the smallest during mid-diastole (4.3± 46%). The UDV method underestimated WSS for the accelerating and decelerating systolic measurements (68 ± 30% and 24 ± 51%), whereas WSS was overestimated for end-diastolic measurements (-44 ± 55%). Our data indicate that UDV estimates of WSS provided limited and largely inaccurate information about WSS and that the complex spatiotemporal flow patterns do not fit well with traditional assumptions about blood flow in arteries. Echo PIV-derived WSS provides detailed information about this important but poorly understood stimulus that influences vascular endothelial pathophysiology.

Three-Dimensional Printed Pediatric Airway Model Improves Novice Learners' Flexible Bronchoscopy Skills With Minimal Direct Teaching From Faculty.

INTRODUCTION: Training in pediatric flexible bronchoscopy (FB) is predominantly completed on patients. Early trainees are less accurate and slower than experienced bronchoscopists. This report describes the development of a three-dimensional printed airway model and describes how the model was used to teach learners basic FB skills. METHODS: Postgraduate year two (PGY2) pediatric residents completing a 1-month pediatric pulmonology rotation with minimal previous exposure to FB were randomized into a simulation trainee group (n = 18) or a control resident group (n = 9). The simulation group received four 15-minute practice sessions (3 self-directed, 1 with feedback). Participants completed a bronchoscopy assessment on the model at prestudy, poststudy, and delayed (at least 2 months after the rotation) time points. Outcomes were identification of markers located in the six lung areas and completion time. RESULTS: There was no difference in prestudy scores between groups. In the poststudy assessment, the simulation participants correctly identified more lung area markers (median = 6 vs 1.5, P < 0.001) and were faster (median = 102 vs 600 seconds, P < 0.001). In the delayed assessment, correct marker identification trended toward improvement in the simulation group compared with controls (median = 4 vs 2, P = 0.077). CONCLUSIONS: With 1 hour of practice time, requiring 15 minutes of direct teaching, novice resident bronchoscopists are able to more accurately identify and visualize the five lung lobes and lingula via FB and are able to do so in less time than control residents. This anatomically accurate model could be used to train basic FB skills at a low cost compared with other models.

Development of an electrospun biomimetic polyurea scaffold suitable for vascular grafting.

The optimization of biomechanical and biochemical properties of a vascular graft to render properties relevant to physiological environments is a major challenge today. These critical properties of a vascular graft not only regulate its stability and integrity, but also control invasion of cells for scaffold remodeling permitting its integration with native tissue. In this work, we have synthesized a biomimetic scaffold by electrospinning a blend of a polyurea, poly(serinol hexamethylene urea) (PSHU), and, a polyester, poly-ε-caprolactone (PCL). Mechanical properties of the scaffold were varied by varying polymer blending ratio and electrospinning flow rate. Mechanical characterization revealed that scaffolds with lower PSHU content relative to PCL content resulted in elasticity close to native mammalian arteries. We also found that increasing electrospinning flow rates also increased the elasticity of the matrix. Optimization of elasticity generated scaffolds that enabled vascular smooth muscle cells (SMCs) to adhere, grow and maintain a SMC phenotype. The 30/70 scaffold also underwent slower degradation than scaffolds with higher PSHU content, thereby, providing the best option for in vivo remodeling. Further, Gly-Arg-Gly-Asp-Ser (RGD) covalently conjugated to the polyurea backbone in 30/70 scaffold resulted in significantly increased clotting times. Reducing surface thrombogenicity by the conjugation of RGD is critical to avoiding intimal hyperplasia. Hence, biomechanical and biochemical properties of a vascular graft can be balanced by optimizing synthesis parameters and constituent components. For these reasons, the optimized RGD-conjugated 30/70 scaffold electrospun at 2.5 or 5 mL/h has great potential as a suitable material for vascular grafting applications. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 278-290, 2018.

Injectable Carbon Nanotube-Functionalized Reverse Thermal Gel Promotes Cardiomyocytes Survival and Maturation.

