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  • 1
    Electronic Resource
    Electronic Resource
    Prospective Randomized Comparison of Two Defibrillation Safety Margins in Unipolar, Active Pectoral Defibrillator Therapy (2003)
    350 Main Street , Malden , MA 02148-5018 , USA . : Blackwell Futura Publishing, Inc.
    Pacing and clinical electrophysiology 26 (2003), S. 0 
    Details
    ISSN: 1540-8159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: CARLSSON, J., et al.: Prospective Randomized Comparison of Two Defibrillation Safety Margins in Unipolar, Active Pectoral Defibrillator Therapy. Various techniques are used to establish defibrillation efficacy and to evaluate defibrillation safety margins in patients with an ICD. In daily practice a safety margin of 10 J is generally accepted. However, this is based on old clinical data and there are no data on safety margins using current ICD technology with unipolar, active pectoral defibrillators. Therefore, a randomized study was performed to test if the likelihood of successful defibrillation at defibrillation energy requirement (DER) +5 J and +10 J is equivalent. Ninety-six patients (86 men; age 61.0 ± 10.3 years; ejection fraction 0.341 ± 0.132 ; coronary artery disease [n = 65],dilated cardiomyopathy [n = 18], other [n = 13]) underwent implantation of an active pectoral ICD system with unidirectional current pathway and a truncated, fixed tilt biphasic shock waveform. The defibrillation energy requirement (DER) was determined with the use of a step-down protocol (delivered energy 15, 10, 8, 6, 4, 3, 2 J). The patients were then randomized to three inductions of ventricular fibrillation at implantation and three at predischarge testing with shock strengths programmed to DER + 5 J at implantation and + 10 J at predischarge testing or vice versa. The mean DER in the total study population was7.88 ± 2.96 J. The number of defibrillation attempts was 288 for +5 J and 288 for +10 J. The rate of successful defibrillation was 94.1% (DER + 5 J) and 98.9% (DER + 10 J;P 〈 0.01for equivalence). Charge times for DER + 5 J were significantly shorter than for DER + 10 J (3.65 ± 1.14vs5.45 ± 1.47 s; P 〈 0.001). A defibrillation safety margin of DER + 5 J is associated with a defibrillation probability equal to the standard DER + 10 J. In patients in whom short charge times are critical for avoidance of syncope, a safety margin of DER + 5 J seems clinically safe for programming of the first shock energy. (PACE 2003; 26[Pt. I]:613–618)
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-9592.2003.00102.x
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  • 2
    Electronic Resource
    Electronic Resource
    Reduction of Pacing Output Coupling Capacitance for Sensing the Evoked Response (2001)
    Oxford, UK : Blackwell Futura Publishing, Inc.
    Pacing and clinical electrophysiology 24 (2001), S. 0 
    Details
    ISSN: 1540-8159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: SPERZEL, J., et al.: Reduction of Pacing Output Coupling Capacitance for Sensing the Evoked Response. Sensing of the intracardiac evoked response (ER) after a pacing stimulus has been used in implantable pacemakers for automatic verification of capture. Reliable detection of ER is hampered by large residual afterpotentials associated with pacing stimuli. This led to the development of various technological solutions, like the use of triphasic pacing pulses and low polarizing electrode systems. This study investigated the effect of reducing the coupling capacitance (CC) in the pacemaker output circuitry on the magnitude of afterpotential, and the ability to automate detection of ventricular evoked response. A CC of 2.2 μF and four different blanking and recharge time settings were clinically tested to evaluate its impact on sensing of the ventricular ER and pacing threshold. Using an automatic step-down threshold algorithm, 54 consecutive patients, aged 70 ± 10 years with acutely (n = 27) or chronically (n = 27) implanted ventricular pacing leads were enrolled for measurement testing. Routine measurements, using a standard pacing system analyzer (PSA), were (mean ± SD) impedance 569 ± 155 Ω, R wave amplitude baseline to peak 9.8 ± 3.7 mV and threshold 0.9 ± 0.7 V at 0.4-ms pulse width. This new capture verification scheme, based on a CC of 2.2 μF and recharge/blanking timing setting of 10/12 ms, was successful in 52 patients which is equivalent to a success rate of 96%. In a subgroup of 26 patients implanted with bipolar ventricular leads (10 chronic, 16 acute), data were collected in unipolar (UP) and bipolar (BP) pace/sense configurations. Also, ER signals were recorded with two different band-pass filters: a wider band (WB) of 6–250 Hz and a conventional narrow band (NB) of 20–100Hz. WB sensing from UP lead configuration yielded statistically significant larger signal to artifact ratios (SAR) than the other settings (P 〈 0.01). A dedicated unipolar ER sensing configuration using a small output capacitor and a wider band-pass filter enables adequate automatic capture verification, without any restrictions on pacing lead models or pacing/sensing configurations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-9592.2001.01377.x
