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. 2023 Mar 14;18(3):e0281340.
doi: 10.1371/journal.pone.0281340. eCollection 2023.

Defibrillation effectiveness and safety of the shock waveform used in a contemporary wearable cardioverter defibrillator: Results from animal and human studies

Marye J Gleva  1 , Joseph Sullivan  2 , Thomas C Crawford  3 , Greg Walcott  4 , Ulrika Birgersdotter-Green  5 , Kelley R Branch  6 , Rahul N Doshi  7 , Kaisa Kivilaid  8 , Kelly Brennan  2 , Ron K Rowbotham  2 , Laura M Gustavson  2 , Jeanne E Poole  6
Affiliations

Defibrillation effectiveness and safety of the shock waveform used in a contemporary wearable cardioverter defibrillator: Results from animal and human studies

Marye J Gleva et al. PLoS One. .

Abstract

Introduction: The wearable cardioverter defibrillator (WCD) is used to protect patients at risk for sudden cardiac arrest. We examined defibrillation efficacy and safety of a biphasic truncated exponential waveform designed for use in a contemporary WCD in three animal studies and a human study.

Methods: Animal (swine) studies: #1: Efficacy comparison of a 170J BTE waveform (SHOCK A) to a 150J BTE waveform (SHOCK B) that approximates another commercially available waveform. Primary endpoint first shock success rate. #2: Efficacy comparison of the two waveforms at attenuated charge voltages in swine at three prespecified impedances. Primary endpoint first shock success rate. #3: Safety comparison of SHOCK A and SHOCK B in swine. Primary endpoint cardiac biomarker level changes baseline to 6 and 24 hours post-shock. Human Study: Efficacy comparison of SHOCK A to prespecified goal and safety evaluation. Primary endpoint cumulative first and second shock success rate. Safety endpoint adverse events.

Results: Animal Studies #1: 120 VF episodes in six swine. First shock success rates for SHOCK A and SHOCK B were 100%; SHOCK A non-inferior to SHOCK B (entire 95% CI of rate difference above -10% margin, p < .001). #2: 2,160 VF episodes in thirty-six swine. Attenuated SHOCK A was non-inferior to attenuated SHOCK B at each impedance (entire 95% CI of rate difference above -10% margin, p < .001). #3: Ten swine, five shocked five times each with SHOCK A, five shocked five times each with SHOCK B. No significant difference in troponin I (p = 0.658) or creatine phosphokinase (p = 0.855) changes from baseline between SHOCK A and SHOCK B. Human Study: Thirteen patients, 100% VF conversion rate. Mild skin irritation from adhesive defibrillation pads in three patients.

Conclusions: The BTE waveform effectively and safely terminated induced VF in swine and a small sample in humans.

Trial registration: Human study clinical trial registration: URL: https://clinicaltrials.gov; Unique identifier: NCT04132466.

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Conflict of interest statement

I have read the journal’s policy and the authors of this manuscript have the following competing interests: One US patent application related to the research presented in this manuscript - Defibrillation Waveforms for a Wearable Cardiac Defibrillator (Pub. No. US 2021/0196965 A1; Pub. Date: Jul 1, 2021) Taylor TG and Medema DK; “ASSURE WCD System” is a product of Kestra Medical Technologies, Inc. There are no other patents, products in development or marketed products to declare. Joseph Sullivan, Kelly Brennan, Ron K. Rowbotham and Laura M. Gustavson are employees and stockholders of Kestra Medical Technologies, Inc.; Marye J. Gleva reports modest speaking honoraria from ZOLL Medical and Gaffney Events Educational Trust, modest consulting honoraria from Kestra Medical Technologies, Inc., compensation from the University of Rochester (Rochester NY) and Prairie Education and Research Institute (Springfield, IL) for research committee participation; Greg Walcott reports institutional research support from Kestra Medical Technologies, Inc.; Kelley R. Branch reports institutional research grant support from Kestra Medical Technologies, Inc.; Jeanne E. Poole reports institutional research grant support from Kestra Medical Technologies, Inc., Biotronik and Atricure, compensation from the University of Rochester (Rochester NY) for research committee participation and from the Heart Rhythm Society for Core Concepts Educational Course and for Editor-in-Chief for the Heart Rhythm O2Journal. Jeanne Poole also reports honoraria from Medtronic for service on the Executive Committee for the WRAP_IT study and from Boston Scientific for participation on the Medical Advisory Board. The remaining authors declare no conflict of interest. This support does not alter our adherence to PLOS ONE policies on sharing data and materials.

