Approach

All patients presenting to hospital with chest pain should be urgently evaluated and cardiac and noncardiac causes differentiated. History, examination, and initiation of therapy need to be done simultaneously.

History

A description of the chest pain (i.e., onset, nature, location, radiation, intensity, duration, associated features) and an enquiry about any associated symptoms or major risk factors for coronary artery disease (e.g., hypertension, diabetes, dyslipidemia, obesity, chronic renal insufficiency, smoking) are essential. Other risk factors for myocardial infarction (MI) include male sex, advanced age, and cocaine use in younger people.

Classically the pain is described as diffuse, severe, "heavy" or "crushing," located centrally in the chest, with radiation to the left arm or jaw and occurring at rest. However, it may be nonclassic by location (i.e., epigastric, jaw, arm, neck pain) or by nature (i.e., burning, throbbing, recent-onset indigestion [particularly if unrelated to meals], sharp or pleuritic chest pain, uneasiness).[67]

Associated features such as nausea, vomiting, dyspnea, palpitations, weakness, dizziness, lightheadedness, confusion, or vague abdominal symptoms are more frequent among patients with diabetes and in women and older people.[67] Some patients can present with only these symptoms and without chest pain.

Physical exam

The clinical picture of acute MI is variable and no signs are specific to this condition. On general inspection, patients are typically distressed, diaphoretic, tachycardic and appear pale or gray. Rales on lung exam suggest heart failure. An audible S3 or S4 on cardiac exam indicates poor cardiac muscle compliance of the infarcted muscle.

Alternatively, the patient may be in cardiogenic shock with a decreasing level of consciousness, profound hypotension, acute shortness of breath, and imminent cardiac arrest.

Investigations

ECG should be ordered as early as possible (i.e., within 10 minutes of presentation).[67]​​​[68]​ If presentation is outside of the hospital, a prehospital ECG should be obtained as early as possible and sent to the receiving hospital.[3][69]​​​​​​​​​​​ Serial ECGs should be checked in patients with a normal initial ECG if there is a high clinical suspicion for myocardial ischemia.[2][67]​​​​​ If the ECG shows ST-segment elevation, the patient should be urgently assessed for reperfusion therapy.[69] ST depression in two or more leads V1-V4 should be strongly considered as a posterior STEMI.[Figure caption and citation for the preceding image starts]: 12-Lead ECG with ST-segment elevation lead V1 to V4From the personal collection of Dr Mahi Ashwath; used with permission [Citation ends].com.bmj.content.model.Caption@1a2e6f4b[Figure caption and citation for the preceding image starts]: 12-Lead ECG with ST-segment elevation in the inferior leads (II, III, and aVF)From the personal collection of Dr Mahi Ashwath; used with permission [Citation ends].com.bmj.content.model.Caption@1902284b[Figure caption and citation for the preceding image starts]: 12-Lead ECG with normal ST segments and without any abnormal Q wavesFrom the personal collection of Dr Mahi Ashwath; used with permission [Citation ends].com.bmj.content.model.Caption@7379b861[Figure caption and citation for the preceding image starts]: 12-Lead ECG 1 week later with borderline anterolateral ST-elevation and reciprocal ST-depression in the inferior leads; also noted is the poor R-wave progression and the presence of septal Q wavesFrom the personal collection of Dr Mahi Ashwath; used with permission [Citation ends].com.bmj.content.model.Caption@101c4ff4[Figure caption and citation for the preceding image starts]: 12-Lead ECG 1 hour later with obvious anterolateral ST-elevation and reciprocal ST-depression in the inferior leads, absence of anterior R waves, and the development of anterior Q wavesFrom the personal collection of Dr Mahi Ashwath; used with permission [Citation ends].com.bmj.content.model.Caption@277e27ff[Figure caption and citation for the preceding image starts]: 12-Lead ECG 3 hours later with completed anterolateral infarct, absence of anterolateral R waves, and the development of anterolateral Q waves; the ST segments are returning to normalFrom the personal collection of Dr Mahi Ashwath; used with permission [Citation ends].com.bmj.content.model.Caption@563ecb1d[Figure caption and citation for the preceding image starts]: 12-Lead ECG the next day with completed anterolateral infarct; ST segments are completely back to baselineFrom the personal collection of Dr Mahi Ashwath; used with permission [Citation ends].com.bmj.content.model.Caption@276af5

The definitive diagnostic test for STEMI is coronary angiography. [ Cochrane Clinical Answers logo ] ​​​ Angiography can lead to immediate treatment as the vessel can often be opened and stented at the same procedure. If angiography is not immediately available, a further history should be taken to exclude contraindications to thrombolysis. Do not use coronary CT angiography in high-risk emergency department patients presenting with acute chest pain. Randomized controlled trials evaluating coronary CT angiography to diagnose coronary artery disease have been limited to those patients with acute chest pain at low or low-intermediate risk of ischemic events or mortality. Early CT may, however, be considered to rule out diagnoses such as aortic dissection or pulmonary embolism.[3][70]

