Short QT syndrome

The QT interval on an electrocardiogram signifies the time required for the heart to repolarize after depolarization. It has long been appreciated that a long QT interval predisposes patients to life-threatening ventricular arrhythmia. Short QT syndrome is a newly described disease characterized by a shortened QT interval and by episodes of syncope, paroxysmal atrial fibrillation or life-threatening cardiac arrhythmias. The syndrome usually affects young and healthy people with no structural heart disease and may be present in sporadic cases as well as in families. Our understanding of a new disease has rarely benefitted so quickly from research in genetics, molecular biology and biophysics. It was first described in 2000 in a handful of patients, and since then 3 different genes associated with the disease and the biophysical basis have been described, and therapy has been made available. Here we review the current understanding of the pathophysiology, clinical presentation and treatment of short QT syndrome.     

Clarithromycin induced torsade de pointes

Background  Clarithromycin is a commonly used macrolide antibiotic. It is known to cause QT prolongation. Medication induced QT prolongation is a major risk factor for the development of torsade de pointes. Methods  A 79-year-old lady presented with frequent episodes of torsade de pointes following commencement of clarithromycin. This was noted to be in association with a prolongation of the QT interval. Conclusion  Knowledge of medications which prolong the QT interval is important to minimize the risk of ventricular arrhythmias, which may lead to sudden death. This is essential in patients with a congenitally long QT interval.     

调脂治疗对急性心肌梗死QT离散度及室性心律失常的影响

目的 探讨调脂治疗对急性心肌梗死患者QT离散度（QTd）及室性心律失常（VA）的作用。方法 86例急生心肌梗死患者随机分成2组，对照组行常规治疗，治疗组在对照组基础上给予他汀类药物调脂治疗，2周后行24h动态心电图检查，治疗前后作12导联心电图。测量QT间期（QTc）并计算QTd。同时观察治疗后24hVA的发生率。结果 治疗组室性心律失常明显减少，QTd显著减小，血脂无明显变化。结论 急性心肌梗死患者早期使用他汀类药物可减少住院期间室性心律失常的发生，缩短QTd。     

Ventricular arrhythmias: Q-T prolongation and left ventricular hypertrophy in adult Nigerians with hypertensive heart disease

Seventy adult Nigerians with hypertensive heart disease (HHD) and 68 healthy controls were studied for ventricular arrhythmias (VA). The roles of QT prolongation and left ventricular hypertrophy in these arrhythmias were received. The mean age of the study population was 49.9 +/- 6.0 years. 14 (20.0%) patients had cardiac arrhythmias with 3 patients having premature ventricular contractions (PVC). Ten (14.3%) cases had QTc prolongation out of which 1 patient had PVC. Some factors that were found to be associated with QT prolongation in HHD include: left ventricular hypertrophy, persistently elevated systolic blood pressure and female gender. There was a positive correlation between left ventricular hypertrophy and QTc prolongation and also between QTc prolongation and frequency of ventricular arrhythmias.     

QT间期延长与肝移植术后近期心律失常的关系

目的总结和探讨肝移植术前心电图提示QT间期延长与肝移植术后近期各类心律失常的关系。方法回顾性分析北京佑安医院2004年6月～2012年1月500例肝移植患者术前心电图的QT间期与术后近期（术后2周内）各种心律失常的发生率及其诊治资料。结果在500例肝移植患者中有82例（16.4％）发生各类心律失常,其中,病态窦房结综合征（包括持续而显著的窦性心动过缓）35例（7．0％）,阵发性室上性心动过速18例（3．6％）,心房颤动21例（4．2％）,室性心动过速8例（1．6％,包括2例尖端扭转性室性心动过速）;82例心律失常患者中心脏骤停4例（0．8％）,由心律失常引起的死亡2例（0．4％）。根据术前心电图检查结果,将患者分为QT间期延长组共103例,QT间期正常组共397例,其中,QT间期延长组中有28例患者发生心律失常,QT间期正常组中有54例患者发生心律失常,肝移植术后近期心律失常的发生与QT间期延长有明显关系（x^2=11．00,P〈0．01）。结论心律失常是肝移植术后常见的并发症．甚至可导致死亡。术前心电图QT间期延长与肝移植术后近期心律失常的发生有明显关系。因此,对于术前QT间期延长的患者应加强监测和评估,并给予预防性措施,如安置临时心脏起搏器,以防止术中及术后心血管意外的发生。     

