心电图Tp-e/QT比值在预测心源性猝死及恶性心律失常中的意义

目的:探讨心电图T波峰末间期(Tp-e)比QT间期(Tp-e/QT)预测心源性猝死及恶性心律失常的意义。方法:收集我院2004年3月-2009年3月发生心源性猝死及恶性心律失常28例患者的完整资料,对其发生心源性猝死前同步12导联心电图Tp-e间期、QT间期及Tp-e/QT比值进行测量并统计分析。结果:猝死前60.71%患者心电图Tp-e/QT0.22,21.42%患者比值0.15,分布有一定规律性。结论:心电图Tp-e/QT对预测心源性猝死有一定价值。     

Idiopathic polymorphic ventricular tachycardia with normal QT interval in a structurally normal heart

Polymorphic ventricular tachycardia (PVT) is a life-threatening arrhythmia that is typically related to long QT syndrome, organic heart disease, electrolyte abnormalities, cardiotoxic drugs, or adrenergic stimulation. A review of the literature reveals that PVT with normal QT interval and without underlying cause is quite rare. We report a case of idiopathic spontaneous PVT with structurally normal heart and without electrolyte abnormalities, drug reactions, or evidence of catecholamine induced arrhythmia. We also review the literature on the electrocardiographic characteristics and management of idiopathic PVT.     

儿童血管迷走性晕厥QT间期离散度及P波离散度研究

目的　探讨儿童血管迷走性晕厥 (VVS)QT间期离散度 (QTd)及P波离散度 (Pd)的变化。方法　不明原因晕厥(UPS)患儿 5 5例 (研究组 ) ,均进行基础直立倾斜试验 (BHUTT)或 (和 )舌下含服硝酸甘油倾斜试验 (SNTTT)。匹配健康儿童 5 5例为对照 (对照组 )。于BHUTT前一天描记 12导联同步体表心电图 (12ECG)。选择波形清晰的 12ECG 3个心动周期 ,测量心率 (HR)、QTd 与Pd。结果　与对照组比较 ,研究组HR减慢 (P <0 0 1) ,QTmax、QTmin、QTd 延长 (P <0 0 1) ,QTcmax、QTcd增大 (P <0 0 1或P <0 0 5 ) ;Pcmax、Pcmin缩短 (P <0 0 1) ,Pd 及Pcd稍延长 (P >0 0 5 )。QTd、QTcd及Pd、Pcd在VVS患儿男女性别之间无差异(P >0 0 5 ) ,HUTT阳性组与阴性组之间亦未见差异 (P >0 0 5 )。结论　QTd 及Pd 在VVS患儿男女性别及HUTT阳性组与阴性组间未见差异。VVS患儿QTd 及QTcd增大 ,Pd 及Pcd延长不明显 ,临床上要警惕VVS患儿发生室性心律失常。     

小儿先天性心脏病QT间期离散度与P波离散度的研究

目的　探讨小儿先天性心脏病QT间期离散度 (QTd)与P波离散度 (Pd)变化。方法　 32 3例 0 0 8～ 16 0 0 (平均3 0 2± 3 0 3)岁先心病患儿 (研究组 )及 77例匹配健康儿童 (对照组 )描记 12导联同步体表心电图。选择波形清晰的 3个心动周期人工测量心率 (HR)、Pd 与QTd。微机数理统计。结果　研究组与对照组比较 ,体重分别为 (12 11± 7 2 0 )kg及 (14 6 3±6 39)kg ,身高分别为 (87 16± 2 2 89)cm及 (94 4 2± 2 1 2 9)cm ;研究组体重减轻 17 2 2 % (P <0 0 1) ,身高降低 7 6 9% (P <0 0 5 )。与对照组比较 ,研究组HR增快 (P >0 0 5 ) ,QTmax及Pmax延长 (P <0 0 1) ,QTd 与Pd 分别增大 5 6 0 3%及 38 33% (P <0 0 1)。结论　先天性心脏病患儿术前心电图QTd 及Pd 明显延长 ,可能与发生室性或房性心律失常有关。     

