1,721,130 research outputs found
Procedural Strategies to Reduce the Incidence of Contrast-Induced Acute Kidney Injury During Percutaneous Coronary Intervention
No full textContrast-induced acute kidney injury (CI-AKI) is a potentially serious complication following coronary angiography and percutaneous coronary intervention (PCI). The incidence of CI-AKI is particularly high in patients with advanced chronic kidney disease (defined as an estimated glomerular filtration rate <30 ml/min/1.73 m2). Although much effort has been dedicated to the identification and implementation of preventive measures for this complication at the pre-intervention stage, much less has been investigated on the procedural strategies and techniques to decrease the risk of CI-AKI during PCI. The mainstay of such approaches relies on the minimization of contrast volume by means of specific strategies or dedicated devices. Invasive imaging, such as intravascular ultrasound or non-contrast-based optical coherence tomography, is another pillar of any ultra-low-contrast-volume PCI protocol. Finally, an array of miscellaneous ancillary measures can be implemented to decrease the risk of CI-AKI, which includes the use of radial access, remote ischemic conditioning, and hemodynamic support in high-risk patients. The present review analyzes the technical aspects as well as the scientific evidence supporting these novel techniques, with the goal to improve the outcomes of patients at high risk for CI-AKI undergoing PCI
Effect of Location on Treatment and Outcomes of Cardiac Arrest Complicating Acute Myocardial Infarction in England & Wales
No full textWe investigated the incidence, management, and outcomes of acute myocardial infarction (AMI) patients according to cardiac arrest location. Patients admitted with a diagnosis of AMI between January 1, 2010 to March 31, 2017 from the Myocardial Ischaemia National Audit Project (MINAP) were studied. We used logistic regression models to evaluate predictors of the clinical outcomes and treatment strategy. The study population consisted of 580,796 patients admitted with AMI stratified into three groups: out of hospital cardiac arrest (OOHCA) (16,278[2.8%]), in-hospital cardiac arrest (IHCA) (21,073[3.7%]), plus a reference group consisting of those without cardiac arrest (non-cardiac arrest (543,418[93.5%]). IHCA declined steadily (from 666 per 1000 in 2010 to 477 per 1000 AMI with cardiac arrest admissions in 2017) with a commensurate rise in OOHCA (from 344 per 1000 to 533 per 1000 AMI with cardiac arrest admissions). Coronary angiography utilization (OOHCA 81.1% vs IHCA 60.3% vs non-cardiac arrest 70.4%, p < 0.001) and PCI (OOHCA 40% vs IHCA 32.8% vs non-cardiac arrest 45.2%, p < 0.001) were higher in OOHCA. In-hospital mortality odds were greatest for IHCA (OR 35.3, 95% CI 33.4-37.2) compared to OOHCA (OR 12.7, 95% CI 11.9-13.6), with the worse outcomes seen in patients on medical wards (OR 97.37, 95% CI 87.02-108.95) and the best outcomes seen in the emergency department (OR 8.35, 95% CI 7.32-9.53). In conclusion, outcomes of AMI complicated by cardiac arrest depended on cardiac arrest location, especially the outcomes of the IHCA.</p
Impact of Left Ventricular End-Diastolic Pressure on the Outcomes of Patients Undergoing Percutaneous Coronary Intervention
No full textLeft ventricular end-diastolic pressure (LVEDP) is an important hemodynamic marker of left ventricular performance and affects coronary perfusion. We evaluated the association of LVEDP with patient outcomes after elective or urgent percutaneous coronary intervention (PCI). We included n = 49,600 patients undergoing elective or urgent PCI. Patients were divided according to LVEDP tertile for descriptive analysis. The primary end point was in-hospital mortality. A recursive partitioning tree model for mortality was built to guide decision-making in patients with high LVEDP undergoing nonemergent PCI. Overall, n = 18,099 patients had an LVEDP 18 mm Hg. Patients in the high LVEDP tertile had a worse clinical and angiographic/procedural profile and experienced a higher incidence of in-hospital post-PCI adverse outcomes, including death (LVEDP 18 mm Hg 0.8%, p..
