Cardiovascular Engineering and Technology最新文献

The prevalence of coronary artery disease (CAD) has become the major cause of death across the world in recent years. The accurate segmentation of coronary artery is important in clinical diagnosis and treatment of coronary artery disease (CAD) such as stenosis detection and plaque analysis. Deep learning techniques have been shown to assist medical experts in diagnosing diseases using biomedical imaging. There are many methods which employ 2D DL models for medical image segmentation. The 2D Pyramid Scene Parsing Neural Network (PSPNet) has potential in this domain but not explored for the segmentation of coronary arteries from 3D Coronary Computed Tomography Angiography (CCTA) images. The contribution of present research work is to propose the modification of 2D PSPNet into 3D PSPNet for segmenting the coronary arteries from 3D CCTA images. The innovative factor is to evaluate the network performance by employing Global processing and Patch based processing methods. The experimental results achieved a Dice Similarity Coefficient (DSC) of 0.76 for Global process method and 0.73 for Patch based method using a subset of 200 images from the ImageCAS dataset.

Purpose: This goal of this study was to determine the impact of vascular motion on acute drug transfer and retention of drug-coated balloons (DCB) or drug-eluting stents (DES).

Methods: Commercially available paclitaxel DCBs (Lutonix & IN.PACT) and a paclitaxel DES (Zilver) were subjected to physiological flow and vascular motion conditions using a peripheral-simulating benchtop bioreactor system. Each DCB- or DES-treated artery was subjected to three sets of movement parameters including pulsatile flow with no twisting/bending (P1), pulsatile flow with 16.8° twist, 25° bend and 3.2 mm compression (P2), and pulsatile flow with 68° twist, 35° bend, 21 mm compression (P3). After 24 h, the treated segments were removed and paclitaxel concentrations were measured using pharmacokinetic analysis.

Results: In the group of arteries treated with the Lutonix DCB, there was a significant decrease in arterial paclitaxel concentrations between the P1 and both the P2 and P3 moving parameters (P1 = 404 ± 195 ng/mg, P2 = 14.9 ± 9.92 ng/mg, P3 = 19.2 ± 15.4 ng/mg; P1-P2 p = 0.007, P1-P3 p = 0.005). For the IN.PACT DCB group, no differences in the mean arterial paclitaxel concentrations were observed for the various movements (p = 0.55). Lastly, in the Zilver DES group, differences were only measured between the P2 and P3 moving parameters (P2 = 84.8 ± 32.7 ng/mg, P3 = 0.11 ± 0.06 ng/mg; P2-P3 p = 0.01).

Conclusion: Acute retention of arterial paclitaxel levels can be adversely impacted by vascular movement in both DES- and DCB- treated arteries.

Introduction: Extracorporeal membrane oxygenation is a lifesaving treatment for patients with refractory acute respiratory, circulatory, or combined cardiopulmonary failure. The patient is cannulated with one or two cannulae for drainage and reinfusion of blood. Blood is drained from the patient, pumped through a membrane lung for oxygenation and returned to the patient. Treatment efficiency depends on correct cannula positioning and interactions between drainage and reinfusion cannula.

Methods: An experimental setup was built to study the isolated drainage performance of 24 Fr rigid models of a blunt and lighthouse tip cannula, both when centered and when tilted towards the vessel wall. Planar particle image velocimetry was used to investigate the flow field with water as the fluid medium.

Results: For similar flow configuration, higher shear stresses were recorded in the blunt tip rather than lighthouse tip cannula. Moreover, in the lighthouse tip cannula, side-holes furthest from the tip (proximal side-holes) had the highest drainage. Results did not change substantially when the cannula was tilted towards the vessel wall.

Conclusions: The effective drainage point of the lighthouse tip cannula was located near the proximal side-holes. Lower shear stresses were recorded in the lighthouse tip cannula when compared with the blunt tip cannula, for all considered flow rate ratios and cannula positions.

Purpose: Aortic valve stenosis (AVS) is the most common valvular disease in developed countries. Surgical or transcatheter bioprosthetic aortic valve (AV) replacement is the standard treatment for severe AVS. However, bioprostheses are prone to structural degeneration. Hence, in terms of lifetime management, there is a need for therapies that can postpone AV replacement. With the aim of fragmenting calcifications and restoring AV leaflets flexibility, a new transcatheter debridement device (TDD) exploiting ultrasound is under development. We performed an ex-vivo study on human hearts to quantify how TDD treatment affects stenotic AVs hemodynamic. Additionally, a qualitative histological analysis was performed to assess TDD's impact on AV leaflets.