The ability of the adult heart to regenerate cardiomyocytes (CMs) lost after injury is limited, generating interest in developing efficient cell-based transplantation therapies. Rigid carbon nanotubes (CNTs) scaffolds have been used to improve CMs viability, proliferation, and maturation, but they require undesirable invasive surgeries for implantation. To overcome this limitation, we developed an injectable reverse thermal gel (RTG) functionalized with CNTs (RTG-CNT) that transitions from a solution at room temperature to a three-dimensional (3D) gel-based matrix shortly after reaching body temperature. Here we show experimental evidence that this 3D RTG-CNT system supports long-term CMs survival, promotes CMs alignment and proliferation, and improves CMs function when compared with traditional two-dimensional gelatin controls and 3D plain RTG system without CNTs. Therefore, our injectable RTG-CNT system could potentially be used as a minimally invasive tool for cardiac tissue engineering efforts.

Circulating miRNAs in Pediatric Pulmonary Hypertension Show Promise as Biomarkers of Vascular Function.

BACKGROUND/OBJECTIVES: The objective of this study was to evaluate the utility of circulating miRNAs as biomarkers of vascular function in pediatric pulmonary hypertension. METHOD: Fourteen pediatric pulmonary arterial hypertension patients underwent simultaneous right heart catheterization (RHC) and blood biochemical analysis. Univariate and stepwise multivariate linear regression was used to identify and correlate measures of reactive and resistive afterload with circulating miRNA levels. Furthermore, circulating miRNA candidates that classified patients according to a 20% decrease in resistive afterload in response to oxygen (O2) or inhaled nitric oxide (iNO) were identified using receiver-operating curves. RESULTS: Thirty-two circulating miRNAs correlated with the pulmonary vascular resistance index (PVRi), pulmonary arterial distensibility, and PVRi decrease in response to O2 and/or iNO. Multivariate models, combining the predictive capability of multiple promising miRNA candidates, revealed a good correlation with resistive (r = 0.97, P2-tailed < 0.0001) and reactive (r = 0.86, P2-tailed < 0.005) afterloads. Bland-Altman plots showed that 95% of the differences between multivariate models and RHC would fall within 0.13 (mmHg-min/L)m2 and 0.0085/mmHg for resistive and reactive afterloads, respectively. Circulating miR-663 proved to be a good classifier for vascular responsiveness to acute O2 and iNO challenges. CONCLUSION: This study suggests that circulating miRNAs may be biomarkers to phenotype vascular function in pediatric PAH.

Echo Particle Image Velocimetry for Estimation of Carotid Artery Wall Shear Stress: Repeatability, Reproducibility and Comparison with Phase-Contrast Magnetic Resonance Imaging.

Measurement of hemodynamic wall shear stress (WSS) is important in investigating the role of WSS in the initiation and progression of atherosclerosis. Echo particle image velocimetry (echo PIV) is a novel ultrasound-based technique for measuring WSS in vivo that has previously been validated in vitro using the standard optical PIV technique. We evaluated the repeatability and reproducibility of echo PIV for measuring WSS in the human common carotid artery. We measured WSS in 28 healthy participants (18 males and 10 females, mean age: 56 ± 12 y). Echo PIV was highly repeatable, with an intra-observer variability of 1.0 ± 0.1 dyn/cm2 for peak systolic (maximum), 0.9 dyn/cm2 for mean and 0.5 dyn/cm2 for end-diastolic (minimum) WSS measurements. Likewise, echo PIV was reproducible, with a low inter-observer variability (max: 2.0 ± 0.2 dyn/cm2, mean: 1.3 ± 0.1 dyn/cm2, end-diastolic: 0.7 dyn/cm2) and more variable inter-scan (test-retest) variability (max: 7.1 ± 2.3 dyn/cm2, mean: 2.9 ± 0.4 dyn/cm2, min: 1.5 ± 0.1 dyn/cm2). We compared echo PIV with the reference method, phase-contrast magnetic resonance imaging (PC-MRI); echo PIV-based WSS measurements agreed qualitatively with PC-MRI measurements (r = 0.89, p < 0.05). Significant differences were observed in some WSS measurements (echo PIV vs. PC-MRI): WSS at peak systole: 21 ± 7.0 dyn/cm2 vs. 15 ± 5.0 dyn/cm2; time-averaged WSS: 8.9 ± 3.0 dyn/cm2 vs. 7.1 ± 3.0 dyn/cm2 (p < 0.05); WSS at end diastole: 3.8 ± 2.8 dyn/cm2 vs. 3.9 ± 2 dyn/cm2 (p > 0.05). For the first time, we report that echo PIV can measure WSS with good repeatability and reproducibility in adult humans with a broad age range. Echo PIV is feasible in humans and offers an easy-to-use, ultrasound-based, quantitative technique for measuring WSS in vivo in humans with good repeatability and reproducibility.

