The assessment and management of chest pain in primary care A focus on acute coronary syndrome

246 | REPRINTED FROM AJGP VOL. 47, NO. 5, MAY 2018 © The Royal Australian College of General Practitioners 2018 CHEST PAIN is a common complaint of patients presenting to primary care physicians and emergency departments. Given that some causes of chest pain are potentially lethal, the challenge is to make an accurate diagnosis.1 This article will focus on diagnosis and early management of patients with possible acute coronary syndrome (ACS). It will discuss key differentials that must be considered, and essential primary care investigations and management. Finally, hospital-based risk stratification and management will be described, providing an outline of what patients can expect from their referral to hospital.

CHEST PAIN is a common complaint of patients presenting to primary care physicians and emergency departments.Given that some causes of chest pain are potentially lethal, the challenge is to make an accurate diagnosis. 1This article will focus on diagnosis and early management of patients with possible acute coronary syndrome (ACS).It will discuss key differentials that must be considered, and essential primary care investigations and management.Finally, hospital-based risk stratification and management will be described, providing an outline of what patients can expect from their referral to hospital.

Differential diagnosis of chest pain
A number of life-threatening and minor conditions may present with chest pain.Where minor conditions are confidently diagnosed, referral to the emergency department may not be necessary.Serious conditions include ACS, pulmonary embolism, aortic dissection and spontaneous pneumothorax (Box 1). 2 Pulmonary embolism (PE) risk factors include the presence or clinical suspicion of deep vein thrombosis (DVT), past history of DVT/PE, active malignancy, recent trauma, surgery or immobility, and use of exogenous oestrogen.Generally, patients complain of a sharp pleuritic pain, and may be short of breath or have haemoptysis, tachycardia and hypoxemia.The electrocardiogram (ECG) may be normal or show non-specific changes including, tachycardia, S1Q3T3 (S wave in lead I, Q wave and T wave inversion in lead III), incomplete/complete right bundle branch block, right axis deviation, inverted T-wave (V2-3), peaked P waves and atrial flutter.Decision rules such as the Wells score or pulmonary embolism ruleout criteria (PERC) assist in determining the probability of pulmonary embolus and guide the use of D-dimer testing and clinical management.A negative D-dimer using quantitative enzymelinked immunoabsorbent assay (ELISA) effectively excludes PE in patients with low pretest probability. 3Definitive diagnosis is made with computed tomography pulmonary angiography (CTPA) in most cases.
Risk factors for aortic dissection include smoking and cocaine use, connective tissue disorders, infection and inflammation, atherosclerosis, previous heart or aortic valve surgery, bicuspid aortic valves, blunt trauma and pregnancy.The pain is typically sudden-onset and described as a tearing or ripping pain radiating through to the inter-scapular area and associated with dyspnoea, syncope, neurological symptoms or abdominal pain.Physical examination may be entirely normal or reveal hypertension, neurological deficits, peripheral ischaemia, blood pressure or pulse differentials between right and left sides, and new murmurs/ muffled heart sounds/pericardial friction rub/jugular venous distension.On suspicion of this diagnosis, the patient should be treated as a medical emergency with immediate referral and transport to hospital by an appropriate prehospital provider.The definitive diagnosis is made using CT aortography.
Spontaneous pneumothorax may occur with underlying lung disease or trauma (secondary), or without (primary), and patients will present with sudden chest pain and/or shortness of breath.Respiratory distress may be minor or significant.On examination, a resonant percussion note and decreased breath sounds may be found.Radiological investigation will provide the diagnosis.Tension pneumothorax can rarely occur in spontaneous pneumothorax and is a surgical emergency.Any suggestion of haemodynamic instability or mediastinal shift requires immediate decompression.
Of the most common life-threatening causes of chest pain, ACS cannot be diagnosed on history or clinical examination alone. 4Many patients do not present with the classic symptom of severe or crushing central chest pain exacerbated by exertion and that radiates to the arms, neck or jaw, and is associated with sweating, nausea and shortness of breath. 4Elderly patients, women and patients with diabetes more frequently present with atypical symptoms. 5The presence or absence of risk factors for ACS (family history of ischaemic heart disease, smoking, hypertension, hyperlipidemia) does not help rule in or rule out ACS for individual patients.][6] The assessment and management of patients with suspected ACS in the primary care setting should include determining the urgency of need for referral.If patients have had any ongoing symptoms within the preceding 24 hours, they should be referred immediately to an emergency department for assessment. 7

Primary care investigations for suspected ACS
The ECG An ECG should be performed within 10 minutes of assessing a patient with suspected ACS for identification of ST-elevation myocardial infarction (STEMI).Such patients require immediate referral via ambulance services to hospital to enable urgent reperfusion therapies to be commenced. 2,5It is recommended that all general practices have a system in place to ensure rapid clinical review of ECGs.
Typical ECG findings in STEMI include ST segment elevation and reciprocal ST segment depression in other leads.An exception to this is the posterior infarction where ST depression in leads V1 to V3 is the predominant abnormality (Figure 1).Another ECG variation occurs with proximal coronary artery occlusion, where the ECG may show widespread ST depression with elevation only in leads aVR and V1.In right ventricular infarction, ST segment elevation is seen in V1, V2 and V3 (Figure 2).This is a significant pattern to recognise as the administration of glyceryl trinitrate (GTN) can reduce preload enough to cause serious haemodynamic compromise. 4,7,8he ECG may show other patterns suggestive of ischaemia, including ST segment depression, T wave flattening or inversion, or hyperacute T waves (peaked) (Figure3). 8,9Online resources may contribute to clinicians' knowledge. 10

Troponin
Troponin is a structural protein unique to cardiac myocytes, detected following acute myocardial infarction (AMI).The presence of troponin indicates cardiac  Patients with any symptoms within the preceding 24 hours should be referred immediately to an emergency department for assessment. 7Patients who have been symptom-free for between 24 hours and 14 days previously and who have no high-risk features (ongoing or recurrent pain, syncope, heart failure, abnormal ECG) may be investigated using troponin testing; 7 however, general practitionerinitiated troponin testing has been shown to place patients at high risk of adverse outcomes, even when the cardiac troponin test result is negative. 11For this reason, caution is recommended in the use of troponin testing in the non-rural primary care setting.Primary care physicians in a rural or remote setting may have requirements for troponin testing, which is usually performed with point-of-care assays.This result will support physicians in determining the degree of urgency with which a patient should be referred or transferred to definitive care.

