Temporary disturbances of the QT interval precede the onset of ventricular tachyarrhythmias in patients with structural heart diseases

An increase in sinus rate prior to ventricular tachyarrhythmias has been demonstrated in previous studies. There is no clear data available concerning changes in ventricular de- and repolarization prior to ventricular tachyarrhythmias, especially in patients with structural heart disease. Therefore, the aim of this study was to analyze the QT and QTc interval (Bazett's formula immediately before the onset of ventricular tachyarrhythmias in stored electrograms of patients with ICDs. The study analyzed 228 spontaneous ventricular tachyarrhythmia episodes in 52 patients (mean age 64 +/- 10 years, 49 men, 3 women) and compared them with 146 electrograms of baseline rhythm recorded during regular ICD follow-up. Mean ventricular cycle length (CL), QT interval, and QTc were measured before the onset of ventricular tachyarrhythmia and during baseline rhythm. Prior to ventricular tachyarrhythmias onset, CL was significantly shorter than during baseline rhythm (714 +/- 139 vs 828 +/- 149 ms, P < 0.0001). By contrast, the QT interval (430 +/- 67 ms) and QTc interval (518 +/- 67 ms) were significantly prolonged before the onset of ventricular tachyarrhythmias as compared to baseline rhythm (QT 406 +/- 67 ms, QTc 450 +/- 61 ms; P < 0.0001). CL, QT, and QTc changes were independent of concomitant treatment with antiarrhythmic drugs. Ventricular tachyarrhythmias are preceded by a significant prolongation of the QT and QTc intervals. This phenomenon may represent a greater than normal disparity of repolarization recovery times possibly facilitating the development of ventricular tachyarrhythmias.     

老年冠心病及血运重建对QT离散度的影响

目的 观察老年冠心病患者经皮冠状动脉介入治疗(PCI)术前后QT离散度(QTd)的变化特点与趋势,并与正常对照组进行对比,探讨QTd与冠状动脉狭窄程度和范围的关系及经皮冠状动脉腔内成形术和PCI对其的影响,以期为临床寻找一种评价PCI术预后的有效无创方法.方法 已行冠状动脉造影术的≥60岁冠心病患者679例,分为冠心病组(经冠状动脉造影证实有单支或多支病变,狭窄程度≥50％)536例.对照组(同期住院冠状动脉造影狭窄程度＜50％)143例.术前分别描记两组的常规12导联心电图,测量QTd、校正QT离散度(QTcd).经冠状动脉造影证实狭窄程度≥75％的393例冠心病患者行PCI术,并再分为3个亚组:单支病变组176例,双支病变组118例,3支病变组99例.对照组:同期住院冠状动脉造影狭窄程度＜50％患者143例.PCI各组术前、术后1天、7天,分别检测QTd、QTcd,进行比较.结果 冠心病组胆红素明显低于对照组(P＜0.01).冠心病组的总胆固醇 (TC)、低密度脂蛋白胆固醇(LDL-C)和血尿酸明显高于对照组(P＜0.01),QTd和QTcd明显比对照组延长(P＜0.01),冠心病3个亚组的QTd和QTcd在术前、术后1天和术后7天均呈逐渐下降趋势,3个亚组在组间、不同时点以及组间和不同时点的交互作用中差异均有统计学意义.单支病变组术前QTd(48.52±12.35)ms,术后1天(41.23±13.35) ms,术后7天(41.12±12.61) ms,术前QTcd(55.34±15.81)ms,术后1天(48.62±14.93) ms,术后7天(48.23±13.65) ms;双支病变组术前QTd(53.26±16.95) ms,术后1天(44.54±14.63)ms,术后7天(43.96±15.32) ms,术前QTcd(59.41±16.72)ms,术后1天(50.35±15.43) ms,术后7天(49.94±15.35)ms;3支病变组术前QTd(58.43±13.72) ms,术后1天(52.82±13.66)ms,术后7天(52.76±13.32)ms,术前QTcd(65.91±18.53)ms,术后1天(60.21±16.38) ms,术后7天(60.19±15.74) ms.结论 QTd、QTcd在冠心病患者明显升高,PCI术后明显降低,并与冠状动脉狭窄的程度和范围有关.说明QTd、QTcd可以作为临床上预测心肌缺血,评估PCI术后预后的有效无创指标.     

