International Circulation: Our questions are about long QT syndrome. Could you please talk about the advances of diagnose and treatment of long QT syndrome?

　　《国际循环》：请您谈谈长QT间期综合征的诊断治疗进展。

　　Prof. Masayasu Hiraoka: Initially， we thought that long QT syndrome was caused by single gene mutation. It turned out there are more than ten to twelve different genes. Among those genes， three major genes account for about 80% of the clinical cases. These three gene mutations have different phenotypes of clinical expressions and responses to treatment， which are identified as type I， type II， and type III. Type I potassium channel mutation is characterized by exercise induced or emotionally induced syncope or cardiac death. This is the very candidate to βblocker treatments.

　　Masayasu Hiraoka教授：首先，我们认为长QT综合证是由于单基因突变引起的。结果表明有超过10-12种不同的基因与此相关。在这些基因中，3中主要基因与80%的临床病例相关。那三种基因突变有不同相关临床表现和治疗反应的表型。这些被命名为I型，II型和III型。I型钾离子通道突变是其主要特征，表现为运动诱导或情绪诱导晕厥或心源性死亡。这是β阻滞剂治疗的主要适应症。

　　Type II is also a potassium channel mutation，which is a little different from type I. Half of the cardiac events in type II patients are provoked by exercise. The other half are provoked by other stimulations such as phone call during the sleep， watch alarm in the early morning. So they need to avoid these kinds of situation.

　　The third type is a sodium channel mutation， which is characterized by occurring of cardiac events dury quiet time or during sleep. In this case， we need to apply the sodium channel blocker mexiletine or flecainide.

　　There are some resistant cases to the treatments mentioned above in all three types. We need to implant ICDs to these patients to prevent sudden cardiac death.

　　Masayasu Hiraoka教授：II型也是钾离子通道突变，与I型有些微的不同。一半的II型心血管事件是有运动引起的。另外一半是由其他刺激包括睡眠中的电话或者早上的警报等诱发。因此他们需要避免这些境况。III型是钠离子通道突变，它的特征是心血管事件发生多在安静状态或睡眠的时候。这种情况，我们需要应用钠离子通道阻滞剂如美西律或富卡尼等。

　　也还有一些对以上所介绍的三型治疗方法抵抗的患者。我们需要为这些患者植入ICDS来预防突然的心源性死亡事件。