Cardiovascular Engineering and Technology最新文献

Background: This study aims to explore the association between LA and RA remodeling and their influences on ablation efficacy in AF patients.

Methods: The study involved AF patients undergoing their first catheter ablation using CARTO 3 system. After isolating pulmonary veins, three-dimensional electro-anatomical mapping (3D-EAM) of LA and RA was conducted during sinus rhythm. Low voltage area (LVA) was defined as regions with bipolar voltage < 0.5 mv. If LVA constituted ≥ 10% of the total area of the ipsilateral atrium, it was considered an extensive LVA (ELVA).

Results: A total of 271 patients (male 58.3%, median age 63 years) were enrolled. Biatrial 3D-EAM found that the RA had a larger volume and volume index, longer total activation time, and higher maximum voltage than the LA (P < 0.001). The presence of LVAs, especially ELVAs, was more common in LA (LVAs: 47 patients (17.3%) vs. 29 patients (10.7%), P = 0.011; ELVAs: 26 patients (9.6%) vs. 7 patients (2.6%), P < 0.001). The multivariate logistic analysis revealed that older age, female gender, persistent AF, and LA enlargement were independent predictors of LA LVAs, while female gender and AF duration were associated with RA LVAs. Strong associations were found between variables reflecting the LA and the RA remodeling. Multivariate Cox regression indicated that ELVA in the LA was the only independent predictor of post-ablation recurrence.

Conclusions: AF patients had different characteristics and intrinsic correlations between LA and RA remodeling. The LVAs, especially the ELVAs, were more prevalent in the LA than in the RA. There were distinctions in related factors and impacts on ablation efficacy between the LA LVAs and the RA LVAs.

In the field of cardiovascular device development, new devices such as heart valves, stents or pressure probes for long term heart failure monitoring are subject to animal trials to evaluate their safety and efficacy. For such applications, swine and sheep are the animal models of choice owed to their similarities to humans with regards to heart size, weight and ventricular kinetics. However, clinical aspects regarding the choice of animal model revolve mainly around anatomical similarities as well as the ability to induce the desired pathology. In the case of pulmonary artery pressure sensors, both swine and sheep appear to be suitable candidates for animal trials since both animals have been used for pre-clinical evaluation. Hemodynamic aspects however, although equally important for device performance, appear rather underrepresented in current research and it remains uncertain whether anatomical similarities between humans and animal model in the region of interest translate to hemodynamic similarities. To provide insight whether pulmonary artery hemodynamics in large animal models are indeed comparable to those in humans, this work presents a computational fluid dynamics-based study on pulmonary artery hemodynamics for humans, swine and sheep. A total of 28 human, 41 porcine and 14 ovine transient simulations of pulmonary artery hemodynamics were performed based on subject-specific geometries reconstructed from computed tomography data. The distributions of wall shear stress (WSS) and oscillatory shear index (OSI) within the cohorts were then compared to assess hemodynamic similarity. Distributions of time averaged WSS were found to be similar between humans and sheep (median 1.2 vs. 1.5 Pa, interquartile range (IQR) 0.8 Pa vs. 0.6 Pa, Wilcoxon rank sum test p = 0.42) but were significantly different for swine (median 1.7, IQR 0.5, p < 0.05), whereas OSI was significantly different for sheep and swine (0.17 ± 0.04 vs. 0.14 ± 0.03 and 0.09 ± 0.02). between sheep and humans. In summary, pulmonary artery vessel wall stresses of both animal models appear broadly similar to humans, however, sheep seem to have a notable edge over swine in our study.

Purpose: Type A Thoracic Aortic Dissections are a highly morbid and complex clinical challenge often managed with hemiarch or total arch repair. Hemiarch repair is more commonly performed due to improved neurologic morbidity profile however it leaves behind a residual dissection flap which can lead to aneurysmal degeneration. Bare metal stent placement in conjunction with hemiarch repair is a novel technique which can theoretically avoid leaving a residual dissection flap. In this paper we analyze the biomechanical changes observed after in silico deployment of a bare metal stent in a post-hemiarch type A aortic dissection.

Methods: We obtain computed tomography scans from pre-operative bare metal stent patients and perform high-fidelity segmentations. This geometry is then utilized for in silico stent deployment via finite element analysis. Deformed geometries are then utilized for computational fluid dynamic simulations to analyze the evolution of pressure gradients in the aorta.

Results: We analyze the resulting geometry from in silico stent deployment for three different stiffness ratios between the flap and aortic wall. We demonstrate an acceptable stress evolution in the stent across all 3 stiffness configurations. We show a reduction in the false luminal volume across all stiffness ratios. Our analysis of pressure distributions that evolve in the aorta show that even in scenarios of high flap stiffness, where the false lumen volume shrinks correspondingly less, we still achieve a reduction in the pressure gradient across the aorta.