一个遗传性长QT综合征初步家系分析及治疗随访

目的：对临床中发现的一个长QT综合征家系进行初步分析并对治疗效果进行随访。方法收集该家系所有成员的临床资料,绘制家系图谱,并对治疗结果进行长期随访。结果该家系成员有四名符合长QT综合征诊断标准,对两名有猝死发作史患者行永久起搏器+美托洛尔缓释片治疗,对一名无症状患者予美托洛尔缓释片治疗,效果明确。结论该家系符合目前报导的长QT综合征家系遗传特点;美托洛尔缓释片及起搏器治疗长QT综合征效果较明确。     

Modern management of arrhythmias

The specialist management of arrhythmias has changed significantly over the past decade. This article outlines current management strategies for atrial flutter and atrial fibrillation, with particular emphasis on curative strategies with catheter ablation and the recent data on rhythm compared with rate control strategies. The expanding role of catheter ablation in the treatment of a wide variety of supraventricular and ventricular arrhythmias is discussed. The current evidence for implantable cardioverter defibrillators in the prevention of sudden cardiac death is summarised. The article also highlights the increasing recognition of a number of inherited syndromes that predispose to sudden cardiac death (for example, Brugada and long QT syndromes).     

QT离散度对扩张型心肌病的临床意义

目的探讨QT离散度(QTd)与扩张型心肌病(DCM)恶性室性心律失常和心功能的关系。方法对42例DCM患者按室性心律失常性质分为恶性室性心律失常组与非恶性室性心律失常组。并按心功能状态分为轻度心力衰竭组和重度心力衰竭组,另选40例无器质性心脏病者作为正常对照组,分别测定12导联心电图QT间期,并计算QTd、QTcd。结果(1)恶性室性心律失常组较非恶性室性心律失常组QTd、QTcd显著延长(P<0.01),非恶性室性心律失常组较正常对照组QTd、QTcd显著延长(P<0.01);(2)重度心力衰竭组较轻度心力衰竭组QTd、QTcd显著延长(P<0.05),轻度心力衰竭组较正常对照组QTd、QTcd显著延长(P<0.01)。结论QTd、QTcd对DCM患者恶性室性心律失常或猝死有一定预防价值,并可作为评价DCM患者心功能状态的一项辅助指标。     

SCN5A基因突变与心律失常的研究进展

近年来分子生物学及分子电生理的迅速发展,开创了心律失常机制研究新纪元。心律失常与离子通道基因表达异常明确相关,多个离子通道基因的突变可引起各种心律失常。目前,已知绝大多数的原发性心电异常都是由编码各主要离子通道亚单位的基因突变引起的,因此,这类病可称为“离子通道病”。Nav1.5通道是人类主要的心脏钠离子通道类型,负责动作电位的起始和传播,由SCN5A基因编码。自从在长QT综合征(long QT syndromeL,QTS)家系中发现心脏钠离子通道α亚基的编码基因SCN5A第一个突变以来,目前已经发现数百个突变与一系列遗传性心律失常有关,如长QT综合征3型(LQT3)、Brugada综合征、进展性心脏传导阻滞(PCCD)、扩张型心肌病(DCM)、婴儿猝死综合征(SIDS)等。近年来发现SCN5A基因突变与病态窦房结综合征(SSS),房性心律失常(心房颤动,心房静止),室性心律失常和起搏夺获不良密切相关。本文将详细阐述近年来SCN5A基因突变在SSS、房性心律失常(心房颤动,心房静止)、起搏夺获不良、室性心律失常和长QT综合征3型的研究进展,SCN5A功能获得性和功能丧失致病突变潜在的机制以及目前存在的问题和挑战。      

急性心肌梗塞病人12导联心电图QT间期离散度的对照研究

目的：观察心肌梗塞病人发病２４h内及发病后４８－７２h r QTd变化情况,了解ＱＴd与心梗发生室性心律失常的关系,方法：本组纳入心梗病人６２例,分发生室性心律失常和未发生室民生心律失常两组,分别测量其发病２４h 及发病后４８－７２h的ＱＴd,并比较两组指标,结果：（１）发生室内性心律失常的心梗病人ＱＴd显著高于未发生心律失常组,（２）心梗发病２４h内ＱＴd显著高于发病后４８－７２h ,结论：急性心梗病人测量ＱＴd对于预则室性心律失常的发生有重要意义。     

