Insights From the Ventricular Fibrillation Waveform Into the Mechanism of Survival Benefit From Bystander Cardiopulmonary Resuscitation

Abstract

Background The mechanism by which bystander cardiopulmonary resuscitation (CPR) improves survival following out‐of‐hospital cardiac arrest is unclear. We hypothesized that ventricular fibrillation (VF) waveform measures, as surrogates of myocardial physiology, mediate the relationship between bystander CPR and survival. Methods and Results We performed a retrospective cohort study of adult, bystander‐witnessed patients with out‐of‐hospital cardiac arrest with an initial rhythm of VF who were treated by a metropolitan emergency medical services system from 2005 to 2018. Patient, resuscitation, and outcome variables were extracted from emergency medical services and hospital records. A total of 3 VF waveform measures (amplitude spectrum area, peak frequency, and median peak amplitude) were computed from a 3‐second ECG segment before the initial shock. Multivariable logistic regression estimated the association between bystander CPR and survival to hospital discharge adjusted for Utstein elements. Causal mediation analysis quantified the proportion of survival benefit that was mediated by each VF waveform measure. Of 1069 patients, survival to hospital discharge was significantly higher among the 814 patients who received bystander CPR than those who did not (0.52 versus 0.43, respectively; P <0.01). The multivariable‐adjusted odds ratio for bystander CPR and survival was 1.6 (95% CI, 1.2, 2.1), and each VF waveform measure attenuated this association. Depending on the specific waveform measure, the proportion of mediation varied: 53% for amplitude spectrum area, 31% for peak frequency, and 29% for median peak amplitude. Conclusions Bystander CPR correlated with more robust initial VF waveform measures, which in turn mediated up to one‐half of the survival benefit associated with bystander CPR. These results provide insight into the biological mechanism of bystander CPR in VF out‐of‐hospital cardiac arrest.

Do Chest Compressions Benefit the Brain Beyond Restoring Circulation? ROSC-Mediated and ROSC-Independent Pathways of Bystander CPR After Out-of-Hospital Cardiac Arrest

“…These estimates sit alongside the small existing literature. Bessen and colleagues found that waveform measures of myocardial physiology mediated 29–53% of the survival benefit of bystander CPR in ventricular fibrillation arrests [ 8 ], and Chen and colleagues, using path analysis in a Beijing cohort, attributed 82.5% of the indirect association with survival to the survived-event pathway [ 9 ]. That figure is a share of the indirect association rather than of the total, so it is not directly comparable with the proportions reported here.…”

Do Chest Compressions Benefit the Brain Beyond Restoring Circulation? ROSC-Mediated and ROSC-Independent Pathways of Bystander CPR After Out-of-Hospital Cardiac Arrest

“…These estimates sit alongside the small existing literature. Bessen and colleagues found that waveform measures of myocardial physiology mediated 29–53% of the survival benefit of bystander CPR in ventricular fibrillation arrests [ 8 ], and Chen and colleagues, using path analysis in a Beijing cohort, attributed 82.5% of the indirect association with survival to the survived-event pathway [ 9 ]. That figure is a share of the indirect association rather than of the total, so it is not directly comparable with the proportions reported here.…”

Smartphone‐activated volunteer responders and survival to discharge after out‐of‐hospital cardiac arrests in Victoria, 2018–23: an observational cohort study

“…We found that larger proportions of people who experienced out‐of‐hospital cardiac arrests received bystander CPR (95.7% v 74.9%) or had initially shockable rhythms (34.6% v 26.0%) in cases in which SAVRs arrived before EMS than in those not attended by SAVRs. Bystander CPR is associated with a greater likelihood of the patient presenting with an initially shockable rhythm 17 and more robust initial ventricular fibrillation waveforms 18 . As having an initially shockable rhythm is associated with increased likelihood of survival after out‐of‐hospital cardiac arrest, 19 the benefit of SAVRs maintaining fibrillation with higher quality CPR may contribute to better survival rates.…”

“…Bystander CPR is associated with a greater likelihood of the patient presenting with an initially shockable rhythm 17 and more robust initial ventricular fibrillation waveforms. 18 As having an initially shockable rhythm is associated with increased likelihood of survival after out‐of‐hospital cardiac arrest, 19 the benefit of SAVRs maintaining fibrillation with higher quality CPR may contribute to better survival rates.…”

Combining Ventricular Fibrillation Features With Defibrillation Waveform Parameters Improves the Ability to Predict Shock Outcomes in a Rabbit Model of Cardiac Arrest

“…Features of the VF waveform have been proposed as a means to provide real‐time evaluation of the probability of shock success. 9 , 10 , 12 On the one hand, compared with other measurable physiological variables, the ECG has an important advantage in that it is routinely collected and analyzed via modern defibrillators. On the other hand, the duration of VF is a major determinant of shock outcomes, and features of the VF waveform are associated with the duration of CA.…”

“…Quantitative VF waveform analysis provides a noninvasive reflection of the pathophysiological changes and metabolic status of a fibrillating heart and is a potentially powerful tool to optimize defibrillation by evaluating the likelihood of a successful defibrillation outcome. 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 Although a variety of quantitative features calculated on the basis of the frequency, amplitude, and organization of the VF waveform have been used to predict shock outcomes, a sensitivity of ≈50% with a specificity of 90% for these features indicates that a single measure extracted from the VF waveform may have reached its maximum prediction power. 19 , 20 To improve the predictive ability, many studies have attempted to combine different features including but not limited to VF features via machine learning methods.…”

Do Chest Compressions Benefit the Brain Beyond Restoring Circulation? ROSC-Mediated and ROSC-Independent Pathways of Bystander CPR After Out-of-Hospital Cardiac Arrest

