Biphasic Truncated Exponential Research Articles

Automated external defibrillator electrode size and termination of ventricular fibrillation in out-of-hospital cardiac arrest

Smaller electrodes allow more options for design of automated external defibrillator (AED) user interfaces. However, previous studies employing monophasic-waveform defibrillators found that smaller electrode sizes have lower defibrillation shock success rates. We hypothesize that, for impedance-compensated, biphasic truncated exponential (BTE) shocks, smaller electrodes increase transthoracic impedance (TTI) but do not adversely affect defibrillation success rates. Methods and ResultsIn this prospective before-and-after clinical study, Amsterdam police and firefighters used AEDs with BTE waveforms: an AED with larger electrodes in 2016–2017 (113 cm2), and an AED with smaller electrodes in 2017–2020 (65 cm2). We analyzed 157 and 178 patient cases with an initial shockable rhythm where the larger and smaller electrodes were used, respectively. A single 200-J shock terminated ventricular fibrillation (VF) in 86% of patients treated with large electrodes and 89% of patients treated with smaller electrodes. Small electrodes had a non-inferior first shock defibrillation success rate compared to large electrodes, with a difference of 3% (95% CI: –3% −9%) with the lower confidence limit remaining above the defined non-inferiority threshold. TTI was significantly higher for the smaller electrodes (median: 100 Ω) compared to the larger electrodes (median: 88 Ω) (p < 0.001). ConclusionsFor AEDs with impedance-compensating BTE waveforms, TTI was higher for smaller electrodes than the large electrode electrodes. Overall defibrillation shock success for AEDs with smaller electrodes was non-inferior to the AEDs with larger electrodes.

A Randomized Comparison of Delivered Energy in Cardioversion of Atrial Fibrillation: Biphasic Truncated Exponential Versus Pulsed Biphasic Waveforms.

A few randomized trials have compared impedance-compensated biphasic defibrillators in clinical use. We aim to compare pulsed biphasic (PB) and biphasic truncated exponential (BTE) waveforms in a non-inferiority cardioversion (CVS) study. This was a prospective monocentric randomized clinical trial. Eligible patients admitted for elective CVS of atrial fibrillation (AF) between February 2019 and March 2020 were alternately randomized to treatment with either a PB defibrillator (DEFIGARD TOUCH7, Schiller Médical, Wissembourg, France) or a BTE high-energy (BTE-HE) defibrillator (LIFEPAK15, Physio-Control Inc., Redmond, WA, USA). Fixed-energy protocol (200–200–200 J) was administered. CVS success was accepted if sinus rhythm was restored at 1 min post-shock. The study design considered non-inferiority testing of the primary outcome: cumulative delivered energy (CDE). Seventy-three out of 78 randomized patients received allocated intervention: 38 BTE-HE (52%), 35 PB (48%). Baseline characteristics were well-balanced between groups (p > 0.05). Both waveforms had similar CDE (mean ± standard deviation, 95% confidence interval): BTE-HE (253.9 ± 120.2 J, 214–293 J) vs. PB (226.0 ± 109.8 J, 188–264 J), p = 0.31. Indeed, effective PB shocks delivered significantly lower energies by mean of 25.6 J (95% CI 24–27.1 J, p < 0.001). Success rates were similar (BTE-HE vs. PB): 1 min first-shock (84.2% vs. 82.9%), 1 min CVS (97.4% vs. 94.3%), 2 h CVS (94.7% vs. 94.3%), 24 h CVS (92.1% vs. 94.3%), p > 0.05. Safety analysis did not find CVS hazards, reporting insignificant changes of myocardial-specific biomarkers, transient and rare ST-segment deviations, and no case of harmful tachyarrhythmias and apnea. Cardioversion of AF with fixed-energy protocol 200–200–200 J was highly efficient and safe for both PB and BTE-HE waveforms. These similar performances were achieved despite differences in the waveforms’ technical design, associated with significantly lower delivered energy for the effective PB shocks. Clinical Trial Registration: Registration number: NCT04032678, trial register: ClinicalTrials.gov.

