Coronary artery disease is a major cause of mortality worldwide. Plaque buildup within an individual’s coronary arteries can lead reduced flows, local ischemia, angina, and even result in a myocardial infarction (heart attack). In the past two decades, coronary stents have become one of the ‘gold standards’ for treating such plaque buildups. Stents are designed to push the plaque up against the vessel walls, so to expand the vessels to its original dimensions; ie., keeping the lumen patent allowing for laminar blood flow. Using the Visible Heart ® Laboratories (1) capabilities, we have implanted coronary stents using various clinical protocols in porcine hearts. These hearts were subsequently scanned with a micro-CT, so they could be modeled and rendered in various 3D programs as well as fluid simulations. The ability to render fluid simulations through coronaries which had stenting procedures performed within, may allow clinicians to prescribe which bifurcation technique may be best suited for a given patient’s specific anatomy.

Coronary arteries are located on the surface of the heart and supply oxygenated blood to the myocardium and other components of the heart. The two coronary arteries located above the aortic arch are the Left Coronary Artery (LCA) and Right Coronary Artery (RCA). The LCA branches into the Left Anterior Descending (LAD) and the Left Circumflex (LCx) while the RCA branches into the Right Marginal Artery (RMA) and Post Descending Artery (PDA). The coronary arteries are likened to a complex tube-like structure, and the motion of the heart cause changes in pressure, which allows proper blood circulation during the systolic and diastolic phases [1]. Since it is essential to understand the physiological and hemodynamical behavior of the heart and coronary arteries, numerous studies have been conducted at different artery locations in the heart. Most of the research has focused on the branches between the LAD and LCx, with little or no attention directed towards the take-off angle the LCA makes with the aortic root. Although it has been reported that certain take-off angles of left main (LM) can be considered anomalous, findings have documented that such take off angles can make the artery prone to atherosclerosis and sudanophilia diseases [2]. Computational Fluid Dynamics (CFD) has in recent years been used to solve a wide variety of fluid flow challenges, and can be used for this study. The goal of this study is to use CFD techniques to study the hemodynamics of the different take-off angles of the left coronary artery from the aortic root. This will help identify areas in the left coronary artery that could be prone to atherosclerosis buildup.

A valveless shear-driven micro-fluidic pump design (SDMFP) for hemodynamic applications is presented in this work. One of the possible medical and biomedical applications is in-vivo hemodynamic (human blood circulation) support/assist. One or more SDMFPs can be inserted/implanted into vascular lumens in a form of a stent/duct in series and/or in parallel (bypass duct) to support blood circulation in-vivo. A comprehensive review of various micro-pump designs up to about mid 2000’s is given in [1,2]. Many of micropump designs considered are not suitable for in-vivo or even in-vitro medical/biomedical applications. Operating principles, design, and SDMFP features are given in [3]. A particular design used in cardiovascular applications has no moving valves. SDMFP with Gourney-flap type valves to support high-pressure applications are developed for other applications. SDMFP could be fully bi-directional and can control its operation on the run using embedded microcontrollers and sensors. Estimated efficiency is high with low leakage resulting in low power consumption. Proprietary “fish-scale” surface coating ShearQ™ designs are implemented to improve unidirectional flow pumping efficiency. Bi-directional feature may be especially critical when clogging of blood vessels is detected. By automatically and temporarily switching into the reverse-mode operation and retrogressive flow, while inducing suction-head for a short time periods it is hoped that possibly blood conduits can be cleared/unclogged and the normal forward-flow operation resumed. Such may be an important feature if SDMFP is used in-vivo, such as, in coronary arteries which are prone to clogging leading to cardiac-arrest.

Left ventricular assist devices (LVADs) are mechanical pumps that provide full or partial support of the circulation in patients with varying degrees of heart failure (HF). This simulation study explores the hemodynamic effects of a continuous flow pump deployed in the Ascending Aorta (AAo) specifically focusing on: (a) perfusion of the coronary arterial circulation and (b) the effect of induced non-physiologic, swirling flow discharged by the pump on perfusion to head-neck vessels of the aortic arch.

Stents are most commonly used in the relief of coronary artery stenosis, but in the last decade have found increasing applications in the treatment of other cardiovascular disease and in particular in heart valve replacement [1]. In transcatheter valve implantation, acquisition of high temporal and spatial resolution images during stenting procedure and patients’ follow-up is required to help the correct positioning of the device and to assess the mechanical performance over time. The imaging techniques routinely used for this purpose are 2D X-ray fluoroscopy and 3D computed tomography (CT), and recent studies have demonstrated their value as diagnostic tools [1–3]. However, these image modalities carry errors and the resulting information might not be accurate enough to be employed in engineering analyses of stent deformations, mechanics, dynamics and fracture. In this study, we aim to evaluate the errors of conventionally used clinical images (fluoroscopy and CT) and post-processing by comparison with ultra-high resolution micro-CT (μCT) as gold standard. Additionally, an optical image acquisition method and a high-radiation CT scan were evaluated as potential techniques to acquire geometrical data that could be used for computational and in-vitro engineering experiments.

Coronary artery stenting has emerged as the gold standard for the treatment of cardiovascular diseases. With this revolutionary technology, stents today have extended their indications from coronary artery diseases to many other applications including carotid, renal, and femoral arteries. A stent is a small, coiled wire-mesh tube that can be deployed into a narrowed artery and expanded by a catheter during angioplasty. Inserting such a foreign body into human is likely to induce adverse biological reactions such as restenosis. It is believed that the low wall shear stress (WSS) region on the stented arterial wall is related to restenosis [1–2].

This paper describes a polymer-based shear stress sensor built on catheter for in vivo measurements and potential application in atherosclerosis diagnosis. MEMS shear stress sensor with backside wire bonding has been used to address in vitro applications for micro-scale hemodynamics with high temporal and spatial resolution. However, to assess shear stress in the tortuous and dynamic arterial circulation, we had to develop a new generation of polymer- and catheter-based sensors that are both flexible and deployable. The individual sensor was packaged near the tip of a catheter for intravascular shear stress analysis. The wire bonding and electrode leads were insulated by a film of Parylene C and were connected to the external circuit along the guide-wire. The sensor was deployed through the catheter into the aorta of New Zealand White (NZW) rabbits by the femoral cut-down procedure. Based on the heat transfer principle, the device was able to detect small temperature perturbation in response to the pulsatile flow at ∼200 beats/minutes in the rabbits. The sensor was calibrated in the presence of rabbit blood flow at 37.8°C. We demonstrated the feasibility of translating a polymerbased device for dynamic intravascular measurement with a potential for clinical applications in detecting coronary artery disease and stroke.