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  • 1
    Electronic Resource
    Electronic Resource
    Internal Defibrillation with Smaller Capacitors: A Prospective Randomized Cross-Over Comparison of Defibrillation Efficacy Obtained with 90-μF and 125-μF Capacitors in Humans (1995)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of cardiovascular electrophysiology 6 (1995), S. 0 
    Details
    ISSN: 1540-8167
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Defibrillation with Small Capacitance. Introduction: The size of current implantable cardioverter defibrillators (ICD) is still large in comparison to pacemakers and thus not convenient for pectoral implantation. One way to reduce ICD size is to defibrillate with smaller capacitors. A trade-off exists, however, since smaller capacitors may generate a lower maximum energy output. Methods and Results: In a prospective randomized cross-over study, the step-down defibrillation threshold (DFT) of an experimental 90-μF biphasic waveform was compared to a standard 125-μF biphasic waveform. The 90-μF capacitor delivered the same energy faster and with a higher peak voltage but provided only a maximum energy output of 20 instead of 34 J. DFTs were determined intraoperatively in 30 patients randomized to receive either an endocardial (n = 15) or an endocardial-subcutaneous array (n = 15) defibrillation lead system. Independent of the lead system used, energy requirements did not differ at DFT for the experimental and the standard waveforms (10.3 ± 4.1 and 9.5 ± 4.9 J, respectively), but peak voltages were higher for the experimental waveform than for the standard waveform (411 ± 80 and 325 ± 81 V, respectively). For the experimental waveform the DFT was 10 J or less using an endocardial lead-alone system in 10 (67%) of 15 patients and in 12 (80%) of 15 patients using an endocardial-subcutaneous array lead system. Conclusions: A shorter duration waveform delivered by smaller capacitors does not increase defibrillation energy requirements and might reduce device size. However, the smaller capacitance reduces the maximum energy output. If a 10-J safety margin between DFT and maximum energy output of the ICD is required, only a subgroup of patients will benefit from 90-μF ICDs with DFTs feasible using current defibrillation lead systems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1540-8167.1995.tb00405.x
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  • 2
    Electronic Resource
    Electronic Resource
    Implantation of a Dual Chamber Pacing and Sensing Single Pass Defibrillation Lead (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: GRADAUS, R., et al.: Implantation of a Dual Chamber Pacing and Sensing Single Pass Defibrillation Lead. Dual-chamber ICDs are increasingly used to avoid inappropriate shocks due to supraventricular tachycardias. Additionally, many ICD patients will probably benefit from dual chamber pacing. The purpose of this pilot study was to evaluate the intraoperative performance and short-term follow-up of an innovative single pass right ventricular defibrillation lead capable of bipolar sensing and pacing in the right atrium and ventricle. Implantation of this single pass right ventricular defibrillation lead was successful in all 13 patients (age 63 ± 8 years; LVEF 0.44 ± 0.16; New York Heart Association [NYHA] 2.4 ± 0.4, previous open heart surgery in all patients). The operation time was 79 ± 29 minutes, the fluoroscopy time 4.7 ± 3.1 minutes. No perioperative complications occurred. The intraoperative atrial sensing was 1.7 ± 0.5 mV, the atrial pacing threshold product was 0.20 ± 0.14 V/ms (range 0.03–0.50 V/ms). The defibrillation threshold was 8.8 ± 2.7 J. At prehospital discharge and at 1-month and 3-month follow-up, atrial sensing was 1.9 ± 0.9, 2.1 ± 0.5, and 2.7 ± 0.6 mV, respectively, (P = NS, P 〈 0.05, P 〈 0.05 to implant, respectively), the mean atrial threshold product 0.79, 1.65, and 1.29 V/ms, respectively. In two patients, an intermittent exit block occurred in different body postures. All spontaneous and induced ventricular arrhythmias were detected and terminated appropriately. Thus, in a highly selected patient group, atrial and ventricular sensing and pacing with a single lead is possible under consideration of an atrial pacing dysfunction in 17% of patients.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-9592.2001.00416.x
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  • 3
    Electronic Resource
    Electronic Resource
    Effect of Ventricular Fibrillation Duration on the Defibrillation Threshold in Humans (2002)
    Oxford, UK : Blackwell Futura Publishing, Inc.
