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Home | Articles | Cardiac | Suspected Acute Coronary Syndrome

Suspected Acute Coronary Syndrome

Last updated 14th December 2023

Chest Discomfort as a Presenting Symptom

  1. Around 1/3 of all medical emergencies are because of chest discomfort
  2. Most patients with acute onset chest discomfort are referred as ?ACS
  3. Most patients with acute chest discomfort will think they are having a heart attack
  4. Only around 1/3 of patients admitted with ?ACS turn out to have ACS.
  5. Never underestimate the importance of a good history.

Differential Diagnosis of Central Chest Discomfort

  1. The one we want to confirm or exclude first is ACS
  2. The differential diagnosis includes both non life threatening and life threatening causes
  3. Common but non life threatening causes of central chest discomfort are gastro-oesophageal, musculoskeletal, acute pericarditis and hyperventilation
  4. Massive PE and aortic dissection are the two important life threatening differentials.

Other Diagnoses if Patient Looks Well

  1. Musculoskeletal – consider if exquisitely tender over sternum or ribs and resolves completely with injection of local anaesthetic – but remember that presence of chest wall tenderness does not exclude ACS
  2. Gastro-oesophageal – pain goes up and down rather than across chest, worse on lying down, may be associated with acid taste in throat, likely if relieved by Gaviscon but may also be relieved by GTN.
  3. Pericarditis – triad of sharp central pain relieved by sitting forwards, pericardial rub and widespread ST elevation concave upwards
  4. Hyperventilation – clue is tingling in fingers and periorally

Other Diagnoses if Patient Looks Unwell

  1. Massive pulmonary embolus – may cause crushing central chest discomfort and dyspnoea with tachycardia, hypotension, raised JVP and S1Q3T3 or RBBB pattern on ECG
  2. Aortic dissection – clinical clues include tearing chest pain which radiates to back, pallor, appears shocked but is hypertensive, loss of pulses, aortic diastolic murmur

History Suggesting Stable Angina

  1. Typical stable angina is defined by presence of all three of the following:
    1. Constricting discomfort in front of chest or in the neck, shoulders, jaw or arms
    2. Precipitated by physical exertion
    3. And relieved by rest or GTN within about 5 minutes
  2. A patient with only two of these features has atypical angina
  3. Patients with none or only one of these features are generally considered to have non anginal chest pain

Investigation of Patients with Suspected Stable Angina

  1. As a general rule it is best to save invasive testing ie coronary angiography for patients most likely to have CHD
  2. Likelihood of CHD determined by age, gender, cardiovascular risk factors, the nature of the symptoms and the resting ECG
  3. Historically, the Exercise Tolerance Test (ETT) has been used to diagnose and evaluate angina in patients with suspected CHD – NICE have recently reviewed the evidence and now no longer recommend ETT in patients with no previous history of CHD
  4. ETT is still recommended as a useful alternative to functional imaging in patients with established CHD who present with new symptoms which could be due to angina
  5. Exercise or dobutamine stress echo currently recommended if CHD thought to be moderately likely (30-60% likelihood) while CT calcium score preferred if risk of CHD is less than this (10-29% likelihood)
  6. No further tests indicated if risk of CHD 10% or less eg male or female under 45 with atypical angina and no cardiovascular risk factors

History Suggesting ACS

  1. Classic presentation is that of crushing central chest pain or discomfort at rest that lasts longer than 15 mins, but not everyone has this so consider also
  2. Any central chest pain and/or pain in arm, back or jaw lasting longer than 15 minutes
  3. Chest pain that is associated with nausea and vomiting, marked sweating, breathlessness or a combination of these
  4. Chest pain associated with haemodynamic instability
  5. Recurrent chest pain occurring frequently and with little or no exertion, and with episodes often lasting longer than 15 minutes
  6. Treatment for suspected ACS follows:

History Highly Unlikely to be ACS

  1. Pain that is sharp and stabbing, lasts seconds only, is made worse by breathing, coughing or movement and can be reproduced by pressure, with no history of effort pain.

