Emergency Management of Cardiac Chest Pain: a Review
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6 Emerg Med J 2001;18:6–10 REVIEW Emerg Med J: first published as 10.1136/emj.18.1.6 on 1 January 2001. Downloaded from Emergency management of cardiac chest pain: a review K R Herren, K Mackway-Jones Chest pain accounts for 2%–4% of all new fer to coronary care, and also to limit the attendances at emergency departments (ED) impact on the patient and healthcare resources. in the United Kingdom.12 Chest pain can be The diagnosis of chest pains less than 12 the presenting complaint in a myriad of disor- hours in duration is an important challenge. ders ranging from life threats such as acute This is for three reasons. Firstly, individual myocardial infarction (AMI) to mild self limit- biochemical markers cannot eVectively rule ing disorders such as muscle strain. Possible out myocardial infarction in the initial 12 hour cardac chest pain can be viewed as a con- period.13 14 Secondly, aspirin and the fibrino- tinuum, ranging from total global AMI to sim- lytic agents are at their most potent during this ple short lived angina. Within this spectrum lie period,815 and finally the majority of AMI the acute coronary syndromes with critical car- related deaths occur in the first 12 hours.4 diac ischaemia and minimal myocardial dam- Ideally a test would be available that age. identifies all AMIs immediately and confi- Nationally over 129 000 deaths a year are dently excludes all non-AMIs. No perfect test attributable to ischaemic heart disease.3 AMI exists; instead tests are combined initially to case mortality is currently 45% with over 70% rule in myocardial infarction (RIMI), and then of these dying before they reach medical care.4 to eVectively rule out myocardial infarction One in eight patients with unstable angina will (ROMI). The clinical eYcacy of diagnostic infarct within two weeks without appropriate tests is evaluated using sensitivity and specifi- treatment. In the UK around 30% of patients city. To be certain of the diagnosis (in this case with chest pain are admitted and 70% RIMI) a test must be have very few false posi- discharged from the ED1 while in the United tives (high specificity). However, to confidently http://emj.bmj.com/ States 60% are admitted and 40% discharged.4 rule out a condition (in this case ROMI) the Despite such high admission rates 3%–4% of test must have minimal false negatives (high 16 AMI are inadvertently discharged from US sensitivity). EDs. In the UK significantly fewer patients are The aim of this review is to discuss the admitted; while the number of missed AMIs is evidence base underlying diagnostic and treat- unknown, recent evidence suggests that some ment strategies for patients with cardiac sounding chest pain. 6% of patients discharged from EDs may have on September 24, 2021 by guest. Protected copyright. prognostically significant myocardial damage.5 Mortality for patients with AMI diVers greatly between admitted and discharged The initial approach to cardiac sounding patients (6% versus 25%).6 Missed AMI chest pain accounts for 20% of US emergency medicine Patients with cardiac sounding chest pain must related litigation dollars.7 Many interventions have rapid access to appropriate care. This including drug therapy and surgery reduce requires robust recognition of the problem, mortality in patients with AMI.8–11 However, early ECG and assessment by a clinician the patient can only benefit if correctly identi- trained to assess clinical risk. This is summa- fied. rised in figure 1. Although it is essential to identify all patients Department of with AMI and unstable angina, it is also Emergency Medicine, important to control costs and not subject Accident and Nurse triage Emergency, patients to unnecessary investigations, in- Cardiac—very urgent Manchester Royal patient care and resultant psychological stress. Infirmary Oxford Forty per cent of patients admitted to CCU Road, Manchester with chest pain will have all ischaemic heart Early M13 9WL, UK disease ruled out.12 The emotional, physical ECG AMI Correspondence to: and economic impact on the patient, their family, their friends and the limited resources Kevin Mackway-Jones, Definite Consultant of the healthcare system should not be under- Clinical risk AMI (kevin.mackway-jones@ estimated. The process of chest pain evaluation assessment man.ac.uk) must therefore be both timely and accurate in Accepted 5 October 2000 order to facilitate early thrombolysis and trans- Figure 1 Initial approach. www.emjonline.com Emergency management of cardiac chest pain 7 NURSE TRIAGE Table 1 History suggesting unstable cardiac ischaemia The first clinical contact between the patient Emerg Med J: first published as 10.1136/emj.18.1.6 on 1 January 2001. Downloaded from and the ED is usually at nurse triage. It is Cardiac sounding chest pain and any of: + Pain the same as a previous AMI essential that cardiac sounding chest pain is + New onset of rest pain identified at this stage, and accorded an appro- + Pain not relieved by standard treatment in standard time 17 + Pain lasting more than 60 minutes priately high (very urgent) clinical priority. + Pain occurring with increasing frequency over the previous This will ensure that an appropriate early path- 24 hours way of care is followed. Once this group of + Pain within six weeks of AMI or revascularisation patients have been identified subsequent man- agement should be presentation sensitive— tion. This will allow appropriate decisions very urgent cardiac pain patients should be about further care to be made. placed in an appropriate area and ECG The ECG findings are considered first— recording should be automatic. ischaemic changes not known to be old predict both a high risk of myocardial infarction and EARLY ECG also a high risk of complications. If the ECG is The initial ECG is performed to RIMI, and normal then clinical risk factors are sought. should be recorded as soon as possible—and Firstly, any history consistent with unstable certainly within 10 minutes. The ECG is an ischaemic heart disease is elicited—a practical excellent tool for RIMI as it is highly specific checklist is shown in table 1. (77%–100%) depending on the criteria used. Secondly, any findings of either hypotension However, the sensitivity of ECG is poor (28%– 11 18 (systolic blood pressure less than 120 mm Hg) 54%) in the first 12 hours, and the presence or significant heart failure (crepitations not just of a normal ECG neither excludes AMI nor including the bases) are noted. If more than provides suYcient assurance to discharge the two clinical risk factors are present then the patient from the ED. At this stage, therefore, patient is at high risk. the ECG is a tool to identify patients for 18–20 If only one risk factor is present or there are consideration of fibrinolytic drugs. none at all, then the history should be CLINICAL RISK STRATIFICATION reconsidered to see whether one of two Acute MI patients with ECG changes should particular scenarios that go along with a mod- therefore be spotted straight away and should erate risk of myocardial infarction are present. then be treated appropriately (see below). The These are shown in table 2. patients who remain will range from those with The whole approach to clinical risk assess- unstable angina to those with musculoskeletal ment is summarised in figure 2. This assessment tool is derived from the pain. While the particular diagnosis in indi- 19 20 vidual patients may take some time to estab- multicentre chest pain study and provides lish, the risks of either myocardial infarction or an objective, evidence based tool for use in the of later complications can be rapidly assessed ED. It ensures AMI and other high risk by considering the ECG, by taking a focused patients are identified rapidly and provides a http://emj.bmj.com/ history and by carrying out a brief examina- framework for subsequent care of all those remaining. Table 2 Clinical scenarios indicating a moderate risk of myocardial infarction in patients with normal ECGs Management Scenario 1: Typical cardiac pain in a patient over 40 years old where the pain is not The management of the patients will depend reproduced by palpation, is not stabbing in nature and does not radiate atypically. on the outcome of the initial screen. Some Scenario 2: A history of anginal pain lasting longer than one hour that was either worse patients will have an ECG positive diagnosis of on September 24, 2021 by guest. Protected copyright. than usual angina pain or as bad as the pain of a previous AMI. myocardial infarction and will need immediate intervention. Others will be at high risk and will need admission for both treatment and ECG further diagnosis. Those at moderate and low changes risk will need myocardial infarction ruled out, N AMI and appropriate follow up arranged. Risk New Definite DEFINITE AMI ischaemia AMI ST elevation (>1 mm in two limb leads or >2 ≤ factors ≥2 1 mm in two chest leads) or acute left bundle branch block in a patient with chest pain are diagnostic of AMI and indicators for the use of Significant High fibrinolytic drugs.815 history Y Patients should receive aspirin unless they have a major contraindication (active peptic ulceration, bleeding disorders and severe al- 21 N Moderate lergy). Aspirin inhibits cyclo-oxygenase- dependent platelet activity—taking one hour to induce complete inhibition of cyclo- oxygenase.22 Therefore the earlier aspirin is given the greater the eVect. Aspirin given Low immediately and continued for one month after AMI prevents 25 deaths and 13 other vas- Figure 2 Clinical risk assessment overview. cular events per 1000 patients treated.10 www.emjonline.com 8 Herren, Mackway-Jones Table 3 Contraindications to the use of fibrinolytic drugs MODERATE RISK GROUP The care of the moderate risk group is moot at Emerg Med J: first published as 10.1136/emj.18.1.6 on 1 January 2001.