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Successful Defibrillation (successful + defibrillation)
Selected AbstractsLaplacian Electrograms and the Interpretation of Complex Ventricular Activation Patterns During Ventricular FibrillationJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 10 2000PH.D., RUBEN CORONEL M.D. Laplacian Electrograms and Ventricular Fihrillation. Introduction. During ventricular fibrillation (VF) interpretation of a local electrogram and determination of the local activation moment are hampered by remote activity or intervening repolarization waves. Successful defibrillation depends on critical timing of the shock relative to local activation. We tested the applicabillity of Laplacian electrograms for detection of the moment of local activation during VF. Methods and Results. From isolated perfased porcine infact heart, 247 local unipolar electrograms were recorded simultaneously (13 × 19 matrix, interelectrode distance 0.3 mm) from the left ventricular wall during sinus rhythm, following pacing or during VF, Activation maps were constructed based on local unipolar electrograms, and Laplacian electrograms were calculated from local electrograms ane its eight neighbors. The Laplacian electrogram displayed a sharp R/S complex with local activation iodicted by the moment of zero crossing without interference from remote activity or repolarization waves. Its amplitude increased with decreasing interelectrode distance, Following epicardial stimulation, Laplacian amplitude was significantly larger than during complexes with different morphology. Collision of wavefronts was associated with entirely positive Laplacian waveforms; "focal" appearancce of acitivity was associated with an entirely negative waveform. Activation block in the activation maps was correlated with the appearance of substanined episodes of negativity or positivity in the Laplacian electrogram (depending on the location of the recording site relative to the line of block). Conclusion. Laplacian electrograms allow detection of the moment of local activation without interference from remote activity or repolarization, especially during complex arrhythmias. The technique applied toe automatic sensing devices, such its the internal defibrillator, may optimize defibrtilation success. (J Cardiovasc Electrophysiol, Vol. 11, pp. 1119-1128, October 2000) [source] A Model of Ischemically Induced Ventricular Fibrillation for Comparison of Fixed-dose and Escalating-dose Defibrillation StrategiesACADEMIC EMERGENCY MEDICINE, Issue 6 2004James T. Niemann MD Abstract Objectives: Fixed- and escalating-dose defibrillation protocols are both in clinical use. Clinical observations suggest that the probability of successful defibrillation is not constant across a population of patients with ventricular fibrillation (VF). Common animal models of electrically induced VF do not represent a clinical VF etiology or reproduce clinical heterogeneity in defibrillation probability. The authors hypothesized that a model of ischemically induced VF would exhibit heterogeneous defibrillation shock strength requirements and that an escalating-dose strategy would more effectively achieve prompt defibrillation. Methods:Forty-six swine were randomized to fixed, lower-energy (150 J) transthoracic shocks (group 1) or escalating, higher-energy (200 J,300 J,360 J) shocks (group 2). VF was induced by balloon occlusion of a coronary artery. After 1 or 5 minutes of VF, countershocks with a biphasic waveform were administered. The primary endpoint was successful defibrillation (termination of VF for 5 seconds) with ,3 shocks. Results: VF was induced with occlusion or after reperfusion in 35 animals. Only five of 17 group 1 animals (29%, 95% CI = 10 to 56) could be defibrillated with ,3 shocks; 15 of 18 group 2 animals (83%, 95% CI = 59 to 96) were defibrillated with ,3 shocks (p < 0.002 vs. group 1). Nine of the group 1 animals (75%) that could not be defibrillated with 150-J shocks were rescued with ,3 shocks ranging from 200 to 360 J. Conclusions: In this ischemic VF animal model, defibrillation shock strength requirements varied among individuals, and when defibrillation was difficult, an escalating-dose strategy was more effective for prompt defibrillation than fixed, lower-energy shocks. [source] The efficacy and safety of external biphasic defibrillation in toy breed dogsJOURNAL OF VETERINARY EMERGENCY AND CRITICAL CARE, Issue 4 2008Seung-Gon Lee DVM Abstract Objective: To evaluate the efficacy and safety of biphasic (BP) defibrillation in toy breed dogs (<5 kg of body weight). Design: Prospective, clinical experimental study. Setting: Veterinary teaching hospital. Animals: Five dogs (pilot study) and 10 dogs (comparison study of biphasic versus monophasic defibrillation). Measurements and main results: The efficacy of defibrillation was compared by estimating E80 (80% probability of successful defibrillation) after biphasic (BP) and monophasic (MP) defibrillations. The E80 for BP defibrillation was 7.24±1.33 J (2.24±0.41 J/kg) and 10.24±1.34 J (3.18±0.12 J/kg) for MP defibrillation. BP waveform required 30% less shock energy for a successful