Elevated Aortic Stiffness after Pediatric Heart Transplantation

In adults, arterial stiffness has been linked to the development of target end-organ damage, thought to be related to abnormal transmission of pulse pressure. Increased arterial stiffness and endothelial dysfunction have been hypothesized to contribute to the development of microvascular dysfunction and coronary allograft vasculopathy (CAV), an important comorbidity after heart transplantation. However, little data exists regarding arterial stiffness in pediatric heart transplantation and its influence on development of coronary allograft vasculopathy is not well understood. We sought to assess aortic stiffness and distensibility in pediatric post-heart transplant patients. A prospective, observational study analyzing the ascending (donor tissue) and descending aorta (recipient tissue) using transthoracic echocardiographic M-mode measurements in patients aged < 21 years was conducted. Descending and ascending aorta M-modes were obtained from the subcostal long axis view, and the parasternal long axis view 3-5mm above the sinotubular junction, respectively. Two independent reviewers averaged measurements over 2-3 cardiac cycles, and Aortic Distensibility (AD) and Aortic Stiffness Index (ASI) were calculated using previously validated methods. We recruited 39 heart transplant (HT) patients and 47 healthy controls. Median end diastolic dimension of the ascending aorta (donor tissue) was significantly larger in the transplant group than the control group (1.92 cm vs. 1.74 cm, p = 0.01). Ascending aortic distensibility in post-transplant patients was significantly lower than in the control group (4.87 vs. 10.53, p < 0.001). Ascending aortic stiffness index was higher in the transplant patients compared to the controls (4.63 vs. 2.21, p < 0.001). There is evidence of altered ascending aortic distensibility and stiffness parameters in post-heart transplant patients. Further studies are required to assess its influence on complications like development of coronary artery vasculopathy.

A Comprehensive Approach to the Management of Patients With HLHS and Related Malformations: An Analysis of 83 Patients (2015-2021)

Background: Some patients with hypoplastic left heart syndrome (HLHS) and HLHS-related malformations with ductal-dependent systemic circulation are extremely high-risk for Norwood palliation. We report our comprehensive approach to the management of these patients designed to maximize survival and optimize the utilization of donor hearts. Methods: We reviewed our entire current single center experience with 83 neonates and infants with HLHS and HLHS-related malformations (2015-2021). Standard-risk patients (n = 62) underwent initial Norwood (Stage 1) palliation. High-risk patients with risk factors other than major cardiac risk factors (n = 9) underwent initial Hybrid Stage 1 palliation, consisting of application of bilateral pulmonary bands, stent placement in the patent arterial duct, and atrial septectomy if needed. High-risk patients with major cardiac risk factors (n = 9) were bridged to transplantation with initial combined Hybrid Stage 1 palliation and pulsatile ventricular assist device (VAD) insertion (HYBRID + VAD). Three patients were bridged to transplantation with prostaglandin. Results: Overall survival at 1 year = 90.4% (75/83). Operative Mortality for standard-risk patients undergoing initial Norwood (Stage 1) Operation was 2/62 (3.2%). Of 60 survivors: 57 underwent Glenn, 2 underwent biventricular repair, and 1 underwent cardiac transplantation. Operative Mortality for high-risk patients with risk factors other than major cardiac risk factors undergoing initial Hybrid Stage 1 palliation without VAD was 0/9: 4 underwent transplantation, 1 awaits transplantation, 3 underwent Comprehensive Stage 2 (with 1 death), and 1 underwent biventricular repair. Of 9 HYBRID + VAD patients, 6 (67%) underwent successful cardiac transplantation and are alive today and 3 (33%) died while awaiting transplantation on VAD. Median length of VAD support was 134 days (mean = 134, range = 56-226). Conclusion: A comprehensive approach to the management of patients with HLHS or HLHS-related malformations is associated with Operative Mortality after Norwood of 2/62 = 3.2% and a one-year survival of 75/83 = 90.4%. A subset of 9/83 patients (11%) were stabilized with HYBRID + VAD while awaiting transplantation. VAD facilitates survival on the waiting list during prolonged wait times.

Impact of 3D Printouts in Optimizing Surgical Results for Complex Congenital Heart Disease

Planning corrective and palliative surgery for patients who have complex congenital heart disease often relies on the assessment of cardiac anatomy using two-dimensional noninvasive cardiac imaging modalities (echocardiography, cardiac magnetic resonance imaging, and computed tomography scan). Advances in cardiac noninvasive imaging now include the use of three-dimensional (3D) reconstruction tools that produce 3D images and 3D printouts. There is scant evidence available in the literature as to what effect the availability of 3D printouts of complex congenital heart defects has on surgical outcomes. Surgical outcomes of study subjects with a 3D cardiac printout available and their paired control subject without a 3D cardiac printout available were compared. We found a trend toward shorter surgical times in the study group who had the benefit of 3D models, but no statistical significance was found for bypass time, cross-clamp time, total time, length of stay, or respiratory support. These preliminary results support the proposal that 3D modeling be made readily available to congenital cardiac surgery teams, for use in patients with the most complex congenital heart disease.

