Scenario: This 12-lead ECG reading was obtained from a 76-year-old African American woman who presented to the emergency department with shortness of breath, fatigue, and a cough for the past month. Prior medical history includes chronic obstructive pulmonary disease, hypertension, and cigarette smoking for more than 40 years. ECG PUZZLER A regular feature of the American Journal of Critical Care, the ECG Puzzler addresses ECG interpretation for clinical practice. We welcome letters to the Editors regarding this feature.