Scenario: This resting 12-lead electrocardiogram (ECG) was obtained from a 71-year-old male veteran in the emergency department. The patient complained of dyspnea, had a history of uncontrolled hypertension, and was taking beta blockers. His ejection fraction (EF) was 20%.

Based on the 2009 American Heart Association and American College of Cardiology’s recommendations for the standardization and interpretation of the ECG,1–6  we have updated the ECG Puzzler to assist clinicians in correctly interpreting the ECG to improve clinical care. The following items provide background information to help the reader answer the new ECG Puzzler questions:

This 12-lead ECG meets Sokolow’s diagnostic criteria (S V1 + R V5 >35 mm) for left ventricular hypertrophy (LVH).

The slightly prolonged QRS duration (>110 ms) and the first degree heart block (PR interval >200 ms) reflect a conduction delay caused by the LVH....

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