Cardioversion of Atrial Fibrillation and Flutter: Comparative Study of Pulsed vs. Low Energy Biphasic Truncated Exponential Waveforms.

Despite the widespread use of biphasic waveforms for cardioversion and defibrillation, the efficacy and safety of shocks has only been compared in a few studies. This retrospective study aims at comparing the efficacy and safety of biphasic truncated exponential (BTE) pulsed energy (PE) waveform with a BTE low energy (LE) waveform for cardioversion of atrial fibrillation (AF) and atrial flutter (AFL). The treatment energies were following an escalating protocol for PE waveform (120-200-200J in AF and 30-120-200J in AFL) and LE waveform (100-200-200J in AF and 30-100-200J in AFL). The protocol was stopped at successful cardioversion (sinus rhythm at 1 minute post-shock), otherwise after the 3rd shock. If the 3rd BTE shock failed, a monophasic shock of 360J was delivered. From May 2008 to November 2017, 193 patients (153 PE, 40 LE) were included in the study. Both groups significantly differed in a few characteristics, including chest circumference (p<0.05). After adjustment, the success rate was not significantly different for the two waveforms (94.5% PE vs 92.5% LE, Odds Ratio [95% Confidence Interval] = 0.25 [0.03-2.2]).There was no difference in safety: post-shock changes in Hsc-TnI levels were similar (p=0.25). The efficient cumulative energy was particularly related with BSA (β = 131.5, p=0.05), AF/AFL duration (β = 0.24, p=0.01) and gender (β = 61.8, p=0.05). The major clinical implications of this study concern the high success rate of cardioversion with both biphasic pulses and no superiority of LE over PE waveform with an excellent safety profile without post-shock myocardial injuries.

Ascending Defibrillation Waveform Significantly Reduces Myocardial Morphological Damage and InjuryCurrent.

This study tested the hypothesis that a biphasic defibrillation waveform with an ascending first phase (ASC) causes less myocardial damage by pathology and injury current than a standard biphasic truncated exponential (BTE) waveform in a swine model. Although lifesaving, defibrillation shocks have significant iatrogenic effects that reduce their benefit for patient survival. An ASC waveform with an 8-ms linear ramp followed by an additional positive 0.5-ms decaying portion withamplitudes of 20J (ASC 20J) and 25J (ASC 25J) was used. The control was a 25-J BTE conventional waveform (BTE25J) RESULTS: The ASC 20J and ASC 25J shocks were both successful in 6 of 6 pigs, but the BTE 25J was successful in only 6of 14 pigs (p<0.05). Post-shock ST-segment elevation (injury current) in the right ventricular electrode was significantly greater with BTE 25J than with ASC 20J and ASC 25J. With a blinded pathology reading, hemorrhage, inflammation, thrombi, and necrosis 24h post-shock were significantly greater with BTE 25J than with ASC 20J and ASC 25J. Troponin levels were also markedly lower at 3, 4, 5, and 6h post-shock. Defibrillation shocks cause electrophysiological, histological, and biochemical signs of myocardial damage and necrosis. These signs of damage are markedly less for an ASC waveform than for a conventional BTEwaveform.

Cardioversion Efficacy Using Pulsed Biphasic or Biphasic Truncated Exponential Waveforms: A Randomized Clinical Trial.