肝硬变患者QT间期延长及QT间期离散度的临床意义

目的探讨肝硬变患者QT间期及QT间期离散度 (QTd)的变化与临床意义。方法测量 13 8例病毒性肝炎肝硬变患者的同步 12导联心电图 ,分析QT间期及QTd ,并与其他消化系疾病的 5 0例住院患者进行对照。结果肝硬变患者中QT间期延长发生率非常显著高于对照组 (P <0 .0 1) ,QTd也显著高于对照组 (P <0 .0 5 ) ;肝硬变患者Child PughA、B、C3级中QT间期延长发生率逐步升高 ,QTd增加也逐渐明显 (均为P <0 .0 5 ) ;肝硬变患者中死亡者的QT间期非常显著长于存活者 ,QTd也非常显著增加 (均为P <0 .0 1)。结论肝硬变患者QT间期延长发生率高 ,QTd增加明显 ,且与肝硬变严重程度相平行。提示QT间期延长及QTd可以作为肝硬变严重程度的指标之一。     

Mechanisms of cardiac arrhythmias and sudden death in transgenic rabbits with long QT syndrome

Long QT syndrome (LQTS) is a heritable disease associated with ECG QT interval prolongation, ventricular tachycardia, and sudden cardiac death in young patients. Among genotyped individuals, mutations in genes encoding repolarizing K+ channels (LQT1:KCNQ1; LQT2:KCNH2) are present in approximately 90% of affected individuals. Expression of pore mutants of the human genes KCNQ1 (KvLQT1-Y315S) and KCNH2 (HERG-G628S) in the rabbit heart produced transgenic rabbits with a long QT phenotype. Prolongations of QT intervals and action potential durations were due to the elimination of IKs and IKr currents in cardiomyocytes. LQT2 rabbits showed a high incidence of spontaneous sudden cardiac death (>50% at 1 year) due to polymorphic ventricular tachycardia. Optical mapping revealed increased spatial dispersion of repolarization underlying the arrhythmias. Both transgenes caused downregulation of the remaining complementary IKr and IKs without affecting the steady state levels of the native polypeptides. Thus, the elimination of 1 repolarizing current was associated with downregulation of the reciprocal repolarizing current rather than with the compensatory upregulation observed previously in LQTS mouse models. This suggests that mutant KvLQT1 and HERG interacted with the reciprocal wild-type alpha subunits of rabbit ERG and KvLQT1, respectively. These results have implications for understanding the nature and heterogeneity of cardiac arrhythmias and sudden cardiac death.     

校正QT间期在Shy-Drager综合征中的变化

目的:比较Shy-Drager综合征(SDS)患者的校正QT间期与正常人间的差异,并探讨其意义。方法:回顾比较20例SDS患者和20名年龄与性别相匹配的正常人的校正QT间期。结果:SDS患者的校正QT间期较正常人显著延长[(0.409±0.029)ms比(0.385±0.024)ms,P<0.05]。结论:SDS患者的校正QT间期延长,该指标对其临床诊断有一定帮助。     

皮肤黏膜淋巴结综合征患儿QT间期离散度和P波离散度变化

目的　探讨用预测可能发生心律失常的心电学指标QT间期离散度 (QTd)和P波离散度 (Pd)来研究皮肤黏膜淋巴结综合征 (MCLS)患儿发生心律失常的可能性。方法　MCLS患儿 6 2例 (13例伴有冠脉扩张 ) ,随机匹配 79例健康儿童为对照。采用广东中山SR - 10 0 0A心电综合自动分析仪描记 12导联同步体表心电图 (12ECG) ,选择波形清晰的 3个心动周期 ,在人工干预下自动测量窦性节律时心率 (HR)、QTmax、QTmin、Pmax、Pmin ,计算QTd及Pd ,连测 3次后取其平均值。结果　与对照组比较 ,MCLS组急性期心率增快 (P <0 0 1) ,QTmax、QTmin缩短 ,QTd增大 ,Pmax增加 ,Pmin缩短 ,Pd增大 ;恢复期QTd、Pmax、Pd延长 ,其差异均有显著性 (P <0 0 1或P <0 0 5 )。伴有冠脉扩张与不伴有冠脉扩张的MCLS患儿之间QTmax、QTmin、QTd、Pmax、Pmin、Pd差异无显著性 (P >0 0 5 )。结论　MCLS能引起QTd及Pd增加 ,有可能发生严重心律失常 ,临床上不容忽视     