Characterization of CMR-derived haemodynamic data in children with pulmonary arterial hypertension.

AIMS: Paediatric pulmonary arterial hypertension (PAH) is manifested as increased arterial pressure and vascular resistive changes followed by progressive arterial stiffening. The aim of this study was to characterize regional flow haemodynamic patterns and markers of vascular stiffness in the proximal pulmonary arteries of paediatric PAH patients, and to explore the association with right ventricular (RV) function. METHODS AND RESULTS: Forty paediatric PAH patients and 26 age- and size-matched controls underwent cardiac magnetic resonance studies in order to compute time-resolved wall shear stress metrics, oscillatory shear index (OSI), and vascular strain as measured by relative area change (RAC), and RV volumetric and functional parameters. Phase-contrast imaging planes were positioned perpendicular to the mid-main and right pulmonary arteries (MPA and RPA, respectively). Compared with controls, the PAH group had decreased systolic wall shear stress (dyne cm-2) and RAC (%) in both MPA (WSSsys: 6.5 vs. 4.3, P < 0.0001; RAC: 36 vs. 25, P < 0.0001) and RPA (WSSsys: 11.2 vs. 7.3, P < 0.0001; strain: 37 vs. 30, P < 0.05). The OSI was significantly higher in the MPA of PAH subjects (0.46 vs. 0.17, P < 0.05). WSS measured in the MPA correlated positively with RAC (r = 0.63, P < 0.0001) and RV ejection fraction (%) (r = 0.63, P < 0.0001). CONCLUSION: Wall shear stress, the principal haemodynamic force driving endothelial functional changes, is severely decreased in paediatric PAH patients and correlates with increased stiffness in the proximal pulmonary vasculature and reduced RV function.

Shape Memory Polymers Containing Higher Acrylate Content Display Increased Endothelial Cell Attachment.

Shape Memory Polymers (SMPs) are smart materials that can recall their shape upon the application of a stimulus, which makes them appealing materials for a variety of applications, especially in biomedical devices. Most prior SMP research has focused on tuning bulk properties; studying surface effects of SMPs may extend the use of these materials to blood-contacting applications, such as cardiovascular stents, where surfaces that support rapid endothelialization have been correlated to stent success. Here, we evaluate endothelial attachment onto the surfaces of a family of SMPs previously developed in our group that have shown promise for biomedical devices. Nine SMP formulations containing varying amounts of tert-Butyl acrylate (tBA) and Poly(ethylene glycol) dimethacrylate (PEGDMA) were analyzed for endothelial cell attachment. Dynamic mechanical analysis (DMA), contact angle studies, and atomic force microscopy (AFM) were used to verify bulk and surface properties of the SMPs. Human umbilical vein endothelial cell (HUVEC) attachment and viability was verified using fluorescent methods. Endothelial cells preferentially attached to SMPs with higher tBA content, which have rougher, more hydrophobic surfaces. HUVECs also displayed an increased metabolic activity on these high tBA SMPs over the course of the study. This class of SMPs may be promising candidates for next generation blood-contacting devices.

A Zero-Dimensional Model and Protocol for Simulating Patient-Specific Pulmonary Hemodynamics From Limited Clinical Data.

In pulmonary hypertension (PH) diagnosis and management, many useful functional markers have been proposed that are unfeasible for clinical implementation. For example, assessing right ventricular (RV) contractile response to a gradual increase in pulmonary arterial (PA) impedance requires simultaneously recording RV pressure and volume, and under different afterload/preload conditions. In addition to clinical applications, many research projects are hampered by limited retrospective clinical data and could greatly benefit from simulations that extrapolate unavailable hemodynamics. The objective of this study was to develop and validate a 0D computational model, along with a numerical implementation protocol, of the RV-PA axis. Model results are qualitatively compared with published clinical data and quantitatively validated against right heart catheterization (RHC) for 115 pediatric PH patients. The RV-PA circuit is represented using a general elastance function for the RV and a three-element Windkessel initial value problem for the PA. The circuit mathematically sits between two reservoirs of constant pressure, which represent the right and left atriums. We compared Pmax, Pmin, mPAP, cardiac output (CO), and stroke volume (SV) between the model and RHC. The model predicted between 96% and 98% of the variability in pressure and 98-99% in volumetric characteristics (CO and SV). However, Bland Altman plots showed the model to have a consistent bias for most pressure and volumetric parameters, and differences between model and RHC to have considerable error. Future studies will address this issue and compare specific waveforms, but these initial results are extremely promising as preliminary proof of concept of the modeling approach.

