Encircling overlapping multipulse shock waveforms for transthoracic defibrillation

The impact of double sequential shock timing on outcomes during refractory out-of-hospital cardiac arrest

BACKGROUND

Animal studies suggest the efficacy of double sequential external defibrillation (DSED) may depend on the interval between the two shocks, or "DSED interval". No human studies have examined this concept.

OBJECTIVES

To determine the relationship between DSED interval and termination of ventricular fibrillation (VFT), return of spontaneous circulation (ROSC), survival to hospital discharge, and favourable neurological status (MRS ≤ 2) for patients in refractory VF.

METHODS

We performed a retrospective review of adult (≥18 years) out-of-hospital cardiac arrest between January 2015 and May 2022 with refractory VF who received ≥1 DSED shock. DSED interval was divided into four pre-defined categories. We examined the association between DSED interval and patient outcomes using general estimated equation logistic regression or Fisher's exact test.

RESULTS

Among 106 included patients, 303 DSED shocks were delivered (median 2, IQR 1-3). DSED intervals of 75-125 ms (OR 0.39, 95% CI 0.16-0.98), 125-500 ms (OR 0.36, 95% CI 0.16-0.82), and >500 ms (OR 0.27, 95% CI 0.11-0.63) were associated with lower probability of VF termination compared to <75 ms interval. DSED interval of >75 ms was associated with lower probability of ROSC compared to <75 ms interval (OR 0.37, 95% CI 0.14-0.98). No association was noted between DSED interval and survival to hospital discharge or neurologic outcome.

CONCLUSIONS

Among patients in refractory VF a DSED interval of less than 75 ms was associated with improved rates of VF termination and ROSC. No association was noted between DSED interval and survival to hospital discharge or neurologic outcome.

DOuble SEquential External Defibrillation for Refractory Ventricular Fibrillation (DOSE VF): study protocol for a randomized controlled trial

Background

Despite high-quality cardiopulmonary resuscitation (CPR), early defibrillation, and antiarrhythmic medications, some patients remain in refractory ventricular fibrillation (VF) during out-of-hospital cardiac arrest. These patients have worse outcomes compared to patients who respond to initial treatment. Double sequential external defibrillation (DSED) and vector change (VC) defibrillation have been proposed as viable options for patients in refractory VF. However, the evidence supporting the use of novel defibrillation strategies is inconclusive. The objective of this study is to compare two novel therapeutic defibrillation strategies (DSED and VC) against standard defibrillation for patients with treatment refractory VF or pulseless ventricular tachycardia (pVT) during out-of-hospital cardiac arrest.

Research question

Among adult (≥ 18 years) patients presenting in refractory VF or pulseless ventricular tachycardia (pVT) during out-of-hospital cardiac arrest, does DSED or VC defibrillation result in greater rates of survival to hospital discharge compared to standard defibrillation?

Methods

This will be a three-arm, cluster randomized trial with repeated crossover conducted in six regions of Ontario, Canada (Peel, Halton, Toronto, Simcoe, London, and Ottawa), over 3 years. All adult (≥ 18 years) patients presenting in refractory VF (defined as patients presenting in VF/pVT and remaining in VF/pVT after three consecutive standard defibrillation attempts during out-of-hospital cardiac arrest of presumed cardiac etiology will be treated by one of three strategies: (1) continued resuscitation using standard defibrillation, (2) resuscitation involving DSED, or (3) resuscitation involving VC (change of defibrillation pads from anterior-lateral to anterior-posterior pad position) defibrillation. The primary outcome will be survival to hospital discharge. Secondary outcomes will include return of spontaneous circulation (ROSC), VF termination after the first interventional shock, VF termination inclusive of all interventional shocks, and number of defibrillation attempts to obtain ROSC. We will also perform an a priori subgroup analysis comparing rates of survival for those who receive “early DSED,” or first DSED shock is shock 4–6, to those who receive “late DSED,” or first DSED shock is shock 7 or later.

Discussion

A well-designed randomized controlled trial employing a standardized approach to alternative defibrillation strategies early in the treatment of refractory VF is urgently required to determine if the treatments of DSED or VC defibrillation impact clinical outcomes.

Trial registration

ClinicalTrials.gov NCT04080986. Registered on 6 September 2019.

Supplementary information

The online version contains supplementary material available at 10.1186/s13063-020-04904-z.

The impact of double sequential external defibrillation on termination of refractory ventricular fibrillation during out-of-hospital cardiac arrest

BACKGROUND

Despite significant advances in resuscitation efforts, there are some patients who remain in ventricular fibrillation (VF) after multiple shocks during out-of-hospital cardiac arrest (OHCA). Double sequential external defibrillation (DSED) has been proposed as a treatment option for patients in refractory VF.