Pocket echocardiography system for detection of patent ductus arteriosus in neonates

BACKGROUND

Neonates are commonly referred for a cardiology consult and an echocardiogram to rule out patent ductus arteriosus (PDA).

OBJECTIVES

Evaluate the usefulness of current pocket echocardiography system (PES) in PDA detection compared to traditional full-featured echo system (FFES).

HYPOTHESIS

The determination of the presence of a PDA in neonates can be done using PES.

METHODS

Fifty newborns with orders for echo evaluation were included in this study. A 5-minute PES scan was performed first. Then a full echo study was performed on a traditional FFES. Images were evaluated by three pediatric cardiologists blinded to the patients and the FFES results.

RESULTS

The overall accuracy of reviewers rating PES versus FFES to rule in PDA had low false-positive rates 9.5% (95% CI: 1.2-30%), 11.8% (95% CI: 1.5-36%), 11.1% (95% CI: 1.4-35%) and the false-negative rate to rule out PDA was 0% (95% CI: 0-18%), 5.5% (95% CI: 0.14-27%), 0% (95% CI: 0-26%) for each reviewer 1, 2, and 3, respectively. Upon further analysis, PES scan was shown not to be accurate on infants with body weight below 1000 g with encouraging results for infants above 1000 g and those >37 weeks gestational age.

CONCLUSIONS

Our results suggest that the current PES could potentially be used in larger and near-term infants but has less than acceptable performance in low birth weight and premature infants in determining who should undergo a FFES study for persistent PDA diagnosis. Improvements in the technology along with developing limited training protocols for noncardiology personnel should make it possible for PES scan to be used as a screening tool and as an extension of physical examination especially in limited resource settings.

Blood Cell Adhesion on a Polymeric Heart Valve Leaflet Processed Using Magnetic Abrasive Finishing

Polymeric heart valves have the potential to improve hemodynamic function without the complications associated with bioprosthetic and mechanical heart valves, but they have exhibited issues that need to be addressed including calcification, hydrolysis, low durability, and the adhesion of blood cells on the valves. These issues are attributed to the valves' material properties and surface conditions in addition to the hemodynamics. To overcome these issues, a new stentless, single-component trileaflet polymeric heart valve with engineered leaflet surface texture was designed, and prototypes were fabricated from a simple polymeric tube. The single-component structure features a trileaflet polymeric valve and conduit that are made of a single tube component to eliminate complications possibly caused by the interaction of multiple materials and components. This paper focuses on the leaflet surface modification and the effects of leaflet surface texture on blood cell adhesion to the leaflet surface. Silicone rubber was chosen as the working material. A magnetic abrasive finishing (MAF) process was used to alter the inner surface of the tubular mold in contact with the silicone leaflets during the curing process. It was hypothesized that the maximum profile height Rz of the mold surface should be smaller than the minimum platelet size of 1 μm to prevent platelets (1–3 μm in diameter) from becoming lodged between the peaks. Cell adhesion studies using human whole blood flushed at low shear stresses over leaflet surfaces with six different textures showed that adhesion of the platelets and red blood cells is greatly influenced by both surface roughness and lay. Leaflets replicated from MAF-produced mold surfaces consisting of short asperities smaller than 1 μm reduced blood cell adhesion and aggregation. Cell adhesion studies also found that either mold or leaflet surface roughness can be used as a measure of cell adhesion.

Efficiency differences in computational simulations of the total cavo-pulmonary circulation with and without compliant vessel walls

The Fontan operation is a palliative surgical procedure performed on children born with congenital defects of the heart that have yielded only a single functioning ventricle. The total cavo-pulmonary connection (TCPC) is the most popular variant of the Fontan procedure. The objective of the study was to quantify and compare the efficiency of numerical models of the TCPC with rigid versus elastic vessel wall models. The pressure drop and power loss through both type TCPC models was measured. Significant differences in efficiencies exist between rigid versus elastic numerical models. We have shown incorporating elasticity into numerical models of the total cavo-pulmonary connection is important when determining circuit efficiencies.