BackgroundSeveral different defibrillators are currently used for cardioversion and defibrillation of cardiac arrhythmias. The efficacy of a novel pulsed biphasic (PB) waveform has not been compared to other biphasic waveforms. Accordingly, this study aims to compare the efficacy and safety of PB shocks with biphasic truncated exponential (BTE) shocks in patients undergoing cardioversion of atrial fibrillation or ‐flutter.Methods and ResultsThis prospective, randomized study included patients admitted for elective direct current cardioversion. Patients were randomized to receive cardioversion using either PB or BTE shocks. We used escalating shocks until sinus rhythm was obtained or to a maximum of 4 shocks. Patients randomized to PB shocks received 90, 120, 150, and 200 J and patients randomized to BTE shocks received 100, 150, 200, and 250 J, as recommended by the manufacturers. In total, 69 patients (51%) received PB shocks and 65 patients (49%) BTE shocks. Successful cardioversion, defined as sinus rhythm 4 hours after cardioversion, was achieved in 43 patients (62%) using PB shocks and in 56 patients (86%) using BTE shocks; ratio 1.4 (95% CI 1.1–1.7) (P=0.002). There was no difference in safety (ie, myocardial injury judged by changes in high‐sensitive troponin I levels; ratio 1.1) (95% CI 1.0–1.3), P=0.15. The study was terminated prematurely because of an adverse event.ConclusionsCardioversion using a BTE waveform was more effective when compared with a PB waveform. There was no difference in safety between the 2 waveforms, as judged by changes in troponin I levels.Clinical Trial Registration URL: http://www.clinicaltrials.gov. Unique identifier: NCT02317029.

BIPHASIC TRUNCATED EXPONENTIAL WAVEFORM IS SUPERIOR COMPARED TO PULSED BIPHASIC WAVEFORM IN CARDIOVERTING ATRIAL FIBRILLATION AND ATRIAL FLUTTER: A RANDOMIZED CONTROLLED TRIAL

Several different biphasic waveforms are currently in clinical use, but few studies have compared their efficiency. The aim of this study was to compare the efficiency of a biphasic truncated exponential (BTE) waveform with a pulsed biphasic waveform (PBW) in patients undergoing elective

Average current is better than peak current as therapeutic dosage for biphasic waveforms in a ventricular fibrillation pig model of cardiac arrest

ObjectiveDefibrillation current has been shown to be a clinically more relevant dosing unit than energy. However, the effects of average and peak current in determining shock outcome are still undetermined. The aim of this study was to investigate the relationship between average current, peak current and defibrillation success when different biphasic waveforms were employed. MethodsVentricular fibrillation (VF) was electrically induced in 22 domestic male pigs. Animals were then randomized to receive defibrillation using one of two different biphasic waveforms. A grouped up-and-down defibrillation threshold-testing protocol was used to maintain the average success rate of 50% in the neighborhood. In 14 animals (Study A), defibrillations were accomplished with either biphasic truncated exponential (BTE) or rectilinear biphasic waveforms. In eight animals (Study B), shocks were delivered using two BTE waveforms that had identical peak current but different waveform durations. ResultsBoth average and peak currents were associated with defibrillation success when BTE and rectilinear waveforms were investigated. However, when pathway impedance was less than 90Ω for the BTE waveform, bivariate correlation coefficient was 0.36 (p=0.001) for the average current, but only 0.21 (p=0.06) for the peak current in Study A. In Study B, a high defibrillation success (67.9% vs. 38.8%, p<0.001) was observed when the waveform delivered more average current (14.9±2.1A vs. 13.5±1.7A, p<0.001) while keeping the peak current unchanged. ConclusionIn this porcine model of VF, average current was better than peak current to be an adequate parameter to describe the therapeutic dosage when biphasic defibrillation waveforms were used.The institutional protocol number: P0805.