OBJECTIVE

We sought to explore the relationship between type of defibrillation (standard vs DSED), the number of defibrillation attempts provided and the outcomes of VF termination and return of spontaneous circulation (ROSC) for patients presenting in refractory VF.

METHODS

We performed a retrospective review of all treated adult OHCA who presented in VF and received a minimum of three successive standard defibrillations over a three-year period beginning on January 1, 2015 in four Canadian EMS agencies. Using ambulance call reports and defibrillator files, we compared rates of VF termination (defined as the absence of VF at the rhythm check following defibrillation and two minutes of CPR) and VF termination to ROSC for patients who received standard defibrillation and those who received DSED (after on-line medical consultation). Cases with public access defibrillation, those with do not resuscitate orders, and those who presented in VF but terminated VF prior to three shocks were excluded.

RESULTS

Of the 252 patients included, 201 (79.8%) received standard defibrillation only and 51 (20.2%) received at least one DSED. Overall, VF termination was similar between standard defibrillation and DSED (78.1% vs. 76.5%; RR: 1.0; 95% CI: 0.8-1.2). In our shock-based analysis, when early defibrillation attempts were considered (defibrillation attempt 4-8), VF termination was higher for those receiving DSED compared to standard defibrillation (29.4% vs. 17.5%; RR: 1.7; 95% CI: 1.1-2.6). Overall, VF termination to ROSC was similar between standard defibrillation and DSED (21.4% vs. 17.6%; RR: 0.8; 95% CI: 0.4-1.6). Additionally, when early defibrillation attempts were considered (defibrillation attempt 4-8), ROSC was higher for those receiving DSED compared to standard defibrillation (15.7% vs. 5.4%; RR: 2.9; 95% CI: 1.4-5.9). When late defibrillation attempts were considered (defibrillation attempt 9-17), VF termination was higher for those receiving DSED compared to standard defibrillation (31.2% vs. 17.1%; RR: 1.8; 95% CI: 1.1-3.0), but ROSC was rare regardless of defibrillation strategy. When DSED terminated VF into ROSC, it did so with a single DSED attempt in 66.7% of cases.

CONCLUSIONS

Our observational findings suggest that while overall VF termination and ROSC are similar between standard defibrillation and DSED, earlier DSED may be associated with improved rates of VF termination and ROSC compared to standard defibrillation for refractory VF. A randomized controlled trial is required to assess the impact of early application of DSED on patient-important outcomes.

Cardiomyocyte lethality by multidirectional stimuli

Multidirectional defibrillation protocols have shown better efficiency than monodirectional; still, no testing was performed to assess cell lethality. We investigated lethality of multidirectional defibrillator-like shocks on isolated cardiomyocytes. Cells were isolated from adult male Wistar rats and plated into a perfusion chamber. Electrical field stimulation threshold (E_T) was obtained, and cells were paced with suprathreshold bipolar electrical field (E) pulses. Either one monodirectional high-intensity electrical field (HEF) pulse aligned at 0° (group Mono0) or 60° (group Mono60) to cell major axis or a multidirectional sequence of three HEF pulses aligned at 0°, 60°, and 120° each was applied. If cell recovered from shock, pacing was resumed, and a higher amplitude HEF, proportional to E_T, was applied. The sequence was repeated until cell death. Lethality curves were built by means of survival analysis from sub-lethal and lethal E. Non-linear fit was performed, and E values corresponding to 50% probability of lethality (E50) were compared. Multidirectional groups presented lethality curves similar to Mono0. Mono60 displayed the highest E50. The novel data endorse the idea of multidirectional stimuli being safer because their effects on lethality of individual cells were equal to a single monodirectional stimulus, while their defibrillatory threshold is lower. Graphical abstract Monodirectional and multidirectional lethality protocol comparison on isolated rat cardiomyocytes. The heart image is a derivative of "3D Heart in zBrush" ( https://vimeo.com/65568770 ) by Laloxl, used under CC BY 3.0 ( https://creativecommons.org/licenses/by/3.0/legalcode )/image extracted from original video.

Effects of biphasic waveforms on outcomes of cardiopulmonary resuscitation in a porcine model of prolonged cardiac arrest

OBJECTIVES

The effects of two clinically available biphasic waveforms on the success of defibrillation and postresuscitation myocardial dysfunction after prolonged ventricular fibrillation were compared with two newly designed dual-path sequential and simultaneous rectilinear biphasic waveforms. Defibrillation via sequential pulses and encircling, overlapping multiple pathway may depolarize a larger myocardial mass and facilitate transthoracic defibrillation.

DESIGN

Animal study.

SETTING

Experimental laboratory.

SUBJECTS

Thirty-two 40 +/- 3 kg pigs.

