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- Bjällmark, Anna, et al.
(författare)
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Effects of hemodialysis on the cardiovascular system: Quantitative analysis using wave intensity wall analysis and tissue velocity imaging
- 2010
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Ingår i: Heart and Vessels. - : Springer Science and Business Media LLC. - 0910-8327 .- 1615-2573.
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Tidskriftsartikel (refereegranskat)abstract
- Cardiovascular disease is the leading cause of death in patients with end stage renal disease (ESRD). The aim of this study was to investigate the changes in cardiovascular function induced by a single session of hemodialysis (HD) by the analysis of cardiovascular dynamics using wave intensity wall analysis (WIWA) and of systolic and diastolic myocardial function using tissue velocity imaging (TVI). Grey-scale cine loops of the left common carotid artery, conventional echocardiography and TVI images of the left ventricle were acquired before and after HD in 45 patients (17 women, mean age 54) with ESRD. The WIWA indexes, W1 preload-adjusted W1, W2 and preload-adjusted W2, and the TVI variables, isovolumic contraction velocity (IVCV), isovolumic contraction time (IVCT), peak systolic velocity (PSV), displacement, isovolumic relaxation velocity (IVRV), isovolumic relaxation time (IVRT), peak early diastolic velocity (E’) and peak late diastolic velocity (A’), were compared before and after HD. The WIWA measurements showed significant increases in W1 (p < 0.05) and preload-adjusted W1 (p < 0.01) after HD. W2 was significantly decreased (p < 0.05) after HD, whereas the change in preload-adjusted W2 was not significant. Systolic velocities, IVCV (p < 0.001) and PSV (p < 0.01), were increased after HD, whereas the AV-plane displacement were decreased (p < 0.01). For the measured diastolic variables, E’ was significantly decreased (p < 0.01) and IVRT was significantly prolonged (p < 0.05), after HD. A few correlations were found between WIWA and TVI variables. The WIWA and TVI measurements indicate that a single session of HD improves systolic function. The load dependency of the diastolic variables seems to be more pronounced than for the systolic variables. Preload-adjusted wave intensity indexes may contribute in the assessment of true LV contractility and relaxation.
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| 5. |
- Bjällmark, Anna, et al.
(författare)
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Ultrasonographic strain imaging is superior to conventional non-invasive measures of vascular stiffness in the detection of age-dependent differences in the mechanical properties of the common carotid artery
- 2010
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Ingår i: European Journal of Echocardiography. - : Oxford University Press (OUP). - 1525-2167 .- 1532-2114. ; 11:7, s. 630-636
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Tidskriftsartikel (refereegranskat)abstract
- Aims: Elastic properties of large arteries have been shown to deteriorate with age and in the presence of atherosclerotic vascular disease. In this study, the performance of ultrasonographic strain measurements was compared to conventional measures of vascular stiffness in the detection of age-dependent differences in the elastic properties of the common carotid artery.Methods and results: In 10 younger (25-28 years, 4 women) and 10 older (50-59 years, 4 women) healthy individuals, global and regional circumferential and radial strain variables were measured in the short-axis view of the right common carotid artery using ultrasonographic two-dimensional (2D) strain imaging with recently introduced speckle tracking technique. Conventional elasticity variables, elastic modulus (Ep) and β stiffness index, were calculated using M-mode sonography and non-invasive blood pressure measurements. Global and regional circumferential systolic strain and strain rate values were significantly higher (p < 0.001, p < 0.01 for regional late systolic strain rate) in the younger individuals, whereas the values of conventional elasticity variables in the same group were lower (p < 0.05). Among all strain and conventional elasticity variables, principal component analysis and its regression extension identified only circumferential systolic strain variables as contributing significantly to the observed discrimination between the younger and older age groups.Conclusion: Ultrasonographic 2D-strain imaging is a sensitive method for the assessment of elastic properties in the common carotid artery, being in this respect superior to conventional measures of vascular elasticity. The method has potential to become a valuable non-invasive tool in the detection of early atherosclerotic vascular changes.
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| 6. |
- Broomé, Michael, et al.