“…These estimates sit alongside the small existing literature. Bessen and colleagues found that waveform measures of myocardial physiology mediated 29–53% of the survival benefit of bystander CPR in ventricular fibrillation arrests [ 8 ], and Chen and colleagues, using path analysis in a Beijing cohort, attributed 82.5% of the indirect association with survival to the survived-event pathway [ 9 ]. That figure is a share of the indirect association rather than of the total, so it is not directly comparable with the proportions reported here.…”

Smartphone‐activated volunteer responders and survival to discharge after out‐of‐hospital cardiac arrests in Victoria, 2018–23: an observational cohort study

“…We found that larger proportions of people who experienced out‐of‐hospital cardiac arrests received bystander CPR (95.7% v 74.9%) or had initially shockable rhythms (34.6% v 26.0%) in cases in which SAVRs arrived before EMS than in those not attended by SAVRs. Bystander CPR is associated with a greater likelihood of the patient presenting with an initially shockable rhythm 17 and more robust initial ventricular fibrillation waveforms 18 . As having an initially shockable rhythm is associated with increased likelihood of survival after out‐of‐hospital cardiac arrest, 19 the benefit of SAVRs maintaining fibrillation with higher quality CPR may contribute to better survival rates.…”

“…Bystander CPR is associated with a greater likelihood of the patient presenting with an initially shockable rhythm 17 and more robust initial ventricular fibrillation waveforms. 18 As having an initially shockable rhythm is associated with increased likelihood of survival after out‐of‐hospital cardiac arrest, 19 the benefit of SAVRs maintaining fibrillation with higher quality CPR may contribute to better survival rates.…”

Combining Ventricular Fibrillation Features With Defibrillation Waveform Parameters Improves the Ability to Predict Shock Outcomes in a Rabbit Model of Cardiac Arrest

“…Features of the VF waveform have been proposed as a means to provide real‐time evaluation of the probability of shock success. 9 , 10 , 12 On the one hand, compared with other measurable physiological variables, the ECG has an important advantage in that it is routinely collected and analyzed via modern defibrillators. On the other hand, the duration of VF is a major determinant of shock outcomes, and features of the VF waveform are associated with the duration of CA.…”

“…Quantitative VF waveform analysis provides a noninvasive reflection of the pathophysiological changes and metabolic status of a fibrillating heart and is a potentially powerful tool to optimize defibrillation by evaluating the likelihood of a successful defibrillation outcome. 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 Although a variety of quantitative features calculated on the basis of the frequency, amplitude, and organization of the VF waveform have been used to predict shock outcomes, a sensitivity of ≈50% with a specificity of 90% for these features indicates that a single measure extracted from the VF waveform may have reached its maximum prediction power. 19 , 20 To improve the predictive ability, many studies have attempted to combine different features including but not limited to VF features via machine learning methods.…”

Do Chest Compressions Benefit the Brain Beyond Restoring Circulation? ROSC-Mediated and ROSC-Independent Pathways of Bystander CPR After Out-of-Hospital Cardiac Arrest

“…These estimates sit alongside the small existing literature. Bessen and colleagues found that waveform measures of myocardial physiology mediated 29–53% of the survival benefit of bystander CPR in ventricular fibrillation arrests [ 8 ], and Chen and colleagues, using path analysis in a Beijing cohort, attributed 82.5% of the indirect association with survival to the survived-event pathway [ 9 ]. That figure is a share of the indirect association rather than of the total, so it is not directly comparable with the proportions reported here.…”

Smartphone‐activated volunteer responders and survival to discharge after out‐of‐hospital cardiac arrests in Victoria, 2018–23: an observational cohort study

“…We found that larger proportions of people who experienced out‐of‐hospital cardiac arrests received bystander CPR (95.7% v 74.9%) or had initially shockable rhythms (34.6% v 26.0%) in cases in which SAVRs arrived before EMS than in those not attended by SAVRs. Bystander CPR is associated with a greater likelihood of the patient presenting with an initially shockable rhythm 17 and more robust initial ventricular fibrillation waveforms 18 . As having an initially shockable rhythm is associated with increased likelihood of survival after out‐of‐hospital cardiac arrest, 19 the benefit of SAVRs maintaining fibrillation with higher quality CPR may contribute to better survival rates.…”

“…Bystander CPR is associated with a greater likelihood of the patient presenting with an initially shockable rhythm 17 and more robust initial ventricular fibrillation waveforms. 18 As having an initially shockable rhythm is associated with increased likelihood of survival after out‐of‐hospital cardiac arrest, 19 the benefit of SAVRs maintaining fibrillation with higher quality CPR may contribute to better survival rates.…”

Combining Ventricular Fibrillation Features With Defibrillation Waveform Parameters Improves the Ability to Predict Shock Outcomes in a Rabbit Model of Cardiac Arrest

“…Features of the VF waveform have been proposed as a means to provide real‐time evaluation of the probability of shock success. 9 , 10 , 12 On the one hand, compared with other measurable physiological variables, the ECG has an important advantage in that it is routinely collected and analyzed via modern defibrillators. On the other hand, the duration of VF is a major determinant of shock outcomes, and features of the VF waveform are associated with the duration of CA.…”

“…Quantitative VF waveform analysis provides a noninvasive reflection of the pathophysiological changes and metabolic status of a fibrillating heart and is a potentially powerful tool to optimize defibrillation by evaluating the likelihood of a successful defibrillation outcome. 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 Although a variety of quantitative features calculated on the basis of the frequency, amplitude, and organization of the VF waveform have been used to predict shock outcomes, a sensitivity of ≈50% with a specificity of 90% for these features indicates that a single measure extracted from the VF waveform may have reached its maximum prediction power. 19 , 20 To improve the predictive ability, many studies have attempted to combine different features including but not limited to VF features via machine learning methods.…”