Abstract 215: First Shock Success Rates Across Waveforms and Energy Levels in Adult Cardiac Arrest: A Systematic Review and Meta-analysis

Objectives: Current guidelines advise a single biphasic shock followed by chest compressions; however, it is unclear if this applies to all waveforms and energy levels. We conducted a systematic review and meta-analysis of the literature to determine the comparative success rates for single-shock defibrillation across waveforms evaluated in out-of-hospital cardiac arrest patients presenting in Ventricular Fibrillation. Methods: A comprehensive search strategy was used across Embase, Medline, Cochrane libraries, dissertation abstracts and clinicaltrials.gov, and unpublished data was sought. Two investigators independently reviewed titles, abstracts and full texts in a hierarchical manner for study eligibility with a quadratic kappa score at each level. Two authors abstracted data independently, and the quality of the articles was assessed using the Jadad scale. Outcomes were termination of fibrillation to any rhythm (TOF), return of organized rhythm (ROOR) and return of spontaneous circulation (ROSC). Results: A total of 3,281 potentially relevant citations were identified and of these 7 RCTs were selected with Kappa values of titles 0.53, abstract 0.71, and article 0.94. Mean quality scores varied from 1-2.5/3. First-biphasic shock success (pooled mean) for TOF were similar: Biphasic Truncated Exponential (BTE) 200J 90.5%, BTE 150J 89.9%, Rectilinear Biphasic (RLB) 120J 84.9% but were lower and divergent for both ROOR BTE 200J 43%, BTE 150J 38%, RLB 23% and ROSC; BTE 200J 39%, BTE 150J 78%, RLB 46%. Median time to first shock (min) varied across trials (5.1 BTE 200/150J, 10.4 RLB) and may contribute to observed differences. Conclusion: First shock success rates as measured by the industry standard of TOF do not significantly differ across biphasic waveforms and energy levels.

GENERATION OF RECTANGULAR BIPHASIC WAVEFORM TO DECREASE DEFIBRILLATION THRESHOLD FOR EXTERNAL DEFIBRILLATOR

Studies have shown that defibrillation threshold for current amplitude of biphasic truncated exponential (BTE) waveform has a hyperbolic strength–duration relationship. Theoretical and experimental results have shown that decreasing the tilt of BTE waveforms decreases the defibrillation threshold. On the other hand, low peak current waveform reduces probability of myocardium damage and burn. Therefore, achieving a waveform with low tilt and low peak current is desired. All DC defibrillators use a capacitor to store and deliver required energy. Because of capacitor discharging nature, the tilt of waveforms is high. In rectilinear biphasic waveform (RBW), which was generated by ZOLL M-series defibrillator, the tilt of the first phase was decreased using an adjustable resistor connected in series with current path. But the defibrillator cannot keep the current constant in the second phase and in the both phases for high transthoracic impedances (TTI) either. In this paper, for solving these problems, a circuit that generates rectangular biphasic waveform is designed. In this circuit, five resistors are used and connected in series. Then an IGBT switch is connected to each resistor in parallel. Also, control of minimum current ripple is applied in order to decide which resistors should be worked in each time. The circuit is simulated in MATLAB/Simulink and a prototype model is constructed. Results demonstrate that the tilt of the waveform is notably reduced to a value less than 10%.

Automated external defibrillators: Comparison of different waveformsStatus: PendingCategory: Defibrillation

Introduction: Automated External Defibrillators (AEDs) use Biphasic Truncated Exponential (BTE) and RectiLinear Biphasic (RLB) waveforms. Guidelines (GL) recommend first shock of at least 150J for BTE and 120J for RLB.

A comparison of rectilinear and truncated exponential biphasic waveforms in elective cardioversion of atrial fibrillation: A prospective randomized controlled trial

