Computational Fluid Dynamics Modeling of the Burr Orbital Motion in Rotational Atherectomy with Particle Image Velocimetry Validation

Heat and mass transfer on MHD rotating Casson Blood-CNTs nanofluid flow in porous channel for biomedical applications

Rotating flow in a channel is a key mechanism in various biomedical applications, including rotating atherectomy, artificial hearts, and hemodialysis systems. While most studies focus on experimental and surgical applications, theoretical investigations on rotating blood flow incorporating carbon nanotubes (CNTs) remain largely unexplored. The channel configuration is considered as effectively represents the cross-section of blood vessels. CNTs nanofluids exhibit superior heat transfer properties compared to conventional fluids and other nanoparticle-based nanofluids, making them highly advantageous for medical applications such as targeted drug delivery and thermal therapies. This study examines the effects of suspending single-wall and multi-wall carbon nanotubes (SWCNTs and MWCNTs) in human blood, modeled as a Casson nanofluid, on the unsteady magnetohydrodynamic (MHD) flow in a rotating channel across a porous medium. The problem is formulated using a set of dimensional partial differential equations (PDEs) under suitable initial and boundary conditions, which are then nondimensionalized using relevant dimensionless variables. The resultant equations are further tackled analytically using the Laplace transform method, yielding closed form of velocity, temperature, and concentration solutions. The results indicate that increasing rotation reduces primary velocity while enhancing secondary velocity, which are essential in preventing vascular diseases. A higher CNTs volume fraction boosts both velocity components, facilitating faster drug transport. The presence of CNTs also improves heat transfer efficiency, with SWCNTs demonstrating a 42.66 % Nusselt number increase at the moving plate and 390.28 % at the stationary plate, outperforming MWCNTs. These findings highlight the potential of CNT-blood nanofluids in medical applications requiring efficient thermal regulation, offering insights into optimizing heat and mass transfer in biomedical devices.

Simulation and experimental study on processing behavior of coronary artery calcified tissue removal

Coronary artery atherosclerosis is a prevalent cardiovascular disease and a leading cause of major adverse cardiovascular events (MACE). Rotational atherectomy (RA) is an effective interventional technique for treating severe calcified stenosis. However, excessive forces, heat, and debris are prone to lead to serious surgical complications, such as slow flow/no-reflow and blood clots. To mitigate excessive force and heat generation during RA, a novel high-performance cutting tool was designed and fabricated for coronary artery calcified tissue removal. An RA simulation model was developed to simulate the procedure. The results showed that the forces, temperatures, and debris size remained within predefined safety thresholds. Using the 1.5 mm tool as an illustration, the peak cutting force was 1.062 N, and the peak temperature rise reached 1.170 °C. Debris distribution exhibited a normal pattern, with 90% of particles measuring below 14 μm. The experimental results closely matched the simulation values, showcasing errors under 10% and affirming the simulation model's precision. This research provides theoretical support for the study of mechanisms and contributes to optimizing the effectiveness of RA.

Drug coated balloons in percutaneous coronary intervention: how can computational modelling help inform evolving clinical practice?

Drug-coated balloons (DCB) represent an emerging therapeutic alternative to drug-eluting stents (DES) for the treatment of coronary artery disease (CAD). Among the key advantages of DCB over DES are the absence of a permanent structure in the vessel and the potential for fast and homogeneous drug delivery. While DCB were first introduced for treatment of in-stent restenosis (ISR), their potential wider use in percutaneous coronary intervention (PCI) has recently been explored in several randomized clinical trials, including for treatment of de novo lesions. Moreover, new hybrid techniques that combine DES and DCB are being investigated to more effectively tackle complex cases. Despite the growing interest in DCB within the clinical community, the mechanisms of drug exchange and the interactions between the balloon, the polymeric coating and the vessel wall are yet to be fully understood. It is, therefore, perhaps surprising that the number of computational (in silico) models developed to study interventions involving these devices is small, especially given the mechanistic understanding that has been gained from computational studies of DES procedures over the last two decades. In this paper, we discuss the current and emerging clinical approaches for DCB use in PCI and review the computational models that have been developed thus far, underlining the potential challenges and opportunities in integrating in silico models of DCB into clinical practice.

Numerical Analysis of Stress Force on Vessel Walls in Atherosclerotic Plaque Removal through Coronary Rotational Atherectomy

Coronary rotational atherectomy is an effective technique for treating cardiovascular disease by removing calcified tissue using small rotary grinding tools. However, it is difficult to analyze the stress force on vessel walls using experiments directly. Using computational fluid dynamics is a better way to study the stress force characteristics of the burr grinding procedure from a fluid dynamics perspective. For this purpose, physical and simulation models of atherosclerotic plaque removal were constructed in this study. The simulation results show that smaller ratios between the burr and arterial diameter (B/A = 0.5) result in a more stable flow field domain. Additionally, the pressure and stress force generated by the 4.5 mm diameter grinding tool reach 92.77 kPa and 10.36 kPa, surpassing those of the 2.5 mm and 3.5 mm grinding tools. The study has demonstrated the use of computational fluid dynamics to investigate wall shear stress characteristics in medical procedures, providing valuable guidance for optimizing the procedure and minimizing complications.

Electroplating a miniature diamond wheel for grinding of the calcified plaque inside arteries

A miniature grinding wheel (0.85 mm diameter) was fabricated by nickel (Ni)-diamond electroplating on a thin (0.65 mm outer diameter) flexible hollow stainless steel drive shaft to remove the calcified plaque in coronary and peripheral arteries by atherectomy procedure. To coat electrically nonconductive diamond grits, the drive shaft was submerged in a pile of diamond grit during Ni electroplating. The electroplating current density and temperature were investigated for better surface finishing and Faraday efficiency. The electroplating time to obtain the designed coating thickness was modeled based on Faraday's law of electrolysis and the geometry of drive shaft, wheel, and diamond grit. To validate the miniature wheel performance in atherectomy, grinding experiments were conducted on an atherectomy cardiovascular simulator with a calcified plaque surrogate. The wheel motion, material removal rate, and wheel surface wear were studied via high-speed camera imaging and laser confocal microscopy. The grinding wheel with 80,000 rpm rotational speed had an orbital speed of 14,300 rpm around the 1.5 mm diameter plaque surrogate lumen. After grinding for 120 s, the plaque surrogate inner diameter was enlarged to 3.03 mm, and no wear or loss of diamond abrasive was observed on the grinding wheel. This study demonstrated that the proposed electroplating process for fabricating miniature grinding wheels could effectively remove the calcified plaque surrogate. This research could lead to a more effective and safer atherectomy device with sub-mm miniature diamond wheels to treat lesions deep in coronary and peripheral arteries.