Methods: Three human hearts affected by AVS were characterized pre- and post-treatment in an ex-vivo beating heart simulator. To replicate physiological flowrates, a pulsatile pump was connected to the left ventricle, while a systemic impedance simulator connected to the aortic root and a reservoir connected to the left atrium closed the hydraulic circuit. Transvalvular pressure drop (ΔPsys), backflow volume, and effective orifice area (EOA) were evaluated. For histological analysis, AV leaflets sections were stained with Haematoxylin/Eosin and AlizarineRedS to highlight calcifications.

Results: The treatment induced a reduction in ΔPsys in all tested samples, improving EOA, but caused an increase in backflow volume. Moreover, histology suggested AV leaflets integrity.

Conclusions: The TDD procedure improved AV fluid-dynamics during systole in all tested samples, without evidence of damage to tissues. This suggests TDD could be a promising option to postpone AV replacement for patients with AVS.

Purpose: Recent studies have identified an effect of glycosaminoglycans (GAG) on residual stresses in the aorta, underscoring the need to better understand their biomechanical roles.

Methods: Aortic ring models for each of the ascending, arch and descending thoracic regions of the porcine thoracic aorta were created in FEBioStudio, using a framework that incorporates the Donnan osmotic swelling in a porous solid matrix. The distribution of fixed charge densities (FCD) through the thickness of the tissue was prescribed as calculated from experimentally quantified sulfated GAG mural distributions. Material parameters for the solid matrix, modeled using a Holmes-Mow constitutive law, were optimized using data from biaxial tensile tests. In addition to modelling the solid matrix as one layer, two layers were considered to capture the differences between the intima-media and the adventitia, for which various stiffness ratios were explored.

Results: As the stiffness of the adventitia with respect to that of the media increased, the simulated opening angle increased. The opening angle also decreased from the ascending to the descending thoracic region in both one- and two-layered solid matrices models. The simulated results were compared against the experimental contribution of GAG to the opening angle, as previously quantified via enzymatic GAG-depletion. When using one layer for the solid matrix, the errors between the simulated opening angles and the experimental contribution of GAG to the opening angle were respectively 28%, 15% and 23% in the ascending, arch and descending thoracic regions. When using two layers for the solid matrix, the smallest errors in the ascending and arch regions were 21% and 5% when the intima-media was modelled as 10 times stiffer, and as twice stiffer than the adventitia, respectively, and 23% in the descending thoracic regions when the intima-media and adventitia shared similar mechanical properties.

Conclusions: Overall, this study demonstrates that GAG partially contribute to circumferential residual stress, and that GAG swelling is one of several regulators of the opening angle. The minor discrepancies between simulated and experimental opening angles imply that the contribution of GAG extends beyond mere swelling, aligning with previous experimental indications of their interaction with ECM fibers in determining the opening angle.

Purpose: Central venous catheters (CVCs) provide a direct route to the venous circulation but are prone to catheter-related thrombosis (CRT). A known CRT risk factor is a high catheter-to-vein ratio (CVR), or a large catheter diameter with respect to the indwelling vein size. In this study, the CVR's effect on CVC hemodynamics and its impact on CRT is investigated with in vitro and in silico experiments.

Methods: An in vitro flow loop is used to characterize the hemodynamics around CVCs using particle image velocimetry. In addition, CRT is investigated using an in vitro flow loop with human blood and clinical catheters. The wall shear rate of flow around the CVC is computed numerically. CVRs of 0.20, 0.33, and 0.49 and Reynolds numbers of 200, 800, and 1300 are evaluated. No flow is used through CVC lumens to model chronic indwelling catheters.

Results: Results show CVR ≥ 0.33 promotes platelet-rich clot growth at the device tip and at an increased rate compared to lower CVR cases. A high wall shear rate gradient on the CVC tip and an extended wake distal to the tip exists for higher CVR cases, promoting the aggregation of platelets and subsequent stagnation for clot formation. Further, the combination of the CVR and Reynolds number are crucial to CRT potential, not the CVR alone. Specifically, thrombosis risk is increased with low (stasis driven) and/or high (platelet activation driven) flow conditions, with the CVR and CVC's geometry playing an additional role in promoting fluid mechanic driven thrombus development. A high CVR (≥ 0.33) and high flow condition (≥ 1300) results in the highest risk for clot growth at the tip of the device; other locations of the device are at risk for thrombus development in lower flow conditions, regardless of the CVR. The importance of the device geometry and flow in promoting thrombus and fibrin sheath formation is also shown for the device investigated.

Conclusions: This work demonstrates that the CVR, flow, and device geometry affect CRT. For clinical cases with CVR ≥ 0.33 and/or Re ≥ 1300, the device tip may be monitored more consistently for clot formation. Thrombosis risks remain on the entire catheter, regardless of the flow condition, for a CVR = 0.49. Device placement should be chosen carefully with respect to the combination of the Reynolds number and CVR. Further study is needed on the effect of catheterization to confirm these findings.