BackgroundSeveral different biphasic waveforms are used clinically, but few studies have compared their efficacy. The two main waveforms are the biphasic rectilinear (BR) and biphasic truncated exponential (BTE) waveforms, both of which have important differences, particularly at the extremes of transthoracic impedance. ObjectiveTo compare the efficacy of two commonly used defibrillation waveforms in the elective cardioversion of atrial fibrillation. MethodsIn a prospective randomized controlled study, sequential adult patients undergoing elective cardioversion for AF were recruited. Patients were randomized to receive synchronized defibrillation using either a BR or BTE waveform, both using a 50J, 100J, 150J, 200J, 200J selected energy escalating protocol. Failure to cardiovert after the fifth shock was classed as failed defibrillation. The power of this study was 80% with 5% significance level to detect a difference of 20% or greater between groups. Survival analysis was used to compare the total energy delivered to achieve successful cardioversion between groups. ResultsA total of 202 patients were recruited, of which data are complete for 199 (100 BR; 99 BTE). Median number of shocks to achieve cardioversion was 2 for the BR waveform and 3 for the BTE waveform (P=0.059). In the BR waveform group, 95/100 (95.0%) achieved sinus rhythm. In the BTE waveform group, 90/99 (90.9%) achieved sinus rhythm and this group required on average 117.1J more energy to achieve the outcome compared to the BR waveform group (P=0.838). ConclusionsBR and BTE waveforms show similar high efficacy in the elective cardioversion of atrial fibrillation.

Abstract 244: A Prospective Randomized Study of the Efficacy of Rectilinear and Truncated Exponential Biphasic Waveforms in the Elective Cardioversion of Atrial Fibrillation

INTRODUCTION: Several different biphasic waveforms are now available for clinical use. Few studies have compared differences in the efficacy of these waveforms. We compared biphasic rectilinear (BR) and biphasic truncated exponential (BTE) waveforms in their efficacy to cardiovert patients undergoing elective cardioversion for atrial fibrillation. METHODS: In a prospective randomised study, sequential adult patients undergoing elective cardioversion for atrial fibrillation were recruited. Patients were randomised to receive synchronised defibrillation using either a BR or BTE waveform, both using a 50J, 100J, 150J, 200J, 200J selected energy escalating protocol. Successful cardioversion was defined as a return to sinus rhythm immediately after a given shock. Failure to cardiovert after a second 200J shock was classed as failed defibrillation. The power of this study was 80% with 5% significance level to detect a difference of 20% or greater between groups. Survival analysis was used to assess the total energy delivered (and number of shocks) to achieve successful cardioversion between groups. RESULTS: A total of 202 patients were recruited over a four-year period, of which data was complete for 199 (100 BR waveform; 99 BTE waveform). There was no major difference in demographic data (Median age; BR 65.5 yrs, BTE 68.0 yrs: Median weight; BR 90.2 kg, BTE 88.9 kg; Median duration of AF; BR 7.0 months, BTE 6.0 months: Amiodarone; BT 23.8%, BTE 18.2%). Cardioversion rates and associated energy delivered are shown below. Median number of shocks to achieve cardioversion was 2 for the BR waveform and 3 for the BTE waveform (Log rank test, P=0.059). CONCLUSIONS: BR and BTE waveforms show similar efficacy in the elective cardioversion of atrial fibrillation.

Comparison between biphasic quasisinusoidal and truncated waveforms in a swine model of VF

Purpose of the study: To compare the effectiveness of biphasic quasisinusoidal (BQ – Gurvich – Venin) waveform (5 ± 1/6 ± 2 ms) and biphasic truncated exponential (BTE) waveform (4.5 ± 0.45/4.5 ± 0.45 ms) in the termination of VF. Materials and methods: This is a controlled experimental study on piglets (n = 14) weighing 25.2 ± 0.73 kg. After induced anesthesia, animals were placed in a supin position, and the trachea was intubated. After intubation, piglets were ventilated with volume – controlled ventilator. VF was induced by drug administration (adrenalin 4 mg and potassium 7.5% – 5 ml intravenously). Induced VF was shocked at 40 s after onset. Two groups were compared (1. BQ waveform by defibrillator DKI – N – 02; 2. BTE waveform by defibrillator DKI – N – 15Ct Biphasic, Metekol, Ukraine). Results: Impedans was no difference between the two groups (59.25 ± 3.7 Ohms vs 58.5 ± 4.5 Ohms). BTE waveform were more safety than BQ – injury threshold 16.7 ± 0.8 amps vs 12.24 ± 1.2 amps and energy injury threshold 50.9 J ± 1.5 vs 23.2 ± 1.6 J. ROSC was achieved in 100% in both groups. Defibrillation threshold was below in BTE waveform group (12.75 ± 1.4 amps vs 21.87 ± 0.8 amps), as and energy defibrillation threshold (22.5 ± 1.7 J vs 57.5 ± 1.3 J). Gurvich electrotherapeutical index1 (correlation between thresholds injury and defibrillation) for BTE waveform 1.30 ± 0.36 vs 0.56 ± 0.29 for BQ waveform. Conclusion: In a swine model VF BTE waveform were more effective and safety than BQ waveform.

