The ECG in Pulmonary Embolism

Electrocardiographic Features

The following ECG changes may be seen in acute pulmonary embolism:

  • Sinus tachycardia - the most common abnormality; seen in 44% of patients.
  • Complete or incomplete RBBB - associated with increased mortality; seen in 18% of patients.
  • Right ventricular strain pattern T wave inversions in the right precordial leads (V1-4) ± the inferior leads (II, III, aVF). This pattern is seen in up to 34% of patients and is associated with high pulmonary artery pressures.
  • Right axis deviation - seen in 16% of patients. Extreme right axis deviation may occur, with axis between zero and -90 degrees, giving the appearance of left axis deviation (“pseudo left axis”).
  • Dominant R wave in V1 - a manifestation of acute right ventricular dilatation.
  • Right atrial enlargement (P pulmonale)peaked P wave in lead II > 2.5 mm in height. Seen in 9% of patients.
  • SI QIII TIII  pattern - deep S wave in lead I, Q wave in III, inverted T wave in III. This “classic” finding is neither sensitive nor specific for pulmonary embolism; found in only 20% of patients with PE.
  • Clockwise rotationshift of the R/S transition point towards V6 with a persistent S wave in V6 (“pulmonary disease pattern”), implying rotation of the heart due to right ventricular dilatation.
  • Atrial tachyarrhythmias - AF, flutter, atrial tachycardia. Seen in 8% of patients.
  • Non-specific ST segment and T wave changes, including ST elevation and depression. Reported in up to 50% of patients with PE.

Simultaneous T wave inversions in the inferior (II, III, aVF) and right precordial leads (V1-4) is the most specific finding in favour of PE, with reported specificities of up to 99% in one study. 


ECG changes in PE are related to:

  • Dilation of the right atrium and right ventricle with consequent shift in the position of the heart.
  • Right ventricular ischaemia.
  • Increased stimulation of the sympathetic nervous system due to pain, anxiety and hypoxia.

Clinical Usefulness

  • The ECG is neither sensitive nor specific enough to diagnose or exclude PE.
  • Around 18% of patients with PE will have a completely normal ECG.
  • However, with a compatible clinical picture (sudden onset pleuritic chest pain, hypoxia), an ECG showing new RAD, RBBB or T-wave inversions may raise the suspicion of PE and prompt further diagnostic testing.
  • In patients with radiologically confirmed PE, there is evidence to suggest that ECG changes of right heart strain and RBBB are predictive of more severe pulmonary hypertension; while the resolution of anterior T-wave inversion has been identified as a possible marker of pulmonary reperfusion following thrombolysis.

 Differential Diagnosis

The ECG changes described above are not unique to PE. A similar spectrum of ECG changes may be seen with any cause of acute or chronic cor pulmonale (i.e. any disease that causes right ventricular strain / hypertrophy due to hypoxic pulmonary vasoconstriction).

Acute cor pulmonale

  • Severe pneumonia
  • Exacerbation of COPD / asthma
  • Pneumothorax
  • Recent pneumonectomy
  • Upper airway obstruction

Chronic cor pulmonale

  • Chronic obstructive pulmonary disease
  • Recurrent small PEs
  • Cystic fibrosis
  • Interstitial lung disease
  • Severe kyphoscoliosis
  • Obstructive sleep apnoea

ECG Examples

Example 1 

  • Sinus tachycardia
  • RBBB
  • T-wave inversions in the right precordial leads (V1-3) as well as lead III


Example 2 

  • RBBB
  • Extreme right axis deviation (+180 degrees)
  • S1 Q3 T3
  • T-wave inversions in V1-4 and lead III
  • Clockwise rotation with persistent S wave in V6


Example 3 

  • Sinus tachycardia.
  • Simultaneous T-wave inversions in the anterior (V1-4) and inferior leads (II, III, aVF).
  • Non-specific ST changes – slight ST elevation in III and aVF.


Example 4

  • Sinus tachycardia.
  • Terminal T-wave inversion in V1-3 (this morphology is commonly seen in PE). There is also T-wave inversion in lead III.

This patient has bilateral PEs confirmed on CTPA.


Example 5

  • Right axis deviation.
  • T-wave inversions in V1-4 (extending to V5).
  • Clockwise rotation with persistent S wave in V6.

This patient had confirmed pulmonary hypertension on echocardiography with dilation of the RA and RV. 


Example 6

  • Sinus tachycardia.
  • RBBB.
  • Simultaneous T-wave inversions in precordial leads V1-3 plus inferior leads III and aVF.


Example 7

  • Sinus tachycardia.
  • Right axis deviation.
  • Marked interventricular conduction delay – most likely RBBB given the RSR’ pattern in V1
  • Persistent S waves in V6.


Example 8

  • RBBB with marked widening of the terminal QRS.
  • Left axis deviation (possibly “pseudo-left axis”).
  • Widespread ST segment abnormalities.

This ECG is an example of massive PE in a young patient with thrombophilia. He suffered a PEA arrest and died shortly after this ECG was taken. For the full story behind this ECG, click here.


Related Topics

Further Reading

Author Credits


  • Chan TC, Brady WJ, Harrigan RA, Ornato JP, Rosen P. ECG in Emergency Medicine and Acute Care. Elsevier Mosby 2005.
  • Harrigan RA, Jones K. ABC of clinical electrocardiography. Conditions affecting the right side of the heart. BMJ. 2002 May 18;324(7347):1201-4. Review. PMID: 12016190. Full text.
  • Kosuge M, Kimura K, Ishikawa T, Ebina T, Hibi K, Kusama I, Nakachi T, Endo M,  Komura N, Umemura S. Electrocardiographic differentiation between acute pulmonary embolism and acute coronary syndromes on the basis of negative T waves. Am J Cardiol. 2007 Mar 15;99(6):817-21. Epub 2007 Jan 30. PMID:17350373.
  • Mattu A, Brady W. ECGs for the Emergency Physician 1, BMJ Books 2003.
  • Mattu A, Brady W. ECGs for the Emergency Physician 2, BMJ Books 2008.
  • Surawicz B, Knilans T. Chou’s Electrocardiography in Clinical Practice (6th edition), Saunders 2008.
  • Wagner, GS. Marriott’s Practical Electrocardiography (11th edition), Lippincott Williams & Wilkins 2007.
Print Friendly


  1. Brian says

    Sinus tachycardia as the most common abnormality. This can be debatable. Ferrari et al. Chest 1997 -- a case series of 80 patients -- precordial T-wave inversion was the most common finding (68%), exceeding sinus tachycardia (26%) and S1Q3T3 (50%). Obviously a small series, but interestingly it is more specific than a sinus tachycardia and may be correlated with severity.