A 45-year-old man with severe mitral stenosis undergoes ECG evaluation. Which finding is most specific for left atrial enlargement?
- A P wave duration >120 ms in lead II with notched appearance and terminal negative portion in V1 >1 mm deep and >40 ms wide ✓
- B P wave amplitude >2.5 mm in lead II
- C Right axis deviation of the P wave vector
- D PR interval prolongation >200 ms
Correct answer: A. P wave duration >120 ms in lead II with notched appearance and terminal negative portion in V1 >1 mm deep and >40 ms wide
Explanation
Left atrial enlargement produces broad (>120 ms), notched P waves in lead II (P mitrale) and a prominent terminal negative deflection in V1 (>1 mm deep, >40 ms duration) representing delayed posterior-left atrial activation. Tall P waves in II indicate right atrial enlargement (P pulmonale). PR interval prolongation reflects AV conduction delay, not atrial enlargement.
Reference: Goldberger's Clinical Electrocardiography, 9th ed.
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