Biphasic Defibrillation Does not Improve Outcomes Compared to Monophasic Defibrillation in Out-of-Hospital Cardiac Arrest

Study Objective. To compare the outcomes of out-of hospital cardiac arrest (OHCA) victims treated with monophasic truncated exponential (MTE) versus biphasic truncated exponential (BTE) defibrillation in an urban EMS system. Methods. We conducted a retrospective review of electronic prehospital andhospital records for victims of OHCA between August 2000 andJuly 2004, including two years before andafter implementation of biphasic defibrillators by the Fresno County EMS agency. Main outcome measures included: return of spontaneous circulation (ROSC), number of defibrillations required for ROSC, survival to hospital discharge, anddischarge to home versus an extended care facility. Results. There were 485 cases of cardiac arrest included. Baseline characteristics between the monophasic andbiphasic groups were similar. ROSC was achieved in 77 (30.6%, 95% CI 25.2–36.5%) of 252 patients in the monophasic group, andin 70 (30.0% 95% CI 24.5–36.2%) of 233 in the biphasic group (p =. 92). Survival to hospital discharge was 12.3% (95% CI 8.8–17%) for monophasic and10.3% (95% CI 7.0–14.9%) for biphasic (p =. 57). Discharge to home was accomplished in 20 (7.9%, 95% CI 5.1–12.0%) of the monophasic, andin 15 (6.4%, 95% CI 3.9–10.4%) of the biphasic group (p =. 60). More defibrillations were required to achieve ROSC (3.5 vs. 2.6, p =. 015) in the monophasic group. Conclusions. We found no difference in ROSC or survival to hospital discharge between MTE andBTE defibrillation in the treatment of OHCA, although fewer defibrillations were required to achieve ROSC in those treated with biphasic defibrillation.

Clinical experience with a low-energy pulsed biphasic waveform in out-of-hospital cardiac arrest

The efficiency of a pulsed biphasic waveform (PBW) was compared with that of biphasic truncated exponential (BTE) waveforms. First defibrillation shock outcome was studied in a population of 104 out-of-hospital cardiac arrest patients in ventricular fibrillation as the presenting rhythm. The call to first shock time was 8.2+/-5.4 min. At 5s post-shock, defibrillation efficiency was 90%. The arrest was witnessed in only 50% of the patients and only 5% received bystander CPR. Despite these limitations 38% of the patients achieved restoration of a spontaneous circulation at departure from scene and 9.8% were discharged from the hospital. These observations demonstrate a rate of first shock success in termination of ventricular fibrillation comparable to that reported with biphasic truncated exponential waveforms in out-of-hospital cardiac arrest.

