| 81. |
- Herreros, Alberto, et al.
(författare)
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Analysis of Changes in the Beat-to-Beat P-wave Morphology Using Clustering Techniques
- 2009
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Ingår i: Biomedical Signal Processing and Control. - : Elsevier BV. - 1746-8094. ; 4:4, s. 309-316
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Tidskriftsartikel (refereegranskat)abstract
- Several pathologies related to the atrial electrical activity can be detected in the electrocardiogram P-wave. A protocol for analyzing P-wave morphology changes has been developed in this article. By using this protocol a study on the beat-to-beat P-wave morphology changes of 89 ECG signals is performed. An algorithmbased on the embedding space techniques has been used to extract the P-wave information of the ECG. The P-waves obtained in several of these ECGs exhibit significant alternate morphology changes. The morphologies have been classified by using the K-means clustering algorithm. The mechanism behind the P-wave morphology change process and its possible pathophysiological importance remains to be clarified.
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| 82. |
- Herreros, Alberto, et al.
(författare)
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Analysis of Changes in the Beat-to-Beat P-Wave Morphology Using Clustering Techniques
- 2008
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Ingår i: Proceedings of the 17th World Congress Proceedings of the 17th World Congress of The International Federation of Automatic Control. - 1474-6670. - 9783902661005 ; 41:1, s. 5215-5220
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Konferensbidrag (refereegranskat)abstract
- Several pathologies related to the atrial electrical activity can be detected in the electrocardiogram P-wave. A study on the beat-to-beat P-wave morphology changes of 89 ECG signals is performed in this article. An algorithm based on the embedding space techniques has been used to extract the P-wave information of the ECG. The P-waves obtained in several of these ECGs exhibit intermittent morphology changes. The morphologies have been classified by using the K-means clustering algorithm. The mechanism behind different P-wave morphologies and its possible pathophysiological importance remains to be clarified.
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| 83. |
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| 84. |
- Hindorf, Ulf, et al.
(författare)
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Characterisation and utility of thiopurine methyltransferase and thiopurine metabolite measurements in autoimmune hepatitis.
- 2010
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Ingår i: Journal of Hepatology. - : Elsevier BV. - 0168-8278 .- 1600-0641. ; 52:1, s. 106-111
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND & AIMS: Corticosteroids alone or in conjunction with azathioprine (AZA) is the standard treatment in autoimmune hepatitis (AiH). Individual variations in thiopurine (TP) metabolism may affect both drug efficacy and toxicity. Our aim was to investigate the utility of thiopurine methyltransferase (TPMT) as well as thioguanine nucleotide (TGN) and methylthioinosine monophosphate (meTIMP) metabolite measurements with regard to clinical outcome. METHODS: Two hundred thirty-eight patients with AiH were included in this cross-sectional study. TPMT status was assessed in all patients, while TGN and meTIMP were measured in patients with ongoing TP medication. Clinical outcome was evaluated by liver tests and the ability to withdraw steroids. RESULTS: TPMT genotyping (n=229) revealed 207 (90.4%) wild-type and 22 heterozygous patients. One hundred forty-three patients had ongoing TP therapy with AZA (n=134) or mercaptopurine (MP; n=9); response was judged as complete response (CR) in 113 patients and partial response (PR) in 30 patients. Both TP dose (1.64 vs 1.19mg/kg; p=0.012) and TPMT activity (14.3 vs 13.5; p=0.05) were higher in PR, resulting in similar TGN levels (PR: 121pmol/8x10(8) red blood cells [RBC]; CR: 113pmol/8x10(8) RBC; p=0.33) but higher meTIMP levels in PR (1350 vs 400pmol/8x10(8) RBC; p=0.004). Patients able to withdraw steroids or who were using 5mg prednisolone daily were treated with lower TP doses than patients on higher steroid doses (1.15 vs 1.18 vs 1.82mg/kg; p<0.001). CONCLUSIONS: TP metabolite measurements are of clinical value in AiH patients who do not respond to standard TP treatment and for the identification of a shifted metabolism, which may demand an alternative treatment strategy.
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| 85. |
- Holm, M., et al.