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  • 3
    Electronic Resource
    Electronic Resource
    Clinical Evaluation of a Prototype Passive Fixation Dual Chamber Single Pass Lead For Dual Chamber ICD Systems (1999)
    Oxford, UK : Blackwell Publishing Ltd
    Pacing and clinical electrophysiology 22 (1999), S. 0 
    Details
    ISSN: 1540-8159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Dual chamber ICD systems use two separate leads for sensing. We developed and tested a new prototype of a single pass dual chamber passive fixation lead for dual chamber ICDs. Methods and Results: The prototype was a modification of the Guidant CPI Endotak DSP lead. The additional sensing electrode for the right atrium consisted of a side-mounted porous atrial ring electrode (AR). Atrial signals were recorded from the lead in patients during normal sinus rhythm (NSR), atrial fibrillation (AFib), and/or atrial flutter (AFl) with the AR in stable contact with the atrial wall or floating. During NSR, with the AR in contact with the atrial wall, an average P wave amplitude of 7.2 ± 1.5 mV (mean ± SD, n = 12) was measured. After induction of AFib/AFl, the single amplitude decreased to 3.6 ± 1.5 mV (n = 8) during AFib and 3.4 ± 1.7 mV (n = 9) during AFl. Amplitudes dropped between 53% and 75% when the AR lost atrial wall contact. The atrial pacing threshold was 1.0 ± 0.4 V (n = 16) when the AR was in contact with the atrial wall. Conclusions: In future dual chamber ICDs the signals from a passive fixation single pass lead could be used for atrial sensing and pacing as long as the sensing electrode for the right atrium remains in contact with the atrial wall. This system might lead to a simpler, less invasive implantation of dual chamber ICD systems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1540-8159.1999.tb00326.x
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  • 4
    Electronic Resource
    Electronic Resource
    Mineral deposit formation in Phanerozoic sedimentary basins of north-east Africa: the contribution of weathering (1994)
    Springer
    International journal of earth sciences 83 (1994), S. 787-798 
    Details
    ISSN: 1437-3262
    Keywords: North-east Africa ; Mineral deposits ; Laterite ; Weathering ; Paleoclimate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract The intra- and epicontinental basins in north-east Africa (Egypt, Sudan) bear ample evidence of weathering processes repeatedly having contributed to the formation of mineral deposits throughout the Phanerozoic. The relict primary weathering mantle of Pan-African basement rocks consists of kaolinitic saprolite, laterite (in places bauxitic) and iron oxide crust. On the continent, the reaccumulation of eroded weathering-derived clay minerals (mainly kaolinite) occurred predominantly in fluvio-lacustrine environments, and floodplain and coastal plain deposits. Iron oxides, delivered from ferricretes, accumulated as oolitic ironstones in continental and marine sediments. Elements leached from weathering profiles accumulated in continental basins forming silcrete and alunite or in the marine environment contributing to the formation of attapulgite/saprolite and phosphorites. The Early Paleozoic Tawiga bauxitic laterite of northern Sudan gives a unique testimony of high latitude lateritic weathering under global greenhouse conditions. It formed in close spatial and temporal vicinity to the Late Ordovician glaciation in north Africa. The record of weathering products is essentially complete for the Late Cretaceous/Early Tertiary. From the continental sources in the south to the marine sinks in the north, an almost complete line of lateritic and laterite-derived deposits of bauxitic kaolin, kaolin, iron oxides and phosphates is well documented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00251076
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