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  • 1.
    Bjällmark, Anna
    et al.
    KTH, School of Technology and Health (STH), Medical Engineering.
    Larsson, Matilda
    KTH, School of Technology and Health (STH), Medical Engineering.
    Brodin, Lars-Åke
    KTH, School of Technology and Health (STH), Medical Engineering.
    Nowak, Jacek
    Lind, Britta
    KTH, School of Technology and Health (STH), Medical Engineering.
    Hayashi, Shirley
    Mazza do Nascimento, Marcelo
    Riella, Miquel
    Seeberger, Astrid
    Effects of hemodialysis on the cardiovascular system: Quantitative analysis using wave intensity wall analysis and tissue velocity imaging2010In: Heart and Vessels, ISSN 0910-8327, E-ISSN 1615-2573Article in journal (Refereed)
    Abstract [en]

    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.

  • 2.
    Bjällmark, Anna
    et al.
    KTH, School of Technology and Health (STH), Medical Engineering.
    Lind, Britta
    KTH, School of Technology and Health (STH), Medical Engineering.
    Brodin, Lars-Åke
    KTH, School of Technology and Health (STH), Medical Engineering.
    Peolsson, Michael
    KTH, School of Technology and Health (STH).
    Shahgaldi, Kambiz
    KTH, School of Technology and Health (STH), Medical Engineering.
    Nowak, Jacek
    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 artery2010In: European Journal of Echocardiography, ISSN 1525-2167, E-ISSN 1532-2114, Vol. 11, no 7, p. 630-636Article in journal (Refereed)
    Abstract [en]

    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.

  • 3. Govind, Satish C.
    et al.
    Gopal, Aasha S.
    Netyo, Anita
    Nowak, Jacek
    Brodin, Lars-Åke
    KTH, School of Technology and Health (STH), Medical Engineering.
    Patrianakos, Alexandros
    Ramesh, S. S.
    Saha, Samir
    Quantification of low-dose dobutamine stress using speckle tracking echocardiography in coronary artery disease2009In: European Journal of Echocardiography, ISSN 1525-2167, E-ISSN 1532-2114, Vol. 10, no 5, p. 607-612Article in journal (Refereed)
    Abstract [en]

    Aims We sought to evaluate the utility of speckle tracking echocardiography (STE) for detecting left ventricular (LV) mechanical abnormalities during low-dose (20 mu g) dobutamine stress (DSE). Methods and results Twenty-nine patients (56 +/- 12 years) with a history of recent acute coronary events (ACE) underwent STE-DSE. Left ventricular images, sampled at frame rates 70-100 Hz, were analysed off-line (Echopac BT 6.0.0). Velocity, strain, and rotational imaging were performed. Twenty patients had LV ejection fraction (EF) >40% (Group 1) whereas nine patients had LVEF <40% (Group 2). Average heart and frame rates were identical during DSE in the two groups (P = ns). Global circumferential strain (%) was significantly lower in Group 2 compared with Group 1 (10.65 +/- 5.30 vs. 16.82 +/- 6.61; P < 0.05) at rest and during peak stress (14.72 +/- 6.51 vs. 21.13 +/- 7.2; P < 0.05). The global peak rotation rate (degree/s) was, however, higher at rest in Group 2 (70 +/- 97 vs. 19 +/- 67; P < 0.05) and 20 mu g stress. Peak systolic velocity increased in three of the four LV walls at 20 mu g ( in Groups 1 and 2). A global rotational rate increased significantly at 20 mu g during systole in both the groups, but was unchanged in Group 2 during diastole. Conclusions Speckle tracking echocardiography dobutamine stress appears to provide comprehensive information on LV mechanical status in the aftermath of ACE. The modality may help risk stratify such patients.

  • 4.
    Hayashi, Shirley
    et al.
    Karolinska Inst, Div Renal Med & Baxter Novum, Stockholm, Sweden..
    Nascimento, Marcelo
    Evangel Med Sch, Curitiba, Parana, Brazil..
    Kind, Brita
    KTH, School of Technology and Health (STH), Medical Engineering.
    Larsson, Matilda
    KTH, School of Technology and Health (STH), Medical Engineering.
    Bjällmark, Anna
    KTH, School of Technology and Health (STH), Medical Engineering.
    Nowak, Jacek
    KTH, School of Technology and Health (STH), Medical Engineering.
    Seeberg, Astrid
    Karolinska Inst, Div Renal Med & Baxter Novum, Stockholm, Sweden..
    Riella, Miguel
    Evangel Med Sch, Curitiba, Parana, Brazil..
    Brodin, Lars-Åke
    KTH, School of Technology and Health (STH), Medical Engineering.
    Lindholm, Bengt
    Karolinska Inst, Div Renal Med & Baxter Novum, Stockholm, Sweden..
    The Prevalence of Right Ventricular Dysfunction in CKD and Dialysis Patients: A Comparative Study2009In: Blood Purification, ISSN 0253-5068, E-ISSN 1421-9735, Vol. 28, no 4, p. 325-325Article in journal (Other academic)
  • 5.
    Kronander, Håkan
    et al.
    KTH, School of Technology and Health (STH), Medical Engineering.
    Fischer-Colbrie, Werner
    Nowak, Jacek
    KTH, School of Technology and Health (STH), Medical Engineering.
    Brodin, Lars-Åke
    KTH, School of Technology and Health (STH), Medical Engineering.
    Elmqvist, Håkan
    KTH, School of Technology and Health (STH), Medical Engineering.
    Diagnostic performance and partition values of exercise electrocardiographic variables in the detection of coronary artery disease - improved accuracy by using ST/HR hysteresis2010In: Clinical Physiology and Functional Imaging, ISSN 1475-0961, E-ISSN 1475-097X, Vol. 30, no 2, p. 98-106Article in journal (Refereed)
    Abstract [en]