(författare)
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A New Method for Analysis of Atrial Activation during Chronic Atrial Fibrillation in Man
- 1996
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Ingår i: IEEE Transactions on Biomedical Engineering. - : Institute of Electrical and Electronics Engineers (IEEE). - 1558-2531 .- 0018-9294. ; 43:2, s. 198-210
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Tidskriftsartikel (refereegranskat)abstract
- To further clarify the mechanisms maintaining chronic atrial fibrillation (CAF), a method identifying preferable activation patterns of the atria during fibrillation, by time averaging of multiple discrete excitation vectors, was developed. Repeated recordings, each of 56 atrial bipolar electrograms simultaneously acquired during 8 s, were made at multiple sites in the right atrial free wall and the left atrial appendage in 16 patients with CAF using a 2.17/spl times/3.54 cm electrode array. The local activation times (LAT's) in each recording were estimated as the median activation time at the respective measurement point. By calculating the time difference between the LAT's at adjacent measurement points in two spatial dimensions, a direction vector was created for each activation wave passing each set of measurement points, a total of 42 sets. By time averaging of the individual direction vectors (typically n=55) at each set of measurement points, preferable activation patterns were determined. Three types of activation patterns were found: 1) inconsistent activation (n=5), 2) consistent activation with preferential propagation directions (n=7) and 3) consistent activation with impulses originating from a localizable site within the recording area (n=4). All activation patterns were reproducible and the two latter patterns were proven significant using statistical tests. It is concluded that this new method is useful in further clarification of the mechanisms involved in the maintenance of atrial fibrillation.
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| 86. |
- Holm, Magnus, et al.
(författare)
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Determination of Preferable Wavelet Propagation Directions in Atrial Fibrillation
- 1993
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Konferensbidrag (refereegranskat)abstract
- M. Holm, P. Blomström, J. Brandt, R. Johansson, C. Lührs, and S. B. Olsson. Determination of preferable wavelet propagation directions in atrial fibrillation. In Erik K. Fernström Symp. Atrial Fibrillation, Lund, Sweden, June 1993.
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| 87. |
- Holm, M, et al.
(författare)
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Effect of cardiac exposure by median sternotomy on atrial fibrillation cycle length
- 1999
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Ingår i: Europace. - : Oxford University Press (OUP). - 1532-2092 .- 1099-5129. ; 1:4, s. 248-257
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Epicardial mapping is a powerful tool that has enabled us to gain insight into the electrical phenomena perpetuating atrial fibrillation and has guided the design of surgical and catheter-based therapeutic strategies. However, epicardial data are acquired during abnormal physiological conditions; the patients are anaesthetized, their chests opened, dislocating the heart and exposing it to air of room temperature, and the autonomic tone is modulated due to the surgery. The effect of intra-operative conditions on atrial electrophysiological properties have not been investigated before. Thus in the present study we assessed the atrial cycle length, shown to be an index of atrial refractoriness, and the ventricular rate before and during open-heart surgery in 10 patients with chronic atrial fibrillation and an underlying heart disease. METHODS AND RESULTS: Using a newly introduced and validated ECG method known as frequency analysis of fibrillatory ECG (FAF-ECG), the atrial cycle length and the ventricular rate were determined just before surgery. After anaesthesia and median sternotomy, epicardial mapping of the entire right atrial free wall was performed. The mean ventricular rate as well as the dominant atrial fibrillation cycle length consistently increased, the former from 71 to 92 beats x min(-1) (mean of all patients, P<0.05) and the latter from 156 to 172 ms (P<0.05). CONCLUSIONS: Atrial fibrillation cycle length, an index of atrial refractoriness, is increased as an effect of anaesthesia and heart exposure during open-heart surgery in patients with chronic atrial fibrillation, implying that atrial activation might be altered, which must be considered when interpreting data from epicardial conduction analysis.
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| 88. |
- Holm, Magnus, et al.
