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  • 1
    Electronic Resource
    Electronic Resource
    Atrial Noninvasive Activation Mapping of Paced Rhythm Data (2003)
    350 Main Street , Malden , MA 02148-5018 , USA , and 9600 Garsington Road , Oxford OX4 2DQ , UK . : Blackwell Science Inc
    Journal of cardiovascular electrophysiology 14 (2003), S. 0 
    Details
    ISSN: 1540-8167
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Introduction: Atrial arrhythmias have emerged as a topic of great interest for clinical electrophysiologists. Noninvasive imaging of electrical function in humans may be useful for computer-aided diagnosis and treatment of cardiac arrhythmias, which can be accomplished by the fusion of data from ECG mapping and magnetic resonance imaging (MRI). Methods and Results: In this study, a bidomain-theory–based surface heart model activation time (AT) imaging approach was applied to paced rhythm data from four patients. Pacing sites were the right superior pulmonary vein, left inferior pulmonary vein, left superior pulmonary vein, coronary sinus, posterior wall of right atrium, and high right atrium. For coronary sinus pacing, the AT pattern of the right atrium was compared with a CARTO map. The root mean square error between CARTO geometry (85 nodal points) and the surface model of the right atrium was 8.6 mm. The correlation coefficient of the noninvasively obtained AT map of the right atrium and the CARTO map was 0.76. All pulmonary vein pacing sites were identified. The reconstructed pacing site of right posterior atrial pacing correlates with the invasively determined pacing catheter position with a localization distance of 4 mm. Conclusion: The individual anatomic model of the atria of each patient enables accurate noninvasive AT imaging within the atria, resulting in a localization error for the pacing sites within 10 mm. Our findings may have implications for imaging of atrial activity in patients with focal arrhythmias or focal triggers. (J Cardiovasc Electrophysiol, Vol. 14, pp. 712-719, July 2003)
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1540-8167.2003.02558.x
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  • 2
    Electronic Resource
    Electronic Resource
    Global P Wave Duration on the 65-Lead ECG: Single-Site and Dual-Site Pacing in the Structurally Normal Human Atrium (2002)
    Oxford, UK : Blackwell Science Inc
    Journal of cardiovascular electrophysiology 13 (2002), S. 0 
    Details
    ISSN: 1540-8167
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Global P Wave Duration on the 65-Lead ECG. Introduction: Pacing is believed to prevent atrial fibrillation by reducing atrial activation time. Exact correlation between P wave duration (PWD) on surface ECG and endocardial atrial activation time is still unexplored. Methods and Results: In 15 patients without structural heart disease (9 women, age 45 ± 14 years), single site [high right atrium (HRA), coronary sinus ostium (CSos), distal CS (CSd), high RA septum (Bachmann's bundle, BB)] and dual-site pacing (various combinations) was performed after ablation of supraventricular tachycardia. A 65-lead surface ECG was recorded simultaneously. Endocardial atrial activation time was measured off-line (stimulus – last bipolar recording), and the respective PWD was assessed using the root mean square and 65-channel summary plots. PWD during pacing from BB was significantly shorter (96 ± 12 msec) than during HRA (121 ± 15 msec), CSos (108 ± 9 msec), and CSd pacing (126 ± 14 msec; P 〈 0,01, respectively). PWD during dual-site pacing (HRA + BB, 91 ± 14 msec; HRA + CSos, 96 ± 7 msec; HRA + CSd, 90 ± 7 msec; BB + CSd, 96 ± 12 msec) was not significantly shorter than during pacing from BB. Correlation between endocardial atrial activation time and PWD was 0.83. Conclusion: PWD during single-site and dual-site atrial pacing represents endocardial atrial activation time and can be measured precisely using the 65-lead surface ECG. The fact that high septal pacing results in the shortest PWD may have implications for preventive pacing in patients with atrial fibrillation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1540-8167.2002.01240.x
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  • 3
    Electronic Resource
    Electronic Resource
    Effects of Cardiac Resynchronization Therapy on Ventricular Repolarization in Patients with Congestive Heart Failure (2005)
    350 Main Street , Malden , MA 02148-5018 , USA , and 9600 Garsington Road , Oxford OX4 2DQ , UK . : Blackwell Science Inc
    Journal of cardiovascular electrophysiology 16 (2005), S. 0 
    Details
    ISSN: 1540-8167