Purpose: Heart failure (HF) is still a leading cause of mortality and morbidity despite considerable advances in therapy. This study aimed to evaluate the efficacy of cardiac contractility modulation (CCM) for treating Chinese patients with HF.

Methods: This retrospective study included six HF patients who had New York Heart Association (NYHA) class II or III and received CCM implantation at the First Affiliated Hospital of Soochow University from May 2022 to May 2023. Assessments were conducted before and after 12 months of CCM treatment to evaluate the left ventricular ejection fraction (LVEF), the left ventricular end-diastolic dimension (LVEDD), the left atrium diameter (LAD), and cardiac function.

Results: After the 12-month follow-up, all outcome measures showed improvement: the LVEF increased from (27 ± 4.73) % to (39.67 ± 7.06) %, the LVEDD decreased from (70.33 ± 1.97) mm to (64.83 ± 3.71) mm, and the LAD decreased from (52.83 ± 7.14) mm to (47.00 ± 7.48) mm. All patients reached NYHA functional class II.

Conclusions: The findings from this small study suggest that CCM therapy can enhance the cardiac functional status, improve LVEF, and reverse ventricular remodeling.

Purpose: Pulmonary valve replacement (PVR) using bioprosthetic valves is a common procedure performed in patients with repaired Tetralogy of Fallot and other conditions, but these valves frequently become dysfunctional within 15 years of implantation. The causes for early valve failure are not clearly understood. The purpose of this study was to explore the impact of changing cardiac output (CO) and valve orientation on local hemodynamics and valve performance.

Methods: A 25 mm bioprosthetic valve was implanted in an idealized 3D-printed model of the right ventricular outflow tract (RVOT). The local hemodynamics at three COs and two valve orientations were assessed using 4D-Flow MRI and high-speed camera imaging.

Results: Noticeable differences in jet asymmetry, the amount of recirculation, leaflet opening patterns, as well as the size and location of reversed flow regions were observed with varying CO. Rotation of the valve resulted in drastic differences in reversed flow regions, but not forward flow.

Conclusion: Flow features observed in the valve with low CO in this study have previously been correlated with calcification, hemolysis, and leaflet fatigue, indicating their potential negative impact on local hemodynamics and leaflet performance.

Purpose: An abdominal aortic aneurysm (AAA) is a dilation of the aorta over its normal diameter (> 3 cm). The minimally invasive treatment adopted uses a stent graft to be deployed into the aneurysm by a catheter to flow blood through it. However, this approach demands frequent monitoring using imaging modalities that involve radiation and contrast agents. Moreover, the multiple follow-ups are expensive, time-consuming, and resource-demanding for healthcare systems. This study proposes a novel wireless implantable medical sensor (WIMS) to measure the aneurysm growth after the endovascular repair.

Methods: The proposed sensor is composed of a Z-shaped inductor, similar to a stent ring. The proposed design of the sensor is explored by investigating the inductance, resistance, and quality factor of different possible geometries related to a Z-shaped configuration, such as the height and number of struts. The study is conducted through a combination of numerical simulations and experimental tests, with the assessment being carried out at a frequency of 13.56 MHz.

Results: The results show that a higher number of struts result in higher values of inductance and resistance. On the other hand, the increase in the number of struts decreases the quality factor of the Z-shaped inductor due to the presence of high resistance from the inductor. Moreover, it is observed that the influence of the number of struts present in the Z-shaped inductor tends to decrease for larger radii.

Conclusions: The numerical and experimental evaluation concludes the ability of the proposed sensor to measure the size of the aneurysm.

Purpose: It is known that elastic laminae (ELs) in the aortic wall, especially the inner layers, are structurally buckled due to residual stresses under unpressurized conditions. Herein, we aimed to develop a realistic computational model, replicating the mechanical behavior of an aortic ring from no-load to physiological conditions by considering inherent residual stresses, which has not been widely included in conventional modeling studies.

Methods: We determined specific conditions to reproduce EL buckling with a "preferable" residual stress distribution under no-load conditions by combining the design of experiments and multiobjective optimization. Subsequently, we applied these conditions to two ring models with distinct wall structures comprised ELs and smooth muscle layers (SMLs), and compared their mechanical responses to assess the effect of implemented residual stresses by tracking changes in stress distribution in the aortic wall and corresponding EL waviness under no-load and pressurized conditions.

Results: We successfully reproduced EL buckling with a steady upward residual stress distribution that was considered "preferable" under no-load conditions. Furthermore, we replicated radially cut ring models that spontaneously opened in vitro, and confirmed that an SML circumferential stress distribution approached a uniform state under pressurized conditions, effectively mediating stress concentrations induced at the inner layers.

Conclusions: We established a ready-to-use scheme to implement intrinsic residual stresses in the aortic wall. Our computational model of the aortic ring, reproducing realistic mechanical responses and behavior, represents a valuable tool that offers essential insights for hypertension prevention and potential new clinical applications.