(författare)
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Epicardial right atrial free wall mapping in chronic atrial fibrillation. Documentation of repetitive activation with a focal spread--a hitherto unrecognised phenomenon in man
- 1997
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Ingår i: European Heart Journal. - : Oxford University Press (OUP). - 1522-9645 .- 0195-668X. ; 18:2, s. 290-310
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Previous studies have shown that atrial fibrillation of recent onset in man is based on a varying number of simultaneously present activation waves reentering either themselves or each other. In the present study, right atrial activation during chronic atrial fibrillation in man was studied. METHODS AND RESULTS: In 16 patients with chronic atrial fibrillation multiple epicardial recordings of 8 s each were made at the right atrial posterior free wall and at the appendage using a 20 x 35 mm electrode array with 56 bipolar measurement points. The preferable activation pattern of each recording and the propagation direction, cycle length and conduction velocity of individual activation waves within each recording were determined. Activation was characterized by unorganised activation with several simultaneously present activation waves: inconsistent preferable activation pattern (n = 5), predominantly organised activation with either frequent episodes of uniform activation: consistent preferable activation pattern (n = 7) or frequent episodes of activation with focal spread; focal preferable activation pattern (n = 4). Random re-entry was frequently documented in recordings with the inconsistent preferable activation pattern and less frequently in recordings with the consistent and focal preferable activation pattern. Complete re-entry circuits were rarely documented. The median fibrillation cycle length was 146, 159 (P < 0.05) and 165 ms (not significant) and the mean conduction velocity during uniform activation was 64, 67 and 83 cm. s-1 (not significant) in recordings with the inconsistent, consistent and focal preferable activation pattern, respectively. CONCLUSIONS: During chronic atrial fibrillation in man, right atrial free wall activation ranges from disorganised activation with multiple co-existing activation waves to predominantly organised activation characterized by either uniform activation consistent with the presence of large re-entry circuits or repetitive activation of unknown mechanism and focal spread.
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| 89. |
- Holm, Magnus, et al.
(författare)
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Non-Invasive Assessment of the Atrial Cycle Length during Chronic Atrial Fibrillation in Man
- 1996
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Ingår i: 69th Scientific Sessions of the American Heart Association, New Orleans, November 10-13, 1996; Circulation, Vol. 94, No. 8 Suppl., pp. I69, 1996.. ; 94, s. 169-169
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Konferensbidrag (refereegranskat)
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| 90. |
- Holmberg, Mats, 1958, et al.
(författare)
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A Longitudinal Study of Medial Temporal Lobe Volumes in Graves Disease
- 2022
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Ingår i: Journal of Clinical Endocrinology and Metabolism. - : The Endocrine Society. - 0021-972X .- 1945-7197. ; 107:4, s. 1040-1052
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Tidskriftsartikel (refereegranskat)abstract
- Context: Neuropsychiatric symptoms are common features of Graves disease (GD) in hyperthyroidism and after treatment. The mechanism behind these symptoms is unknown, but reduced hippocampal volumes have been observed in association with increased thyroid hormone levels. Objective: This work aimed at investigating GD influence on regional medial temporal lobe (MTL) volumes. Methods: Sixty-two women with newly diagnosed GD underwent assessment including magnetic resonance (MR) imaging in hyperthyroidism and 48 of them were followed up after a mean of 16.4±4.2 SD months of treatment. Matched thyroid-healthy controls were also assessed twice at a 15-month interval. MR images were automatically segmented using multiatlas propagation with enhanced registration. Regional medial temporal lobe (MTL) volumes for amygdalae and hippocampi were compared with clinical data and data from symptom questionnaires and neuropsychological tests. Results: Patients had smaller MTL regions than controls at inclusion. At follow-up, all 4 MTL regions had increased volumes and only the volume of the left amygdala remained reduced compared to controls. There were significant correlations between the level of thyrotropin receptor antibodies (TRAb) and MTL volumes at inclusion and also between the longitudinal difference in the levels of free 3,5,3′-triiodothyronine and TRAb and the difference in MTL volumes. There were no significant correlations between symptoms or test scores and any of the 4 MTL volumes. Conclusion: Dynamic alterations in the amygdalae and hippocampi in GD reflect a previously unknown level of brain involvement both in the hyperthyroid state of the condition and after treatment. The clinical significance, as well as the mechanisms behind these novel findings, warrant further study of the neurological consequences of GD.
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