Emergency medicine: Acute coronary syndromes

Emergency care for patients with suspected MI.

Despite recent impressive reductions in premature mortality from cardiovascular disease, acute coronary syndromes (ACS) continue to present a significant burden and mortality risk for patients.

The British Heart Foundation estimates there are 175,000 'heart attacks' in the UK per annum.

The spectrum of ACS covers unstable angina, non-ST segment elevation MI (nSTEMI) and ST segment elevation MI (STEMI). ACS may be particularly challenging in the community setting where GPs will see many patients with chest pain but encounter very few patients who actually have STEMI.

Identifying the 'true positive' ACS patient can be life saving; conversely, identifying the 'true negative' can reduce unnecessary hospitalisation, distress and inconvenience for the patient and family. 

The threshold for referral for further assessment has traditionally been low.

Guidance from NICE on chest pain of recent onset (due for review in 2016), and STEMI (published in 2013), are intended to reflect contemporary evidence and improve care across the ACS spectrum.

When to suspect ACS

Recent NICE guidance summarises the typical ACS presentation:

  • Pain in the chest (and/or the arms, back or jaw) lasting longer than 15 minutes.
  • Chest pain associated with nausea and vomiting, marked sweating, breathlessness or a combination of these.
  • Chest pain with haemodynamic instability.
  • New-onset chest pain or abrupt deterioration in previously stable angina, with frequent recurrent pain and with little or no exertion, and lasting longer than 15 minutes.

Role of the GP

Unless the area the practice serves is very rural, a GP should call for an ambulance and allow the paramedics to treat the patient. The presence of a GP has been shown to significantly add to the delay in hospital admission and reperfusion treatment. GPs can give aspirin 300mg orally, preferably in soluble form.

The more comprehensive medical education of physicians compared with ambulance staff allows for a detailed assessment of the patient and consideration of the range of differential diagnoses and treatments, but in cases where true ACS is present, the ambulance service is best placed to provide resuscitation and expedite hospital admission.

Moreover, ambulances carry defibrillators, paramedics can provide morphine for pain relief, and they are equipped with 12-lead ECG machines and often, the capability to transmit images for cardiology opinion.

Treatment of ACS

In recent years there has been a major shift to primary percutaneous coronary intervention (PCI) instead of thrombolysis. The vast majority of patients with STEMI are now taken direct to a specialist centre rather than to the local district general hospital if the attending paramedic considers the patient to meet the agreed criteria, based largely on ECG findings.

Systems of care such as regional heart attack networks have developed across the UK to facilitate this. The consequences for patients are better outcomes - and a very short hospital stay, typically three days or so compared to a week or 10 days traditionally - if PCI can be provided in timely fashion in a centre that performs high volumes of this procedure.

The consequences for families are that they may have to travel further for visiting and, where patients are critically ill or have a prolonged stay, this can be challenging particularly if the partner/spouse cannot drive, there are no willing drivers or public transport links are inadequate. Overall, the benefits to patients outweigh these concerns.

Awareness of defibrillators

Automated external defibrillators are increasingly available in the community for public use. Ambulance services will often know where these are and might ask a caller to go and collect one where a patient is judged at risk of cardiac arrest, such as those with typical symptoms suggestive of a heart attack.

This provides a useful 'safety net' in case the patient suddenly develops ventricular fibrillation which is lethal unless converted rapidly with a defibrillator. The public and professionals including GPs should be aware that these devices are available and can be used by anyone without prior training.

Key priorities

The traditional mnemonic 'MONA' (morphine, oxygen, nitrates and aspirin) has come under scrutiny lately. Morphine was found, in a large US registry2, to be associated with increased mortality in ACS patients, and oxygen may also be harmful (relative risk of death was 3.03 compared with air in MI, according to a recent Cochrane review, albeit possibly due to chance).3

Recent data from Australia suggest oxygen use in normoxic STEMI patients is associated with increased infarct size.4 A very large randomised trial, powered for mortality, is underway in Sweden which will provide insight into the benefit or harm associated with oxygen use for this group of patients.5

There is no evidence of a mortality benefit from nitrates; although affording symptomatic relief, NICE recommends that response to nitrates is not used to make a diagnosis. This leaves aspirin as the sole intervention, for which there is good evidence of benefit.

If ST elevation is present in two or more contiguous ECG leads then the patient requires reperfusion with either primary angioplasty or thrombolysis - the former is now the preferred treatment in UK practice, with well organised 'networks' emerging across the country.

Timely reperfusion is of the essence. Around a fifth of all STEMI patients still do not receive any reperfusion and have poorer outcomes a result. Making the diagnosis early and ensuring the patient goes to the right place, ideally a heart attack centre providing 24/7 primary angioplasty, may improve this.

For patients where there is clinical suspicion but the ECG does not show ST elevation, the situation remains urgent and admission for further evaluation is required.

Temporal changes in the ECG are not infrequent and ECGs should be repeated, especially if there is ongoing or recurrent pain or haemodynamic upset, but this should not delay transport to hospital.

Key learning points
  • It is worth noting a significant minority of patients present atypically. For example, those with diabetes and the elderly.
  • The first priority is to find a defibrillator and someone to use it, since cardiac arrest from ventricular fibrillation is most likely in the early minutes and hours after symptom onset.
  • Only administer oxygen if the patient is hypoxaemic.
  • Immediate management depends on the findings of the 12-lead ECG.
  • A normal or non-diagnostic ECG should not be used to exclude ACS.
  • Professor Quinn is professor of cardiovascular care at the University of Surrey and was previously clinical lead for NHS Evidence - cardiovascular, stroke and vascular collections.

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  1. Rowley JM, Mounser P, Harrison EA et al. Management of myocardial infarction: implications for current policy derived from the Nottingham Heart Attack Register. Br Heart J 1992; 67(3): 255-62.
  2. W F Peacock, J E Hollander, D B Diercks, et al. Morphine and outcomes in acute decompensated heart failure: an ADHERE analysis. Emerg Med J 2008; 25: 205-9.
  3. Cabello JB, Burls A, Emparanza JI et al. Oxygen therapy for acute myocardial infarction. Cochrane Database Syst Rev 2013 Aug; 21; 8: CD007160. doi: 10.1002/14651858.CD007160.pub3.
  4. Stub D, Smith K, Bernard S, et al; AVOID Investigators. Air Versus Oxygen in ST-Segment-Elevation Myocardial Infarction. Circulation. 2015 Jun 16;131(24):2143-50


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