defibrillation. In order to compare the safety of defibrillation, we evaluated changes in cardiac biomarkers, electrocardiogram, echocardiographical left ventricular index, and aortic pressure during and after BP and MP defibrillation. All dogs treated by either BP or MP defibrillation survived. Pulseless electrical activity occurred in 2 of 5 dogs during MP defibrillation. The levels of cardiac biomarkers were elevated and sustained for longer periods in the MP defibrillation group. Electrocardiographic changes (e.g., QT prolongation, the time to return to an isoelectric ST segment after shocks) were more severe and longer in the MP defibrillation group. In addition, overall left ventricular cardiac performance was severely depressed in the MP group compared with the BP group. Conclusion: Our findings suggest that BP defibrillation is more effective and safer than MP defibrillation. We determined the acceptable shock energy to be 2,4 J/kg for toy breed dogs. [source] Atrial Activation Occurring Immediately after Successful Cardioversion of Atrial FibrillationPACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 1 2008ARTURO MARTÍN PEÑATO MOLINA M.D. Background and Objective: Electrical defibrillation is very effective in interrupting atrial fibrillation (AF). However, its mechanism is not completely understood. We report our observations in patients subjected to external electriocardioversion (ECV) of atrial fibrillation and contrast them with recent theories about defibrillation mechanism. Methods: In 13 consecutive patients transthoracic electrical cardioversion for AF was performed during an electrophysiological study (11 monophasic -200,360 J- and 9 biphasic shocks -50,150 J-). About 10,16 electrograms were obtained with multipolar catheters recording right atrium, coronary sinus, and right pulmonary artery. AF was defined by interelectrogram intervals and changing sequences among recordings, indicating complete lack of organization. We evaluated the presence of propagated activations immediately (<300 ms) after successful shocks (,1 discrete electrogram in all recordings). In unsuccessful shocks we evaluated changes in electrogram morphology (discrete/fragmented) and interelectrogram intervals before and after defibrillation. Results: About 16/20 shocks terminated AF. In 6/16 one or two cycles of atrial activation were recorded just after the shock and before AF ended. In 10/16 AF was interrupted immediately after the shock. 4/20 shocks did not interrupt the arrhythmia. After these shocks, transient organization of recorded activity with longer interelectrogram cycle length and disappearance of fragmented activity were transiently observed. Conclusion: Our clinical findings in atrial defibrillation in vivo reproduce experimental data that show myocardial activations early after successful direct current shocks. These observations suggest that successful defibrillation depends not only on the immediate effects of the shock, but also on transient effects on electrophysiological properties of the myocardium, capable of interrupting persistent or reinitiated activations. [source] Effect of Ventricular Fibrillation Duration on the Defibrillation Threshold in HumansPACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 1 2002RAINER GRADAUS 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. [source] The Effectiveness and Cost Effectiveness of Public-Access DefibrillationCLINICAL CARDIOLOGY, Issue 7 2010Roger A. Winkle MD Many sudden cardiac deaths are due to ventricular fibrillation (VF). The use of defibrillators in hospitals or by outpatient emergency medical services (EMS) personnel can save many cardiac-arrest victims. Automated external defibrillators (AEDs) permit defibrillation by trained first responders and laypersons. AEDs are available at most public venues, and vast sums of money are spent installing and maintaining these devices. AEDs have been evaluated in a variety of public and private settings. AEDs accurately identify malignant ventricular tachyarrhythmias and frequently result in successful defibrillation. Prompt application of an AED shows a greater number of patients in VF compared with initial rhythms documented by later-arriving EMS personnel. Survival is greatest when the AED is placed within 3 to 5 minutes of a witnessed collapse. Community-based studies show increased cardiac-arrest survival when first responders are equipped with AEDs rather than waiting for paramedics to defibrillate. Wide dissemination of AEDs throughout a community increases survival from cardiac arrest when the AED is used; however, the AEDs are utilized in a very small percentage of all out-of-hospital cardiac arrests. AEDs save very few lives in residential units such as private homes or apartment complexes. AEDs are cost effective at sites where there is a high density of both potential victims and resuscitators. Placement at golf courses, health clubs, and similar venues is not cost effective; however, the visible devices are good for public awareness of the problem of sudden cardiac death and provide reassurance to patrons. Copyright © 2010 Wiley Periodicals, Inc. [source] | ||||||||||