Vorticity is a marker of diastolic ventricular interdependency in pulmonary hypertension.

Our objective was to determine whether left ventricular (LV) vorticity (ω), the local spinning motion of a fluid element, correlated with markers of ventricular interdependency in pulmonary hypertension (PH). Maladaptive ventricular interdependency is associated with interventricular septal shift, impaired LV performance, and poor outcomes in PH patients, yet the pathophysiologic mechanisms underlying fluid-structure interactions in ventricular interdependency are incompletely understood. Because conformational changes in chamber geometry affect blood flow formations and dynamics, LV ω may be a marker of LV-RV (right ventricular) interactions in PH. Echocardiography was performed for 13 PH patients and 10 controls for assessment of interdependency markers, including eccentricity index (EI), and biventricular diastolic dysfunction, including mitral valve (MV) and tricuspid valve (TV) early and late velocities (E and A, respectively) as well as MV septal and lateral early tissue Doppler velocities (e'). Same-day 4-dimensional cardiac magnetic resonance was performed for LV E (early)-wave ω measurement. LV E-wave ω was significantly decreased in PH patients (P = 0.008) and correlated with diastolic EI (Rho = -0.53, P = 0.009) as well as with markers of LV diastolic dysfunction, including MV E(Rho = 0.53, P = 0.011), E/A (Rho = 0.56, P = 0.007), septal e' (Rho = 0.63, P = 0.001), and lateral e' (Rho = 0.57, P = 0.007). Furthermore, LV E-wave ω was associated with indices of RV diastolic dysfunction, including TV e' (Rho = 0.52, P = 0.012) and TV E/A (Rho = 0.53, P = 0.009). LV E-wave ω is decreased in PH and correlated with multiple echocardiographic markers of ventricular interdependency. LV ω may be a novel marker for fluid-tissue biomechanical interactions in LV-RV interdependency.

4D magnetic resonance flow imaging for estimating pulmonary vascular resistance in pulmonary hypertension.

PURPOSE: To develop an estimate of pulmonary vascular resistance (PVR) using blood flow measurements from 3D velocity-encoded phase contract magnetic resonance imaging (here termed 4D MRI). MATERIALS AND METHODS: In all, 17 patients with pulmonary hypertension (PH) and five controls underwent right heart catheterization (RHC), 4D and 2D Cine MRI (1.5T) within 24 hours. MRI was used to compute maximum spatial peak systolic vorticity in the main pulmonary artery (MPA) and right pulmonary artery (RPA), cardiac output, and relative area change in the MPA. These parameters were combined in a four-parameter multivariate linear regression model to arrive at an estimate of PVR. Agreement between model predicted and measured PVR was also evaluated using Bland-Altman plots. Finally, model accuracy was tested by randomly withholding a patient from regression analysis and using them to validate the multivariate equation. RESULTS: A decrease in vorticity in the MPA and RPA were correlated with an increase in PVR (MPA: R(2) = 0.54, P < 0.05; RPA: R(2) = 0.75, P < 0.05). Expanding on this finding, we identified a multivariate regression equation that accurately estimates PVR (R(2) = 0.94, P < 0.05) across severe PH and normotensive populations. Bland-Altman plots showed 95% of the differences between predicted and measured PVR to lie within 1.49 Wood units. Model accuracy testing revealed a prediction error of ∼20%. CONCLUSION: A multivariate model that includes MPA relative area change and flow characteristics, measured using 4D and 2D Cine MRI, offers a promising technique for noninvasively estimating PVR in PH patients. J. MAGN. RESON. IMAGING 2016;44:914-922.