| 55621. |
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| 55622. |
- Truedsson, Lennart, et al.
(författare)
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Complement deficiencies and systemic lupus erythematosus
- 2007
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Ingår i: Autoimmunity. - : Informa UK Limited. - 0891-6934 .- 1607-842X. ; 40:8, s. 560-566
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Tidskriftsartikel (refereegranskat)abstract
- The complement system involves both the innate and the adaptive immune systems and has important roles in the pathogenesis of SLE. Complement deficiencies within the classical pathway (C1q, C4 and C2) of activation predispose for development of the autoimmune disease SLE. The association between complement deficiencies and SLE could be explained by several mechanisms, including impaired clearance of immune complexes and impaired handling of apoptotic cells, aberrant tolerance induction or changes in cytokine regulation. Also during SLE disease flares, the complement system is activated giving rise to partial deficiency or dysfunction due to consumption. On the other hand, complement also takes part in the inflammatory reaction in the disease that gives rise to the tissue and organ damage. In this review various aspects of the relation between complement and SLE are discussed.
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| 55623. |
- Trulsson, Martin, et al.
(författare)
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Repulsion between oppositely charged macromolecules or particles
- 2007
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Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 23:23, s. 11562-11569
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Tidskriftsartikel (refereegranskat)abstract
- The interaction of two oppositely charged surfaces has been investigated using Monte Carlo simulations and approximate analytical methods. When immersed in an aqueous electrolyte containing only monovalent ions, two such surfaces will generally show an attraction at large and intermediate separations. However, if the electrolyte solution contains divalent or multivalent ions, then a repulsion can appear at intermediate separations. The repulsion increases with increasing concentration of the multivalent salt as well as with the valency of the multivalent ion. The addition of a second salt with only monovalent ions magnifies the effect. The repulsion between oppositely charged surfaces is an effect of ion-ion correlations, and it increases with increasing electrostatic coupling and, for example, a lowering of the dielectric permittivity enhances the effect. An apparent charge reversal of the surface neutralized by the multivalent ion is always observed together with a repulsion at large separation, whereas at intermediate separations a repulsion can appear without charge reversal. The effect is hardly observable for a symmetric multivalent salt (e.g., 2:2 or 3:3).
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| 55624. |
- Trägårdh, Elin
(författare)
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Adjuncts to the Conventional 12-Lead ECG: Assessment of High-Frequency QRS Components and Additional Leads
- 2007
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The standard 12-lead electrocardiogram (ECG) is one of the most commonly used methods for diagnosing heart disease. Standard ECG is not always optimal, however, and new ECG methods can provide additional information. Analysis of high-frequency QRS components (HF-QRS) has been shown to increase the diagnostic performance of the ECG. Since the amplitudes of the HF-QRS are low compared with those visible in the standard ECG, analysis of HF-QRS requires a low noise level, a sampling rate of at least 1000 Hz, and multibeat signal averaging. Methods for analyzing HF-QRS have been developed in collaboration with the Department of Electroscience at the Faculty of Engineering, Lund University. Another method for increasing the diagnostic performance of the ECG is to add electrodes to provide leads that see parts of the heart not covered by conventional leads. This could be particularly interesting in diagnosing conditions such as acute myocardial infarction (MI), for example, for which it is important to initiate reperfusion treatment as soon as possible. The overall objectives of the thesis are to investigate whether analysis of HF-QRS has the ability to provide information not available from the standard ECG and to investigate whether information from additional ECG leads can improve the diagnosis of acute MI. In Study I, patients with ischemic heart disease had significantly lower HF-QRS compared with normal individuals. There was substantial interindividual variability, however, which probably limits the clinical usefulness of this method. The study also showed that HF-QRS are not related to sex or age. In Study II, we investigated whether the amplitude of HF-QRS correlates to the left ventricular mass. This has been shown to be the case in previous studies in rabbits. Our study, however, showed that analysis of HF-QRS is no better than analysis of standard 12-lead ECG for determination of left ventricular mass. In Study III, patients with intraventricular conduction delay had lower HF-QRS in leads with a positive electrode facing the area of the heart with the conduction delay. In areas of the heart with normal conduction velocity, the amplitudes of HF-QRS were normal or almost normal. These findings support the theory that HF-QRS relate to the conduction velocity of the heart. In Study IV, we investigated whether additional leads can improve the diagnosis of acute MI. The accuracy of the conventional 12-lead ECG is poor for finding acute MI when certain coronary arteries are involved. Conventional 12-lead ECG was compared with 16-lead ECG (12-lead ECG plus 4 additional electrodes) as well as with 24-lead ECG (12-lead ECG plus the inverted leads of these 12 leads). The sensitivity for detecting acute MI increased when using the 16-lead or 24-lead ECG compared with the 12-lead ECG. The specificity, however, decreased slightly. If the aim is to increase sensitivity for detecting MI, clinicians should be advised to use the 24-lead ECG, since no additional electrodes are required.