1个遗传性长QT间期综合征家系成员的遗传位点检测

目的对遗传性长QT间期综合征(long QT syndrome,LQTS)家系进行遗传分析,观察该家系成员发病的临床症状和心电图特点,推测其相应的致病基因型。方法家系共有6个成员被纳入研究。采集家系成员外周血,提取其基因组DNA。分析先证者及家系成员的临床资料和心电图资料,用PCR和直接测序法对致LQTS的KCNQ1、KCNH2、SCN5A基因编码区全部序列进行基因突变筛查。结果家系成员中共有LQTS患者3例,其中猝死1例,晕厥发作1例,无明显症状1例;共采集到2例LQTS患者心电图2例,QT间期分别为0.6 s和0.54 s。经基因检测发现,在两例患者中均发现了1个LQTS易感的单核苷酸多态性(SNP)位点SCN5A H558R,其他基因均未发现异常。结论在此遗传性LTQS中发现了一个易感SNP位点,推测此两例遗传性LQTS患者均为3型。     

Risk markers of sudden cardiac death in standard 12-lead electrocardiograms

Abstract

The annual incidence of sudden cardiac death (SCD) is estimated at 1 per 1,000 for adults over the age of 35 years, and 1 per 100,000 for adolescents and young adults. Although the overall incidence of unexpected SCD among previously healthy persons is small, the emotional impact of these events is devastating. The 12-lead electrocardiogram (ECG) has been used as a risk assessment tool from healthy occupational applicants and athletes to patients with cardiovascular disorders. The ECG is also routinely recorded in the majority of patients hospitalized for non-cardiovascular causes. Thus, it is a widely used tool intended for identification of unsuspected heart disease generally, as well as for diagnosing specific disorders predisposing to fatal arrhythmias in subjects who have not experienced such events but who are at increased risk. Recognition of specific ECG features is of importance for prevention of SCD in asymptomatic persons. The purpose of this review is to catalog the disorders associated with SCD that may be reflected in 12-lead ECGs seen in office or hospital practices and to discuss their prevalence and the magnitude of risks. The focus is on ECG findings suggesting increased SCD risk among the asymptomatic subjects without previously diagnosed cardiac disease.     

QT间期离散度及P波离散度与小儿扩张型心肌病预后的关系

目的　探讨QT间期离散度 (QTd)及P波离散度 (Pd)与小儿扩张型心肌病 (DCM)预后关系。方法　 5 2例DCM患儿 (研究组 ) ,男 31例 ,女 2 1例 ,年龄 3个月～ 18岁 ,平均 (5 79± 5 17)岁 ,死亡 5例。随机匹配健康儿童 5 2例为对照 (对照组 )。受检对象描记 12导联同步体表心电图 ,选择波形清晰的 3个心动周期自动分析合并人工干预测量心率 (HR)、QTd与Pd。结果　研究组较对照组心率增快 (P <0 0 5 ) ,P -R间期 (P <0 0 5 )、QRS间期 (P <0 0 1)及QTc间期 (P <0 0 1)延长 ;QT max增加 (P >0 0 5 ) ,QTd、Pmax、Pmin及Pd延长 (P <0 0 1)。死亡组与存活组比较QTd与Pd无差异 (P >0 0 5 )。结论　QTd和Pd在DCM患儿明显增大 ,但其对估测DCM预后价值有限。     

Nifekalant and disopyramide in a patient with short QT syndrome: evaluation of pharmacological effects and electrophysiological properties

We assessed several pharmacological effects on electrocardiogram parameters and effective refractory period (ERP) in a patient with a short QT syndrome (SQTS). Pharmacological challenge tests revealed that disopyramide and selective I_kr blocker, nifekalant normalized QT interval, and ERP of the atrial and ventricular myocardium. This study suggested that disopyramide and nifekalant should be feasible for the drug treatment of the SQTS. Moreover, QT interval was paradoxically prolonged at higher heart rates induced with isoproterenol infusion or an exercise test, although the mechanism of this QT prolongation remains to be investigated.     

