A pregnant woman taking phenytoin (Dilantin) for a previous diagnosis of epilepsy was…

A pregnant woman taking phenytoin (Dilantin) for a previous diagnosis of epilepsy was referred to the cardiology clinic due to premature ventricular complexes (PVCs). Because of previous miscarriages, she was given the β-adrenergic agonist terbutaline in order to postpone preterm labor. She experienced palpitations, PVCs, 2:1 AV block, and QT prolongation (520 msec) at a sinus rhythm of 90 bpm. (QT = 634 msec by the Bazett method, normal QT < 460 msec for adult females). The patient’s mother had died suddenly