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A 70 year old woman suffered an out of hospital cardiac arrest whilst playing golf. She received bystander cardiopulmonary resuscitation and two shocks from an automated external defibrillator which restored spontaneous circulation. She was intubated at the scene  and arrived in the resuscitation department cardiovascularly stable, well oxygenated and unconscious in the context of propofol sedation.

There was no prodrome suggestive of a specific aetiology for the cardiac arrest but information from relatives described an ex-smoker with hypercholesterolaemia and diet controlled diabetes mellitus who had previously undergone percutaneous coronary intervention (PCI) for ischemic heart disease. She took regular aspirin, statin and beta-blocker. A post resuscitation 12 lead ECG showed sinus rhythm, left axis deviation and non-specific lateral ischaemia. Troponin was elevated above 200 ng/L.

In view of this she was loaded with dual antiplatelet therapy and underwent emergency coronary angiography which demonstrated occlusion of two small branches (OM1 and PLV) but no large vessel coronary artery occlusion to explain the cardiac arrest. The occluded vessels were not stented. Subsequent echocardiogram and cardiac MRI demonstrated old circumflex territory scar but an otherwise normal heart and ultimately it was agreed that the cause of cardiac arrest was probably ventricular arrhythmia secondary to scar.

She was ventilated for 24 hours with targeted temperature management before being woken and extubated. Although she was initially confused, her neurology improved over approximately 48 hours such that she was discharged with no apparent neurological injury. An implantable cardiac defibrillator was placed prior to discharge to prevent sudden cardiac death from any future arrhythmia.

Clinical questions:

1. In survivors of out of hospital cardiac arrest should we proceed to early coronary angiography with a view to PCI?
2. If so, should we apply this approach to all such patients or only a subset?
3. If we do proceed to early coronary angiography, should this occur before or after other investigations, specifically computed tomography (CT) of the head and chest to look for intracerebral bleed and pulmonary embolism?

Matt Taylor

Management of the cardiac arrest survivor with ST elevation

The approach to survivors of cardiac arrest who have ST elevation or new left bundle block on their post-resuscitation ECG and no obvious extracardiac cause for cardiac arrest is relatively straightforward. They should generally be managed with emergency coronary angiography and PCI, and this view is supported by the European Resuscitation Council ¹, the American College of Cardiology Foundation, the American Heart Association Task Force ², and the National Institute for Health and Clinical Excellence ³.

The evidence base for this comes from retrospective analysis of several cohort databases. Of note these databases tend to select hemodynamically stable patients with a bias towards VF/VT arrest rhythms and thus the external validity outside of these boundaries may be limited.

These patients will have an acute “culprit” coronary artery lesion amenable to PCI in 74-85% of cases ^4-6, which means the positive predictive value of ST elevation for a significant coronary artery lesion is good. Survival following successful PCI in this setting is 54-60% which significantly exceeds the baseline of approximately 30%, and a favourable neurological outcome (defined as cerebral performance category 1 or 2; normal life or disabled but independent) is obtained in 86-96% of survivors.^5,7 Based on this non-randomised retrospective data the absolute risk reduction for death with PCI is 24-30% giving a number needed to treat for survival of four or less.

Multivariate analysis of the factors influencing survival suggests that primary PEA or asystolic arrests are associated with worse outcome, as are older age (>59), longer down time, higher lactate and diabetes mellitus.⁵

In summary patients who survive cardiac arrest, have no obvious extracardiac cause and ST elevation should undergo emergency coronary angiography because the majority will have a lesion amenable to PCI and this will infer a large survival benefit with generally good neurological outcome. We may be less optimistic in those with an initial non-shockable rhythm.

Management of the  cardiac arrest survivor with no ST elevation

The approach to survivors of cardiac arrest who do not have ST elevation or new left bundle block on their post resuscitation ECG and no obvious extracardiac cause is more complicated.

About a third (28-33%) will have an acute “culprit” coronary lesion amenable to PCI.^6,8 With emergency PCI these patients will do better (cerebral performance category of 1 or 2 at hospital discharge in 43% vs 33%, p = 0.02).⁸ However we cannot tell who this third will be because our usual diagnostic tests are inaccurate: the absence of ST elevation on an ECG has a negative negative predictive value of only (67%),⁶ and troponin elevation has a sensitivity and sensitivity of only 66% at best ⁹.

If we look at early (usually immediate but at least within 24 hours) versus late coronary angiography strategy in these patients and ignore whether they ultimately have PCI or not then the results are conflicting.