Porcine defibrillation thresholds with chopped biphasic truncated exponential waveforms

Conventional biphasic truncated exponential (BTE) waveforms have been studied extensively but less is known about "chopping modulated" BTE shocks. Previous studies comparing chopped and unchopped waveforms have found conflicting results. This study compared the defibrillation thresholds (DFTs) of a variety of chopped and unchopped BTE waveforms. Six anesthetized pigs were defibrillated after 15s of electrically induced ventricular fibrillation (VF). Three waveform types were studied: unchopped BTE, "short" duration chopped, and "long" duration chopped waveforms. Each type included waveforms generated with 50, 100, and 200 microF capacitances, giving 9 total waveforms. Shocks were delivered in a standard up-down protocol and the order of the waveforms was randomized. Defibrillation thresholds were calculated using a Bayesian logistic regression model. DFTs of the 50, 100, and 200 microF unchopped waveforms were 122+/-22, 124+/-22, and 126+/-22 J. Short chopped DFTs were at least 75+/-23 J higher than unchopped DFTs. Long chopped DFTs averaged 66+/-20 J more than short chopped DFTs. There is a 99.5% probability that the best of the chopped waveforms has a higher DFT than the worst of the unchopped waveforms, and a 95% probability that the difference is at least 37 J. DFT differences between capacitor values were less than 7 J for all waveform types. When treating swine with short-duration VF, chopped waveforms require more energy to defibrillate than unchopped waveforms. More study is required to assess the performance of chopped waveforms when treating cardiac arrest patients.

Prospective, randomized comparison of two biphasic waveforms for the efficacy and safety of transthoracic biphasic cardioversion of atrial fibrillation

The purpose of this study was to determine if there is a difference in commercially available biphasic waveforms. Although the superiority of biphasic over monophasic waveforms for external cardioversion of atrial fibrillation (AF) is established, the relative efficacy of available biphasic waveforms is less clear. We compared the effectiveness of a biphasic truncated exponential (BTE) waveform and a biphasic rectilinear (BR) waveform for external cardioversion of AF. Patients (N = 188) with AF were randomized to receive transthoracic BR shocks (50, 75, 100, 120, 150, 200 J) or BTE shocks (50, 70, 100, 125, 150, 200, 300, 360 J). Shock strength was escalated until success or maximum energy dose was achieved. If maximum shock strength failed, patients received the maximum shock of the opposite waveform. Analysis included 141 patients (71 BR, 70 BTE; mean age 66.5 +/- 13.7. Forty-seven randomized patients were excluded because of flutter on precardioversion ECG upon blinded review (n = 25), presence of intracardiac thrombus (n = 7), or protocol deviation (n = 15). Groups were similar with regard to clinical and echocardiographic characteristics. The success rate was similar for the two waveforms (93% BR vs 97 BTE, P = .44), although cumulative selected and delivered energy was less in the BTE group. Only AF duration was significantly different between successful and unsuccessful patients. No significant complications occurred. Biphasic waveforms were very effective in transthoracic cardioversion of AF, and complication rates were low. No significant difference in efficacy was observed between BR and BTE waveforms. Impedance was not an important determinant of success for either biphasic waveform.

Efficacy of lower-energy biphasic shocks for transthoracic defibrillation:: A follow-up clinical study

ObjectiveThis clinical study prospectively evaluated the first-shock defibrillation efficacy of 150-joule impedance-compensated, 200-μF biphasic truncated exponential (BTE) shocks in patients with electrically-induced ventricular fibrillation (VF), and compared it with a historical control group treated with 200-J monophasic damped sine (MDS) shocks. MethodsVentricular tachyarrhythmias were induced in patients undergoing electrophysiologic (EP) testing for ventricular arrhythmias or testing of an implantable cardioverter-defibrillator (ICD). A 150-J shock was delivered as the primary therapy to terminate induced arrhythmias in the EP group, and as a “rescue” shock when a single ICD shock failed to terminate the arrhythmias in the ICD group. ResultsNinety-six patients received study shocks. The preshock rhythm was classified as VF in 77 patients and as ventricular tachycardia (VT) in 19 patients. First-shock success rates for VF and VT were 75 out of 77 (97.4%) and 19 out of 19 (100%) for the 150-J BTE compared with the historical control rates of 61 out of 68 (89.7%) and 29 out of 31 (94%) for 200-J MDS. The first-shock success rate for VF treated with 150-J BTE was technically equivalent to that of 200-J MDS (p=0.001). The transthoracic impedance did not vary between groups, yet the peak current delivered by the 150-J BTE shock was about 50% lower. ConclusionsThis study demonstrated that 150-J shocks of this impedance-compensated, 200-μF BTE waveform provided very high efficacy for defibrillation of short duration, electrically-induced VF. These lower-energy biphasic shocks had a success rate equivalent to that of 200-J MDS shocks, and they provided this efficacy while exposing patients to much less current than the monophasic shocks.