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| 55625. |
- Trägårdh, Elin, et al.
(författare)
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Detection of acute myocardial infarction using the 12-lead ECG plus inverted leads versus the 16-lead ECG (with additional posterior and right-sided chest electrodes).
- 2007
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Ingår i: Clinical Physiology and Functional Imaging. - 1475-0961. ; 27:6, s. 368-374
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Tidskriftsartikel (refereegranskat)abstract
- Background: The electrocardiographic (ECG) diagnosis of acute myocardial infarction (MI) should be improved. This might be done either by regarding all 24 aspects (both positive and negative leads), or a subset hereof (e.g. 19-lead ECG), of the conventional 12-lead ECG or by using additional electrodes. The purpose of this study was to investigate the accuracy of the different ECG methods in diagnosing acute ST-elevation MI. Methods: The study population consisted of 479 patients admitted to Lund University Hospital with acute chest pain. One conventional ECG plus leads V4R, V5R, V8 and V9 were recorded for each patient within 24 h of admittance. Biochemical markers were used as the 'gold standard' for diagnosis of MI. We measured ST-segment elevations in the 12-, 16- and 24-lead postadmission ECGs as well as in the 12-, 19- and 24-lead admission ECGs. Results: The sensitivity for detecting acute MI was 28% for the postadmission 12-lead ECG, 33% for the 16-lead ECG and 37% for the 24-lead ECG. The specificities were 97%, 93% and 95%, respectively. For admission ECGs, the sensitivity was 33% for the 12-lead ECG, 45% for the 19-lead ECG and 49% for the 24-lead ECG, with specificities of 97%, 96% and 94%, respectively. Conclusion: The sensitivity for detecting acute MI was higher for the 16-, 19- and 24-lead ECGs than for the conventional 12-lead ECGs. Their specificity, however, was slightly lower. If increased sensitivity for detecting MI is desired, the 24-lead or 19-lead should be used as no additional electrodes are required.
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| 55626. |
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| 55627. |
- Trägårdh, Elin, et al.
(författare)
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High-frequency QRS electrocardiogram
- 2007
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Ingår i: Clinical Physiology and Functional Imaging. - 1475-0961. ; 27:4, s. 197-204
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Forskningsöversikt (refereegranskat)abstract
- The standard 12-lead electrocardiogram (ECG) is one of the most commonly used methods for diagnosing heart disease. Standard ECG is not always optimal, however, and new ECG methods can provide additional information. Analysis of high-frequency QRS components (HF-QRS) has been shown to increase the diagnostic performance of the ECG. Several investigators have studied HF-QRS in different cardiac conditions, including acute myocardial ischaemia and myocardial infarction, but more knowledge is needed about the characteristics of HF-QRS before clinicians can use it as an adjunct to standard ECG.
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| 55628. |
- Trägårdh, Elin, et al.
(författare)
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Reduced high-frequency QRS components in electrocardiogram leads facing an area of the heart with intraventricular conduction delay due to bundle branch block.
- 2007
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Ingår i: Journal of Electrocardiology. - : Elsevier BV. - 1532-8430 .- 0022-0736. ; 40:2, s. 127-132
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Tidskriftsartikel (refereegranskat)abstract
- Background: The mechanisms underlying high-frequency QRS components (HF-QRS) are incompletely understood. One theory is that HF-QRS are related to the conduction velocity of the heart. The purpose was to test this hypothesis by comparing HF-QRS in patients with left or right bundle branch block (LBBB and RBBB, respectively) to those in healthy subjects and in patients with ischemic heart disease (IHD). Methods: Twenty-two patients with LBBB, 19 patients with RBBB, 63 normal subjects, and 64 patients with IHD were included. Twelve-lead electrocardiograms were analyzed in the frequency interval 150 to 250 Hz. Results: The study showed reduced HF-QRS in patients with LBBB compared with healthy subjects and patients with IHD. The difference, however, was small in lead V-1 and V-2. In patients with RBBB, no differences in HF-QRS could be detected except in few leads; among those is lead V-1. Conclusion: The results support the theory that HF-QRS are related to the conduction velocity of the heart. (c) 2007 Elsevier Inc. All rights reserved.
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| 55629. |
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| 55630. |
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