Noninvasive Thrombolysis Using Histotripsy Pulsed Ultrasound Cavitation Therapy.
Get PDFHistotripsy is a noninvasive ultrasound therapy that utilizes short, high-amplitude, focused ultrasound pulses to mechanically reduce targeted tissue structures to liquid debris by acoustic cavitation. In this work, the physical mechanisms of histotripsy and its application as a method of thrombolysis were investigated.
Cavitation activity which causes tissue breakdown during histotripsy was studied by high-speed photography. It was found that cavitation clouds form due to scattering of shock waves in a focused ultrasound pulse from individual inertial cavitation bubbles. The scattered shock is a large tensile wave which expands clusters of cavitation bubbles when the tensile pressure is greater than a measured threshold of approximately 30 MPa. The interaction of this cavitation with tissue and cells was explored with a phantom containing agarose and red blood cells to measure cavitation-based mechanical damage. The observations indicated that cell lysis may be achieved by bubble-induced tensile strain upon expansion, causing membrane rupture.
Based on these studies, focused histotripsy therapy transducers were designed to controllably generate cavitation clouds in the vasculature for performing thrombolysis. Transducers were integrated with ultrasound imagers to provide feedback for targeting and monitoring progress of treatment. Rapid thrombolysis was observed when histotripsy was applied to clots in-vitro, and the resulting debris was mainly subcellular and unlikely to cause embolism. Additionally, it was observed that histotripsy can attract, trap, and destroy free clot fragments in a vessel phantom. Based on these observations, a noninvasive embolus trap (NET) was developed, acting as a filter to prevent embolism during the thrombolysis procedure. An in-vivo porcine model of deep-vein thrombosis was used to evaluate the safety and efficacy of the histotripsy thrombolysis technique. These experiments demonstrated the feasibility of the treatment and suggest histotripsy can achieve rapid clot breakdown in a controlled manner.PhDBiomedical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/91496/1/adamdm_1.pd
Grinding Wheel Motion and Force Analysis in Atherosclerotic Plaque Removal by Atherectomy
Get PDFAtherectomy is a catheter-based interventional procedure to remove the atherosclerotic plaque off the arterial wall to restore the blood flow and treat cardiovascular diseases. During atherectomy, a metal bond diamond grinding wheel driven by a long flexible drive shaft is inserted into patient’s artery and rotates up to 230,000 rpm to pulverize the plaque into fine debris absorbable by blood and vessels. The grinding wheel motion inside the artery and the grinding force applied on the lesion are poorly understood though critical to the procedure complications including dissection, restenosis, vasospasm, and slow-flow/no-reflow.
This dissertation studies the grinding wheel motion and the associated blood hydraulic force and plaque grinding force during atherectomy. First, an experiment utilizing a transparent tissue-mimicking artery phantom, a high-speed camera, and a piezoelectric dynamometer was conducted to visualize the grinding wheel motion and measure the force on the artery phantom. Second, a computational fluid dynamics model was established to understand the blood flow field near the grinding wheel and the hydraulic force and validated by the particle imaging velocimetry. Third, a grinding force model was built based on the Hertz contact and the smoothed particle hydrodynamics simulation to describe the impact and cutting forces on the plaque and experimentally validated.
The grinding wheel orbits around the vessel lumen in the direction of its rotation. The orbital speed increases with the rotational speed and the size of the grinding wheel. This orbital motion is caused by the rotation-induced blood flow. The hydraulic force on the grinding wheel during orbiting is small comparing to the grinding force. The grinding force is 1.84, 1.92, and 2.22 N at 135,000, 155,000, and 175,000 rpm rotational speed, respectively, when a 2.38 mm diameter burr is tested in a bovine bone sample with a 4 mm lumen. While orbiting around the lumen, the grinding wheel bounces on the wall of the plaque, leaving discrete grinding marks. The bouncing grinding wheel impact force is the dominant component of the grinding force and the cutting component for plaque removal is relatively small.PhDMechanical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/135846/1/yhzheng_1.pd
Can our choice of contrast media impact renal and cardiovascular outcomes?