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Introduction: Biventricular pacing has been shown to improve the clinical status of patients with congestive heart failure, but little is known about its influence on ventricular repolarization. The aim of our study was to evaluate the effect of biventricular pacing on ECG markers of ventricular repolarization in patients with congestive heart failure. Methods and Results: Twenty-five patients with congestive heart failure, sinus rhythm (SR), and complete LBBB (6 females; age 61 ± 8 years; NYHA class II–III; echocardiographic ejection fraction 21 ± 5%; QRS ≥ 130 ms) underwent permanent biventricular DDDR pacemaker implantation. A high-resolution 65-lead body-surface ECG recording was performed at baseline and during right-, left-, and biventricular pacing, and the total 65-lead root mean square curve of the QRST complex and the interlead QT dispersion were assessed. The QRS duration was increased during right (RV)- and left ventricular (LV) pacing (127 ± 26% and 117 ± 40%; P 〈 0.05), as compared to SR (100%) and biventricular pacing (93 ± 16%; ns). The QTc interval was increased during RV and LV pacing (112 ± 12% and 114 ± 14%; P 〈 0.05) as compared to SR (100%) or biventricular pacing (99 ± 12%). There was no effect on JT interval during all pacing modes. The Tpeak-end interval was increased during right (120 ± 34%; P 〈 0.01) and LV pacing (113 ± 29%; P 〈 0.05) but decreased during biventricular pacing (81 ± 19%; P 〈 0.01). A similar effect was found for the Tpeak-end integral and the Tpeak amplitude. QT dispersion was increased during right ventricular (129 ± 16 ms; P 〈 0.05) and decreased during biventricular pacing (90 ± 12 ms; P 〈 0.01), as compared to SR (114 ± 22 ms). Conclusions: Using a high-resolution surface ECG, biventricular pacing resulted in a significant reduction of ECG markers of ventricular dispersion of repolarization.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1540-8167.2005.40496.x
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  • 4
    Electronic Resource
    Electronic Resource
    Uniform high frequency approximation to scattering from infinite strip (1997)
    College Park, Md. : American Institute of Physics (AIP)
    Journal of Mathematical Physics 38 (1997), S. 2308-2331 
    Details
    ISSN: 1089-7658
    Source: AIP Digital Archive
    Topics: Mathematics , Physics
    Notes: A new technique for approximating the high frequency scattering amplitude from flat obstacles is used to solve the problem of acoustic plane wave scattering from an infinite soft strip. This method yields the leading order terms in a uniform high frequency asymptotic expansion for the scattering amplitude which reduce to the results found with the geometrical theory of diffraction in the regions in which that theory is valid. The asymptotic expressions derived here are compared with exact numerical solutions and are found to be accurate for all angles of incidence and reflection. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.531976
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  • 5
    Electronic Resource
    Electronic Resource
    Sodium and Calcium Currents in Glial Cells of the Mouse Corpus Callosum Slice (1992)
    Oxford, UK : Blackwell Publishing Ltd
    European journal of neuroscience 4 (1992), S. 0 
    Details
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: We studied Na+ and Ca2+ currents in glial cells during the development of the corpus callosum in situ. Glioblasts and oligodendrocytes from frontal brain slices of postnatal day (P) 3 to P18 mice were identified based on morphological and ultrastructural features after characterization of the currents with the patch-clamp technique. Slices from P3-P8 mice contained predominantly glioblasts with immature morphological features. These cells showed Na+ and Ca2+ currents, but the population with these currents decreased between P3 and P8. Na+ currents were blocked in Na+-free bathing solution and in the presence of tetrodotoxin, Ca2+ currents were only observed when a high concentration of extracellular Ba2+ was present. The cells from the corpus callosum of P10 – P18 mice predominantly had morphological features of oligodendrocytes. In these cells, which in some cases were shown to form myelin, neither Na+ nor Ca2+ currents were detected. To compare these in situ results with those from the electrophysiologically and immunocytochemically well-characterized cultured glial cells, we determined the expression pattern of stage-specific antigens in the corpus callosum in situ. The first O4 antigen-positive glial precursors were observed at P1, the earliest stage examined. The oligodendrocytic antigens O7 and O10 appeared at P6 and P14, respectively, and prominent labelling with the corresponding markers was seen at P12 and P18, respectively. Despite the existence of numerous mature, O10-positive oligodendrocytes at P18, which expressed Ca2+ channels in vitro, we failed to detect Ca2+ currents in situ at this stage.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1460-9568.1992.tb00153.x
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  • 6
    Electronic Resource
    Electronic Resource
    Homogeneous distribution of large-conductance calcium-dependent potassium channels on soma and apical dendrite of rat neocortical layer 5 pyramidal neurons (2005)
    Oxford, UK : Blackwell Science Ltd
    European journal of neuroscience 21 (2005), S. 0 
    Details
