A Common Cause of Sudden Death in Young People


Tired jogger

长QT综合征（LQTS）是心脏电气系统. LQTS can lead to a sudden,意外的，威胁生命的类型ventricular tachycardiacommonly called尖端扭转.患有LQT的人面临着晕厥(loss of consciousness) and sudden death,often at a young age.


People with LQTS have prolonged QT intervals on theirECGs. The QT interval represents repolarization,or "recharge," of a cardiac cell.在心脏的电脉冲刺激心脏细胞（从而使其跳动）之后，必须进行充电，以使电池准备好接受下一个电脉冲。qt间期（从qrs波开始到t波结束测量）是放电所需的总时间，然后给心脏细胞充电。In LQTS,QT间期延长。QT间期异常是导致LQTS相关心律失常的原因。


LQTS是一种遗传性疾病。Several genes have been identified that affect the QT interval,so several varieties of LQTS exist.有些家族有很高的Lqts发病率。因为有这么多基因可以影响qt间期，Lqts的许多变异已经被鉴定出来。Some of these ("classic" LQTS) are associated with a high incidence of dangerous arrhythmias and sudden death,which often occur in several family members.其他形式的lqts（“lqts变体”）危险性要小得多。Many of these genetic variants are characterized by a normal baseline QT interval,而心律失常一般只有在一些附加因素（如药物治疗、心脏病、心脏病、心脏病等）下才会出现。或明显的电解质失衡）会延长QT间期。然而，当有这种Lqts变异的人的qt间期延长时，dangerous arrhythmias do occur.


Classic LQTS is present in approximately one of 5000 people.LQTS是年轻人猝死的常见原因之一，每年造成2000到3000人死亡。Variants of LQTS are much more common,可能影响到2-3%的人口。


The symptoms of LQTS occur only when the patient develops an episode of dangerous ventricular tachycardia,and the degree of symptoms depends on the length of time the arrhythmia persists.如果只是短暂的持续，a few seconds of extreme dizziness may be the only symptom.如果持续时间超过10秒左右，syncope occurs.And if it lasts for more than a few minutes,受害者通常不会恢复知觉。

In those with some varieties of LQTS,episodes are often triggered by sudden bursts of adrenaline;such as might occur during physical exertion,当受到严重惊吓时，or when becoming extremely angry.



医生应该考虑任何晕厥或心脏骤停的患者的LQTS。以及已知Lqts的家庭成员。Any young person with syncope that occurs during exercise,or in any other circumstance in which a surge of adrenaline levels was likely to have been present,should have LQTS specifically ruled out.

The diagnosis of LQTS is usually made by observing an abnormally prolonged QT interval on the ECG.Sometimes atreadmill testis necessary to bring out the ECG abnormalities.Genetic testing for LQTS and its variants is becoming much more commonly used than it was just a few years ago.


许多显性LQTS患者接受了beta blockers.Beta blockers blunt the surges of adrenaline that trigger episodes of arrhythmias in these patients.Unfortunately,it has not yet been proven that beta-blockers significantly reduce the overall incidence of syncope and sudden death in patients with LQTS.

It is particularly important for people with LQTS and its variants to avoid the many drugs that cause a prolongation of the QT interval.In these people,such drugs are very likely to provoke episodes of torsades de pointes.Drugs that prolong the QT interval are unfortunately common.The major offenders are,具有讽刺意味的是，这个抗心律失常药;一些抗抑郁药物，and antibiotics such as erythromycin,克拉霉素红霉素，还有阿奇霉素。信用证maintains a list of drugs that often prolong the QT interval.

For many people with LQTS,这个implantable defibrillator是最好的治疗方法。This device should be used in patients who have survived cardiac arrests,可能是因为Lqts导致晕厥的患者，尤其是在已经服用β受体阻滞剂时发生晕厥的患者。


钠通道阻滞剂可用于LQTS 3型。

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