In a subset whose initial rhythm was VF/VT, an early coronary angiogram strategy was associated with better survival (65.6% vs. 48.6%; p=0.017) and neurological function (CPC 1 or 2 in 60.7% vs 40.5% p=0.017) at discharge which remained evident at 5 months follow up. Only a third of these patients ultimately had PCI but about a fifth of the early group had a mechanical LV support device placed compared to almost none of the late group and therefore this may have accounted for some of the survival benefit.¹⁰

In contrast a cohort including 25% with a non-shockable rhythm, an early coronary angiography did not not alter survival (48 vs 54%, p=0.82).¹¹ Indeed, multivariate analysis of the Parisian region out of hospital cardiac arrest (PROCAT) registry tells us that an initial shockable rhythm is associated with better outcome and is the only variable than can predict successful PCI. Short resuscitation times (less than 20 minutes) and a lower dose of adrenaline also predicted better survival.⁸

How to best manage these patients with no ST elevation after cardiac arrest remains unanswered. Two trials are currently addressing this issue by prospectively randomising patients to early coronary angiography or standard treatment so hopefully our future management strategies will be better informed.^12,13

In summary, based on our current understanding, patients who survive cardiac arrest, have no obvious extracardiac cause and no ST elevation should be considered for emergency coronary angiography. The presence of an initial shockable rhythm should be an important factor in the decision making process because this group are more likely to have a lesion amenable to PCI and a strategy of emergency coronary angiography appears to confer a significant survival benefit, probably due to early PCI and/or the ability to mechanically support the left ventricle.

The timing of other diagnostic tests

Analysis of the PROCAT registry shows CT of the brain and chest will provide a diagnosis in 20% of patients who have survived cardiac arrest and do not have an obvious extracardiac cause, whilst coronary angiography will provide a diagnosis in 61% cases.¹⁴  Therefore it would seem sensible to proceed to coronary angiography ahead of CT. The anxiety with this approach is that one must load the patient with dual antiplatelet therapy without having excluded intracerebral bleed. However cardiac arrest from an intracerebral cause can usually be identified from a neurological prodrome and it is usually fatal (universally in one cohort) so pragmatism supports accepting this risk and treating the coronary arteries first.¹⁵

 

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Lessons learnt

Based on the evidence above, an approach to survivors of cardiac arrest could proceed in the following manner:

1. If conscious, assess and manage them as a patient presenting with the same history but without cardiac arrest.
2. If unconscious, consider whether there is an obvious extracardiac cause for their presentation and if so investigate and manage that.
3. If no extracardiac cause is apparent, look for ST elevation or new left bundle branch block and if present prioritise early coronary angiography in most cases ahead of other investigations.
4. If there is no ST elevation, discuss the merits of early coronary angiography with cardiology colleagues and the factors that guide our decision should be the initial rhythm, resuscitation time, adrenaline dose, risk factors for coronary artery disease and history.

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References

1. Nikolaou NI. European Resuscitation Council Guidelines for Resuscitation 2015 Section 8. Initial Management of Acute Coronary Syndromes Resuscitation 2015;95:263-76.
2. O’Gara P. 2013 ACCF/AHA guideline for the management of ST-elevation myocardial infarction: a report of the American College of Cardiology Foundation/American Heart Association Task Force on Practice Guidelines. Circulation 2013;127:e362-425.
3. Acute coronary syndromes in adults Quality standard Published: 5 September 2014. NICE.
4. Garcia-Tejada J. Post-resuscitation electrocardiograms, acute coronary findings and in-hospital prognosis of survivors of out-of-hospital cardiac arrest. Resuscitation 2014;85:1245-50.
5. Dumas F. Immediate Percutaneous Coronary Intervention Is Associated With Better Survival After Out-of-Hospital Cardiac Arrest Insights From the PROCAT (Parisian Region Out of Hospital Cardiac Arrest) Registry. Circ Cardiovasc Interv. 2010;3:200-207
6. Zanuttini D. Predictive value of electrocardiogram in diagnosing acute coronary artery lesions among patients with out-of-hospital-cardiac-arrest. Resuscitation 2013;84:1250-4.
7. Kern K. Optimal Treatment of Patients Surviving Out-of-Hospital Cardiac Arrest. J Am Coll Cardiol Intv 2012;5:597–605
8. Dumas F. Emergency Percutaneous Coronary Intervention in Post–Cardiac Arrest Patients Without ST-Segment Elevation Pattern: Insights From the PROCAT II Registry. JACC Cardiovasc Interv. 2016 May 23;9(10):1011-8
9. Dumas F. Can early cardiac troponin I measurement help to predict recent coronary occlusion in out-of-hospital cardiac arrest survivors? Crit Care Med 2012;40:1777-84.
10. Hollenbeck RD. Early cardiac catheterization is associated with improved survival in comatose survivors of cardiac arrest without STEMI. Resuscitation 2014;85:88-95.
11. Dankiewicz J. Survival in patients without acute ST elevation after cardiac arrest and association with early coronary angiography: a post hoc analysis from the TTM trial. Intensive Care Med. 2015 May;41(5):856-64.
12. PEARL study: http://heart.arizona.edu/Pearl.
13. DISCO study: https://clinicaltrials.gov/ct2/show/NCT02309151.
14. Chelly J. Benefit of an early and systematic imaging procedure after cardiac arrest: insights from the PROCAT (Parisian Region Out of Hospital Cardiac Arrest) registry. Resuscitation 2012;83:1444-50.
15. Arnaout M. Out-of-hospital cardiac arrest from brain cause: epidemiology, clinical features, and outcome in a multicenter cohort. Crit Care Med 2015;43:453-60.