支架置入与冠状动脉粥样硬化性心脏病患者QT离散度及校正QT离散度变化

目的:探讨支架置入临床应用特点及其对冠状动脉粥样硬化性心脏病患者QT离散度及校正QT离散度的影响.方法:应用万方数据库和中国期刊全文数据库(CNKI),由第一作者以支架置入,QT离散度,校正QT离散度等检索1998/2010时限内与支架置入对冠状动脉粥样硬化性心脏病患者QT离散度影响有关的文献.排除重复研究或较陈旧文献.结果:依据纳入排除标准共保留文献22篇.常用支架为金属裸支架与药物支架.金属裸支架置入操作简便易行,并具有形状记忆效应及良好的生物相容性等临床应用优势,但术后早期再狭窄发生率高;药物支架有效降低术后再狭窄发生率,但远期安全性尚不明确.同时因经济投入高、置放技术要求严格等不易进行临床推广.从临床应用效果来看,支架置入显著缩短冠心病患者QT离散度以及校正QT离散.结论:支架置入显著缩短QT离散度以及校正QT离散,有效改善心肌再灌注,降低恶性心血管事件发生率,改善患者长期预后.但不同类型支架置入引起QT离散度的对应性变化,尚需进一步研究.     

非瓣膜性心脏病患者心房颤动发作持续时间不同对P波离散度的影响

目的　分析非瓣膜性心脏病患者心房颤动发作持续时间不同对P波离散度的影响。方法　根据房颤发作持续时间不同将 6 7例非瓣膜性心脏病患者分为两组 :短时房颤组 (≤ 4 8小时 ) 35例和长时房颤组 (>4 8小时 ,<3个月 ) 32例。同步体表 12导联心电图 ,计算P波最大时限和P波离散度 ;超声心动图测定左心房内径 ;分析P波最大时限和P波离散度与临床、超声参数之间的相关关系。结果　两组在年龄、性别和基础疾病组成方面无差别。长时房颤组左心房内径显著高于短时房颤组 [(40 .5 9± 2 .5 8)mmvs (38.6 0± 3.4 3)mm ,t =2 .70 4 ,P =0 .0 0 9]、P波最大时限长 [(12 2 .91± 11.74 )msvs(114 .6 9± 9.2 2 )ms,t =3.16 8,P =0 .0 0 2 ]、P波离散度大 [(6 0 .5 3± 11.14 )msvs(5 1.6 6± 10 .6 1)ms ,t =3.331,P =0 .0 0 1]。相关分析显示P波最大时限和P波离散度均与房颤发作持续时间 (r值分别为 0 .6 88,0 .5 4 6 ;P 均 <0 .0 0 1)和左心房内径相关 (r值分别为 0 .716 ,0 .6 0 3;P 均 <0 .0 0 1) ,与年龄无关。结论　长时房颤组较短时房颤组P波最大时限长和P波离散度大 ,与左心房扩大有关。     

Ablation of ventricular tachycardia in patients with structural heart disease

Catheter ablation is an important therapeutic option for controlling recurrent ventricular arrhythmias in patients with heart disease. Although implantable defibrillators are generally first line therapy in this patient population, a substantial number of patients require additional therapy with either antiarrhythmic drugs, ablation, or both. Studies of mapping and ablation have produced further insights into pathophysiologic mechanisms of these arrhythmias, which are now well characterized. The majority is due to reentry through regions of ventricular scar. Methods for identifying scar based on electrogram characteristics now allow arrhythmogenic areas to be targeted for ablation during stable sinus rhythm, such that ablation is often an option even when multiple and unstable ventricular tachycardia are present. Ablation failure can also be due to anatomical obstacles; however, methods for accessing the pericardial space for mapping and ablation and technological progress can be expected to further improve its efficacy.     

中老年高血压患者脉压与QT离散度相关性研究

目的　探讨脉压对中老年高血压患者心血管事件危险性的预测作用。方法　 2 18例中老年高血压患者分别进行 12导联同步心电图、动态心电图检查 ,并计算QT离散度 (QTd) ,同时统计心电图异常及左室肥厚检出率。分组观察所有对象脉压与QTd、心电图异常之间的关系 ,并比较脉压、收缩压与QTd的相关性大小。结果　脉压与QTd正相关 ,相关系数r为 0 .75 83,P <0 .0 1;收缩压与QTd正相关 ,相关系数r为 0 .36 79,P <0 .0 5 ;QTd≥ 6 0ms与QTd <6 0ms两组比较 ,心电图异常率及左室肥厚检出率的差异均有统计学意义 (P <0 .0 5 )。结论　脉压与QTd的相关性强于收缩压 ,提示在预测高血压患者心血管事件危险性方面 ,脉压优于收缩压     

