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Biomedical subjects

E I Bluth

Publications and source records attributed to E I Bluth.

At least 37 records · Page 2Linked to original sources
PubMed1998

Extracranial carotid arteries: intraplaque hemorrhage and surface ulceration.

The identification of intraplaque hemorrhage with high resolution gray scale ultrasound imaging has been shown to be achievable by those using appropriate technique and attention to detail. Plaque can be classified as either heterogeneous (classifications 1 and 2) or homogeneous (classifications 3 and 4), This presentation describes the methods for distinguishing different types of plaque accurately. Uniformity of terminology is necessary before multi institutional outcome studies can be undertaken concerning the value of plaque characterization before information published in the literature can be adopted and applied to clinical situations around the world.

Arteriosclerosis↗
PubMed1997

Evaluation and characterization of carotid plaque.

Doppler sonography, combining high-resolution imaging and Doppler spectrum analysis, has proven to be the best choice for safe, noninvasive, low-cost screening for the etiology of stroke. With high-resolution imaging, plaque can be characterized relative to the risk for intraplaque hemorrhage, thought by many to be the precursor of plaque ulceration. Using high-resolution ultrasound, heterogeneous plaque has been shown to be associated with intraplaque hemorrhage. Criteria for distinguishing heterogeneous from homogeneous plaque are discussed, as are techniques for characterizing plaque. Several published articles strongly suggest that, when heterogeneous plaques are identified, the incidence of neurological symptoms and stroke on follow-up increases, relative to patients with homogeneous plaques. Additional long-term follow-up studies of heterogeneous plaque are needed. Most recently, carotid wall thickness has been evaluated as a physiological marker for atherosclerotic disease and as a gauge of the effectiveness of medical therapies. It is likely that carotid wall thickness will become important in the diagnosis and management of atherosclerosis. Radiologist are encouraged to learn this new form of ultrasound examination, which is reviewed briefly in this article.

Arteriosclerosis↗
PubMed1996

Steady flow in models of abdominal aortic aneurysms. Part I: Investigation of the velocity patterns.

As an investigation into the mechanical factors that lead to rupture of abdominal aortic aneurysms, both color Doppler flow imaging and laser Doppler velocimetry measurements of steady flow through a series of aneurysm models are presented. The flow pattern in each model consisted of a core of relatively fast-moving fluid traveling through the center of the dilation, surrounded by an outer annulus of slowly recirculating fluid. At flow rates below a Reynolds number of 1750 +/- 150, the flow was smooth, steady, and laminar. At higher flow rates (Reynolds number above 2250 +/- 250), the flow was always irregular and turbulent. Between these fully laminar and fully turbulent regimes the flow was intermittently turbulent. Larger models showed a tendency to become turbulent at lower Reynolds numbers than smaller models. In addition, turbulence was amplified in the distal half of the model dilation, with the largest models producing velocity fluctuations as great as 35% of the time-average centerline velocities. These data suggest that larger aneurysms in vivo may be subject to more frequent and intense turbulence than smaller aneurysms. Concomitantly, increased turbulence may contribute significantly to risk of rupture, as is discussed in Part II.

Aorta, Abdominal↗
PubMed1996

Steady flow in models of abdominal aortic aneurysms. Part II: Wall stresses and their implication for in vivo thrombosis and rupture.

In a continuing investigation into the mechanical factors that lead to rupture of abdominal aortic aneurysms, wall pressure and shear stress measurements are presented for steady flow through the series aneurysm models described in Part I. These models simulate in vivo aortic aneurysms of diameters from 3.3 to 7.5 cm; the flow rates through the models were dynamically matched to aortic flows under conditions ranging from rest to exercise. For all models, at all flow rates, a pressure maximum was found at the midpoint of the model bulge. This maximum increased with bulge diameter, suggesting that the largest aneurysms in vivo are exposed to the greatest pressures. When the flow was turbulent, the mean wall shear stress at the proximal end of the model bulge had magnitude 2 to 4 dynes/cm2, approximately equal to its value in an undilated tube. However, at the distal end of the model bulge the mean shear stress increased to 5 to 10 dynes/cm2, whereas the peak instantaneous shear stress exceeded the mean by an order of magnitude. When extrapolated to in vivo parameters, the maximum distal wall shear stress reached levels near those capable of disrupting endothelium. This suggests that turbulence in in vivo aneurysms may precipitate thrombus formation. Subsequent decreased luminal diameters in the presence of thrombus would then lessen the likelihood of turbulent flow and reduce the strength of any turbulence that did occur. It would also reduce the pressure in the aneurysmal bulge. Thus, the presence of turbulent flow may significantly affect risk of rupture.

Aorta, Abdominal↗
PubMed1994

Development of turbulence in steady flow through models of abdominal aortic aneurysms.

As part of a general examination of the effects of blood flow patterns on the risk of rupture of abdominal aortic aneurysms, we have investigated steady flow through a series of polyvinyl chloride models of fusiform aneurysms. A series of steady flow rates between 460 ml/min and 2.0 l/min have been delivered through the models, and the resulting flow patterns have been evaluated by color Doppler flow imaging. At low volume flow rates, the pattern of flow through the model is smooth and laminar. At higher flow rates, however, this is replaced by an irregular, fluctuating, and apparently turbulent motion. This finding is consistent with previous clinical observations. Turbulence appears initially at the distal end of the model aneurysm and then spreads proximally to fill the whole model only if the flow rate continues to increase. The onset of irregular, turbulent flow is found to be governed by both the overall flow rate through the model and the model diameter. Critical conditions for the appearance of turbulence are presented and discussed, and the critical value of the Reynolds number for both the initial distal transition and the final full transition is shown to decrease as the size of the model aneurysm increases.