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Voltage-gated conductances on dendrites of layer 5 pyramidal neurons participate in synaptic integration and output generation. We investigated the properties and the distribution of large-conductance calcium-activated potassium channels (BK channels) in this cell type using excised patches in acute slice preparations of rat somatosensory cortex. BK channels were characterized by their large conductance and sensitivity to the specific blockers paxilline and iberiotoxin. BK channels showed a pronounced calcium-dependence with a maximal opening probability of 0.69 at 10 µm and 0.42 at 3 µm free calcium. Their opening probability and transition time constants between open and closed states are voltage-dependent. At depolarized potentials, BK channel gating is described by two open and one closed states. Depolarization increases the opening probability due to a prolongation of the open time constant and a shortening of the closed time constant. Calcium-dependence and biophysical properties of somatic and dendritic BK channels were identical. The presence of BK channels on the apical dendrite of layer 5 pyramidal neurons was shown by immunofluorescence. Patch-clamp recordings revealed a homogeneous density of BK channels on the soma and along the apical dendrite up to 850 µm with a mean density of 1.9 channels per µm2. BK channels are expressed either isolated or in clusters containing up to four channels. This study shows the presence of BK channels on dendrites. Their activation might modulate the shape of sodium and calcium action potentials, their propagation along the dendrite, and thereby the electrotonic distance between the somatic and dendritic action potential initiation zones.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1460-9568.2005.03934.x
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  • 7
    Electronic Resource
    Electronic Resource
    Associative somatodendritic interaction in layer V pyramidal neurons is not affected by the antiepileptic drug lamotrigine (2004)
    Oxford, UK : Blackwell Science Ltd
    European journal of neuroscience 20 (2004), S. 0 
    Details
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The antiepileptic drug lamotrigine was described to exert its effects on neuronal excitability via voltage-gated sodium and calcium, as well as hyperpolarization-activated conductances. In order to define the effects of lamotrigine on the excitability of layer V pyramidal cells of the rat somatosensory cortex we performed patch-clamp recordings from the soma and dendrite of this major cortical output cell type in acute slices. Voltage-clamp experiments revealed the blockade of the persistent sodium current by 50–100 µm lamotrigine as well as by 50 µm of the anticonvulsant drug phenytoin. In somatic current-clamp studies lamotrigine, in a therapeutic concentration range, depolarizes the membrane potential reflecting the activation of the hyperpolarization-activated current. This depolarization reduces the rheobase and increases the spiking frequency at the onset of the spike train. For long depolarizing current pulses under lamotrigine, however, a use-dependent block of sodium channels reduces spiking frequency and spike amplitude. The depolarization due to 50–100 µm lamotrigine reduces additionally the critical frequency of back-propagating spikes necessary to elicit a dendritic calcium action potential. Ten to thirty micromolar lamotrigine, in contrast, did not change the critical frequency. Lamotrigine blocks long-lasting, high frequent spiking activity due to its use-dependent sodium channel block, while burst activity is not impaired due to a depolarizing shift of the membrane potential. This drug therefore dampens epileptic activity while leaving the somatodendritic association in layer V pyramidal cells intact.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1460-9568.2004.03617.x
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  • 8
    Electronic Resource
    Electronic Resource
    ELECTRIC FIELD EFFECTS IN SELECTED BIOLOGIC SYSTEMS (1974)
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 238 (1974), S. 0 
    Details
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1749-6632.1974.tb26809.x
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  • 9
    Electronic Resource
    Electronic Resource
    Subglottic fibrinous cast (2005)
    Oxford, UK : Blackwell Science Ltd
    Pediatric anesthesia 15 (2005), S. 0 
    Details
    ISSN: 1460-9592
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1460-9592.2005.01659.x
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  • 10
    Electronic Resource
    Electronic Resource
    Congenital laryngotracheo-oesophageal cleft: successful ventilation with the Laryngeal Mask AirwayTM (2003)
    Oxford, UK : Blackwell Science Ltd
    Pediatric anesthesia 13 (2003), S. 0 
    Details
    ISSN: 1460-9592
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: A congenital laryngotracheo-oesophageal cleft is a rare airway malformation which results from incomplete separation of the larynx and trachea from the hypopharynx and oesophagus. Patients usually present with stridor, aspiration and cyanosis associated with feeding. For early diagnosis, a high index of suspicion is needed. Unless an appropriate diagnostic approach is taken, the diagnosis can be missed. The successful ventilation of a neonate with the Laryngeal Mask AirwayTM is described.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-9592.2003.00955.x
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