冠心病的心率变异性与QT离散度的相关性研究

目的　通过对冠心病患者和冠脉造影正常者的心率变异性 (HRV)与QT离散度 (QTd)检查 ,来了解冠心病对心脏自主神经功能和心肌电稳定性的影响。方法　经选择性冠状动脉造影检查证实为心绞痛患者 12 1例 ;心肌梗死患者 5 0例 ;冠脉造影正常者 75例。于选择性冠状动脉造影术前 1天内晨 8∶30～ 10∶30用EPX采样机采样 5分钟心电图 ,经计算机处理得到HRV时域和频域分析结果 ;而QTd的测量则是在同一时间 ,同一安静检查室内同时记录标准 12导联心电图 (纸速 5 0mm/s) ,通过手工测量、计算得到QT离散度和校正的QT离散度结果。结果　心肌梗死、心绞痛患者QTd和QTcd较冠状动脉造影正常者显著延长 (P <0 .0 5 ) ;且心肌梗死患者QTd和QTcd较心绞痛者亦明显延长 (P <0 .0 5 ) ;心肌梗死的HRV指标超低频段功率谱密度 (ULFP)、极低频段功率谱密度 (VLFP)、低频段功率谱密度 (LFP)、高频段功率谱密度 (HFP)、总频谱密度 (TP)、窦性R R间期的标准差 (SDNN)较冠状动脉造影正常者及心绞痛患者显著减低 (P <0 .0 5 ) ;其中心绞痛组的HFP、LFP、SDNN亦明显低于冠状动脉造影正常者 (P<0 .0 5 ) ;3组的QT离散度与HRV均有相关关系 (P <0 .0 5 )。结论　冠心病患者的自主神经活动与心肌电稳定性受损 ,心肌梗死患者更加明显 ;冠心     

氦氖激光血管内照射对冠心病患者心电图QT离散度的影响

目的：了解低能量氦氖激光血管内照射（ＩＬＩＢ）对冠心病患者心电图ＱＴ离散度（ＱＴｄ）的影响,并评价其临床价值。方法：选择８０例心率校正后的ＱＴｄ（ＱＴｃｄ）＞５０ｍｓ的冠心病患者,按是否接受ＩＬＩＢ治疗分为两组,比较治疗前后ＱＴｃｄ的变化。所有资料以ｘ±ｓ表示,治疗后两组结果比较采用两样本均数差异比较的ｔ检验。结果：接受ＩＬＩＢ治疗者治疗后ＱＴｃｄ值（５６．４８±２４．７２）ｍｓ比未接受ＩＬＩＢ治疗者ＱＴｃｄ值（６８．４２±２６．３４）ｍｓ明显减少,两者差异有显著性（ｔ＝２．９２,Ｐ＜０．０１）。结论：ＩＬＩＢ能有效地降低冠心病患者心电图ＱＴ离散度,使心室肌组织间复极时间趋向一致,从而可减少室性心律失常的发生,预防心源性猝死。     

冠状动脉病变支数及介入治疗对冠心病患者QT离散度的影响

目的探讨冠状动脉病变支数及介入治疗对QT离散度(QTd)的影响。方法对72例成功进行经皮冠状动脉腔内成形和支架术的冠心病患者,计算手术前后12导联同步心电图QTd及校正后QTd(QTcd)。结果冠心病不同类型和冠状动脉病变不同支数术前QTd及QTcd无明显差别(P>0.05),术后QTd及QTcd均较术前显著下降[稳定型心绞痛、不稳定型心绞痛和急性心肌梗死QTd为(49±20)msvs(57±24)ms、(46±18)msvs(61±18)ms、(48±18)msvs(61±20)ms,P<0.05;QTcd为(56±28)msvs(68±25)ms、(56±18)msvs(71±20)ms、(59±20)msvs(69±22)ms,P<0.05];单支病变组术后QTd、QTcd较其他病变组下降显著[术后单支血管病变与2支病变、3支病变的比较为QTd(38±18)msvs(50±24)msvs(52±16)ms,F=15.86,P<0.01;QTcd(45±20)msvs(56±18)msvs(58±27)ms,F=9.60,P<0.01]。结论介入治疗前冠心病患者QTd及QTcd与受累病变血管支数无关,在介入治疗后随着心肌缺血及心室复极不均一性的改善而降低。     

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.     

Beyond the 12 lead: Review of the use of additional leads for the early electrocardiographic diagnosis of acute myocardial infarction

Despite known limitations, the standard 12 lead ECG is the principal risk stratification device for patients presenting with chest pain to the ED. However, it has a sensitivity of less than 60% for MI. One reason for this is that the standard placement of chest leads fails to interrogate many areas of the myocardium. Various workers have addressed this problem through the use of additional leads or body surface mapping. Additional leads on the posterior and right thoracic surface have been shown to give additional information, which may be important to the emergency physician. This review demonstrates the need for additional leads in the acute setting and makes recommendations about the utility of using additional leads in the ED.     

