Department of Cardiology, Peking Union Medical College Hospital and Chinese Academy of Medical Sciences, Beijing, China.
Clin Cardiol. 2009 Jun;32(6):E79-82. doi: 10.1002/clc.20248.
Prolonged QT interval is usually seen on routine electrocardiogram (ECG), but in some patients it may only be seen immediately before the evolution of torsades de pointes (Tdp). To unmask the potential risk of Tdp in a patient with normal or borderline prolongation of QTc interval and recurrent syncope, dobutamine was given intravenously at a rate of 20 microg/kg/min. Strikingly, QTc prolongation was induced along with syncope after dobutamine infusion. Torsades de pointes occurred 5 d later when the patient received an implantable cardioverter defibrillator (ICD). Genetic testing revealed a mutation of the KNCQ(1)-gene encoding serine instead of glycine. The patient was treated with 75 mg of metoprolol twice daily, and at 12 mo follow-up he had no syncope or chest tightness. The ICD revealed no ventricular tachyarrhythmias or therapy delivered.
QT 间期延长通常在常规心电图（ECG）上可见，但在某些患者中，它可能仅在尖端扭转型室性心动过速（Tdp）演变之前出现。为了揭示 QTc 间期正常或临界延长且反复晕厥患者发生 Tdp 的潜在风险，以 20μg/kg/min 的速度静脉内给予多巴酚丁胺。令人惊讶的是，多巴酚丁胺输注后出现 QTc 延长和晕厥。5 天后，当患者接受植入式心脏复律除颤器（ICD）时，发生尖端扭转型室性心动过速。基因检测显示编码丝氨酸而不是甘氨酸的 KNCQ(1)-基因突变。患者每天服用 75mg 美托洛尔两次，12 个月随访时无晕厥或胸闷。ICD 未显示室性心动过速或心律失常或治疗。