    P>Exercise electrocardiography is widely used for initial identification of patients with coronary artery disease (CAD). This study compares the measurements of ST-segment changes during exercise and during early postexercise recovery in terms of diagnostic discrimination capacity and optimal partition values. Data from 1876 patients undergoing a routine bicycle exercise test were analysed. CAD was angiographically verified in 668 patients, and excluded by angiography (n = 119), myocardial scintigraphy (n = 250), and on clinical grounds (n = 839) in 1208 patients. Postexercise ST/HR hysteresis was calculated as normalized for heart rate (HR) ST/HR loop area during the first 3 min of recovery. ST/HR index was obtained by dividing the overall ST amplitude change during exercise by exercise-induced HR change, and ST/HR slope was calculated using linear regression analysis of ST/HR data pairs during exercise. ST-segment depression was measured during, and for 3 min after the exercise. Discriminating capacity of the methods was evaluated in terms of receiver operating characteristic areas and optimal partition values providing the combination of the best sensitivity and specificity were established. The best diagnostic discrimination was provided by ST/HR hysteresis at optimal partition value of -15 mu V, followed by postexercise ST amplitude measurements at gender-specific partition values of -10 to -90 mu V, ST/HR slope [partition value 2 center dot 4 mu V (beats/min)-1], ST/HR index [partition value 1 center dot 6 mu V (beats/min)-1], and ST-segment depression during exercise (partition value 70 mu V in men and 90 mu V in women). The results demonstrate that analysis of postexercise ST/HR hysteresis offers the most accurate and gender indifferent identification of patients with CAD.

  • 6.
    Nowak, Jacek
    et al.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Bakowski, Mietek
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Lisik, Z.
    Wozny, J.
    Owczarek, M.
    Modelling of the power pin diode under surge current conditions2004In: MODERN PROBLEMS OF RADIO ENGINEERING, TELECOMMUNICATIONS AND COMPUTER SCIENCE, PROCEEDINGS, LVOV: LVIV POLYTECH NATL UNIV , 2004, p. 529-532Conference paper (Refereed)
    Abstract [en]

    Fast recovery silicon power diodes, having radiation induced recombination centres, operating under forward bias at large current densities and high temperatures, have been studied in a detailed way, both experimentally and with the help of device simulation Medici package. The comparison of the dynamic I-V characteristics with the results of numerical simulations is possible only when all the specific features of the measurement set-up are taken into account in the simulations. Such evaluation of the electro-thermal numerical model of the diode under experiment combined with the electro-thermal model of the experimental set-up as the boundary condition for Medici simulation is being presented. The main issue is the definition of the thermal boundary conditions.

  • 7.
    Shirley, Hayashi
    et al.
    KTH. Karolinska Inst, Div Renal Med & Baxter Novum, Stockholm, Sweden.;Royal Inst Technol, Dept Med Engn, Stockholm, Sweden..
    Marcelo, Nascimento
    Evangel Med Sch, Curitiba, Parana, Brazil..
    Lind, Brita
    KTH, School of Technology and Health (STH), Medical Engineering.
    Larsson, Matilda
    KTH, School of Technology and Health (STH), Medical Engineering.
    Bjällmark, Anna
    KTH, School of Technology and Health (STH), Medical Engineering.
    Nowak, Jacek
    KTH, School of Technology and Health (STH), Medical Engineering.
    Seeberg, Astrid
    Karolinska Inst, Div Renal Med & Baxter Novum, Stockholm, Sweden..
    Brodin, Lars-Åke
    KTH, School of Technology and Health (STH), Medical Engineering.
    Lindholm, Bengt
    Karolinska Inst, Div Renal Med & Baxter Novum, Stockholm, Sweden..
    The Prevalence of Intraventricular Dyssynchrony, Detected by Tissue Synchronization Imaging, In HD, PD and CKD Patients Stages 3 and 42009In: Blood Purification, ISSN 0253-5068, E-ISSN 1421-9735, Vol. 28, no 4, p. 325-325Article in journal (Other academic)
  • 8.
    Shirley, Hayashi
    et al.
    Karolinska Inst, Div Renal Med & Baxter Novum, Stockholm, Sweden..
    Nascimento, Marcelo
    Evangel Med Sch, Curitiba, Parana, Brazil..
    Lind, Britta
    KTH, School of Technology and Health (STH), Medical Engineering.
    Seeberg, Astrid
    Karolinska Inst, Div Renal Med & Baxter Novum, Stockholm, Sweden..
    Nowak, Jacek
    KTH, School of Technology and Health (STH), Medical Engineering.
    Larsson, Matilda
    KTH, School of Technology and Health (STH), Medical Engineering.
    Bjällmark, Anna
    KTH, School of Technology and Health (STH), Medical Engineering.
    Brodin, Lars-Åke
    KTH, School of Technology and Health (STH), Medical Engineering.
    Lindholm, Bengt
    Karolinska Inst, Div Renal Med & Baxter Novum, Stockholm, Sweden..
    Improvement of Left Ventricular Synchronicity Assessed by Tissue Synchronization Imaging after a Single HD Session2009In: Blood Purification, ISSN 0253-5068, E-ISSN 1421-9735, Vol. 28, no 4, p. 306-306Article in journal (Other academic)
1 - 8 of 8
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