    Pacing and clinical electrophysiology 25 (2002), S. 0 
    Details
    ISSN: 1540-8159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: GRADAUS, R., et al.: Effect of Ventricular Fibrillation Duration on the Defibrillation Threshold in Humans. Early during ventricular fibrillation, the defibrillation threshold may be low, as ventricular fibrillation most probably arises from a localized area with only a few wavefronts and the effects of global ischemia, ventricular dilatation, and sympathetic discharge have not yet fully developed. The purpose of this study was to explore the effect of the timing of shock delivery in humans. During implantation of an ICD in 26 patients (24 men, 60 ± 11 years, 19 coronary artery disease, NYHA 2.2 ± 0.4, left ventricular ejection fraction 0.42 ± 0.16), the defibrillation threshold was determined after approximately 10 and 2 seconds of ventricular fibrillation. Ventricular fibrillation was induced by T wave shocks. Mean defibrillation threshold was 9.9 ± 3.6 J after 10.3 ± 1.0 seconds. Within 2 seconds, 20 of 26 patients could be successfully defibrillated with ≤ 8 J. In these patients, the mean defibrillation threshold was 4.0 ± 2.1 J after 1.4 ± 0.3 seconds compared to 9.5 ± 3.1 J after 10.2 ± 1.1 seconds (P 〈 0.001). There were no clinical differences between patients who could be successfully defibrillated within 2 seconds and those patients without successful defibrillation within 2 seconds. In the majority of patients, the defibrillation threshold was significantly lower within the first few cycles of ventricular fibrillation than after 10 seconds of ventricular fibrillation. These results should lead to exploration of earlier shock delivery in implantable devices. This could possibly reduce the incidence of syncope in patients with rapid ventricular tachyarrhythmias and ICDs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-9592.2002.00014.x
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  • 4
    Electronic Resource
    Electronic Resource
    Trans venous-Subcutaneous Defibrillation Leads: (1994)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of cardiovascular electrophysiology 5 (1994), S. 0 
    Details
    ISSN: 1540-8167
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Effect of Transvenous Electrode Polarity on DFT. Introduction: The defibrillation threshold (DFT) of a transvenous-subcutaneous electrode configuration is sometimes unacceptably high. To obtain a DFT with a sufficient safety margin, the defibrillation field can be modified by repositioning the electrodes or more easily by a change of electrode polarity. In a prospective randomized cross-over study, the effect of transvenous electrode polarity on DFT was evaluated. Methods and Results: In 21 patients receiving transvenous-subcutaneous defibrillation leads, the DFT was determined intraoperatively for two electrode configurations. Two monophasic defibrillation pulses were delivered in sequential mode between either the right ventricular (RV) electrode as common cathode and the superior vena cava (SVC) and subcutaneous electrodes as anodes (configuration I) or the SVC electrode as common cathode and the RV and subcutaneous electrodes as anodes (configuration II). In each patient, both electrode configurations were used alternately with declining energies (25, 15, 10, 5, 2 J) until failure of defibrillation occurred. The DFT did not differ between both configurations (18.3 ± 8.2 J vs 18.9 ± 8.9 J; P = 0.72). Eleven patients had the same DFT with both electrode configurations, 5 patients a lower DFT with the RV electrode as cathode, and 5 patients a lower DFT with the SVC as cathode. Four patients had a sufficiently low DFT (≤ 25 J) with only 1 of the 2 configurations. Conclusion: A change of electrode polarity of transvenous-subcutaneous defibrillation electrodes may result in effective defibrillation if the first electrode polarity tested fails to defibrillate. In general, neither the RV electrode nor the SVC electrode is superior if used as a common cathode in combination with a subcutaneous anodal chest patch.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1540-8167.1994.tb01131.x
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  • 5
    Electronic Resource
    Electronic Resource
    A Prospective Randomized Cross-Over Comparison of Mono- and Biphasic Defibrillation Using Nonthoracotomy Lead Configurations in Humans (1994)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of cardiovascular electrophysiology 5 (1994), S. 0 
    Details
