Angiographic features and transarterial embolization of retained placenta with abnormal vaginal bleeding

Objectives To clarify characteristic angiographic features and clinical efficacy of selective transarterial embolization (TAE) of retained placenta with abnormal vaginal bleeding. Methods The study cohort comprised 22 patients (mean age, 33.5 years; range, 22–24 years) who underwent selective TAE for retained placenta with abnormal bleeding between January 2018 and December 2020 at our institution. Angiographic images were reviewed by two certified radiologists with consensus. Medical records were reviewed to evaluate the efficacy of TAE. Angiographic features of retained placenta, technical success (disappearance of abnormal findings on angiography), complications, clinical outcomes (hemostatic effects and recurrent bleeding) were evaluated. Results Pelvic angiography showed a dilated vascular channel mimicking arteriovenous fistulas or an aneurysm contiguous with dilated uterine arteries in the mid-arterial–capillary phase in 20 patients; it showed contrast brush in the remaining two patients. TAE technical success was achieved in all patients. No major complications were observed in any patients. Fifteen patients were followed up with expectant management after TAE; all but one patient showed no re-bleeding during the follow-up period (mean follow-up interval, 3.4 months; range, 1–17 months). One patient showed minor rebleeding, which resolved spontaneously. Seven patients underwent scheduled hysteroscopic resection within 1 week after TAE, and no excessive bleeding was observed during or after the surgical procedure in all seven patients. Conclusions The characteristic angiographic feature of retained placenta is “dilated vascular channel that mimic low flow AVM.” TAE is a safe and effective treatment to manage retained placenta with abnormal bleeding.

Abstract 342: Analysis of Mechanism of a Novel Drug Candidate using an Organ-level Functional Microdevice that Reconstitutes Human Pulmonary Thrombosis

Pulmonary microvascular thrombosis is a catastrophic medical condition and yet, it is very difficult to predict response and study mechanism of action of potential drug candidates to humans. This is partly so because currently available in vitro assays do not recapitulate physiologically-relevant forces and animal models can also be very complex, making it impossible to analyze intercellular signaling within the lung that occurs under coagulation or drug administration. We designed a model of lung thrombosis in which human primary alveolar and endothelial cells are co-cultured and maintained up to 2 weeks. The device consists of a top chamber seeded with human alveolar epithelial cells (AE) and a lower chamber seeded with endothelial cells, separated by a porous matrix-coated membrane. Whole blood was perfused at a physiological shear stress through the vascular channel and clots were visualized in real-time. When healthy cells were cultured, no intravascular blood clotting was observed, even when lipopolysaccharide (LPS) endotoxin was administered. In contrast, when LPS was added to the AE channel, it caused a significant increase in platelet adhesion at the endothelium, demonstrating that the presence of alveolar epithelium is critical to LPS-induced intravascular thrombosis in vitro . We evaluated this device by analyzing a novel protease activator receptor-1 (PAR1) antithrombotic compound, termed parmodulin 2 (PM2). When the endothelium was cultured along with PM2 under the condition of LPS stimulated AE, we found inhibition of clotting, demonstrating the therapeutic effect of PM2 in the presence of epithelial-endothelial-blood cell signaling. Finally, to test if PM2 performs the therapeutic function of Activated Protein C (APC) that has been reported to stimulate its cytosolic effects via the β-arrestin pathway, we knocked down β-arrestin in the endothelium and analyzed clot formation again. We found that clotting reoccurred in vascular channel, thus showing that PM2 acts like an APC-like drug candidate. In conclusion, the lung alveolus-on-a-chip reconstitutes organ-level responses to blood clotting and may offer a valuable platform for drug development by allowing to dissect contributions of various cells in their mechanism of action.

Vibration Characteristics of Magnetic Nano Fluids-Filled Flexible Cantilevers Under Varied Magnetic Fields

In this paper, the influence of an external magnetic field on the vibration responses and damping ratios of a vascular beam filled with three different magnetic nanofluids are investigated. First, the equation of motion of a fluid-filled beam is derived based on the published works and some amendments are made to simultaneously include the damping ensuing from the surrounding air and also the effects of viscosity of the fluid inside the vascular channel. Then, the effects of an external magnetic field on the viscosity of the fluid is studied and incorporated into the equation of motion of the beam. Finally, based on three magnetic nanofluid samples, simulations are conducted to represent the changes in frequency response functions and damping ratios of the vascular channel beam. The maximum increase observed in the viscosity of the magnetic nanofluid samples under the influence of magnetic field with the intensity of 1 Tesla was 16%, while the reduction in the vibration amplitude found 12.7% and 33.8% for the first and second vibration mode under the influence of the maximum magnetic field intensity of 0.3 Tesla. Moreover, the maximum decrement of the damping ratio was 1.1% under the same magnetic field. However, it seems that the higher values for vibration reduction can be achieved by using the magnetic nanofluid with higher magnetic particle concentrations and viscosities.