Definition of Significant CHD

  1. Significant CHD found during invasive coronary angiography is ≥70% stenosis of at least one of the major arteries or ≥50% stenosis of the left main coronary artery
  2. Anaemia, coronary spasm, tachycardia, LVH eg due to aortic stenosis, proximal lesions and longer stenoses will allow less severe lesions to provoke angina
  3. Well developed collaterals and distal lesions may reduce the risk of angina in a patient with a significant stenosis

Definition of Myocardial Infarction

  1. MI currently defined by NICE as “evidence of myocardial necrosis in a clinical setting consistent with myocardial ischaemia”
  2. Type 1 MI is a primary coronary event due to plaque erosion and/or rupture
  3. Type 2 MI is secondary to ischaemia due to some other cause eg coronary spasm, anaemia, arrhythmia, hypertension or hypotension
  4. The main clinical definition requires a rise and/or fall of cardiac biomarkers, preferably troponin, with at least one value above the 99th centile of the upper reference limit (TnT ≥14ng/l in Dumfries) AND at least one of:
    1. Symptoms of ischaemia
    2. Resting ECG showing new ST-T changes or new LBBB
    3. Development of new pathological Q waves in the ECG
    4. Imaging evidence of new loss of viable myocardium or new regional wall motion abnormality
  5. It follows from the above that a normal ECG does not exclude MI


  1. Troponins I and T are proteins released into blood stream by damaged cardiac muscle – we measure Troponin T (TnT) in Dumfries
  2. Serum levels ≥14ng/L (a value exceeding the 99th centile of a reference control group) in the setting of typical pain and/or new ST-T changes or new LBBB should be considered distinctly abnormal and likely to represent ACS with myocyte necrosis (acute MI).
  3. Two measurements should suffice: the first as soon as possible after admission and the second, 3 hours later. Results will be available within 2hours of receipt.
  4. Unfortunately a raised troponin does not necessarily confirm MI. Other causes include PE, aortic dissection, myocarditis, heart failure and CKD. To make matters more difficult still some patients turn out to have chronically elevated troponin for no very obvious cause.
  5. Therefore request troponin only if ACS is suspected with a good history and/or fresh ECG changes and not as part of a ‘routine’ screen
  6. Patients with TnT <14ng/L on two occasions may still have ischaemic chest pain – if history typical and/or ECG suggestive, then diagnosis may be ACS with no myocyte necrosis (unstable angina). Depending on the level of clinical suspicion further tests to rule out CHD may still be required

Interpreting Troponin

  1. Patients presenting to primary care with signs / symptoms consistent with Acute Coronary Syndrome (ACS) should be referred to secondary care immediately.
  2. A single undetectable troponin <5ng/L taken AT LEAST 3 HOURS AFTER the onset of ischaemic sounding chest pain in a patient with a normal ECG rules out Non ST Elevation MI (NSTEMI).
  3. Undetectable troponin <5ng/l taken within 3 hours of onset of chest pain in a patient with a normal ECG requires a second sample 3 hours after the first to exclude NSTEMI.
  4. A single troponin within the normal reference range (<14ng/l) in patients presenting with CONTINUOUS pain that lasts more than 90 minutes rules out both unstable angina and NSTEMI if sample taken at least 3 hours after onset of pain and ECG is normal.  NB unstable angina only ruled out if pain continuous.
  5. A single troponin within the normal reference range (<14ng/L) in patients presenting MORE THAN 12 HOURS AFTER after onset of pain rules out NSTEMI if the ECG is normal.

Guidelines for the Assessment of Acute Coronary Syndrome

Click here to print and use the Low Risk Cardiac Chest Pain Pathway [pdf]
See also:

Chest Pain Top Tips

  1. Recurrent chest pain occurring frequently and with little or no exertion, and with episodes often lasting longer than 15 minutes is suggestive of ACS
  2. If the patient uses the word ‘tight’ to describe his or her chest pain then you need to take it seriously
  3. Do not rule out ACS on the basis of a normal resting ECG
  4. Do not rule out ACS on the basis of chest wall tenderness
  5. Do not use response to GTN to make or exclude a diagnosis of ACS
  6. Do not assess symptoms of ACS differently in men and women
  7. Do not assess symptoms of ACS differently in different ethnic groups
  8. Only request TnT when you think ACS is likely because of history and/or presence of new ECG changes
  9. Do not give oxygen routinely – monitor oxygen saturation and use oxygen only to keep SpO2 in the optimum range for that patient.
  10. Do not use ETT to make a new diagnosis of CHD