    ISSN: 1540-8167
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Biphasic Defibrillation with Nonthoracotomy Leads. Introduction: For current implantable defibrillators, the nonthoracotomy approach to implantation fails in a substantial number of patients. In a prospective randomized cross-over study the defibrillation efficacy of a standard monophasic and a new biphasic waveform was compared for different lead configurations. Methods and Results: Intraoperatively, in 79 patients receiving nonthoracotomy defibrillation leads, the defibrillation threshold was determined in the initial lead configuration for the mono-and biphasic waveform. In each patient, both waveforms were used alternately with declining energies (20, 15,10, 5 J) until failure of defibrillation occurred. Three different initial lead configurations were tested in different, consecutive, nonrandomized patients using a bipolar endocardial defibrillation lead alone (A; n = 36) or in combination with a subcutaneous defibrillation patch (B; n = 24) or array (C; n = 19) lead. The lowest successful defibrillation energy with the biphasic waveform was less than, equal to, or higher than with the monophasic waveform in 64%, 28%, and 8% of patients, respectively, and on average significantly lower with the biphasic waveform for all three lead configurations (A: 11.3 ± 4.4 J vs 14.5 ± 4.5.); B: 9.7 ± 4.7 J vs 15.1 ± 4.5 J; C: 7.9 ± 4.5 J vs 12.4 ± 4.9 J). Defibrillation efficacy at 20 J was significantly improved by the biphasic waveform (91% vs 76%). Conclusion: In combination with nonthoracotomy defibrillation leads, the biphasic waveform of a new implantable cardioverter defibrillator showed superior defibrillation efficacy in comparison to the standard monophasic waveform. Defibrillation thresholds were improved for lead systems with and without a subcutaneous patch or array lead.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1540-8167.1994.tb01299.x
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  • 6
    Electronic Resource
    Electronic Resource
    Defibrillation Efficacy Comparing a Subcutaneous Array Electrode versus an “Active Can” Implantable Cardioverter Defibrillator and a Subcutaneous Array Electrode in Addition to an “Active Can” Implantable Cardioverter Defibrillator: Results from Active Can versus Array Trials I and II (2001)
    Oxford, UK : Blackwell Science Inc
    Journal of cardiovascular electrophysiology 12 (2001), S. 0 
    Details
    ISSN: 1540-8167
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Defibrillation Efficacy. Introduction: Placement of implantable cardioverter defibrillators (ICDs) has been simplified by using the shell of a pectorally implanted ICD as a defibrillation electrode in combination with an endocardial right ventricular defibrillation lead. However, a sufficiently low defibrillation threshold (DFT) cannot be obtained in a few patients. Therefore, alternative approaches were systematically tested in the Active Can versus Array Trial (ACAT). Methods and Results: In the first of two prospective randomized studies, the DFT of a subcutaneous left dorsolateral array anode introduced from a pectoral incision was compared to that of a standard active can anode in 68 patients. Intraoperatively, the DFT was determined twice in each patient using either the active can or, in patients with a subcutaneous array lead, once with all three fingers and once omitting the middle finger of the array. The second prospective randomized study included 40 patients. DFT also was determined twice in each patient using an active can in a left pectoral position as anode alone and combined with a left dorsolateral array electrode with two fingers. In ACAT I, stored energy at DFT decreased from 13.1 ± 7.7 J (active can) to 9.6 ± 6.1 J (three-finger array lead) (P = 0.04), impedance decreased from 53 ± 8 Ω to 40 ± 6 Ω (P 〈 0.0001). Omitting the middle finger of the array lead, stored energy at DFT increased by 0.9 J (P = 0.47) and impedance by 2 Ω (P 〈 0.0001). In ACAT II, DFT and impedance using an active can device were significantly lower when a two-finger array lead was added that decreased stored energy at DFT from 10.1 ± 5.2 J to 6.9 ± 3.9 J (P = 0.001) and impedance from 56 ± 5 Ω to 42 ± 5 Ω (P 〈 0.0001). Conclusion: In combination with a right ventricular defibrillation electrode, a left pectoral subcutaneous array lead improves defibrillation efficacy if used instead of, or in addition to, a left pectoral active can ICD device. Implantation of the array lead can be simplified by using two instead of three fingers, without a significant loss of defibrillation efficacy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1540-8167.2001.00921.x