Improved working capacity following theophylline infusion in patients with ischaemic heart disease

Summary. The effect of theophylline on the working capacity of patients with ischaemic heart disease was evaluated in a double-blind, randomized cross-over study. Eight patients, receiving no medication, with stable effort-provoked angina pectoris and typical exercise-induced ST depressions were studied. Following intravenous administration of theophylline or placebo, the patients did a supine leg exercise limited by intolerable chest pain. The workload was continuously increased by 10 W/min. Following theophylline treatment the workload at the onset of chest pain increased from 71 ± 9 to 114 ± 14 W (P< 0·002). The ST depression was less pronounced following theophylline at submaximal exercise (-0·01 ± 0·00 vs. -0·09 ± 0·02 mV, P< 0·005, at 70 W). The maximum tolerable workload increased from 129 ± 15 after placebo infusion to 153 ± 12 W after theophylline infusion P<0·01). It is speculated that this beneficial effect of the adenosine receptor antagonist theophylline may possibly be due to inhibition of a pathophysiological coronary steal induced by elevated levels of adenosine during ischaemia.     

QT 离散度与冠心病关系的研究进展

QT离散度（QTd）对冠心病预测心肌缺血程度、范围及预后具有重要参考价值,近年来受到广泛关注。QTd[体表心电图12导联中最大QT间期（QTmax）与最小QT间期（QTmin）之间的差值]反映心室肌细胞复极过程不均一性与冠心病心肌缺血有关系。QT离散度可用于评价冠状动脉病变特点,从而指导冠心病患者血运重建,对评估介入治疗术前及术后预后具有重要的临床意义。     

Immediate diagnosis of acute inferior wall myocardial infarction with electrocardiographic pattern of only R-wave loss in inferior leads: a case report

The 12-lead electrocardiogram is an easily obtained, non-invasive method to assist in the diagnosis of an acute myocardial infarction. Traditional electrocardiographic criteria for diagnosing inferior myocardial infarction emphasize abnormalities of the initial large Q wave or ST segment elevation in leads II, III, and aVF. We report a case that has acute R-wave loss in inferior leads as an initial manifestation of acute inferior wall myocardial infarction. The patient was stabilized by coronary angioplasty.     

Relationship of baseline electrocardiographic characteristics with the response to cardiac resynchronization therapy for heart failure

Prospective identification of patients most and least likely to respond to cardiac resynchronization therapy (CRT) for congestive heart failure (CHF) will allow clinicians to target this intervention most efficiently. The authors hypothesized that ECG variables including RBBB and indicators of RV dysfunction and extensive prior myocardial infarction would correlate with diminished response to CRT. This study analyzed preimplantation ECGs in 110 patients with ICD indications and CHF due to left ventricular systolic dysfunction randomized to active biventricular pacing in the MIRACLE ICD trial. Clinical and ECG variables on the outcome of change in peak oxygen consumption from baseline to 6 months (Delta-VO2 ) were evaluated. For this cohort, average peak VO2 improved from 13.4 to 14.3 mL/kg per minute. Among clinical variables, the strongest predictors of increasing Delta-VO2 were reduced exercise time and peak VO2 at baseline. A dominant R wave in lead a VR, RBBB, and evidence of prior anterior infarction were each associated with significantly smaller average improvements in Delta-VO2 than their absence in univariate analysis. Alternative ECG criteria, including QRS duration, had no relationship with the outcome. In a multivariate model, only baseline VO2 (beta=-0.3, P=0.001) and ECG evidence of prior anterior infarction (beta=-1.3, P=0.03) were associated with the outcome. ECG markers of anterior infarction and RV dilation may help identify CHF patients unlikely to benefit from biventricular pacing. Further assessment is needed of these and other predictors of therapeutic response to CRT.     

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。     

QT dispersion in children with ventricular arrhythmia and a structurally normal heart

In adults, increased QT dispersion has been shown to predict arrhythmic risk as well as risk of sudden death in several clinical settings. It is not known whether or not QT dispersion is increased in children with idiopathic ventricular arrhythmia. We studied three groups of children: (1) 20 patients with idiopathic VT (aged 3-18 years; mean 11.2 years); (2) 30 patients with benign PVCs (aged 1-20 years; mean 10.5 years); and (3) 30 control subjects (aged 4-17 years; mean 12 years). Standard ECGs were reviewed and the dispersion of both QT and JT intervals was compared. No patient had structural heart disease or long QT syndrome. The QT and QTc dispersion (QT delta, QTc delta) among the three groups did not differ: QTc delta of the VT group was 70 ms +/- 30 ms, QTc delta of PVC patients was 60 ms +/- 30 ms, and the QTc delta of the control group was 65 ms +/- 30 ms. The JTc delta among the three groups did not differ as well: JTc delta of the VT group was 70 ms +/- 30 ms, the JTc delta of the PVC group was 60 msec +/- 25 msec, and the JTc delta of the control group was 70 ms +/- 30 ms. We conclude that QT and JT dispersion are not significantly altered in children with idiopathic VT or benign PVCs when compared to control subjects. QT dispersion is not a reliable marker for arrhythmic risk in children with idiopathic ventricular arrhythmias and structurally normal hearts.