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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
441

Surgical Mortality and Morbidity Following Open Heart Surgery : A Clinical Study of Complications Following Intracardiac Surgery in 1880 Patients Admitted to the Department of Cardiovascular Surgery, Presbyterian Hospital of Pacific Medical Center, from 1956 to 1969

Sharma, Giridhari 01 January 1969 (has links) (PDF)
From the introduction: What follows in the next pages is a tabulation of results of open heart surgery in 1880 patients who were admitted to the cardiovascular surgery unit during the period May, 1956-May, 1969. Surgical mortality and morbidity data are presented in a brief manner. I have tried to interpret the results in light of the similar experience of others. This digestion of the work of others with enzymes of one's personal experience is not always palatable, especially when the latter is admittedly limited.
442

Interplay between Ephaptic and Gap Junctional Coupling in Cardiac Conduction

George, Sharon Ann 24 March 2016 (has links)
Sudden cardiac death occurs due to aberrations in the multifactorial process that is cardiac conduction. Conduction velocity (CV) and its modulation by several determinants, like cellular excitability, tissue structure and electrical coupling by gap junctions (GJ), have been extensively studied. However, there are several discrepancies in cardiac electrophysiology research that have extended over decades, suggesting elements that are still not completely understood about this complex phenomenon. This dissertation will focus on one such mechanism, ephaptic coupling (EpC). The purpose of this work is twofold, 1) to identify ionic determinants of EpC, and its interactions with gap junctional coupling (GJC) and, 2) to investigate the possible role of serum ion modulation in cardiac arrhythmia therapy. First, the effects of altering extracellular ion concentration – sodium, potassium and calcium at varying GJ protein expression were studied. Briefly, reducing sodium was related to CV slowing under conditions of reduced EpC (wide intercalated disc nanodomains – perinexi) and GJC (reduced GJ protein – Connexin43). On the other hand, increasing potassium slowed CV in hearts with wide perinexi independent of GJC. Elevating calcium, reduced perinexal width and was associated with fast CV during physiologic sodium concentration. However, under conditions associated with disease, like hyponatremia, elevating calcium still reduced perinexal width but slowed CV. These findings are the first to suggest that ionic modulators of EpC could modulate CV during health and disease. Next, the potential of perfusate ion modulation in cardiac arrhythmia therapy was investigated. Briefly, in a model of myocardial inflammation, TNFα, a pro-inflammatory cytokine, slowed CV relative to control conditions and this was associated with widening of the perinexus (reduced EpC). Increasing extracellular calcium restored CV to control values by improving not only EpC but also GJC. Finally, in a model of metabolic ischemia in the heart, CV response due to solutions with varying sodium and calcium concentrations were tested. The solutions that were associated with wider perinexi and elevated sodium performed best during ischemia by attenuating CV slowing, reducing arrhythmias and increasing time to asystole. Taken together, these findings provide evidence for the possibility of ionic determinants of EpC in cardiac arrhythmia therapy. / Ph. D.
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443

The role of the nurse in promoting cardiac rehabilitation in women

Morey, Melissa 01 January 2010 (has links)
Since its inception, cardiac rehabilitation has been effective at reducing risk factors for cardiovascular disease, improving quality of life, and decreasing morbidity and mortality rates. While women benefit as much as men from the therapeutic effects of cardiac rehabilitation, a disparity exists between referral, participation, and completion rates between men and women. The intent of this thesis was to examine recent literature to determine if those disparities still exist, to identify barriers that prevent women from participating, and to determine the role of the nurse in the promotion of cardiac rehabilitation among women. Current literature reveals that women are often older, single, financially unstable, less physically active, and diagnosed with more co-morbidities at the time of their first cardiac event. Women often lack strong physician referral and support, education about cardiac rehabilitation programs, and motivation to attend programs. Evidence gathered from current literature suggests that gender is not the primary reason for the disparity between cardiac rehabilitation participation rates among men and women, but rather the disparity exist~ because of the characteristics of these older women at the time of their first cardiac event. The nurse is the vital component to increasing cardiac rehabilitation participation rates among women. The nurse must serve as a patient advocate- providing information and structure to the referral process, as an educator- teaching women the benefits and safety of cardiac rehabilitation, and as social support- providing women with encouragement and follow-up during a frightening and life-changing experience.
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444