QT hysteresis in long-QT syndrome children with exercise testing

Background Congenital long QT syndrome (LQTS) is an inherited ion channel disorder resulting in abnormal cardiac repolarization that can cause syncope and sudden death associated with a prolonged rate-corrected QT interval and polymorphic ventricular tachycardia. Several studies in adults showed that LQTS patients have altered QT adaptation to heart rate changes compared with normal subjects which forming a “hysteresis loop” in the QT-circle length plot. This study was to observe the QT interval changing during exercise testing in children long QT syndrome (LQTS) patients, explore the new diagnosis methods of LQTS. Methods The subjects were divided into 3 groups according to 1993 LQTS diagnostic criteria. Group 1: LQTS group (n=17) who scored &gt; or = 4 points indicating definite LQTS. Group 2: Middle group (n=16), patients who have prolonged QT interval but scored 1.5 to 3.5. Group 3: Normal control group (n=18). The average age of all study population is (12.3±5.8) years. No case had beta-adrenergic antagonists administration before exercise testing. All subjects were underwent tread mill exercise testing and electrocardiograph in whole exercise testing and recovery were recorded. QT and heart rate changing during whole exercise testing period were recorded. △QT, the QT interval at 1, 2, 4, 6 minutes into recovery subtract from the QT interval at a similar heart rate during exercise, were calculated.Results In all three groups, QT intervals were shortening with the increasing of heart rate, but QTc had no significant change. △QT at 1 minute ((45±11) ms), 2 minutes ((37±15) ms), 4 minutes ((23±12) ms) into recovery in LQTS group were significantly greater than that of the other two groups (P&lt;0.05, P&lt;0.01, P&lt;0.01, respectively). There was no △QT significant difference between middle group and normal control group at recovery time. During the recovery phase in LQTS group, the QT interval remained shortened despite a decelerating heart rate, forming a hysteresis “loop” in the curve relating the QT interval to the cycle length．Conclusions In children LQTS patients, there is significant QT hysteresis loop in the relation of QT interval with heart rate during recovery of exercise testing, which could be useful to the early diagnosis for LQTS.     

The QT interval and serum ionized calcium

The correlation between serum ionized calcium (Ca++) levels and three ECG QT intervals (Q-OTC, Q-ATC, and Q-ETC) was assessed in 20 adult patients. The relationship between each QT interval and Ca++ level, based on 209 Ca++ determinations through a range of 1.0 to 4.0 mEq/liter, is best described by a hyperbolic function. Although Q-OTC and Q-ATC predict Ca++ levels more accurately than Q-ETC, all QT intervals are clinically unreliable as guides to the presence of hypercalcemia. Similarly, the usefulness of the QT intervals in the diagnosis of hypocalcemia is limited by the wide distribution of normal values.     

三导联QT离散度与心率变异性的相关性研究

目的:QT离散度与心肌梗死(MI)后恶性室性心律失常密切相关,它对急性心肌梗死(AMI)的预后作用已引起人们的关注.但是,目前对基于动态心电图记录的三导联QT离散度检测方法及其作用研究甚少.本研究的目的旨在探讨基于动态心电图记录的三导联QT离散度检测方法以及其与心率变异性的相关性.方法:符合WHO诊断标准的48例AMI患者均于发病6小时内接受动态心电图监测.采用Oxford Prima Holter System动态分析仪,计算基于动态心电图记录的三导联QT离散度指标(QTd、QTpd)及心率变异性指标,并分析其相关性.结果:AMI病人QTd、QTpd与SDNN、HF、LF/HF之间均有显著相关性(r绝对值=0.614～0.808,P分别＜0.05).结论:基于动态心电图记录测量的QT离散度、QTp离散度与心率变异性的时域指标SDNN及频域指标LF/HF有很好的相关性,它们能用于评价AMI病人的预后.     

胺碘酮在充血性心力衰竭并室性心律失常治疗中的效果分析

目的:探讨胺碘酮治疗充血性心力衰竭并室性心律失常的临床效果及使用安全性。方法:选择我院2010年1月-2012年12月期间住院的76例充血性心力衰竭并室性心律失常的患者,分为治疗组(在常规抗心力衰竭治疗的基础上加胺碘酮治疗)和对照组(常规抗心力衰竭治疗),观察治疗后两组患者的抗心律失常及心功能改善比率,比较心率、血压、左室射血分数(LVEF)、QT间期及药物不良反应。结果:治疗组抗室性心律失常、心功能改善效果及LVEF明显高于对照组,差异有统计学意义(P<0.05),治疗组心率、QT间期较对照组明显改善,差异有统计学意义(P<0.05),两组的不良反应差异无统计学意义(P>0.05)。结论:胺碘酮对充血性心力衰竭合并室性心律失常的治疗有效安全。     

高血压病患者QT离散度分析(附135例报告)