Cardiac biomarkers (e.g., cardiac-specific troponins) should be ordered on presentation for any patient with chest pain and risk factors. High-sensitivity cardiac troponins are preferred.[67][68]​​ ​​​​​​Cardiac troponin levels remain elevated for around 10 days, which can make it difficult to determine the time of myocardial injury.[71] Patients with elevated troponin levels have a worse prognosis than those with normal troponin levels.​[72][73]​​ ​​Alternative causes for raised troponin levels should also be considered. These may be cardiac (e.g., myocarditis, aortic dissection, severe heart failure) or noncardiac (e.g., pulmonary embolism, impaired renal function, underlying sepsis).[74] It is important to remember that even with an alternative underlying cause, raised troponin may still indicate myocardial injury.​​​​ Creatine kinase-MB fraction (CK-MB) and myoglobin are less sensitive and less specific and should not be ordered in the diagnosis of STEMI.[2][3]​​[75][76]​​​​

A basic metabolic panel and complete blood count should also be performed, and serum glucose and lipids should be measured. Cholesterol levels may be lowered by high catecholamine levels produced by the MI in its early phases, and serum lipids should therefore be repeated in 30-60 days.[77][78]

Do not delay coronary reperfusion treatment to wait for blood results.[3]

Arterial blood gases should only be checked when there is severe dyspnea, hypoxia, and/or clinical evidence of pulmonary edema or cardiogenic shock, and in survivors of cardiac arrest.

Chest x-ray (with a portable machine) is done to exclude other diagnoses, such as aortic dissection, and to look for evidence of heart failure.[67]​​[68]​ 

Point-of-care transthoracic echocardiogram can be used to:

  • Look for regional wall motion abnormalities of the left ventricle in patients with an atypical presentation or equivocal ECG[79][80]

  • Assess the patient’s eligibility for coronary reperfusion therapy in the event of a delayed presentation

    • In practice, however, the patient's clinical status and the presence of pathologic Q waves in the ECG are usually enough to assess their eligibility for coronary reperfusion therapy if presentation is delayed

  • Look for mechanical complications of acute MI, particularly in hemodynamically unstable patients[2][79]

    • Left ventricular function

    • Right ventricular function

    • Ventricular septal rupture

    • Left ventricular free wall rupture

    • Acute mitral regurgitation

    • Pericardial effusion

    • Cardiac tamponade.

​An echocardiogram can also be used to:

  • Exclude STEMI in patients who present with global saddle-shaped ST-segment elevation (as seen with acute pericarditis).[79]

  • Confirm the diagnosis of takotsubo cardiomyopathy (usually after normal coronary arteries are found on a STEMI angiogram).[2][79]

  • Suggest alternative etiologies associated with chest pain (e.g., acute aortic disease, pulmonary embolism).[3][79]​​

A predischarge echocardiogram is indicated for all patients post-acute MI to assess left ventricular function after coronary reperfusion therapy.[69]​​[79][80]

It is important to remember that imaging/other tests must not delay coronary reperfusion therapy.[79]

Do not perform stress tests in patients with acute chest pain and high probability of acute coronary syndrome. A stress test, such as cardiac MRI stress test, can increase risk and delay treatment in patients with acute chest pain and markers of high risk, such as ST segment elevation and/or positive cardiac biomarkers.[81]

Emerging investigations

Cardiac myosin-binding protein C (cMyC)

CMyC is a cardiac-restricted protein that is released more rapidly than cardiac troponin after acute MI. CMyC is also more abundant than cardiac troponins. CMyC may perform better than cardiac troponin T or I in patients who present early after symptom onset.[82]​ It may become the gold standard test for the early diagnosis of acute MI, though is not currently used in clinical practice.​

Venepuncture and phlebotomy: animated demonstration
Venepuncture and phlebotomy: animated demonstration

How to take a venous blood sample from the antecubital fossa using a vacuum needle.

How to perform an ECG: animated demonstration
How to perform an ECG: animated demonstration

How to record an ECG. Demonstrates placement of chest and limb electrodes.

Risk stratification

The American College of Cardiology/American Heart Association recommend the use of validated chest pain risk scores as part of standardized clinical decision pathways to determine which patients require further investigation, particularly in settings where high-sensitivity cardiac troponin assays are not available.[67][68]

Risk scoring systems provide a summative assessment of the risk of a patient experiencing a major adverse cardiovascular event, or death, within the next 30 days from presentation with a possible acute coronary syndrome.[67] They combine troponin levels with other clinical information, such as age, ST segment changes on ECG, symptoms, and coronary artery disease (CAD) risk factors. Urgent diagnostic testing for suspected CAD is not needed for patients deemed low risk.[67]

Examples of validated risk scores include the Thrombolysis in Myocardial Infarction (TIMI) risk score and the Global Registry of Acute Coronary Events (GRACE) risk model.[5]​​​ [ Thrombolysis in Myocardial Infarction (TIMI) Score for Unstable Angina Non ST Elevation Myocardial Infarction Opens in new window ] [ GRACE Score for Acute Coronary Syndrome Prognosis Opens in new window ]

Do not order a coronary artery calcium (CAC) test in patients with known atherosclerotic disease, including those with stents and bypass grafts, as this offers limited incremental prognostic value for these individuals.​[70][84][85]

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