Conclusion: We show that bare metal stent deployment hemodynamically stabilizes the aorta via our finite element analysis and subsequent computational fluid dynamic modelling.

Purpose: Ventricular assist devices (VADs) are most often computationally evaluated as isolated devices subjected to idealized steady-state blood flow conditions. In clinical practice, these devices are connected to, or within, diseased pulsatile ventricles of the heart, which can dramatically affect the hemodynamics, hence hemocompatibility-related adverse events such as hemolysis, bleeding, and thrombosis. Therefore, improved simulations are needed to more realistically represent the coupling of devices to the assisted ventricle.

Methods: To address this need, we present a hybrid biophysics co-simulation strategy to evaluate the blood flow dynamics of a percutaneous catheter VAD in-situ within a pulsatile ventricle coupled to the circulation. Our hybrid strategy utilizes a computationally inexpensive lumped parameter network (LPN) to compute cardiac dynamics and provide one-way coupled physiologically-realistic boundary conditions to a high-fidelity computational fluid dynamics (CFD) model to simulate detailed hemodynamics of the VAD and the VAD-assisted left heart.

Results: Numerical simulation of a high-speed rotodynamic catheter pump configured as a left ventricular assist device (LVAD) generated a realistic reproduction of the unsteady blood velocity field over one complete cardiac cycle. The biophysics co-simulation strategy resulted in approximately one order of magnitude speed-up compared to a bidirectionally coupled CFD co-simulation. The simulated flow fields revealed persistent swirling blood flow within the ventricle, unsteady flow discharged to aorta by the pump, and significant variations of surface washing around the pump housing during the cardiac cycle.

Conclusions: This study represents a stepping stone toward physiologically and anatomically realistic evaluation of mechanical circulatory support devices that directly complements and reduces extensive in-vivo studies to mitigates risk of adverse events in the clinical setting.

Purpose: In this work we investigate a mathematical model in order to reproduce experimental data of arterial compliance under the action of vasoconstrictors and vasodilators related to pharmacological studies.

Methods: The considered model is a 3D-shell with active fibers. Model parameters are identified by means of an optimization procedure.

Results: The resulting model was able to reproduce the experimental data and predict the system behavior in scenarios other than those used for the parameter estimation. This enables the assessment of different scenarios concerning the impact of the molecules on the active or passive contributions of the arterial wall.

Conclusion: The results suggest that smooth muscle cell contraction modulates stiffness through direct fiber-induced regulation of vascular tone, while parameters related to the passive arterial wall component remain relatively stable across different vasoactive scenarios.

Purpose: Resuscitative thoracotomy, a high-risk procedure involving open heart massage, serves as a last resort for life-threatening conditions like penetrating chest wounds, severe blunt trauma, or surgery-related cardiac arrest. However, its success rate remains low, even when primarily carried out by highly trained specialists. This research investigates the potential of an external biventricular assist device (BiVAD). By replacing open heart massage with our BiVAD device during resuscitative thoracotomy, we aim to achieve sufficient cardiac output, maintain physiological pressure levels, and potentially improve patient survival in these critical situations.

Methods: The proposed BiVAD system features a 3D printed patch design for direct cardiac attachment, an actuation device, and a vacuum pump. The straightforward design allows quick application in emergency situations. The BiVAD system was tested in an in vitro hydraulic mock circulation, utilizing a silicone heart. Three actuation modes were tested for proof-of-concept: manual patch actuation, standard cardiac hand massage, and utilizing full capabilities of our BiVAD patch system with actuation device operation. Overall performance was assessed on ventricular pressure and flow rate data.

Results: Focusing on achieving the optimal cardiac output of 1.5 L/min (critical for patient survival), we tested our patch system against cardiac hand massage at a fixed rate of 60 bpm. The results include raw and statistically evaluated flow rate and pressure measurements for both the left and the right ventricle. Notably, our BiVAD system not only achieved to operate in the range of required cardiac output but also significantly reduced peak pressure in both ventricles compared to standard cardiac hand massage.

Conclusion: This initial evaluation using a silicone heart model demonstrates the potential of our BiVAD system to achieve sufficient cardiac output while reducing peak pressure compared to cardiac hand massage. Further development holds promise for effective cardiac support in resuscitative thoracotomy.

Purpose: Myocardial infarction results in extensive cardiac remodeling that can lead to heart failure. Human pluripotent stem cell-derived cardiomyocyte (hPSC-CM) injection can improve heart function but may lead to engraftment-associated ventricular tachycardia (VT). Optogenetics uses light stimulation to control electrical activity of cells genetically modified to express light-sensitive proteins (opsins). This study aims to use computational simulations to test the feasibility of optogenetically suppressing hPSC-CM ectopic activity without inhibiting the ability to undergo excitation by upstream wavefronts (i.e., engrafted cells could activate harmoniously with surrounding host myocardium during propagation of a normal sinus beat).

