Impact of time to Defibrillation on ROSC

Sep 05, 2024

The rates of Pulseless Electrical Activity (PEA) in out of hospital cardiac arrests (OHCA) is rising, however survival from PEA is low. The majority of survivors from OHCA have an initial rhythm of ventricular fibrillation. The approach of defibrillation versus CPR has varied and although there is no evidence that a short period of CPR prior to attempted defibrillation of VF is superior to defibrillation first, the 2023 ILCOR guidelines still make the recommendation for a period of CPR prior to defibrillation.

This study(1) in review aimed "to investigate the relationship of intra-arrest VF/ pVT duration and ROSC in patients with OHCA presenting with recurrent/refractory VF or pVT requiring four or five shocks."

What They Did

This was a retrospective study using registry data was used (Salt Lake City Fire Department) for all OHCA patients in whom resuscitation was attempted, to create two datasets:

VF/paroxysmal VT patients that received appropriate shock

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What They Did

This was a retrospective study using registry data was used (Salt Lake City Fire Department) for all OHCA patients in whom resuscitation was attempted, to create two datasets:

VF/paroxysmal VT patients that received appropriate shocks and the outcome of each shock
Adult patients with OHCA with an initial presentation of VF or paroxysmal VT who received four or five defibrillations for recurrent or persistent arrhythmia.

Patients were excluded if:

<18 years of age
Had a non-shockable initial rhythm
A defibrillator that is not normally used by the fire department was used prior to EMS arrival
Patients receiving < four defibrillations
Patients receiving > 5 defibrillators

N= 142 patients met all criteria.

What They Found

622 shocks were included in the study

204 shocks (32.8%) resulted in ROSC
418 shocks (67.2%) did not result in ROSC

There was a significantly shorter VF/paroxysmal VT duration in the group who achieving ROSC (0.83 min) compared to the group that did not (1.28 min) p = 0.004.

This study again highlights what we know, that prolonged ventricular arrhythmia cardiac arrests decrease successful resuscitation. The shorter the time to defibrillation, the greater the likelihood of achieving ROSC.

Discussion

The limitations of this study included:

Data was sourced from an OHCA registry.
The results from this study are not validated outside this one region.
Other factors including
- chest compression rate,
- rhythms before the recurrence of VF/paroxysmal VT,
- comorbidities,
- medications,
Inappropriate shocks we delivered during resuscitation

My Take on This

This study reinforces what we already know from animal models; that more prolonged VF times increase myocardial ischaemia, depleting myocardial ATP stores and making it difficult to successfully achieve ROSC. The specifically found that for every minute the patient is in VF/paroxysmal VT there is a 19% decrease in the odds of achieving ROSC.

The faster we defibrillate these malignant arrhythmias, the greater the chance of return of ROSC and potentially neurologically intact survivors. Is it time to rethink the 2 minutes of CPR and then a rhythm check? Is it of greater benefit to have shorter duration of CPR by identifying the underlying rhythm and attempt defibrillation sooner? Can we do this by using adaptive filters on our defibrillators that give a rhythm analysis whilst CPR is being performed? They aren't quite prime time as yet.

POINTS TO TAKE AWAY

This was a retrospective registry study
They included patients VF or paroxysmal VT who received four or five defibrillations for recurrent or persistent arrhythmia
They found that earlier defibrillation of malignant arrhythmias, was associated with an increased ROSC (something we have known)

References

Awad E. The impact of time to defibrillation on return of spontaneous circulation in out-of-hospital cardiac arrest patients with recurrent shockable rhythms.Resuscitation 201 (2024) 110286. Ahead of Print