Aortic Aneurysm, Abdominal↗
PubMed1994

Inter-observer variability in ultrasonic evaluation of abdominal aortic aneurysms.

This study was undertaken to assess the consistency in 16 independent observations of the diameters of abdominal aortic aneurysms by diagnostic ultrasound. Confidence intervals were developed for the anterior-posterior dimension and the transverse dimension. Clinical treatment decisions should be made with appreciation that measurements of diameter increases greater than 0.21 cm in the anterior-posterior dimension and 0.31 cm in the transverse dimension are significant and are not a result of inter-observer variation.

Aortic Aneurysm, Abdominal↗
PubMed1993

Screening and managing abdominal aortic aneurysms at the Ochsner Clinic: suggested algorithm and method of derivation. Department of Surgery and Ochsner Clinic Quality Assurance Committee.

An algorithm for screening and management of abdominal aortic aneurysms was developed at the Ochsner Medical Institutions to address the considerable variation identified in clinical practice. A consensus panel of physicians whose opinions differed regarding the management of abdominal aortic aneurysms was convened to develop the algorithm. Based on a literature review and clinical experience, the panel established criteria to determine how frequently and by which methodologies patients with abdominal aortic aneurysms should be followed and when a referral to a vascular surgeon is appropriate. The algorithm developed by the consensus panel method was used to establish practice guidelines that are flexible enough to address individual patient needs yet structured enough to eliminate inappropriate care. Data are being collected and analyzed in real time to determine whether elements of the algorithm should be revised.

Aftercare↗
PubMed1993

Protocol Doppler color flow imaging immediately after kidney transplantation.

Doppler color flow imaging has been used to identify obstruction, rejection, and nonfunctioning renal allografts. When done in the immediate posttransplant period on poorly functioning kidneys, it allows early and accurate detection of surgically correctable changes such as arterial or venous thrombosis or early obstruction by blood, urine, or lymph. Further, it determines changes in intrarenal flow patterns that may indicate early transplant dysfunction, such as acute tubular necrosis and/or acute rejection as well as obstruction. Additionally, baseline values can be obtained in uncomplicated cases for serial follow-up. Between July 1980 and February 1991, 20 transplant patients had Doppler color flow imaging in the immediate posttransplant period. The kidney contour, perirenal collections, vessel flow patterns, and resistive indexes were assessed. In two patients, immediate surgical intervention salvaged the allograft. In several other patients with primary nonfunctioning kidneys, the study distinguished between acute tubular necrosis and obstruction due to external compression. We concluded that protocol Doppler color flow imaging is valuable in the immediate posttransplant period for determining surgically correctable complications.

Adult↗
PubMed1993

Quality improvement techniques: value to improve the timeliness of preoperative chest radiographic reports.

OBJECTIVE: Continuous quality improvement is being advocated as a process that, if adopted, could lead to greater efficiency and productivity in medical institutions. To determine whether continuous quality improvement techniques could be effective in radiology departments, we undertook a model project that sought to improve our ability to interpret preoperative chest radiographs before surgery. All the preoperative films had been ordered by internists who determined, after seeing the patient, that the radiographic examination was warranted. MATERIALS AND METHODS: An eight-member team consisting of all persons involved in obtaining and interpreting preoperative chest radiographs was empowered to evaluate the existing process and make appropriate changes. Techniques used included studying and plotting the process, collecting data on the causes of delay, and basic statistical analysis of the data using histograms, Pareto diagrams, and control charts. On the basis of the data analysis, the team instituted changes, which included identifying the preoperative cards with a small flag, placing the processed films in yellow-colored jackets, and collating these jacketed films after their interpretation. RESULTS: After continuous quality improvement intervention, when the process for obtaining and interpreting preoperative radiographs was modified, the percentage of chest radiographs interpreted before surgery improved from approximately 83% to 98% (p < .001). The average waiting period between patient check-in at the outpatient reception area and interpretation of the preoperative chest radiograph was reduced from 275 to 77 min, a 72% reduction (p < .0302). CONCLUSION: Adoption of the quality improvement techniques of analyzing customer-supplier relations, understanding the causes of variation, and using data to solve problems appears to be a desirable management option that should be considered by all medical institutions interested in maximizing the quality of care offered while concurrently minimizing its cost.

Humans↗
PubMed1992

A qualitative investigation of turbulence in flow through a model abdominal aortic aneurysm.

RATIONALE AND OBJECTIVES: As part of a general examination of the effect of blood flow patterns on the growth and risk of rupture of abdominal aortic aneurysms, the authors investigated the flow through an experimental model of a fusiform aneurysm. MATERIALS AND METHODS: Aneurysms were simulated in polyvinyl chloride tubing. A steady flow of 450 mL/minute to 2 L/minute was investigated by color Doppler flow imaging. RESULTS: Two types of flow patterns existed in the model aneurysm, depending on the overall flow rate through the model. At low velocity flow, this pattern is smooth, steady, and laminar, whereas at higher flows it is irregular and turbulent. CONCLUSION: This finding corresponds to recent clinical observations. The onset of unsteadiness and irregularity in the flow through the model is related to flow velocity.

Aorta, Abdominal↗