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  • 7
    Electronic Resource
    Electronic Resource
    Ischemic Preconditioning by Unstable Angina Reduces the Release of CK-MB Following CABG and Stimulates Left Ventricular HSP-72 Protein Expression (2005)
    350 Main Street , Malden , MA 02148-5020 , USA and 9600 Garsington Road , Oxford OX4 2XG , England . : Blackwell Science Inc
    Journal of cardiac surgery 20 (2005), S. 0 
    Details
    ISSN: 1540-8191
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract  Background and Aim: Whether the CK-MB reducing effect of ischemic preconditioning (IP) by unstable angina within 24 to 48 hours before CABG is achieved by early or by delayed preconditioning of left ventricular myocardium in humans is unknown. We investigated whether IP is associated with phosphorylation of p38 MAPK (characteristic for early preconditioning) or with increased protein expression of HSP-72 (characteristic for delayed preconditioning) at the time of CABG in patients. Methods: Nineteen patients were grouped according to the occurrence of ischemic episodes within 48 hours before CABG. The patients without angina were assigned to the control group (CON, n = 10) whereas patients who had experienced angina within 48 hours before CABG were assigned to the preconditioned group (IP, n = 9). The effect of IP on the CABG induced maximal release of creatine kinase (CK) and CK-MB was examined. Left ventricular biopsy specimens taken immediately before cross clamping from ischemic (ISCH) and from reference (REF) areas were processed to analyze p38 MAPK phosphorylation and HSP-72-protein expression. Results: While IP significantly reduced CK-MB (18.7 ± 1.3 vs. 13.8 ± 1.5 U/L, mean ± SEM, p 〈 0.05), it only tended to reduce CK (292.7 ± 32.8 vs. 274.1±31.1 U/L, p = NS, mean ± SEM). CK-MB release for any given cross-clamp time was significantly reduced by IP (regression lines: CON, y= 0.4x+ 2, r= 0.8; IP, y= 0.1x+ 10, r= 0.2; p 〈 0.01, ANCOVA). There was no effect of IP on left ventricular p38 MAPK phosphorylation. IP increased left ventricular HSP-72-protein expression in ischemic areas when compared to reference areas (1.78 ± 0.35 vs. 2.58 ± 0.65, REF vs. ISCH, PhosphorImager units ×106, mean ± SEM, p 〈 0.05, ANCOVA). Conclusions: Thus, in the human left ventricular myocardium there is a second window of protection lasting for at least 48 hours, while at that time the early phase of preconditioning has already gone.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1540-8191.2005.2004107.x
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  • 8
    Electronic Resource
    Electronic Resource
    Nonthoracotomy Implantable Cardioverter Defibrillator Placement in Children: Use of Subcutaneous Array Leads and Abdominally Placed Implantable Cardioverter Defibrillators in Children (2001)
    Oxford, UK : Blackwell Science Inc
    Journal of cardiovascular electrophysiology 12 (2001), S. 0 
    Details
    ISSN: 1540-8167
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Nonthoracotomy ICD in Children. Introduction: The need to access the right ventricle might preclude transvenous placement of a defibrillation lead at implantable cardioverter defibrillator (ICD) placement, especially in small children or children with complex congenital heart defects. We investigated a subcutaneous array lead in addition to an abdominally placed “active can” ICD device in two children to avoid a thoracotomy. Methods and Results: The first child (age 12 years, 138 cm, 41 kg) had transposition of the great arteries with a subsequent surgical intra-atrial correction by the Mustard technique. The second child (age 14 years, 161 cm, 54 kg) had a single atrium and a single ventricle, d-transposition of the aorta, and atresia of the main pulmonary artery with a surgical anastomosis between the aorta and the right pulmonary artery by the Cooley technique. The defibrillation threshold was 18 J and 〈 20 J at initial implantation and at generator replacement in the first patient and 20 J in the second patient. During follow-up of 6 years and 1 month, respectively, no ICD-related complications occurred. Conclusion: In children in whom endocardial, right ventricular placement of a defibrillation lead is precluded, defibrillation is possible and safe between an abdominally placed “active can” ICD device and a subcutaneous array lead. This approach may avoid a thoracotomy in children with no possibility for transvenous ICD placement.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1540-8167.2001.00356.x