A randomized trial comparing monophasic and biphasic waveform shocks for external cardioversion of atrial fibrillation

Background We compared efficacy of and pain felt after biphasic truncated exponential (BTE) and monophasic damped sine (MDS) shocks in patients undergoing external cardioversion of atrial fibrillation (AF). Methods Patients with AF were randomized to BTE or MDS waveform cardioversion. Successive shocks were delivered at 70, 100, 200, and 360 J until successful cardioversion, with one 360 J attempt of the alternate waveform when all 4 shocks failed. Success was determined by blinded over-read of electrocardiograms. Peak current was calculated from energy and impedance. Patients rated their pain at 1 and 24 hours after cardioversion. Results Fourteen of 37 (38%) patients treated with MDS and 34 of 35 (97%) treated with BTE shocks were cardioverted at ≤200 J ( P < .0001). Success rates of MDS versus BTE shocks were 5.4% versus 60% for 70 J, 19% versus 80% for ≤100 J, and 86% versus 97% for ≤360 J. BTE shocks cardioverted with less peak current (14.0 ± 4.3 vs 39.5 ± 11.2 A, P < .0001), less energy (97 ± 47 vs 278 ± 120 J, P < .0001), and less cumulative energy (146 ± 116 vs 546 ± 265 J, P < .0001). Patients felt less pain after BTE than MDS shocks at 1 hour ( P < .0001) and 24 hours ( P < .0001) after cardioversion. Conclusion This BTE waveform is superior to the MDS waveform for cardioversion of AF, requiring much less energy and current, and causing less postprocedural pain.

EFFICACY OF LOWER-ENERGY BIPHASIC SHOCKS FOR TRANSTHORACIC DEFIBRILLATION: A FOLLOW-UP CLINICAL STUDY

Objective. This clinical study prospectively evaluated the first-shock defibrillation efficacy of 150-joule impedance-compensated, 200-µF biphasic truncated exponential (BTE) shocks in patients with electrically-induced ventricular fibrillation (VF), and compared it with a historical control group treated with 200-J monophasic damped sine (MDS) shocks. Methods. Ventricular tachyarrhythmias were induced in patients undergoing electrophysiologic (EP) testing for ventricular arrhythmias or testing of an implantable cardioverter-defibrillator (ICD). A 150-J shock was delivered as the primary therapy to terminate induced arrhythmias in the EP group, and as a “rescue” shock when a single ICD shock failed to terminate the arrhythmias in the ICD group. Results. Ninety-six patients received study shocks. The preshock rhythm was classified as VF in 77 patients and as ventricular tachycardia (VT) in 19 patients. First-shock success rates for VF and VT were 75 out of 77 (97.4%) and 19 out of 19 (100%) for the 150-J BTE compared with the historical control rates of 61 out of 68 (89.7%) and 29 out of 31 (94%) for 200-J MDS. The first-shock success rate for VF treated with 150-J BTE was technically equivalent to that of 200-J MDS (p = 0.001). The transthoracic impedance did not vary between groups, yet the peak current delivered by the 150-J BTE shock was about 50% lower. Conclusions. This study demonstrated that 150-J shocks of this impedance-compensated, 200-µF BTE waveform provided very high efficacy for defibrillation of short duration, electrically-induced VF. These lower-energy biphasic shocks had a success rate equivalent to that of 200-J MDS shocks, and they provided this efficacy while exposing patients to much less current than the monophasic shocks.