Malignant T-Wave Alternans

36-year-old woman was referred after her son had syncopal episodes associated with a markedly pro- longed QT interval, which was treated with b-blockers and a subsequent pacemaker. The mother had a history of "sei- zures" as a child that had been treated with various medica- tions, which did not appear to affect her events. She contin- ued to have episodes 2 to 3 times a year, and witnesses said she would "stiffen up and gasp for air." She had had no syncope for many years but had episodes of dizziness and near syncope when anxious or under emotional stress. These episodes were not associated with palpitations. Her ECG revealed a corrected QT interval of 496 (Bazzett's formula), and an echocardiogram was remarkable for moderate mitral regurgitation without prolapse. Her QT interval did not shorten during treadmill testing. During recovery, she dem- onstrated biphasic inferolateral T-wave changes that were more pronounced with hyperventilation. On the basis of her long QT interval, she was placed on a b-blocker, and in view of her near syncopal symptoms, an event recorder was placed.