Inappropriate ICD Discharge Due to T-Wave Oversensing in a Patient with Short QT Syndrome

A 45-year-old man with diagnosis of short QT syndrome underwent successful implantation of dual-chamber implantable cardioverter-defibrillator (ICD) to prevent sudden cardiac death. Ten days after implantation, the patient was treated by inappropriate ICD discharges for frequent T-wave oversensing. After careful reprogramming of the ICD, the T-wave oversensing was eliminated and no T-wave oversensing or inappropriate discharge was documented during 6-month follow-up period. (PACE 2010; 113–116)     

Acute effect of methylphenidate on QT interval duration and dispersion in children with attention deficit hyperactivity disorder

Among childhood psychiatric disorders, attention deficit hyperactivity disorder (ADHD) is of greatest interest to practitioners. Methylphenidate (MPH) is a drug that is widely used in the treatment of children in whom ADHD has been diagnosed. Although this treatment has been used for years, its effects on the heart remain the subject of debate. The QT interval comprises the ventricular activation and recovery periods as seen on electrocardiogram (ECG). The acute effect of MPH on QT interval dispersion is unknown. Researchers in the present study sought to investigate the acute effects of MPH on QT interval as seen on ECG. A total of 25 patients with ADHD (mean age, 9.4±2.1 y) who were treated with MPH were enrolled in the study. Twelve-lead derivation ECGs were taken before and 2 h after administration of 10 mg of MPH. Maximum QT interval, minimum QT interval, and interval durations were measured, and QT dispersion was calculated, for each ECG. QT dispersion measured after medication administration decreased significantly from 59.6±16.3 ms to 50.8±10.9 ms (P=.016); corrected QT dispersion decreased significantly from 70.9±17.6 ms to 61.3±13.3 ms (P=.011). Maximum QT interval duration decreased from 373.7±21.8 ms to 361.8±29.0 ms (P=.006); minimum QT interval duration rose from 317.0±23.3 ms to 322.3±21.6 ms (P=.312). In conclusion, the findings of this study show that MPH reduces QT dispersion during the acute period shortly after its administration.     

Comparative Reproducibility of QT, QT Peak, and T Peak-T End Intervals and Dispersion in Normal Subjects, Patients with Myocardial Infarction, and Patients with Hypertrophic Cardiomyopathy

Abnormal repolarizaiion is associated with arrhythmogenesis. Because of controversies in existing methodology, new computerized methods may provide more reliable tools for the noninvasive assessment of myocardial repolarization from the surface electrocardiogram (ECC). Measurement of the interval between the peak and the end of the T wave (TpTe interval) has been suggested for the detection of repolarization abnormalities, but its clinical value has not been fully studied. The intrasubject reproducibility and reliability of automatic measurements of QT, QT peak, and TpTe interval and dispersion were assessed in 70 normal subjects, 49 patients with acute myocardial infarction (5th day; MI), and 37 patients with hypertrophic cardiomyopathy (HC). Measurements were performed automatically in a set of 10 ECCs obtained from each subject using a commercial software package (Marquette Medical Systems, Milwaukee, WI, U.S.A.). Compared to normal subjects, all intervals were significantly longer in HC patients (P < 0.001 for QT and QTp; p < 0.05 for TpTe); in MI patients, this difference was only significant for the maximum QT and QTp intervals (P < 0.05). In both patient groups, the QT and QTp dispersion was significantly greater compared to normal subjects (P < 0.05) but no consistent difference was observed in the TpTe dispersion among all three groups. In all subjects, the reproducibility of automatic measurement of QT and QTp intervals was high (coefficient of variation, CV, 1%-2%) and slightly lower for that of TpTe interval (2%–5%; p < 0.05). The reproducibility of QT, QTp, and TpTe dispersion was lower (12%–24%, 18%–28%, 16%–23% in normal subjects, MI and HC patients, respectively). The reliability of automatic measurement of QT, QTp, and TpTe intervals is high but the reproducibility of the repeated measurements of QT, QTp and TpTe dispersion is comparatively low.     

