ECG changes in Pulmonary Embolism

Electrocardiographic Features

The ECG changes associated with acute pulmonary embolism may be seen in any condition that causes acute pulmonary hypertension, including hypoxia causing pulmonary hypoxic vasoconstriction.

Key ECG findings include:

  • 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 rotation – shift 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. 


PTE findings compared to Acute Coronary Syndrome

While T wave inversions are commonly associated with acute coronary syndromes, there are several findings associated with pulmonary embolism that differentiate this diagnosis from ACS.

  • ACS is rarely associated with tachycardia
  • Both ACS and PE will present with elevated troponin
  • Ultrasonography may be useful in differentiating the two
  • Kosuge et al have shown that simultaneous inversion in III and V1 are diagnostically significant:

Negative T waves in leads III and V1 were observed in only 1% of patients with ACS compared with 88% of patients with Acute PE (p less than 0.001). The sensitivity, specificity, positive predictive value, and negative predictive value of this finding for the diagnosis of PE were 88%, 99%, 97%, and 95%, respectively. In conclusion, the presence of negative T waves in both leads III and V1 allows PE to be differentiated simply but accurately from ACS in patients with negative T waves in the precordial leads.

Kosuge et al 2007

Mechanisms

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 
ECG Massive bilateral pulmonary embolus

Massive bilateral pulmonary embolus

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

Example 2 
ECG Massive bilateral pulmonary embolus

Massive bilateral pulmonary embolus

  • 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 
ECG Massive PE PTE pulmonary embolus 2

Massive pulmonary embolus

  • 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
ECG bilateral PE

This patient has bilateral PEs confirmed on CTPA.

  • 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.

Example 5
ECG right sided pulmonary embolus
  • Right axis deviation.
  • T-wave inversions in V1-4 (extending to V5).
  • Clockwise rotation with persistent S wave in V6.

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


Example 6
ECG pulmonary embolus
  • Sinus tachycardia.
  • RBBB.
  • Simultaneous T-wave inversions in precordial leads V1-3 plus inferior leads III and aVF.

Example 7
Massive-PTE-RBBB-RAD

Saddle embolus confirmed on CTPA

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

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Emergency Physician in Prehospital and Retrieval Medicine in Sydney, Australia. He has a passion for ECG interpretation and medical education | ECG Library |

2 Comments

  1. Hi Dr. Burns, can you list the studies that you use for the above percentages / findings? Thanks!

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