(författare)
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Closed-loop real-time simulation model of hemodynamics and oxygen transport in the cardiovascular system
- 2013
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Ingår i: Biomedical engineering online. - 1475-925X. ; 12:1, s. 69-
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Tidskriftsartikel (refereegranskat)abstract
- Background: Computer technology enables realistic simulation of cardiovascular physiology. The increasing number of clinical surgical and medical treatment options imposes a need for better understanding of patient-specific pathology and outcome prediction. Methods: A distributed lumped parameter real-time closed-loop model with 26 vascular segments, cardiac modelling with time-varying elastance functions and gradually opening and closing valves, the pericardium, intrathoracic pressure, the atrial and ventricular septum, various pathological states and including oxygen transport has been developed. Results: Model output is pressure, volume, flow and oxygen saturation from every cardiac and vascular compartment. The model produces relevant clinical output and validation of quantitative data in normal physiology and qualitative directions in simulation of pathological states show good agreement with published data. Conclusion: The results show that it is possible to build a clinically relevant real-time computer simulation model of the normal adult cardiovascular system. It is suggested that understanding qualitative interaction between physiological parameters in health and disease may be improved by using the model, although further model development and validation is needed for quantitative patient-specific outcome prediction.
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| 8. |
- Falkmer, Marita, et al.
(författare)
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Recognition of facially expressed emotions and visual search strategies in adults with Asperger syndrome
- 2011
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Ingår i: RES AUTISM SPECTR DISORD. - : Elsevier BV. - 1750-9467 .- 1878-0237. ; 5:1, s. 210-217
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Tidskriftsartikel (refereegranskat)abstract
- Can the disadvantages persons with Asperger syndrome frequently experience with reading facially expressed emotions be attributed to a different visual perception, affecting their scanning patterns? Visual search strategies, particularly regarding the importance of information from the eye area, and the ability to recognise facially expressed emotions were compared between 24 adults with Asperger syndrome and their matched controls. While wearing a head mounted eye tracker, the participants viewed 12 pairs of photos of faces. The first photo in each pair was cut up into puzzle pieces. Six of the 12 puzzle pieced photos had the eyes bisected. The second photo showed a happy, an angry and a surprised face of the same person as in the puzzle pieced photo. Differences in visual search strategies between the groups were established. Adults with Asperger syndrome had greater difficulties recognizing these basic emotions than controls. The distortion of the eye area affected the ability to identify emotions even more negatively for participants with Asperger syndrome.
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| 9. |
- Falkmer, Marita, et al.
(författare)
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The importance of the eye area in face identification abilities and visual search strategies in persons with Asperger syndrome
- 2010
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Ingår i: Research in Autism Spectrum Disorders. - : Elsevier BV. - 1750-9467 .- 1878-0237. ; 4:4, s. 724-730
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Tidskriftsartikel (refereegranskat)abstract
- Partly claimed to explain social difficulties observed in people with Asperger syndrome, face identification and visual search strategies become important. Previous research findings are, however, disparate. In order to explore face identification abilities and visual search strategies, with special focus on the importance of the eye area, 24 adults with Asperger syndrome and matched controls viewed puzzle pieced photos of faces, in order to identify them as one of three intact photos of persons. Every second puzzle pieced photo had the eyes distorted. Fixation patterns were measured by an eye tracker. Adults with Asperger syndrome had greater difficulties in identifying faces than controls. However, the entire face identification superiority in controls was found in the condition when the eyes were distorted supporting that adults with Aspergers syndrome do use the eye region to a great extent in face identification. The visual search strategies in controls were more effective and relied on the use of the 'face information triangle', i.e. the two eyes and the mouth, while adults with Asperger syndrome had more fixations on other parts of the face, both when obtaining information and during the identification part, suggesting a less effective use of the 'face information triangle'.
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| 10. |
- Falkmer, Marita, et al.
(författare)
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The influences of static and interactive dynamic facial stimuli on visual strategies in persons with Asperger syndrome
- 2011
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Ingår i: Research in Autism Spectrum Disorders. - : Elsevier BV. - 1750-9467 .- 1878-0237. ; 5:2, s. 935-940
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Tidskriftsartikel (refereegranskat)abstract
- Several studies, using eye tracking methodology, suggest that different visual strategies in persons with autism spectrum conditions, compared with controls, are applied when viewing facial stimuli. Most eye tracking studies are, however, made in laboratory settings with either static (photos) or non-interactive dynamic stimuli, such as video clips. Whether or not these results are transferable to a "real world" dialogue situation remains unclear. In order to examine the consistency of visual strategies across conditions, a comparison of two static conditions and an interactive dynamic "real world" condition, in 15 adults with Asperger syndrome and 15 matched controls, was made using an eye tracker. The static stimuli consisted of colour photos of faces, while a dialogue between the participants and the test leader created the interactive dynamic condition. A within-group comparison showed that people with AS, and their matched controls, displayed a high degree of stability in visual strategies when viewing faces, regardless of the facial stimuli being static or real, as in the interactive dynamic condition. The consistency in visual strategies within the participants suggests that results from studies with static facial stimuli provide important information on individual visual strategies that may be generalized to "real world" situations.
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