Which ECG finding is associated with pulmonary embolism?

• A. ST elevation in leads II and aVF
• B. S1-Q3-T3 pattern
• C. T wave inversion in V1-V3
• D. U waves in V3

Answer: (B)

Pulmonary embolism often causes acute strain of the right ventricle, which can show up on the ECG as the classic S1Q3T3 pattern. This means a deep S wave in the leftward lead (a strong S in lead I), a Q wave in the right‑sided lead III, and T wave inversion in lead III. It reflects the sudden right‑sided pressure and chamber enlargement from the embolus pulling blood away from the lungs.

This pattern is a well-known clue to PE, though it isn’t always present and isn’t perfectly sensitive. The other options point to different problems: ST elevation in the inferior leads suggests an acute inferior myocardial infarction; T wave inversion in the anterior leads V1–V3 can occur with various conditions but isn’t the classic PE finding; U waves in V3 are more associated with electrolyte problems like hypokalemia. So the S1Q3T3 pattern best fits pulmonary embolism in the context of an ECG finding.