Tiny Tips: PETMAC as a mnemonic for the 6 deadly causes of chest pain

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An estimated 300,000-500,000 patients present to the emergency department (ED) every year in
Canada with complaints of chest pain.​1​ In USA, the numbers are even more staggering at 8
million per year.​2​ Given its prevalence, having a structured and rapid approach to chest pain is
essential. Use the mnemonic PETMAC as an approach to these 6 cannot-miss causes of chest
pain in the ED. Just think of your friendly neighbourhood pet, Mac!

P: Pulmonary Embolism

  • Classically presents with pleuritic chest pain, shortness of breath, and
    tachycardia. However, PE may often present with only a single symptom – see Wells’ criteria
    for PE.​3​

E: Esophageal Rupture

  • Sudden onset, sharp chest pain, usually following endoscopic procedures or
    forceful vomiting.​3​

T: Tension Pneumothorax

  • Sudden onset, sharp, unilateral chest pain, with tracheal deviation and
    decreased breath sounds on the affected side.
  • Pearl: These patients will often be in respiratory distress. Additionally, always consider this in patients presenting with chest trauma. It is a cause of obstructive shock and immediately life-

M: Myocardial Infarction (and Acute Coronary Syndrome)

  • Dull chest pain worsened with activity and improved with rest. Pain
    can radiate to the arms or jaw, with associated diaphoresis, dyspnea, and
  • Pearl: Many patients (females, elderly, pts with DM or psychiatric disease) can present
    atypically. As a result, keep ACS in mind if these patients come in with generalized fatigue and
    abdominal discomfort!​4​

A: Aortic Dissection

  • Sudden onset, severe, tearing/ripping chest pain radiating to the back
    between the scapulae. Can be associated with focal neurological findings.​3​

C: Cardiac Tamponade

  • No clinical sign or symptom is very obvious for cardiac tamponade, so
    look for pericardial free fluid on an echocardiogram and low voltage QRS complexes on
    the ECG. This may be in the context of hypotension and tachycardia from obstructive
  • Pearl: Look for cardiac tamponade in a trauma situation, in an oncologic patient with
    malignant pericardial effusion, or weeks after a myocardial infarction.​4​

This post was copy edited by Nicholas Swanson and was edited by Daniel Ting.


  1. 1.
    Christenson J, Innes G, McKnight D, et al. Safety and efficiency of emergency department assessment of chest discomfort. CMAJ. 2004;170(12):1803-1807. doi:10.1503/cmaj.1031315
  2. 2.
    Syed S, Gatien M, Perry J, et al. Prospective validation of a clinical decision rule to identify patients presenting to the emergency department with chest pain who can safely be removed from cardiac monitoring. CMAJ. 2017;189(4):E139-E145. doi:10.1503/cmaj.160742
  3. 3.
    Lane S, Mahler S. Chest Pain. In: Tintinalli’s Emergency Medicine: A Comprehensive Study Guide, 9e. ; 2020:1000.
  4. 4.
    Walls R, Hockberger R, Gausche-Hill M. Emergency Medicine : Concepts and Clinical Practice. 9th ed. Elsevier; 2018.

Reviewing with the Staff

Chest pain is one of the most worrisome presentations to the ED. Using the PETMAC mnemonic helps you to think about the most dangerous diagnoses associated with chest pain in the ED. However, it’s helpful to remember that in the ED, with presentations such as chest pain, the goal is often to rule out the most worrisome causes (PETMAC), while being comfortable with the fact that you will often send the patient home without a final diagnosis. Get your mind used to the fact that your job in the ED (when it comes to chest pain) is to rule out the bad, not necessarily diagnose the exact cause. That’s why a mnemonic like PETMAC can be so helpful.

Hans Rosenberg
Hans is an Emergency Physician at the Ottawa Hospital and assistant professor with the Department of Emergency Medicine. His interests include digital scholarship, knowledge dissemination and anything related to his kids’ activities.

Samantha Buchanan

Samantha is a medical student at the University of Ottawa. Her academic interests include emergency medicine, mentorship, and medical education. In her free time, you can find her hiking, running, hanging out with her puppy, or finding the best pizza in Ottawa.

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