This patient had a long history of supraventricular tachycardia. This electrocardiogram shows the atrial tachycardia with 2:1 A/B block. Although this can be seen with digitalis excess, this was not the case here. The patient required several cardioversions and could not be kept out of her tachycardia in spite of treatment with amiodarone, calcium entry blockers, and digoxin.