QT interval dispersion in ventricular beats: a noninvasive marker of susceptibility to sustained ventricular arrhythmias

Increased QT dispersion (QTd) calculated from sinus beats has been shown to identify patients prone to sustained VT. However, predictive accuracy of this parameter is limited. Electrophysiological properties of the myocardium may be altered by a premature ventricular beats, which is a well-established trigger for sustained VT. Therefore, the author hypothesised that QTd in spontaneous or paced ventricular beats may improve identification of patients with inducible sustained VT. In 28 consecutive patients (men, mean age 61 +/- 13 years) who underwent programmed ventricular stimulation, the values of QTd calculated in sinus and ventricular beats were compared between inducible and noninducible patients. The mean QTd values obtained using three different methods differed significantly, QTd in paced ventricular beats being the highest, QTd in spontaneous ventricular beats was intermediate, and QTd in sinus beats was the lowest (83.9 +/- 30 vs 63.0 +/- 29 ms vs 53.9 +/- 27 ms, P < 0.0001 and P < 0.004, respectively). In 13 (46%) patients sustained VT was induced. QTd values were significantly higher in inducible than noninducible patients (QTd sinus beats: 67.5 +/- 31 vs 42.1 +/- 11 ms, P = 0.02; QTd spontaneous ventricular beats: 79.3 +/- 35 vs 46.7 +/- 13 ms, P = 0.008, and QTd-paced ventricular beats: 104.8 +/- 32 vs 65.9 +/- 9 ms, P = 0.0009). The receiver operator characteristic curves showed that at a sensitivity level of 100%, the highest specificity for identification of inducible patients had QTd measured in paced ventricular beats (87%) followed by QTd in spontaneous ventricular beats (45%), and QTd in sinus beats (40%). In conclusion, (1) QTd in ventricular beats is greater than in sinus beats, and (2) QTd calculated from paced ventricular beats identifies patients with inducible sustained VT better than QTd measured during sinus rhythm.     

Effect of telmisartan on QT interval variability and autonomic control in hypertensive patients with left ventricular hypertrophy

Objectives

The aim of the study was to examine the effect of the antihypertensive AT1 receptors antagonist telmisartan on cardiovascular autonomic function and QT dispersion in hypertensive patients with LVH.

Methods

Twenty-five patients (18 males and seven women, mean age 49.8 ± 5.2 years) with mild essential arterial hypertension and LVH were compared with 25 age-matched healthy controls. All the participants underwent a complete clinical examination, including electrocardiogram for QT interval measurements and 24 h ambulatory ECG monitoring for measurement of heart rate variability. The ECG, 24 h ambulatory ECG, and echocardiogram were repeated after eight weeks of treatment.

Results

At baseline, hypertensive patients showed QT dispersion (p < 0.001) and QTc dispersion (p < 0.001) significantly higher than control subjects. An eight-week telmisartan treatment significantly reduced blood pressure (p < 0.0001), without significant change in left ventricular mass. Telmisartan-based treatment induced an increased vagal activity without significant change of sympathetic activity and a reduction of QT dispersion (p < 0.001) and QTc dispersion (p < 0.001).

Conclusions

These data suggest that therapy with telmisartan significantly improves the sympathovagal balance increasing parasympathetic activity, and cardiac electrical stability reducing the heterogeneity of ventricular repolarization in hypertensive subjects. These effects could contribute to reduce arrhythmias as well as sudden cardiac death in at-risk hypertensive patients.     

早期康复治疗对无合并症急性心肌梗死患者QT间期离散度的影响

目的 :探讨早期康复治疗对无合并症急性心肌梗死 (AMI )患者QT间期离散度 (QTd)的影响。方法 :113例研究对象前瞻性随机分为早期康复治疗组 (5 4例 )及对照组 (5 9例 )。两组主要基线资料具可比性。早期康复组采用期康复治疗方案 ,对照组采用传统方案。所有研究对象分别在入院当时 (平均 9.3h± 1.9h)、第 1周末、第 2周末、第 3周末记录标准 12导联心电图。QT间期的测量从QRS波起点至T波终点 ,同一导联测量 3个心动周期 ,取其平均值。不同导联最大QT值减去最小为QTd值。结果 :早期康复组入院当时、第 1周末、第 2周末、第 3周末QTd(分别为 6 4± 14ms,4 6± 15ms ,4 3± 12ms,39± 13ms )与对照组 (分别为 6 7± 12ms,4 8± 16ms ,4 1± 13ms,4 0± 15ms)比较统计学上无显著性差异 (P >0 .0 5 )。结论 :无合并症AMI患者实行早期康复治疗不影响QTd值 ,因而不影响心肌电稳定性 ,提示该组患者早期康复治疗安全可行