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Peak Voltage (peak + voltage)

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Medical Sciences100%

Selected Abstracts

Defibrillation Efficacy and Pain Perception of Two Biphasic Waveforms for Internal Cardioversion of Atrial Fibrillation

JOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 8 2003
Jens Jung M.D.
Introduction: We evaluated the influence of the peak voltage of waveforms used for internal cardioversion of atrial fibrillation on defibrillation efficacy and pain perception. A low peak voltage biphasic waveform generated by a 500-,F capacitor with 40% tilt was compared to a standard biphasic waveform generated by a 60-,F capacitor with 80% tilt. Methods and Results: In 19 patients with paroxysmal atrial fibrillation (79% male, age 55 ± 11 years, 21% with heart disease), the atrial defibrillation threshold (ADFT) was determined during deep sedation with midazolam for both waveforms in a randomized fashion using a step-up protocol. Internal cardioversion with a single lead (shock vector: coronary sinus to right atrium) was successful in 18 (95%) of 19 patients. ADFT energy and peak voltage were significantly lower for the low-voltage waveform (2.1 ± 2.4 J vs 3.5 ± 3.9 J, P < 0.01; 100 ± 53 V vs 290 ± 149 V, P < 0.01). Sedation then was reversed with flumazenil after ADFT testing. Two shocks at the ADFT (or a 3-J shock if ADFT >3 J) were administered to the patient using each waveform in random order. Pain perception was assessed using both a visual scale and a numerical score. ADFTs were above the pain threshold in 17 (94%) of 18 patients, even though the ADFT with the 500-,F waveform was <100 V in 63% of the patients. Pain perception was comparable for both waveforms (numerical score: 6.5 ± 2.4 vs 6.3 ± 2.6; visual scale: 5.4 ± 2.6 vs 5.2 ± 3.1; P = NS, 500-,F vs 60-,F). The second shock was perceived as more painful in 88% of the patients, independent of the waveform used. Conclusion: Despite a 66% lower peak voltage and a 40% lower energy, the 40% tilt, 500-,F capacitor biphasic waveform did not change the pain perceived by the patient during delivery of internal cardioversion shocks. Pain perception for internal cardioversion probably is not influenced by peak voltage alone and increases with the number of applied shocks. (J Cardiovasc Electrophysiol, Vol. 14, pp. 837-840, August 2003) [source]

New Approach to Biphasic Waveforms for Internal Defibrillation:

JOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 8 2000
Fully Discharging Capacitors
Internal Defibrillation with Fully Discharging Capacitors. Introduction: The use of two independent, fully discharging capacitors for each phase of a biphasic defibrillation waveform may lead to the design of a simpler, smaller, internal defibrillator. The goal of this study was to determine the optimal combination of capacitor sizes for such a waveform. Methods and Results: Eight full-discharge (95/95% tilt), biphasic waveforms produced by several combinations of phase-1 capacitors (30, 60, and 90 ,F) and phase-2 capacitors (1/3, 2/3, and 1.0 times the phase-1 capacitor) were tested and compared to a single-capacitor waveform (120 ,F, 65/65% tilt) in a pig ventricular fibrillation model (n = 12, 23 ± 2 kg). In the full-discharge waveforms, phase-2 peak voltage was equal to phase-1 peak voltage. Shocks were delivered between a right ventricular lead and a left pectoral can electrode. E50s and V50s were determined using a ten-step Bayesian process. Full-discharge waveforms with phase-2 capacitors of ,40 ,F had the same E50 (6.7 ± 1.7 J to 7.3 ± 3.9 J) as the single-capacitor truncated waveform (7.3 ± 3.7 J), whereas waveforms with phase-2 capacitors of ,60 ,F had an extremely high E50 (14.5 ± 10.8 J or greater, P < 0.05). Moreover, of the former set of energy-efficient waveforms, those with phase-1 capacitors of ,60 ,F additionally exhibited V50s that were equivalent to the V50 of the single-capacitor waveform (344 ± 65 V to 407 ± 50 V vs 339 ± 83 V). Conclusion: Defibrillation efficacy can be maintained in a full-discharge, two-capacitor waveform with the proper choice of capacitors. [source]

A Pilot Study of a Low-Tilt Biphasic Waveform for Transvenous Cardioversion of Atrial Fibrillation: Improved Efficacy Compared with Conventional Capacitor-Based Waveforms in Patients

PACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 8 2008
BENEDICT M. GLOVER M.D.
Background:The optimal waveform tilt for defibrillation is not known. Most modern defibrillators used for the cardioversion of atrial fibrillation (AF) employ high-tilt, capacitor-based biphasic waveforms. Methods:We have developed a low-tilt biphasic waveform for defibrillation. This low-tilt waveform was compared with a conventional waveform of equivalent duration and voltage in patients with AF. Patients with persistent AF or AF induced during a routine electrophysiology study (EPS) were randomized to receive either the low-tilt waveform or a conventional waveform. Defibrillation electrodes were positioned in the right atrial appendage and distal coronary sinus. Phase 1 peak voltage was increased in a stepwise progression from 50 V to 300V. Shock success was defined as return of sinus rhythm for ,30 seconds. Results:The low-tilt waveform produced successful termination of persistent AF at a mean voltage of 223 V (8.2 J) versus 270 V (6.7 J) with the conventional waveform (P = 0.002 for voltage, P = ns for energy). In patients with induced AF the mean voltage for the low-tilt waveform was 91V (1.6 J) and for the conventional waveform was 158 V (2.0 J) (P = 0.005 for voltage, P = ns for energy). The waveform was much more successful at very low voltages (less than or equal to 100 V) compared with the conventional waveform (Novel: 82% vs Conventional 22%, P = 0.008). Conclusion:The low-tilt biphasic waveform was more successful for the internal cardioversion of both persistent and induced AF in patients (in terms of leading edge voltage). [source]