The effect of five physical activities on the cardiac output

Hartzler, Ruth Arlene, Radke, Karen Jean January 1966 (has links)
Thesis (M.S.)--Boston University / PLEASE NOTE: Boston University Libraries did not receive an Authorization To Manage form for this thesis or dissertation. It is therefore not openly accessible, though it may be available by request. If you are the author or principal advisor of this work and would like to request open access for it, please contact us at open-help@bu.edu. Thank you. / 2999-01-01
445

Predicting physical fitness outcomes of exercise rehabilitation: An retrospective examination of program admission data from patient records in a hospital-based early outpatient cardiac rehabilitation program

Fabiato, Francois Stephane 10 September 1998 (has links)
Economic justification for rehabilitative services has resulted in the need for outcome based research which could quantify success or failure in individual patients and formulate baseline variables which could predict outcomes. The purpose of this study is to investigate the utilization of baseline clinical, exercise test, and psychosocial variables to predict clinically relevant changes in exercise tolerance of cardiac patients who participated in early outpatient cardiac rehabilitation. Clinical records were analyzed retrospectively to obtain clinical, psychosocial and exercise test data for 94 patients referred to an early outpatient cardiac rehabilitation program at a large urban hospital in the Southeast US. All patients participated in supervised exercise training 3d/wk for 2-3 months. A standardized training outcome score STO) was devised to evaluate training effect by tabulating changes in patients predicted VO2, body weight and exercising heart rates after 8-12 weeks of exercise based cardiac rehabilitation. STO = Predicted VO2 change + BW change- HR change. The Multi-Factorial Analysis was applied to derive coefficients in the STO formula so that the STO scores reflected the independent effects of BW, HR and Predicted V02 changes on training outcome. Patients were classified into one of three possible outcome categories based on STO scores, i.e. improvement, no change, or decline. Thresholds for classifying patients were the following; STO scores greater than or equal to 3 SEM above the mean = improved, (N= 40: 41%), STO scores less than or equal to 3 SEM below the mean = decline, (N=34: 35%), STO scores within 3 SEM= no change, (N=23: 24%). Multiple logistic regression was used to identify patient attributes predictive of improvement, decline, or no change from measures routinely collected at the point of admission to rehabilitation. The model for prediction of improvement correctly classified 70% of patients as those who improved vs. those who did not (sensitivity 70%, specificity 71%). This model generated the following variables as having predictive capabilities; recent CABG, emotional status, social status, calcium channel blocker, recent angioplasty, maximum diastolic BP, maximum systolic BP and resting systolic BP. The model for predicting those who declined vs. those who did not decline demonstrated higher correct classification rate of 74% and specificity (84%). This model generated the following variables as having predictive capabilities; social status, calcium channel blocker, orthopedic limitation, role function, QOL score and Digitalis. However, these models may include certain bias because the same observations to fit the model were also used to estimate the classification errors. Therefore, cross validation was performed utilizing the single point deletion method; this method yielded somewhat lower fraction correct classification rates (66%,69%) and sensitivity rates (56%,44%) for improvement vs. no improvement and decline vs. no decline groups respectively. Conclusion A combined set of baseline clinical, psychosocial and exercise measures can demonstrate moderate success in predicting training outcome based on STO scores in hospital outpatient cardiac rehabilitation. In contrast psychosocial data seem to account for more of the variance in prediction of decline than other types of baseline variables examined in this study. Baseline blood pressure responses both at rest and during exercise were the greatest predictors of improvement. However, cross validation of these models indicates that these results could be biased eliciting overly optimistic predictive capabilities, due to the analysis of fitted data. These models need to be validated in independent sample with patients in similar settings. / Master of Science
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446