A classifier based on the artificial neural network approach for cardiologic auscultation in pediatrics

OBJECTIVE

This research work was aimed at developing a reliable screening device for diagnosis of heart murmurs in pediatrics. This is a significant problem in pediatric cardiology because of the high rate of incidence of heart murmurs in this population (reportedly 77-95%), of which only a small fraction arises from congenital heart disease. The screening devices currently available (e.g. chest X-ray, electrocardiogram, etc.) suffer from poor sensitivity and specificity in detecting congenital heart disease. Thus, patients with heart murmurs today are frequently assessed by consultation as well with advanced imaging techniques. The most prominent among these is echocardiography. However, echocardiography is expensive and is usually only available in healthcare centers in major cities. Thus, for patients being evaluated with a heart murmur, developing a more accurate screening device is vital to efforts in reducing health care costs.

METHODS AND MATERIAL

The data set was collected from incoming pediatrics at the cardiology clinic of The Children's Hospital (Denver, Colorado), on whom echocardiography had been performed to identify congenital heart disease. Recordings of approximately 10-15s duration were made at 44,100Hz and the average record length was approximately 60,000 points. The best three cycles with respect to signal quality sounds were extracted from the original recording. The resulting data comprised 241 examples, of which 88 were examples of innocent murmurs and 153 were examples of pathological murmurs. The selected phonocardiograms were subject to the digital signal processing (DSP) technique of fast Fourier transform (FFT) to extract the energy spectrum in frequency domain. The spectral range was 0-300Hz at a resolution of 1Hz. The processed signals were used to develop statistical classifiers and a classifier based on our in-house artificial neural network (ANN) software. For the latter, we also tried enhancements to the basic ANN scheme. These included a method for setting the decision-threshold and a scheme for consensus-based decision by a committee of experts.

RESULTS

Of the different classifiers tested, the ANN-based classifier performed the best. With this classifier, we were able to achieve classification accuracy of 83% sensitivity and 90% specificity in discriminating between innocent and pathological heart murmurs. For the problem of discrimination between innocent murmurs and murmurs of the ventricular septal defect (VSD), the accuracy was higher, with sensitivity of 90% and specificity of 93%.

CONCLUSIONS

An ANN-based approach for detection and identification of congenital heart disease in pediatrics from heart murmurs can result in an accurate screening device. Considering that only a simple feature set was used for classification, the results are very encouraging and point out the need for further development using improved feature set with more potent diagnostic variables.

Computational simulations of the total cavo-pulmonary connection: insights in optimizing numerical solutions

The Fontan procedure is a palliative surgical technique that is used to treat patients with congenital heart defects that include complex lesions such as those with a hypoplastic ventricle. In vitro, in vivo, and computational models of a set of modifications to the Fontan procedure, called the total cavopulmonary connection (TCPC), have been developed. Using these modeling methods, attempts have been made at finding the most energy efficient TCPC circuit. Computational modeling has distinct advantages to other modeling methods. However, discrepancies have been found in validation studies of TCPC computational models. There is little in the literature available to help explain and correct for such discrepancies. Differences in computational results can occur when choosing between steady flow versus transient flow numerical solvers. In this study transient flow solver results were shown to be more consistent with results from previous TCPC in vitro experiments. Using a transient flow solver we found complex fluctuating flow patterns can exist with steady inflow boundary conditions in computational models of the TCPC. To date such findings have not been reported in the literature. Furthermore, our computational modeling results suggest fluctuating flow patterns as well as the magnitudes of these secondary flow structures diminish if the TCPC offset between vena cavae is increased or if flanged connections are added. An association was found between these modifications and improvements in TCPC circuit flow efficiencies. In summary, development of accurate computational simulations in the validation process is critical to efforts in finding the most efficient TCPC circuits, efforts aimed at potentially improving the long term outcome for Fontan patients.

Modeling 3-D compliant blood flow with FOSLS

Blood flow in large vessels is typically modeled using the Navier-Stokes equations for the fluid domain and elasticity equations for the vessel wall. As the wall deforms, additional complications are introduced because the shape of the fluid domain changes, necessitating the use of a re-mapping or re-griding process for the fluid region. Typically, this system (fluid, solid, mapping) is solved using an iterative approach in which the fluid, elastic, and mapping equations are solved in series until the iterations converge. We present a new approach based on multilevel minimization of the finite element approximation error using a least-squares (LS) norm. This approach allows for minimization of the error for the entire system or in selected parts. The multilevel LS approach overcomes many shortcomings of standard techniques. Most notably, the computational cost of solving the problem increases linearly with the degrees of freedom and the associated least-squares functional provides an a posteriori error measure. This paper compares the LS finite element approach to other popular numerical methods, specifically, the commercial package CFD-ACE. The focus of the comparison is on accuracy, computational cost, scalability (both parallel and serial), and flexibility. We show that the multilevel LS finite element approach scales optimally (i.e., linearly in serial environments), while the other methods degrade substantially as the problem size increases.

