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:

  1. Calibration and Leads Placement: Electrocardiographs provide clinicians with a caliber (see figure) that quantifies the voltage used to obtain the recording. Each volt resembles 10 small squares. This ratio changes if calibration is changed. Also, when chest leads (V1–V6) are properly placed,...

You do not currently have access to this content.