Methods: We simulated electrophysiology in single-cell hPSC-CM and tissue-scale ventricular models derived from histology images. The latter comprised host myocardium, hPSC-CM graft, and non-conductive scar. Ventricular and hPSC-CM cellular models were used in the host myocardium and hPSC-CM graft regions, respectively. Optogenetic modification of hPSC-CMs was simulated via incorporation of a photocycle model with the approximate properties of WiChR, a light-sensitive potassium channel. To test the efficacy of the proposed approach for silencing graft activity, we simulated sustained blue light illumination at 488 nm.

Results: Sustained optogenetic stimulation suppressed spontaneous excitation altogether in opsin-expressing hPSC-CM models while maintaining cellular excitability. At the tissue scale, optogenetic suppression of VT-associated ectopic excitations was feasible with epicardial illumination. Opsin-expressing grafts in optogenetically silenced histology models remained excitable under simulated sinus rhythm-like excitation from the endocardium; however, potentially arrhythmogenic spatial heterogeneity of action potential duration was seen in model geometries with greater wall thickness.

Conclusions: Our simulations suggest WiChR-based optogenetic suppression of hPSC-CM graft-associated arrhythmia is likely feasible but must be carefully calibrated to avoid inadvertently pro-arrhythmic side effects.

Purpose: Percutaneous coronary intervention is used extensively for the restoration of blood flow in diseased arteries. The influence of stent implantation on the physiology and flow of blood is an important and still not fully understood issue. The current work evaluated possible stent-induced changes in hematological, hemorheological and hemodynamic parameters.

Methods: Experiments were performed for blood flow in single and overlapping stent configurations, in both straight and curved tube geometries, in order to reproduce various stented coronary artery morphologies. Two different flow regimes were utilized to reflect a range of physiological and more intense flow conditions. Blood samples were obtained from a healthy human population and commercially available stents were inserted in clear perfluoroalkoxy alkane tubing, connected to a syringe/syringe-pump/pressure-sensor setup. Hematological measurements, red blood cell (RBC) deformability and aggregation, and whole blood viscosity tests were performed using standard techniques. The pressure drop across the stented area was measured via an in-line pressure sensing setup.

Results: In terms of hematology, RBC count, hematocrit, and mean corpuscular volume show a slight influence from the longer exposure to elevated stresses. Regarding hemorheology, the most profound effect was observed on RBC aggregation, with an increasing trend primarily in the female population of the study. Further, differences were found in the hemodynamics of the flow, as the pressure drop was altered according to the stent configuration. The viscosity of the blood samples is also found affected in the higher flow rate cases.

Conclusions: The presence of the stent was found to have a distinct effect on specific hemorheological and hemodynamic parameters according to the setup and stent configuration.

Background: Radiofrequency cardiac ablation (RFCA) is a widely utilized treatment for atrial fibrillation (AF). However, its therapeutic efficacy can be compromised by either insufficient or excessive ablation, potentially leading to serious adverse effects. Therefore, precise control of the thermal lesion size generated during RFCA is critical for surgical success. Neural network is an implementation method of artificial intelligence, which has a strong ability to learn and adapt to complex data patterns, and shows significant application potential in the field of prediction. This study aimed to construct an artificial neural network (ANN) model capable of predicting the depth, width, and volume of ablation thermal lesions.

Methods: A two-branch ANN model was developed to predict lesion size on the basis of four key parameters: RF power, ablation duration, catheter‒tissue contact force, and contact angle. The training dataset for the model was derived from a finite element model of radiofrequency cardiac ablation. The model incorporated two types of RF power; catheter-tissue contact forces of 10 g, 20 g, 30 g, and 40 g; and contact angles of 0°, 45°, and 90°. The test dataset was obtained from ex vivo experiments conducted on a swine model, involving ten sets of experiments.

Results: The finite element model effectively simulated the process of thermal lesion formation during RFCA, generating a substantial amount of effective training data. The ex vivo experiments provided reliable test data. The two-branch ANN model was able to predict the depth, width, and volume of thermal lesions, with errors of 0.1986 mm, 0.7891 mm, and 4.9384 mm³, respectively.

Conclusion: This study introduces a two-branch ANN model that serves as an efficient and reliable tool for predicting lesion size for RFCA. The two-branch ANN model proposed in this study enhances the model's ability to fit complex relationships through activation functions and nonlinear combination features. Compared with other models, it has superior predictive capabilities regarding the depth, width, and volume of ablation thermal lesions.