What is ‘S1Q3T3 sign’?

S1Q3T3 sign is Seen in ECG

Pulm embolism

R.W.Koster, CC BY-SA 3.0 https://creativecommons.org/licenses/by-sa/3.0, via Wikimedia Commons

  • Image – points to note
  • S wave present in lead -I
  • Q wave and inverted T wave in lead III

S1Q3T3 sign reflects

[A] Right atrial strain
[B] Right ventricular strain
[C] Left ventricular strain
[D] Pulmonary artery strain

S1Q3T3 sign

S1Q3T3 sign

  1. Prominent S wave in lead I
  2. Q wave and inverted T wave in lead III
  3. This is a sign of acute cor pulmonale
  4. Suggests – acute pressure and volume overload of the right ventricle because of pulmonary hypertension
  5. Reflects right ventricular strain

S1Q3T3 findings on ECG and diagnosis of pulmonary embolism

S1Q3T3 findings on ECG – is present in 15% to 25% of patients ultimately diagnosed with pulmonary emboli

S1Q3T3 findings on ECG and acute cor pulmonale 

Any cause of acute cor pulmonale can result in the S1Q3T3 findings on ECG,

  1. Pulmonary embolism
  2. Acute bronchospasms
  3. Pneumothorax

Pulmonary embolism – findings on ECG

S1Q3T3 findings on ECG

Other ECG findings noted during the acute phase of a PE include

  1. New right bundle branch block (complete or incomplete)
  2. Rightward shift of the QRS axis
  3. ST-segment elevation in V1 and aVR
  4. Generalized low amplitude QRS complexes
  5. Atrial premature contractions
  6. Sinus tachycardia
  7. Atrial fibrillation/flutter
  8. T wave inversions in leads V1-V4
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