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- Holm, Magnus, et al.
(författare)
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A Computer Algorithm for Determining Local Activation Times in Electrograms Obtained during Atrial Fibrillation
- 1993
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Ingår i: Proc. IEEE Computers in Cardiology, London, 5-8 Sep 1993. ; , s. 855-858
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Konferensbidrag (refereegranskat)abstract
- A critical factor in analyzing the propagation of activation waves in the myocardium is the definition of local activation times (LAT) in the electrogram. The authors have formulated and tested a definition of LAT in bipolar electrograms applicable to atrial electrograms containing deflections with wide variation in complexity, e.g. those obtained during rapid, irregular atrial rhythm, i.e. atrial fibrillation. The definition, implemented as an algorithm in a computer program, consists of two parts: the first part identifies local activations in the electrogram and the second calculates the corresponding LAT using criteria that define the LAT as the median activation time of cells located between the bipolar electrodes.
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| 2. |
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| 3. |
- Svensson, Mats Y., 1960, et al.
(författare)
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Pressure Effects in the Spinal Canal During Whiplash Extension Motion - A Possible Cause of Injury to the Cervical Spinal Ganglia
- 1993
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Ingår i: Proceedings of the International Research Committee on the Biomechanics of Impacts (IRCOBI) conference, Eindhoven, Netherlands. ; , s. 189-200
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Konferensbidrag (refereegranskat)abstract
- impact-velocities (<20 km/h) often cause pain in the neck region as well as a number of other neurological symptoms, most of which can be related to the nerve paths that pass through the cervical intervertebral foramina. When the neck is flexed or extended in the sagittal plane the length of the cervical spinal canal alters but the cross-sectional area of the canal remains almost constant. During flexion-extension motion of the cervical spine, the size of the inner volume of the spinal canal will change. Since the tissues inside the canal can be considered incompressible, an alteration will take place of either the amount of cerebro spinal fluid or the amount of blood in the veinplexa of the epidural space, or both. This requires fluid transportation through the intervertebral foramina as well as along the spinal canal. During a whiplash extension motion, the flow velocity can be expected to rise far above physiologically normal levels and pressure gradients can thus be expected to occur. In turn, the soft tissues inside and around the cervical spine and particularly in the intervertebral foramina will sustain mechanical strain and stress. Anaesthetised pigs were exposed to a swift extension-flexion motion of the neck while the pressure inside the spinal canal and the skull was measured. Pressure pulses of magnitudes up to 150 mmHg (20 kPa) were observed during the motion. The magnitude of pressure is for each moment dependent on the position of the neck, the velocity and the acceleration of the motion. Plasma membrane dysfunction was indicated by the results from light microscopic analyses of the cervical and the three upper thoracic spinal ganglia revealing the staining of nerve cells and satellite cells by protein complexed to the Evans Blue dye.
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| 4. |
- Magnusson, Måns, et al.
(författare)
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Dynamic Properties of Feedback Control of Human Posture in Subjects with Vestibular Neuritis
- 1993
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Ingår i: Acta Oto-Laryngologica. - : Informa UK Limited. - 1651-2251 .- 0001-6489. ; 113:S503, s. 47-48
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Tidskriftsartikel (refereegranskat)abstract
- Postural control was studied in 22 subjects with vestibular neruitis within 14 days after the onset of symptoms. Dynamic feed back control of posture were evaluated by analyzing the postural responses to vibration toward calf muscles applied according to a PRBS schedule. Properties of the dynamic control was normalized as swiftness, stiffness and damping of the responses. There was no prominent group differences between the 22 subjects with vestibular neuritis and 17 normal subjects. However, when studying the change in parameters evoked by presence or absence of visual information it was found that the abundant changes of control parameters, especially in stiffness, met in normal subjects had declined in subjects with vestibular neuritis. The present finding suggests that although subjects after an acute vestibular lesion may achieve a sufficient postural control by utilizing information from other somatosensory receptors, this is concomitant with changes of the feed back control.
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