This is secondary analysis of a paper which analysed the change in ECG morphology following ROSC from out-of-hospital Cardiac Arrest.
The Study
Naas, CJ et al. Associations with resolution of ST-segment elevation myocardial infarction criteria on out-of-hospital 12-lead electrocardiograms following resuscitation from cardiac arrest. Resuscitation, Volume 209, 110567.
What They Did
This was a secondary analysis of the original paper(1), which found that a significant number of ECGs changed morphology from a STEMI, post resuscitation in the out of hospital environment to a NSTEMI, on arrival to hospital. This study aimed to identify treatments, cardiac arrest characteristics, and time factors associated with this ECG change.
Characteristics of the arrests, "times, and treatments were analyzed for association with change in ECG classification between the Out-of-Hospital(OOH)" and Emergency Department (ED).
N=176
What They Found
- 49/176 (27.8%) patients had STEMI
- In 33/49 (67.3%) of the patients, the STEMI had resolved on repeat ECG in the ED
- 16/49 (32.7%) of patients had sustained STEMI on repeat ED ECG
- All patients presenting with OOH STEMI accounted for 16/21 (76.2%) of all STEMIs in the ED.
- 61/176 (34.7%) of patients had ischemia
- Of these patients, 3/61(4.9%) had a STEMI in the ED.
- 22/61 (36%) remained ischemic
- 36/61 (59%) had resolution of ischemia on ED ECG.
- 66/176 (37.5%) of patients had non-ischemic classifications on the out of hospital ECG.
Factors significantly associated with a resolution of STEMI on ED ECG
- Lower adrenaline dose
- Lower rate of noradrenaline administration
- Shorter time from CPR to ROSC
- Shorter time from ROSC to ECG acquisition
- Greater time between OOH and ED ECG
Factors associated with sustained ischaemia or evolution to STEMI on ED ECG
- Greater age
- Greater OOH, ED and total defibrillations
- Initial shockable rhythm (VF, VT, or AED shock advised)
Discussion
This was a review of a restrospective series of data, from a single site, with potential issues of data accuracy and potential selection bias. Patients did not routinely have a coronary angiogram performed.
Why may there be a change in the ECG? (2-4)
Vasospasm is found in a small percentage of patients with STEMI following out-of-hospital cardiac arrest. This same vasospasm may be caused or exacerbated transiently, by the use of vasopressors. The degree of adrenaline use has also been inversely associated with post-ROSC perfusion.
Hypoperfusion due to prolonged resuscitation has also been associated with false-positive STEMI ECGs post ROSC.
The degree of STEMI on ECG, early post ROSC and its resolution may be explained, by hypoperfusion associated with length of resuscitation and time to ECGs being performed. This time, potentially allowing for improvement of perfusion and metabiolic derangementa. This study showed statistical significance of shorter time from ROSC to OOH ECG and resolution of OOH STEMI during ED evaluation.
In this tudy more defibrillations and an initial rhythm of VT/VF was associated with more ischaemic evolution in patients with initial non-STEMI ECGs. This follows, given that patients with VF cardiac arrest are more likely to have a coronary occlusion.
The lessons from this secondary analysis are important:
- The initial ECG showing STEMI, may resolve. This means that serial ECGs are important. We cannot assume that it will resolve, nor that it will remain a STEMI. The mean time between OOH and ED ECGs showing a resolved STEMI, was just over 52 minutes.
- The reason that serial ECGs are important is that not only can the ischaemic pattern resolve, but it can also evolve.
- How long should we wait? My approach is that following an ECG that is positive for STEMI on arrival to ED, in the post ROSC patient, is to immediately contact Cardiology. I think about 20 minutes post ROSC is probably the point at which I am starting to be convinced that this is a STEMI. Of course, the cardiac team may decide to activate the catheter lab prior to this. The key is serial ECGs. I would perform them certainly for the first 60 minutes at 10-15 minute intervals.
References
- Aufderheide T.T., et al. Change in out-of-hospital 12-lead ECG diagnostic classification following resuscitation from cardiac arrest. Resuscitation 169 (2021) 45-52.
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Tateishi K, et al. Clinical value of ST-segment change after return of spontaneous cardiac arrest and emergent coronary angiography in patients with out-of-hospital cardiac arrest: diagnostic and therapeutic importance of vasospastic angina. Eur Heart J Acute Cardiovasc Care 2018;7 (5):405–13.
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Kalra R, et al. Delaying electrocardiography in cardiac arrest: a pause for the cause. JAMA Netw Open 2021;4(1)e2033360.https://doi.org/10.1001/jamanetworkopen.2020.33360.
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Yannopoulos D, et al. Advanced reperfusion strategies for patients with out-of-hospital cardiac arrest and refractory ventricular fibrillation (ARREST): a phase 2, single centre, open-label, randomised controlled trial. Lancet 2020;6736 (20):1–10.