目的 对比观察高血压病患者及其并发左室肥大,脑血管病和肾脏损害时的ＱＴ间期离散度。方法：描记同步１２导联心电图并测量ＱＴ间期及ＱＴ间期离散度。结果 高血压病患者ＱＴｄ大于对照组（Ｐ〈０．０１）,高血压左室肥大组ＱＴｄ大于脑血管病组和肾脏损害组（Ｐ〈０．０１）。结论ＱＴｄ可以作为评估高血压并发左室肥大的１个预测指标。     

Providers’ Response to Clinical Decision Support for QT Prolonging Drugs

Commonly used drugs in hospital setting can cause QT prolongation and trigger life-threatening arrhythmias. We evaluate changes in prescribing behavior after the implementation of a clinical decision support system to prevent the use of QT prolonging medications in the hospital setting. We conducted a quasi-experimental study, before and after the implementation of a clinical decision support system integrated in the electronic medical record (QT-alert system). This system detects patients at risk of significant QT prolongation (QTc>500ms) and alerts providers ordering QT prolonging drugs. We reviewed the electronic health record to assess the provider’s responses which were classified as “action taken” (QT drug avoided, QT drug changed, other QT drug(s) avoided, ECG monitoring, electrolytes monitoring, QT issue acknowledged, other actions) or “no action taken”. Approximately, 15.5% (95/612) of the alerts were followed by a provider’s action in the pre-intervention phase compared with 21% (228/1085) in the post-intervention phase (p=0.006). The most common type of actions taken during pre-intervention phase compared to post-intervention phase were ECG monitoring (8% vs. 13%, p=0.002) and QT issue acknowledgment (2.1% vs. 4.1%, p=0.03). Notably, there was no significant difference for other actions including QT drug avoided (p=0.8), QT drug changed (p=0.06) and other QT drug(s) avoided (p=0.3). Our study demonstrated that the QT alert system prompted a higher proportion of providers to take action on patients at risk of complications. However, the overall impact was modest underscoring the need for educating providers and optimizing clinical decision support to further reduce drug-induced QT prolongation.     

急性心肌梗死患者QTV及HRV与室性心律失常的相关性

目的分析AMI患者QTV及HRV与室性心律失常的关系。方法比较27例急性心肌梗死患者和30例健康对照组24h动态心电图,分析心肌梗死组和健康对照组心率变异性、QT变异度、QT变异系数等。结果健康对照组QT间期与心率呈直线相关(r=-0.822,P<0.01);急性心肌梗死组QT间期与心率呈直线相关(r=-0.891,P<0.01)。SDNN与心肌梗死严重程度具有相关性(r=-0.511,P<0.01);QTV与心肌梗死严重程度具有相关性(r=-0.613,P<0.01);QTCV与心肌梗死严重程度具有相关性(r=-0.648,P<0.01)。结论急性心肌梗死患者平均心率、QTV、QT间期、SDNN均发生变化,对预测室性心律失常及猝死的发生可能具有重要临床意义。     

急性心肌梗塞QT离散度变化及溶栓治疗的影响

目的：分析急性心肌梗塞（ＡＭＩ）患者早期ＱＴ离散度（ＱＴｄ）及溶栓治疗前后ＱＴｄ,ＱＴｃｄ的变化,探讨其在ＡＭＩ时室性心律失常预测及溶栓疗疗评定中意义。方法：测量９８例ＡＭＩ患者常规１２导联心电图ＱＴ间期及其中４０例经溶栓治疗者溶栓前后ＱＴ间期,计算其ＱＴｄ及校正后的ＱＴ离散度,并设正常对照组。     

急性心肌梗死患者经皮冠状动脉介入治疗对QT离散度的影响

目的 探讨经皮冠状动脉介入治疗对急性心肌梗死QT离散度的影响及其临床意义。方法 回顾性分析资料较完整的急性心肌梗死紧急冠脉介入治疗患者138例,测算术前和术后第1天心电图QT间期、QT离散度、心率校正QT间期和心率校正QT离散度。病例分心肌梗死发病6 h内(72例)和6 h以上(66例)两组。结果 两组QT间期和心率校正QT间期术后与术前相比均无显著性差异,但术后QT离散度和心率校正QT离散度较术前显著减小(P<0.01),且发病6 h内组显著小于发病6 h以上组(P<0.05);两组住院期间死亡率分别为4.2%和7.6%(P=0.394)。结论 成功的介入治疗能显著减小心肌梗死患者的QT离散度,介入治疗施行越早则减小QT离散度的效果越好。