Referral and ongoing management in primary care
Patients with suspected ACS, including new-onset angina, should be referred urgently to the nearest emergency department.Patients identified as having a STEMI or ongoing chest pain, dyspnoea, syncope/presyncope or palpitations should be transferred as an emergency via ambulance. 5Many ambulance services have capability to directly transmit 12-lead ECGs to the hospital (emergency department and interventional cardiologist), enabling direct transfer of patients to the cardiology catheter laboratory.Therefore, expediting contact with ambulance services is critical to support reduction in door-to-device time. 12In all other scenarios, patients should be advised not to drive themselves.While awaiting transfer, management should occur, provided transport to hospital is not delayed.Referral to an emergency department is best done by direct phone call to the hospital while ambulance transport is arranged for the patient.Supporting documentation should include the patient's ECG recordings.
Some aspects of the initial management of patients with proven or suspected ACS have been recently updated. 5Routine use of oxygen is no longer recommended unless oxygen saturations are measured at <93% (<88-92% in chronic obstructive airways disease [COAD] to maintain hypoxic drive). 5,13GTN should be administered to symptomatic patients whose chest pain is thought to be caused by ACS.The exceptions to this include cases with suspected right ventricular myocardial infarction, or if the patient has recently taken a phosphodiesterase type 5 inhibitor (eg sildenafil, tadalafil), as the combined effect can cause precipitous and severe hypotension. 5The dose is 0.3-0.6 mg (tablet) or 0.4-0.8mg (spray) sublingually every five minutes for three doses.Oral aspirin, 300 mg, should be given to all with suspected ACS as it significantly decreases the risk of serious vascular events, including myocardial infarction and stroke, without observable increases in the risk of bleeding.The only absolute contraindication is hypersensitivity. 5ntravenous opioids are recommended to treat pain that does not respond to GTN, but recent research suggests that morphine may decrease the absorption of oral antiplatelet agents. 5,14For this reason, fentanyl is the preferred opioid for analgesia in suspected ACS.

Hospital-based risk stratification for ACS
Further assessment, including risk stratification for ACS, will occur in hospital.The National Heart Foundation and Cardiac Society of Australia and New Zealand 2016 risk classification for suspected cardiac causes of chest pain classifies patients as high, intermediate or low risk. 5The classification includes features of history and examination, as well as investigations such as troponin and ECG results (Box 2).There are other risk stratification scoring systems in use worldwide; the most common include TIMI, 15,16 GRACE 17 and HEART 18 scores.However, none of these have been assessed for use in the primary care setting.
As a single troponin test is not able to rule out AMI in patients presenting acutely with suspected ACS, serial testing is performed.A delay of up to three hours for troponin release to be detected in the setting of AMI may occur. 5The finding of an elevated troponin value also does not rule in AMI, with many causes of elevated troponin identified (Box 3). 7This demonstrates the need for a contextual approach to troponin testing, as well as for serial sampling (to evaluate if a rise and fall pattern in troponin values occurs over time). 19Serial ECGs are also performed, and some patients may require ongoing ECG monitoring during their assessment and management.
Individual health services should use a protocol for the risk stratification and subsequent assessment of patients with suspected ACS, which may include exercise stress testing, myocardial perfusion scanning, stress echocardiography or computed tomographic coronary angiography.Further management in the case of proven ACS that may be instituted in hospital include medical therapies, interventional cardiology procedures such as percutaneous coronary intervention (PCI) and surgical options (eg coronary artery bypass graft [CABG]).In patients with STEMI angiography with coronary revascularisation, PCI or CABG is the treatment of choice, or fibrinolysis (if PCI is unavailable within 90 minutes) followed by angiography +/-PCI within 24 hours. 5

Conclusion
ACS is common and life-threatening, and must be considered in all patients with chest pain who present to general practice.A focused history and examination will define high-risk patients; however, this will not exclude a diagnosis of ACS.An ECG is the key immediate investigation primary care physicians must obtain.Close liaison with the nearest emergency department will ensure further risk stratification and that optimum management can be started as early as possible.

Box 1 .*
Differential diagnosis of (non-traumatic) chest pain* Life-threatening diagnoses • Acute coronary syndrome (acute myocardial infarction, unstable angina pectoris) This differential diagnosis is not intended to be exhaustive Adapted with permission from the Medical Journal of Australia, from Parsonage WA, Cullen L and Younger JF.The approach to patients with possible cardiac chest pain.Med J Aust 2013;199(1):30-34.

Figure 2 .Figure 3 .
Figure 2. ECG showing inferior and right ventricular myocardial infarction with ST elevation Box 2. National Heart Foundation and Cardiac Society of Australia and New Zealand risk classification for possible cardiac causes of chest pain Adapted from Aroney CN and Cullen C. Appropriate use of serum troponin testing in general practice: A narrative review.Med J Aust 2016;205(2):91-94.© Copyright 2016 The Medical Journal of Australia -reproduced with permission.