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This blog is based on a case study in the literature.
A 60 yo male with a recent previous history of angina (with a cardiac stent), has intermittent left sided chest pain. His past medical history is Hypertension and Diabetes. He is haemodynamically stable with a heart rate of 93bpm and Blood Pressure of 122/80 and a respiratory rate of 18.
His ECG shows Q waves in leads III and aVF and his troponin is normal.

4 hours later he crashes,  becomes diaphoretic and tachypnoeic, with a heart rate of 136 bpm and a BP of 70mmHg.
An ECG is done and shown below. Based on this, the patient is taken to the cath lab.
​What does it show? What is the diagnosis?


Source: Vascular 2019


  • Sinus tachycardia
  • ST elevation in III, aVF and aVR and V1 with reciprocal changes in precordial leads and lateral leads. The ST elevation and reciprocal changes are consistent with a STEMI

​Can you see anything else?
…. There is an S1Q3T3

There was no coronary artery obstruction was found.
​A CTPA was done that revealed a large saddle pulmonary embolism.

​Let’s look at PE mimicking an acute infarction.

Clinical Presentation of PE

Match the following percentages with the following symptoms:
79%,   57%,   47%,   26%

  1. Pleuritic chest pain
  2. Tachycardia
  3. Tachypnoea
  4. New dyspnoea at rest or exertion


  1. Pleuritic chest pain. 47%
  2. Tachycardia. 26%
  3. Tachypnoea. 57%
  4. New dyspnoea at rest or exertion. 79%

What are some of the ECG Findings in PE?

Findings on ECG, for the most, are non-specific for diagnosing pulmonary embolism.
Some of the more typical findings include:

  • Sinus Tachycardia
  • S1Q3T3
  • S1Q3
  • Right Axis
  • Bundle Branch Block (complete or incomplete)
  • T wave inversions in the right precordial leads (right heart strain).
Is st elevation a typical ecg finding in pulmonary embolism?


Not normally. However if it is present, it is usually in anteroseptal leads rather than inferior leads and is least likely to be present in the lateral leads.

Other ECG abnormalities

In a study by Sreeram et al, it was found that > 3 of the following increased probability of PE:

  • RBBB (complete or incomplete) + STE and positive T wave in V1
  • Right axis deviation
  • S waves >1.5mm in I and aVL
  • Shift of transition zone in precordial leads to V5
  • Q waves in III and aVF (but not II)
  • T wave inversion in III, aVF, V1-4
  • Low voltage QRS in limb leads of <5mm
why is there a troponin leak in pulmonary embolism?


Troponin leaks can occur from myocardial stretching secondary to right ventricular afterload increases.

It’s hard to remember everything

You can’t remember everything, so look these up next time a patient presents. The ECG must be looked at with the patient’s presenting complaint and past history.
I remember  to look for 5 things:

  1. Unexplained Sinus Tachycardia
  2. S1Q3T3 or S1Q3
  3. RBBB (complete or incomplete) + right axis deviation
  4. T wave inversion in III and V1-4
  5. S wave in I (+ aVL)

Topics on Pulmonary embolism in the members section include:

  • The ECGs of Pulmonary Embolism
  • ECG findings that predict your patient is about to crash
  • What are the symptoms and clinical signs of pulmonary embolism?
  • Scoring systems
  • Investigations such as the ABG and D-dimer
  • PE in Pregnancy
  • What about sub-segmental PE’s?
  • Who needs thrombolysis?
  • The most important studies in management of PE


    1. Villablanca P A et al. Case report and systematic review of pulmonary embolism mimicking ST-elevation myocardial infarction. Vascular 2019, Vol 27(I) 90-97.
    2. Falterman TJ, et al. Pulmonary embolism with ST segment elevation in leads V1 to V4: case report and review of the literature regarding electrocardiographic changes in acute pulmonary embolism. J Emerg Med 2001; 21: 255–261. 
    3. Sreeram N, et al. Value of the 12-lead electrocardiogram at hospital admission in the diagnosis of pulmonary embolism. Am J Cardiol 1994; 73: 298–303. 


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