ECG of the month. Bigeminal rhythm VIII. Sinus rhythm with normal antegrade atrioventricular (A-V) conduction and slow retrograde conduction back to the atria, producing atrial reentry or echo complexes and suggesting dual A-V nodal pathways or an accessory A-V pathway that conducts slowly from the ventricles to the atria.

A 55-year-old woman came to the emergency department because of an episode of post-prandial upper abdominal pain radiating to her back and associated with nausea and vomiting. The pain had been recurring intermittently for approximately six months. While in the emergency department, she had another episode of pain and felt lightheaded. Her pulse rate at that point was between 30 and 40 beats per minute, and an electrocardiogram was recorded (Figure).