Validation of a new method of determining cardiac output in neonatal foals

Corley, Kevin Thomas Trent 21 August 2001 (has links)
Hypotension is a common finding in hospitalized, critically ill neonatal foals. Hypotension may be a function of low cardiac output or increased cardiac output and decreased systemic vascular resistance. In the first instance, treatment would include fluids and/or inotropes and in the second, fluids and/or vasopressors. Therefore, cardiac output measurements are expected to help guide the treatment of hypotension associated with critical illness and/or anesthesia in neonatal foals. However, a practical and safe method of measuring cardiac output has not been described for the foal. Lithium dilution, a new method of cardiac output determination not requiring cardiac catheterization, has recently been reported in adult horses. We compared this method to thermodilution in isoflurane anesthetized, 30 to 42 hour old foals and found good agreement (mean bias 0.0474L/min; limits of agreement -3.03 to 3.12) between the two methods in a range of cardiac outputs from 5.4 to 20.4 liters/min. The lithium dilution technique is a practical and reliable method of measuring cardiac output in anesthetized neonatal foals, and warrants investigation in critically ill conscious foals. / Master of Science
447

Image quality based x-ray dose control in cardiac imaging

Davies, A.G., Kengyelics, S.M., Gislason-Lee, Amber J. 03 1900 (has links)
Yes / An automated closed-loop dose control system balances the radiation dose delivered to patients and the quality of images produced in cardiac x-ray imaging systems. Using computer simulations, this study compared two designs of automatic x-ray dose control in terms of the radiation dose and quality of images produced. The first design, commonly in x-ray systems today, maintained a constant dose rate at the image receptor. The second design maintained a constant image quality in the output images. A computer model represented patients as a polymethylmetacrylate phantom (which has similar x-ray attenuation to soft tissue), containing a detail representative of an artery filled with contrast medium. The model predicted the entrance surface dose to the phantom and contrast to noise ratio of the detail as an index of image quality. Results showed that for the constant dose control system, phantom dose increased substantially with phantom size (x5 increase between 20 cm and 30 cm thick phantom), yet the image quality decreased by 43% for the same thicknesses. For the constant quality control, phantom dose increased at a greater rate with phantom thickness (>x10 increase between 20 cm and 30 cm phantom). Image quality based dose control could tailor the x-ray output to just achieve the quality required, which would reduce dose to patients where the current dose control produces images of too high quality. However, maintaining higher levels of image quality for large patients would result in a significant dose increase over current practice. / This work has been performed in the project PANORAMA, funded by grants from Belgium, Italy, France, the Netherlands, and the United Kingdom, and the ENIAC Joint Undertaking.
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448

