Vincent G M
Department of Internal Medicine, LDS Hospital, Salt Lake City, Utah 84143, USA.
Annu Rev Med. 1998;49:263-74. doi: 10.1146/annurev.med.49.1.263.
The congenital long QT syndrome is an autosomal-dominant genetic disorder of cardiac electrical repolarization. It is caused by mutations of at least six genes, of which four, all encoding for cardiac ion channels, have been identified: KVLQT1, HERG, and Min K encode for cardiac potassium ion channels, and SCN5A encodes for the cardiac sodium ion channel. In each case the altered ion channel function produces prolongation of the action potential and propensity to torsade de pointes ventricular tachycardia. A fifth gene locus is known to be on chromosome 4, but the gene has not been isolated. At least one other gene must exist, and there may be several more. Long QT syndrome is a frequent but often overlooked cause of unexpected syncope and sudden death in children and young adults. Characteristic findings are prolongation of the QT interval and T wave abnormalities on the electrocardiogram. However, the QT interval at presentation is normal about 10% of the time and just borderline prolonged another 30%, so diagnosis may be difficult. Symptoms are syncope and sudden death, typically occurring during exercise or emotional upset. The manifestations vary, depending on the genotype present. The phenotype also probably varies, depending on the specific mutation involved. Phenotypic heterogeneity is also caused by variable penetrance and expressivity.
先天性长QT综合征是一种常染色体显性遗传的心脏电复极障碍性疾病。它由至少六个基因的突变引起，其中四个已被确定，均编码心脏离子通道：KVLQT1、HERG和Min K编码心脏钾离子通道，SCN5A编码心脏钠离子通道。在每种情况下，离子通道功能改变都会导致动作电位延长，并易发生尖端扭转型室性心动过速。已知第五个基因位点位于4号染色体上，但该基因尚未分离出来。至少还存在一个其他基因，而且可能还有更多。长QT综合征是儿童和年轻人意外晕厥和猝死的常见但常被忽视的原因。特征性表现是心电图上QT间期延长和T波异常。然而，就诊时QT间期正常的情况约占10%，仅临界延长的情况占另外30%，因此诊断可能困难。症状为晕厥和猝死，通常在运动或情绪激动时发生。表现因存在的基因型而异。表型可能也因具体涉及的突变而有所不同。表型异质性还由可变的外显率和表现度引起。
