Transcatheter Closure of a Secundum Atrial Septal Defect with Deficient Aortic Rim Through the Left Internal Jugular Vein in a Child with Situs Inversus and Interrupted Inferior Vena Cava: Device's Choice Matters

Percutaneous closure of secundum atrial septal defect (sASD) in children with interrupted inferior vena cava is challenging, especially in case of deficient aortic rim. Trans-jugular access is generally preferred in this scenario. Patients with situs inversus and sASD also carry technical difficulties for transcatheter closure because of the orientation of the atrial septum. We report a successful case of percutaneous closure of a sASD with deficient aortic rim using an occlutech figulla flex II ASD device through the left internal jugular vein in a child with situs inversus, dextrocardia, and interrupted IVC. This case was facilitated by the absence of left-sided hub of the Occlutech device to provide stable opening of the device into the left atrium, whereas the ball-connection of the delivery system allowed an angle of almost 180 degrees between the device and the atrial septum.

Case report of a Gore-Tex TCPC conduit dissection causing severe stenosis

Background

The patient is a 15-year-old male with situs inversus, dextrocardia, bilateral superior caval veins, atrioventricular discordance with a single outlet, large perimembranous ventricular septal defect, aortic override, pulmonary atresia, and right aortic arch. The complex anatomy with a Ventricular Septal Defect (VSD) distant from the aorta (unsuitable for baffling to the aorta) meant he was unsuitable for biventricular repair and proceeded down a univentricular palliation pathway.

Case summary

Post-total cavopulmonary connection his clinical course was uneventful until the age of 5 when he developed fatigability with desaturation. An accessory hepatic vein was surgically banded with improved saturations and exercise tolerance. At the age of 15, cardiovascular magnetic resonance (CMR) was performed to investigate borderline saturations and as workup for transition to adult services. Cardiovascular magnetic resonance and cardiac computed tomography (CT) imaging demonstrated an eccentric thrombus causing stenosis of the extracardiac conduit and a thrombus outside of the lumen contained by the thin outer membrane of the Gore-Tex conduit. Collateralization suggested this was longstanding. Cardiac catheterization demonstrated a 4 mm × 6 mm stenosis at the junction of the conduit with the pulmonary arteries. The region was successfully balloon dilated and stented with a 34 mm-long Cheatham Platinum stent, with no complications.

Discussion

To date, this is the first documented case of a dissecting thrombus of a Gore-Tex graft in the literature. This case emphasizes the need for anticoagulation and serial cross-sectional imaging (CT or CMR) in Fontan patients with prosthetic grafts throughout a patients’ lifetime.

Computational model to probe cellular mechanics during epithelial-mesenchymal transition

During the epithelial to mesenchymal transition (EMT), polarized cells in the epithelium can undergo a transformation characterized by the loss of cell-cell junctions and increased migratory activity into nonpolarized invasive cells. These cells adopt a mesenchymal shape and migrate into the basal lamina. Such transitions have been observed in developmental processes and have been linked to cancer cell metastasis. Most experimental studies on EMT search for molecular markers indicating an epithelial or mesenchymal conformation, focussing on afferent signaling pathways received by cells undergoing this transformation; however, these approaches are unable to track mechanical changes in the cell and the possible role this plays in EMT. In order to address this gap in our understanding, we have used a quantitative approach to study population level effects of single cell changes typically occurring during EMT. We have developed a computational model making use of the advantages of both single cell migratory models and agent-based cell population models to study the effect of cellular molecular processes in EMT. The disruption of a cell sheet representing the epithelium over a dense extracellular matrix (ECM) is simulated using interaction forces between different cells and between cells and discrete fibers representing the ECM. In our study, two different parameters were varied: protrusion force magnitude and E-cadherin (cell-cell junction) concentration. The cell population was tracked for 3 days and the number of cells that leave the layer, the depth of invasion, and the percentage of initial number of cells that remain in the layer (a measure of epithelium disruption) were monitored. Our studies suggest that having a high protrusion force or a reduction in cell-cell attachments is enough to cause EMT. Our results also demonstrate that the morphological progression in membrane disruption has an effect on the number of cells becoming invasive, with epithelial layers broken into clusters hindering the further exodus of cells. The results reveal the quantitative interplay between two key parameters involved in EMT and suggest potential avenues for further exploration of a systems level understanding of EMT.

Integrin clustering in two and three dimensions

Integrins are transmembrane proteins that allow cells to bind to their external environment. They are the primary regulators of cell-matrix interactions, with direct roles in cell motility and signaling, which in turn regulate numerous physiological processes. Under common experimental conditions, integrins tend to cluster for sturdy and effective binding to extracellular matrix molecules. These clusters often evolve into focal adhesions, which regulate downstream signaling. However, integrin clusters are more pronounced and have longer lifetimes in two-dimensional assays than in more realistic three-dimensional environments. While a number of models and theoretical approaches have focused on integrin binding and diffusion, the reasons for the differences between two- and three-dimensional clustering have remained elusive. In this study, we model an individual cluster attached to a two-dimensional collagen film and attached to collagen fibers of various sizes in three-dimensional matrices. We then discuss how our results explain differences in size and lifetime, and how they hint at reasons for other differences between the two environments. Further, we make predictions regarding the stability of clusters based on different overall intracellular conditions. Our results show good agreement with experiments and provide a quantitative basis for understanding how matrix dimensionality and structure regulate integrin behavior in environments that mimic in vivo conditions.

Haemodynamics of stable renal transplant recipients

1. Haemodynamics, blood volume, plasma renin concentration and creatinine clearance were evaluated in 24 stable renal transplant recipients. 2. The mean cardiac index of the transplant recipients was not different from that of the normal subjects. 3. The transplant recipients comprised eight hypertensive and 16 normotensive patients. The mean cardiac index was the same in eight hypertensive and 16 normotensive patients. Thus the hypertension of stable renal transplant recipients is sustained by a high total peripheral resistance. 4. The mean blood volume, plasma renin concentration and creatinine clearance were similar in eight hypertensive and 16 normotensive patients. Therefore the hypertension of stable renal transplant recipients is not related to blood volume expansion, elevated peripheral renin or low creatinine clearance. The cause of the elevated total peripheral resistance in hypertension in stable renal transplant recipients remains to be elucidated.

Immune complex glomerulonephritis in a case of retroperitoneal fibrosis

The nephropathology associated with retroperitoneal fibrosis has been commonly related to compression of the ureters and hydronephrosis. This assumption has been made without the use of immunofluorescent microscopy and electron microscopy. The authors studied renal tissue from a patient with retroperitoneal fibrosis by light microscopy, immunofluorescent microscopy and electron microscopy. In addition to the gross and microscopic changes of obstructive nephropathy, histologic findings of glomerular immune-complex deposition were also present. It is postulated that in some cases of retroperitoneal fibrosis, destruction may be mediated by both obstructive and immunologic processes.