No full textPeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/117550/1/ccd26483.pd
Fiber Based Infrared Lasers and Their Applications in Medicine, Spectroscopy and Metrology.
Get PDFIn my thesis, I have demonstrated the development of fiber based infrared lasers and devices for applications in medicine, spectroscopy and metrology. One of the key accomplishments presented in this thesis for medical applications is the demonstration of a focused infrared laser to perform renal denervation both in vivo and in vitro. Hypertension is a significant health hazard in the US and throughout the world, and the laser based renal denervation procedure may be a potential treatment for resistant hypertension. Compared to current treatment modalities, lasers may be able to perform treatments with lesser collateral tissue damage and quicker treatment times helping to reduce patient discomfort and pain. An additional medical application demonstrated in this thesis is the use of infrared fiber lasers to damage sebaceous glands in human skin as a potential treatment for acne.
Another significant work presented in this thesis is a field trial performed at the Wright Patterson Air Force Base using a Short Wave Infrared (SWIR) Supercontinuum (SC) laser as an active illumination source for long distance reflectance measurements. In this case, an SC laser developed as part of this thesis is kept on a 12 story tower and propagated through the atmosphere to a target kept 1.6 km away and used to perform spectroscopy measurements. In the future this technology may permit 24/7 surveillance based on looking for the spectral signatures of materials. Beyond applications in defense, this technology may have far reaching commercial applications as well, including areas such as oil and natural resources exploration. Beyond these major contributions to the state-of-the-art, this thesis also describes other significant studies such as power scalability of SWIR SC sources and non-invasive measurement of surface roughness.PhDElectrical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/99780/1/vinalex_1.pd
Noninvasive Thrombolysis using Microtripsy
Get PDFThrombosis refers to blood clot formation and when pathological, is the cause of many vascular diseases. For example, deep vein thrombosis (DVT), which affects three million Americans per year, is the formation of clots in the deep veins of the legs. Current clinical treatments include thrombolytic drugs and catheter-based surgical procedures. Both methods have significant drawbacks, such as excessive bleeding, invasiveness, and long treatment time. Ultrasound has been combined with thrombolytic drugs and/or microbubbles to enhance drug delivery. However, these methods are still quite slow and share the drawbacks of thrombolytic drugs.
Histotripsy is a tissue ablation method that mechanically fractionates soft tissue via well-controlled acoustic cavitation generated by microsecond-long, high-pressure ultrasound pulses. The initial feasibility and safety of using histotripsy as a noninvasive, drug-free, and image-guided thrombolysis technique has been demonstrated both in vitro and in vivo.
The overriding goal of this dissertation is clinical translation of histotripsy thrombolysis. First, an integrated image-guided histotripsy thrombolysis system suitable for clinical DVT treatment are designed and constructed. Second, the recently discovered technical innovations, microtripsy and bubble-induced color Doppler (BCD), are investigated for histotripsy thrombolysis application to further improve treatment efficacy. Microtripsy is a new histotripsy approach and uses an intrinsic threshold mechanism to generate more reproducible and predictable cavitation via a single ultrasound pulse, which can minimize vessel damage by confining cavitation within vessel lumen and eliminate cavitation on vessel wall. BCD is developed to monitor tissue motion induced by histotripsy pulses and investigated as a real-time quantitative feedback for histotripsy thrombolysis. Finally, a comprehensive pre-clinical study in a large animal DVT model is conducted to validate the safety and efficacy of this clinically designed system incorporating these technical innovations. It is our hope that this dissertation work will establish a foundation for the translation of this noninvasive thrombolysis technology into relevant clinical applications.PhDBiomedical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/135813/1/xizh_1.pd
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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