Comparison of in vitro velocity measurements in a scaled total cavopulmonary connection with computational predictions

Minimizing pressure drop through the total cavopulmonary surgical connection (TCPC), where the superior and inferior vena cavae (SVC), (IVC) are connected directly to the right and left pulmonary arteries, is an important clinical consideration. Computational fluid dynamics (CFD) models have been used to examine the impact of connection configuration on TCPC pressure drop. However, few studies have validated CFD results with experimental data. This study compares flow field measurements on two different TCPC models at varying SVC:IVC flow rate ratios using CFD and digital particle image velocimetry (DPIV). Although the primary flow fields generated by CFD and DPIV methods were similar for the majority of flow conditions, three key differences were found: (1) the CFD model did not reproduce the 3D complexity of flow interactions in the no-offset model with 50:50 flow ratio; (2) in vitro results showed consistently higher secondary flow components within the pulmonary artery segments, especially for the no-offset model; (3) recirculation areas for the 1/2 diameter offset model were consistently higher for in vitro versus CFD results. We conclude that this numerical model is a reasonable means of studying TCPC flow, although modifications need to be addressed to ensure that numerical results reproduce secondary flow characteristics.

Reverse flow in compliant vessels and its implications for the Fontan procedure: numerical studies

The Total Cavopulmonary Connection (TCPC), a variant of the Fontan operation used for palliative cardiovascular repair of patients with single ventricle physiology, creates a passive system of blood flow into the pulmonary circulation for which energy efficiency may be critical to long term outcome. Clinical studies have shown that reverse flow in the TCPC is an indication of poor clinical status in these patients. Using numerical simulations, we demonstrate that reverse flow leads to increased energy losses in compliant vessels. Such an effect can potentially set off a series of spiraling negative events with decreased ventricular function leading to reverse flow, which causes decreased energy efficiency, which in turn leads to worsening function, and so forth, thereby suggesting one cause of progressive heart failure in this patient group.

A novel paradigm for telemedicine using the personal bio-monitor

The foray of solid-state technology in the medical field has yielded an arsenal of sophisticated healthcare tools. Personal, portable computing power coupled with the information superhighway open up the possibility of sophisticated healthcare management that will impact the medical field just as much. The full synergistic potential of three interwoven technologies: (1) compact electronics, (2) World Wide Web, and (3) Artificial Intelligence is yet to be realized. The system presented in this paper integrates these technologies synergistically, providing a new paradigm for healthcare. Our idea is to deploy internet-enabled, intelligent, handheld personal computers for medical diagnosis. The salient features of the 'Personal Bio-Monitor' we envisage are: (1) Utilization of the peripheral signals of the body which may be acquired non-invasively and with ease, for diagnosis of medical conditions; (2) An Artificial Neural Network (ANN) based approach for diagnosis; (3) Configuration of the diagnostic device as a handheld for personal use; (4) Internet connectivity, following the emerging bluetooth protocol, for prompt conveyance of information to a patient's health care provider via the World Wide Web. The proposal is substantiated with an intelligent handheld device developed by the investigators for pediatric cardiac auscultation. This device performed accurate diagnoses of cardiac abnormalities in pediatrics using an artificial neural network to process heart sounds acquired by a low-frequency microphone and transmitted its diagnosis to a desktop PC via infrared. The idea of the personal biomonitor presented here has the potential to streamline healthcare by optimizing two valuable resources: physicians' time and sophisticated equipment time. We show that the elements of such a system are in place, with our prototype. Our novel contribution is the synergistic integration of compact electronics' technology, artificial neural network methodology and the wireless web resulting in a revolutionary new paradigm for healthcare management.

Spontaneous pericardial hematoma in an infant

The finding of a pericardial hematoma is rare in the pediatric population. Its occurrence in an otherwise healthy 3-month-old infant is unprecedented in the literature. The hematoma was initially identified by echocardiography. Computerized tomography and magnetic resonance imaging did not contribute to the identification of the mass. An exploratory thoracotomy was necessary to rule out a neoplastic process. The final diagnosis of hemorrhagic pericarditis was made.

Giant blood cyst of the aortic valve

Beyond infancy, blood cyst of the aortic valve is not known to occur. We describe a 16-year-old girl who had aortic valve stenosis and regurgitation and giant blood cyst of the aortic valve. Serial echocardiograms over a 12-year period demonstrated gradual enlargement of the cyst.

Reversible cardiomyopathy in an infant with unrecognized congenital adrenal hyperplasia

We describe an infant who had a dilated cardiomyopathy and who was later found to have congenital adrenal hyperplasia. The cardiomyopathy resolved after replacement of glucocorticoid and mineralocorticoid. We believe that glucocorticoid deficiency may have played a direct role in the evolution of this cardiomyopathy.