Figures

Fig 1
Fig 1. Flowchart of the defibrillation safety and efficacy studies.
Flowchart describing objectives, endpoints and sample sizes for the three animal studies and one human study providing a comprehensive assessment of defibrillation safety and efficacy of the new BTE waveform designed for use in a WCD.
Fig 2
Fig 2. Typical Biphasic Truncated Exponential (BTE) shock waveform.
Graphical representation of the typical BTE waveform showing current as a function of time. I1 = Peak current, I2 = Phase 1 trailing edge current, I3 = Phase 2 peak current, I4 = Phase 2 trailing edge current, T1 = Phase 1 period, T2 = Phase 2 period, T3 = Interphase delay.
Fig 3
Fig 3. Animal Study #1 experimental setup.
Image illustrating laboratory setup to enable ventricular fibrillation (VF) induction, monitoring and defibrillation in swine. ECG = Electrocardiogram.
Fig 4
Fig 4. Animal Study #1 shock sequence.
Figure illustrating shock sequence and randomization of shock type for each animal.
Fig 5
Fig 5. Animal Study #2 experimental setup.
Image illustrating laboratory setup to enable ventricular fibrillation (VF) induction, monitoring and defibrillation in swine. ECG = Electrocardiogram, att = attenuated.
Fig 6
Fig 6. Animal Study #2 charge voltage determination.
Image illustrating the process to establish the charge voltage for 50% defibrillation success of attSHOCK A and the subsequent calculation of the charge voltage for attSHOCK B at each target impedance. NSR = normal sinus rhythm, att = attenuated.
Fig 7
Fig 7. Animal Study #2 shock sequence.
Figure illustrating attSHOCK A and attSHOCK B defibrillation shock sequence for each animal. att = attenuated.
Fig 8
Fig 8. Animal Study #3 experimental setup.
Image illustrating laboratory setup to enable shock delivery during normal sinus rhythm and monitoring in swine. ECG = Electrocardiogram.
Fig 9
Fig 9. Animal Study #3 shock sequence.
Figure illustrating shock sequence and randomization of shock type for each animal.
Fig 10
Fig 10. Human study experimental setup.
Anterior and posterior views of the thorax for the human study of the 170J BTE waveform (SHOCK A) in the electrophysiology laboratory. The test system showing the WCD defibrillation unit and adapter module is shown in the lower left. Two sets of defibrillation patches are shown, with the test system connected to the yellow patches and rescue defibrillator connected to the gray patches. The test system pads (yellow) were applied in standard anterior and posterior positions, with the anterior pad in the left parasternal region and the posterior pad in the left infrascapular position. The rescue defibrillation pads (gray) were placed in the standard anterior-apical position on the subject’s torso for defibrillation from a commercially available external defibrillator. Surface ECG was monitored with electrophysiology laboratory recording equipment. WCD = wearable cardioverter defibrillator; ICD = implantable cardioverter defibrillator; EP = Electrophysiology.
Fig 11
Fig 11. Animal Study #2 results.
(A) Observed first shock success rates for termination of ventricular fibrillation with attSHOCK A (blue) and attSHOCK B (red) at 50, 85 and 125 ohm impedances. (B) Difference in observed first shock success rates (attSHOCK A–attSHOCK B). At each of the three impedance levels, the mean difference (dot) and the 95% confidence interval of the difference (whiskers) in first shock success rates is shown. attSHOCK A was non-inferior to attSHOCK B as the entire 95% confidence interval of the difference (attSHOCK A–attSHOCK B) in first shock success rates was above the -10% prespecified non-inferiority margin (dotted line). At 85 and 125 ohms, the first shock success rate of attSHOCK A was superior to attSHOCK B as the entire 95% confidence interval of the difference in first shock success rates was above 0%. See text for details.
Fig 12
Fig 12. Human study consort flowchart.
Of the 88 patients assessed for eligibility, 13 met inclusion criteria and consented to enroll in the study. Defibrillation study procedure was completed on all 13 enrolled patients and included in the Intention-to-Treat analysis. Study monitoring identified that an enrolled patient had been prescribed Amiodarone during an emergency room visit (three weeks prior to study enrollment) and continued taking it for 6 days (protocol eligibility deviation). Twelve patients were included in the Per-Protocol analysis.
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