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  • 9
    Electronic Resource
    Electronic Resource
    Intraoperative Radiofrequency Ablation of Chronic Atrial Fibrillation: A Left Atrial Curative Approach by Elimination of Anatomic “Anchor” Reentrant Circuits (1999)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of cardiovascular electrophysiology 10 (1999), S. 0 
    Details
    ISSN: 1540-8167
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Intraoperative Ablation of Atrial Fibrillation. Introduction: The percutaneous approach to radiofrequency (RF) catheter ablation for curative treatment of atrial fibrillation (AF) is an investigational technique, and the optimal composition of lesion lines is unknown. We tested an intraoperative RF ablation concept with elimination of left atrial anatomic “anchor” reentrant circuits. Methods and Results: In 12 patients with an indication for valve surgery and chronic AF, a right atrial-transseptal approach was chosen for access to the left atrium. AF had been present for 4.3 ± 3.9 years; the left atria measured 56 ± 7 mm. Under direct vision, contiguous lesion lines were placed endocardially with temperature-guided RF energy applications for treatment of AF with a specially designed probe. The lesion lines were placed between the mitral annulus and the left lower pulmonary vein, further to the left upper pulmonary vein, from there to the right upper pulmonary vein, and finally to the right lower pulmonary vein. The antiarrhythmic ablation procedure lasted 19 ± 4 minutes. One patient died postoperatively of low cardiac output. During follow-up of 11 ± 6 months, chronic AF was ablated successfully in 9 of 11 patients (82%). Six patients were in stable sinus rhythm or intermittent pacemaker rhythm, and three patients were in sinus rhythm with intermittent atypical atrial flutter. Conclusions: Intraoperative RF energy application for induction of contiguous lesion lines is feasible. Elimination of anatomically defined “anchor” reentrant circuits within the left atrium prevented chronic AF in 〉 80% of the patients treated. Intraoperative validation of lesion line concepts for curative treatment of AF may he transferred to percutaneous ablation techniques.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1540-8167.1999.tb00256.x
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  • 10
    Electronic Resource
    Electronic Resource
    Directct Epicardial Mapping Can Differentiate Hibernating from Scarred Myocardium: A Validation Study with 18F-FDG-PET (2002)
    Oxford, UK : Blackwell Publishing Ltd
    Annals of noninvasive electrocardiology 7 (2002), S. 0 
    Details
    ISSN: 1542-474X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Aim: This study investigated the value of epicardial mapping immediately before CABG in the differentiation of hibernating from scarred myocardium in correlation to the noninvasive gold standard 18F-FDG PET.Methods and Results: In 35 patients with CAD, myocardial perfusion (99mTc-Tetrofosmin-SPECT), viability (18F-FDG-PET), and function (LVangiography) were assessed before CABG. 102 bipolar epicardial electrograms per patient (n = 3570 electrograms) were recorded simultaneously with a ventricular jacket array. Based on the scintigraphic and LV angiographic data at the site of each electrode with good myocardial contact (n = 1963), segments (n = 492, 14.1 ± 5.6 per patient; mean ± SD) were classified into three groups: hibernating (n = 139), scarred (n = 104), and control (n = 249). Regional mean bipolar voltage values were calculated for Receiver Operating Characteristic (ROC) analysis. Mean bipolar voltage was significantly lower in scarred when compared to hibernating myocardium. ROC curve analysis (area under the curve of O.92 ± 0.47, mean ± SE) for mean bipolar voltage to discriminate between hibernating and scarred myocardium revealed a sensitivity of 94% with a specificity of 83% at a cut-off value of 8.75 mV.Conclusion: Hibernating myocardium can be differentiated correctly from scarred myocardium by direct epicardial mapping. In the future, hibernating myocardium may be detectable by body surface mapping techniques using inverse solutions. A.N.E. 2002;7(4):349–356
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1542-474X.2002.tb00184.x
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