Dose optimization in pediatric cardiac x-ray imaging

Gislason-Lee, Amber J., Davies, A.G., Cowen, A.R. 16 September 2010 (has links)
No / The aim of this research was to explore x-ray beam parameters with intent to optimize pediatric x-ray settings in the cardiac catheterization laboratory. This study examined the effects of peak x-ray tube voltage kVp and of copper Cu x-ray beam filtration independently on the image quality to dose balance for pediatric patient sizes. The impact of antiscatter grid removal on the image quality to dose balance was also investigated. Methods: Image sequences of polymethyl methacrylate phantoms approximating chest sizes typical of pediatric patients were captured using a modern flat-panel receptor based x-ray imaging system. Tin was used to simulate iodine-based contrast medium used in clinical procedures. Measurements of tin detail contrast and flat field image noise provided the contrast to noise ratio. Entrance surface dose ESD and effective dose E measurements were obtained to calculate the figure of merit FOM , CNR2 / dose, which evaluated the dose efficiency of the x-ray parameters investigated. The kVp, tube current mA , and pulse duration were set manually by overriding the system’s automatic dose control mechanisms. Images were captured with 0, 0.1, 0.25, 0.4, and 0.9 mm added Cu filtration, for 50, 55, 60, 65, and 70 kVp with the antiscatter grid in place, and then with it removed. Results: For a given phantom thickness, as the Cu filter thickness was increased, lower kVp was favored. Examining kVp alone, lower values were generally favored, more so for thinner phantoms. Considering ESD, the 8.5 cm phantom had the highest FOM at 50 kVp using 0.4 mm of Cu filtration. The 12 cm phantom had the highest FOM at 55 kVp using 0.9 mm Cu, and the 16 cm phantom had highest FOM at 55 kVp using 0.4 mm Cu. With regard to E, the 8.5 and 12 cm phantoms had the highest FOM at 50 kVp using 0.4 mm of Cu filtration, and the 16 cm phantom had the highest FOM at 50 kVp using 0.25 mm Cu. Antiscatter grid removal improved the FOM for a given set of x-ray conditions. Under aforesaid optimal settings, the 8.5 cm phantom FOM improved by 24% and 33% for ESD and E, respectively. Corresponding improvements were 26% and 24% for the 12 cm phantom and 6% and 15% for the 16 cm phantom. Conclusions: For pediatric patients, using 0.25–0.9 mm Cu filtration in the x-ray beam while maintaining 50–55 kVp, depending on patient size, provided optimal x-ray image quality to dose ratios. These settings, adjusted for x-ray tube loading limits and clinically acceptable image quality, should provide a useful strategy for optimizing iodine contrast agent based cardiac x-ray imaging. Removing the antiscatter grid improved the FOM for the 8.5 and 12 cm phantoms, therefore grid removal is recommended for younger children. Improvement for the 16 cm phantom declined into the estimated margin of error for the FOM; the need for grid removal for older children would depend on practical feasibility in the clinical environment. / Philips Healthcare
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449

Context sensitive cardiac x-ray imaging: a machine vision approach to x-ray dose control

Kengyelics, S.M., Gislason-Lee, Amber J., Keeble, C., Magee, D.R., Davies, A.G. 21 September 2015 (has links)
Yes / Modern cardiac x-ray imaging systems regulate their radiation output based on the thickness of the patient to maintain an acceptable signal at the input of the x-ray detector. This approach does not account for the context of the examination or the content of the image displayed. We have developed a machine vision algorithm that detects iodine-filled blood vessels and fits an idealized vessel model with the key parameters of contrast, diameter, and linear attenuation coefficient. The spatio-temporal distribution of the linear attenuation coefficient samples, when appropriately arranged, can be described by a simple linear relationship, despite the complexity of scene information. The algorithm was tested on static anthropomorphic chest phantom images under different radiographic factors and 60 dynamic clinical image sequences. It was found to be robust and sensitive to changes in vessel contrast resulting from variations in system parameters. The machine vision algorithm has the potential of extracting real-time context sensitive information that may be used for augmenting existing dose control strategies. / Project PANORAMA, funded by grants from Belgium, Italy, France, the Netherlands, United Kingdom, and the ENIAC Joint Undertaking.
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450

Machine vision image quality measurement in cardiac x-ray imaging

Kengyelics, S.M., Gislason-Lee, Amber J., Keeble, C., Magee, D., Davies, A.G. 16 March 2015 (has links)
Yes / The purpose of this work is to report on a machine vision approach for the automated measurement of x-ray image contrast of coronary arteries lled with iodine contrast media during interventional cardiac procedures. A machine vision algorithm was developed that creates a binary mask of the principal vessels of the coronary artery tree by thresholding a standard deviation map of the direction image of the cardiac scene derived using a Frangi lter. Using the mask, average contrast is calculated by tting a Gaussian model to the greyscale pro le orthogonal to the vessel centre line at a number of points along the vessel. The algorithm was applied to sections of single image frames from 30 left and 30 right coronary artery image sequences from di erent patients. Manual measurements of average contrast were also performed on the same images. A Bland-Altman analysis indicates good agreement between the two methods with 95% con dence intervals -0.046 to +0.048 with a mean bias of 0.001. The machine vision algorithm has the potential of providing real-time context sensitive information so that radiographic imaging control parameters could be adjusted on the basis of clinically relevant image content. / Project PANORAMA, funded by grants from Belgium, Italy, France, the Netherlands, and the United Kingdom, and the ENIAC Joint Undertaking.
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