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Acute Pulmonary Embolism: Size does matter and ECG can give us clues



Acute pulmonary embolism (PE)  is a common condition that can be both severe and difficult to diagnose. Half of all acute PE cases are diagnosed in the emergency department, and acute PE follows acute coronary syndrome as the second most common cause of sudden unexpected death in outpatients. Also, right ventricular dysfunction is a consequence of massive/submassive acute pulmonary embolism and correlates with a poor prognosis and high mortality rate. Although an ECG lacks both sensitivity and specificity for acute PE, there are some clues that can help in determining the size of an acute PE.

What are some of the common ECG changes seen with massive acute PE? 1

ECG Changes Massive PE (%) Non-Massive PE (%)
Anterior Ischemic Pattern 85 19
S1Q3T3 54 54
Sinus Tachycardia 36 0
Low Voltage 36 36
RBBB 22 24
Pulmonary P Waves 7 0

Study methodology: 80 patients enrolled, prospective study


Anterior ischemic pattern (inverted T waves) on ECG was the most frequently observed ECG abnormality in patients with massive acute PE.

  • Had the best sensitivity (85%), specificity (81%), PPV (93%), and NPV (65%) for massive acute PE
  • Correlated highly with a Miller index of >50% (90%) and mean pulmonary artery pressure (PAP) >30 mmHg (81%)

What are some of the common ECG changes seen with right ventricular dysfunction due to acute PE? 2–4

ECG Changes RV Dysfunction (%) Without RV Dysfunction (%)
T-Wave Inversion in Leads V1 – V3 75 5 – 12
RBBB 30 – 46.4 3 – 17
Qr in Lead V1 31 3
S1Q3T3 25 – 35 5.5 – 10
Normal ECG 8 49

Study methodology: 204 patients enrolled with acute PE


T-wave inversion in leads V1 – V3 was the most prevalent finding on ECG with right ventricular dysfunction due to acute PE.

  • Sensitivity of 75%
  • Specificity of 88–95%
  • NPV of 86–95.5%
  • PPV of 73.1-78%


In general, the ECG is not very sensitive or specific for acute PE, but T-wave inversions in leads V1 – V3 seem to be the most common ECG finding in massive/submassive acute PE with a diagnostic accuracy of close to 80%.

Ferrari E, Imbert A, Chevalier T, Mihoubi A, Morand P, Baudouy M. The ECG in pulmonary embolism. Predictive value of negative T waves in precordial leads–80 case reports. Chest. 1997;111(3):537-543. [PubMed]
Kucher N, Walpoth N, Wustmann K, Noveanu M, Gertsch M. QR in V1–an ECG sign associated with right ventricular strain and adverse clinical outcome in pulmonary embolism. Eur Heart J. 2003;24(12):1113-1119. [PubMed]
Punukollu G, Gowda R, Vasavada B, Khan I. Role of electrocardiography in identifying right ventricular dysfunction in acute pulmonary embolism. Am J Cardiol. 2005;96(3):450-452. [PubMed]
Kim S, Park D, Choi H, et al. The best predictor for right ventricular dysfunction in acute pulmonary embolism: comparison between electrocardiography and biomarkers. Korean Circ J. 2009;39(9):378-381. [PubMed]
Salim Rezaie, MD

Salim Rezaie, MD

ALiEM Associate Editor
Clinical Assistant Professor of EM and IM
University of Texas Health Science Center at San Antonio
Founder, Editor, Author of R.E.B.E.L. EM and REBEL Reviews
  • Daren M Beam

    I would be wary of using the ECG to predict the size of pulmonary embolism. The conduction of the system on the heart is complex with many different factors contributing and volume overloading from PE is only one of many. For size of the PE, I would go to the tool of choice for diagnosis for PE, the CT. If the patient is clinically and unstable with a high suspicion, then bedside ultrasound showing RV/LV ratio would be a good indicator as well. What I do like and agree with is the ECG can tell the strain on the heart. Anyone with a diagnosed PE, and and suspicion of high clot burden, the ECG showing right heart strain (either from S1Q3T3 or iRBB) could clinically correlate your suspicion and help direct your therapy.

    • Salim R. Rezaie

      Hello Daren,
      I do not disagree with your comments. The gold standard for PE would still be CT, and I also like US better for signs of right heart strain. My only point was that ECG could give additional useful info to help support this. Obviously, with massive PE thrombolytics are indicated, and still there is debate on submassive PE as well. Either way, right heart dysfunction is a poor prognostic indicator and ECG could add further information, but by no means was the purpose of the post to say that ECG should be used as the sole tool. TY for your comments and taking the time to read the post.


  • Nilesh Patel

    Any idea why you get low voltage with a PE? I surmise it is from decreased conduction to EKG leads from RV dysfunction or shock. I cannot find the reason described anywhere, however.


    • Salim R. Rezaie

      Hello Nilesh,
      This was not something I was able to find either, but I suspect it is from the increased RV dysfunction. I tried doing a literature search for this as well, and was not successful in finding the exact pathophysiology. It is a great question, and if I find a reason I will let you know.


  • Nadim Lalani

    Salim! nice work 🙂

    If I am not mistaken Twave inv in III together with vi-v3 v specific for PE. I call it “PE3 pattern”

    here are other useful Links from Amal mattu And Dr Smith:

    thanks N