Scenario: A 72-year-old female who had quadruple coronary artery bypass surgery 1 year earlier suddenly awoke at home with nausea and felt her heart racing. She took a nitroglycerine tablet because she thought she was having “heart problems,” then suddenly she felt faint. She called 911. Following is the 12-lead ECG obtained in the ambulance. The patient’s blood pressure was 70/40 mm Hg.

Atrial fibrillation with rapid ventricular response and right bundle branch block (RBBB)

Hallmarks of atrial fibrillation are observed, including irregular ventricular activity with absence of discrete P waves. Random atrial fibrillatory waves represent atrial activity where only impulses of sufficient magnitude depolarize through the AV node, resulting in a QRS complex. In addition, there is an RBBB pattern as evidenced by the rSR’ waveform configuration in lead V1 and a wide QRS complex. Of note, although the computer interpretation was accurate, human interpretation is still necessary....

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