INTERVENTIONS

Ventricular fibrillation was ischemically induced in 32 pigs. After 7 mins of untreated ventricular fibrillation, cardiopulmonary resuscitation was initiated and continued for 5 mins. Animals were then randomized to receive up to three shocks with a) single-path rectilinear biphasic waveform; b) single-path biphasic truncated exponential waveform; c) dual-path rectilinear biphasic sequential defibrillation; or d) dual-path rectilinear biphasic simultaneous defibrillation.

MEASUREMENTS AND MAIN RESULTS

Rectilinear biphasic, dual-path sequential defibrillation, and simultaneous defibrillation had significantly fewer shocks (1.1 +/- 0.4, 1.4 +/- 0.5, 1.3 +/- 0.7, respectively) before restoration of spontaneous circulation than biphasic truncated exponential waveform (2.6 +/- 1.4, p < .005) and less postresuscitation myocardial dysfunction (p < .05). Also, dual-path sequential defibrillation had higher postresuscitation ejection fraction than rectilinear biphasic and dual-path simultaneous defibrillation (p < .005).

CONCLUSIONS

The energy requirements for terminating ischemically induced ventricular fibrillation were significantly lower and minimized early postresuscitation myocardial dysfunction in the rectilinear biphasic, dual-path sequential defibrillation, and simultaneous defibrillation than the biphasic truncated exponential waveform. Dual-path sequential defibrillation had less postresuscitation myocardial dysfunction than rectilinear biphasic and dual-path simultaneous defibrillation, but at 72 hrs these differences were no longer significant.

Quadriphasic waveforms are superior to triphasic waveforms for transthoracic defibrillation in a cardiac arrest swine model with high impedance

BACKGROUND

We have demonstrated previously that triphasic waveform shocks were superior to biphasic waveform shocks for transthoracic defibrillation. Our purpose was to compare the efficacy and safety of quadriphasic versus triphasic shocks for transthoracic defibrillation in a porcine model.

METHODS

Sixteen adult swine (19-25 kg, mean: 21.5 kg) were deeply anesthetized and intubated. To simulate impedance of the human chest, fixed electrical resistors (25 or 50 ohms) was placed in series with the defibrillator and the chest of each pig. After 30 s of electrically induced VF, each pig received transthoracic shocks, using either a truncated exponential triphasic waveform (5 ms positive pulse duration, 5 ms negative pulse duration and 5 ms positive pulse duration, total waveform duration 15 ms) or a quadriphasic waveform (5/5/5/5 ms, total waveform duration 20 ms). Each pig received transthoracic triphasic and quadriphasic shocks at three selected energy levels (50, 100 and 150 J) in random sequence. Four shocks were delivered at each energy level to construct an energy versus % success curve. Success was defined as VF termination at 5 s after shock. The total shocks were divided into three groups based on the delivered energy actually delivered to the animal: <40, 40-65 and >65 J. Delivered energy = (animal impedance/total impedance) times selected energy of the shock.

RESULTS

For high-impedance animals (86-102 ohms), quadriphasic waveform shocks achieved significantly higher percent shock success than triphasic shocks for the termination of VF at the energy levels of >65 J actually delivered (quadriphasic 72.7+/-12.2%, triphasic 38.9+/-7.7%, p<0.02). No differences in the shock success between quadriphasic and triphasic waveforms were found for other two energy levels. There were no differences in ventricular tachycardia or asystole after shocks between quadriphasic and triphasic waveforms.

CONCLUSION

In this porcine model, 20 ms (5/5/5/5) quadriphasic shocks were superior to 15 ms (5/5/5) triphasic shocks for transthoracic defibrillation in animals with impedances that simulated high impedance in humans.

Automatic external defibrillators: changing the way we manage ventricular fibrillation

OBJECTIVE

To discuss recent developments in automatic defibrillation and to review the evidence that first-responders equipped with automatic external defibrillators (AEDs) improve survival from out-of-hospital cardiac arrest.

DATA SOURCES

MEDLINE search from 1966 to 1999 (articles in English only) and examination of bibliographies.

STUDY SELECTION

Published studies of out-of-hospital cardiac arrest and first-responders equipped with AEDs. Studies had to have a control group and to report survival to hospital discharge from ventricular fibrillation (VF).

DATA EXTRACTION

Six studies met the selection criteria (two prospective randomised trials, two prospective controlled trials, and one cohort study and one retrospective study, both with historical controls).

DATA SYNTHESIS

A random effects meta-analysis of odds ratios for survival from VF.

CONCLUSIONS

Meta-analysis suggests that equipping first-responders with AEDs increases the probability of survival to hospital discharge after out-of-hospital cardiac arrest (odds ratio, 1.74; 95% CI, 1.27-2.38; P < 0.001). However, most of the studies lacked sufficient power to draw definitive conclusions. Until the impact of wide deployment of AEDs is fully understood, first-responder defibrillation in Australia should only occur as part of coordinated multicentre research studies.