肝硬化患者Pd、QTd和JTd测定的临床意义

目的测定肝硬化患者心电图P波离散度（Pd）、QT离散度（QTd）及JT离散度（JTd）数值，探讨其临床意义。方法按Child分级标准将60例肝硬化患者分为A、B、c级三组，测量同步12导联心电图Pd、QTd和，rd数值变化以及与总胆红索、白蛋白的相关性，并与30例健康者（对照组）比较。结果肝硬化患者出现心电图改变者占61．7％，高于对照组（36．7％，P〈0．05）；Pd、QTd和，JTd数值高于对照组（P〈0．01）；且三组间比较，差异有统计学意义（P〈0．01）；Pd、QTd和JTd与总胆红索呈正相关（P〈0．01），与白蛋白呈负相关（P〈0．01）。结论肝硬化患者存在着心电图的改变，Pd、QTd和JTd数值的变化可评价肝硬化的严重程度，并能了解预后及指导临床治疗。     

Female gender is a risk factor for drug-induced long QT and cardiac arrhythmias in an in vivo rabbit model

INTRODUCTION: Clinical observations and in vitro experimental data indicate that females have a longer QT interval than males, which is associated with a higher risk of drug-induced cardiac arrhythmias. Little is known about this gender difference in anesthetized animals, which may affect the outcome of in vivo drug tests. METHODS AND RESULTS: We evaluated potential gender differences in ventricular repolarization (QT, QTc, JT, and JTc interval) and its dispersion, as well as in its response to dofetilide, an IKr blocker, in anesthetized rabbits challenged with the alpha1-adrenoceptor agonist methoxamine. A 12-lead ECG was recorded during the experiments. At baseline, there were no significant gender differences in ventricular repolarization values in male and female rabbits under anesthesia. Dofetilide (0.04 mg/kg/min IV for 60 min; n = 10 per gender) produced marked prolongation of the ventricular repolarization time and its dispersion, associated with a high incidence of polymorphic ventricular tachycardia (PVT; 100% in females vs 80% in males) and ventricular fibrillation (VF; 80% in females vs 50% in males; P > 0.05). QT and JT interval at 2 minutes as well as QT and JT dispersion at 10 and 30 minutes during dofetilide infusion were significantly higher in female than in male rabbits. After 30 minutes of dofetilide infusion, 10 of 10 female rabbits had severe cardiac arrhythmias (complete AV block, PVT, or VF), so ECG parameters were impossible to assess (vs 3/10 males with severe cardiac arrhythmias; P < 0.05). During dofetilide infusion, female rabbits developed complete AV block, PVT, or VF at doses about 50% lower than those given to males. CONCLUSION: The present study indicates that female rabbits are more susceptible to drug-induced long QT and cardiac arrhythmias than are male rabbits; therefore, female rabbits are more appropriate for testing drug-induced cardiac arrhythmias.     

急性心肌梗塞早期QT间期离散度、JT间期离散度增加与近期预后的关系

测定１０７例急性心肌梗塞（ＡＭＩ）患者第三心肌梗塞日的ＱＴ间期离散度（ＱＴｄ）和ＪＴ间期离散度（ＪＴｄ）．并以１００例正常人作对照。结果显示：ＡＭＩ组ＱＴｄ、ＪＴｄ较对照组显著增大（均Ｐ＜０．００１）。住院期间死亡组（３Ｏ例）ＱＴｄ与ＪＴｄ较存活组（７７例）明显增大（均Ｐ＜０．００１）。提示以ＱＴｄ、ＪＴｄ增大来评价ＡＭＩ患者的近期预后有一定意义。     

QRS波群增宽时心室复极时间的判断及JT间期的正确校正

目的探讨QRS波群增宽时心室复极时间的判断方法及如何对JT间期进行校正。方法测量计算了26例预激综合征和87例左、右束支传导阻滞患者的QRS波群时间和QT、JT间期，应用Bazett公式对QT间期进行校正，应用两种不同的公式对JT间期进行校正比较。结果观察组的校正QT间期较对照组延长，而校正JT间期无差异。Bazett曲线与JTc=JT√RR QRS√RR-QRS相平行，而与JTc=JT√RR不相平行。结论JT间期是反映心室复极时间的更好指标。JTc=JT√RR QRS√RR-QRS是校正JT间期的正确公式。     

心室偏心性除极时复极离散度指标的应用

目的　评价显性预激综合征时心室复极离散度指标 ( QTd和 JTd)的临床价值 ,以阐明偏心性心室除极是否导致心室复极离散度异常。方法　选择 4 6例成人显性预激综合征患者行射频消融术 ,观察射频消融前后的心室复极离散度指标 ( QTd和 JTd)的变化。结果　射频消融后最大 QRS时间较消融前缩短 ( 4 6± 2 8) ms,随着预激波消失和 QRS的“正常化”,消融后的 QTd[( 3 0± 13 ) ms]和 QTcd[( 3 7± 19) ms]较消融前的 QTd[( 5 1± 2 3 ) ms]和 QTcd[( 60± 2 7) ms]明显缩短( P值均 <0 .0 5 ) ,而消融后的 JTd[( 2 5± 10 ) ms]和 JTcd[( 2 8± 10 ) ms]与消融前的 JTd[( 2 7± 12 )ms]和 JTcd[( 3 2± 12 ) ms]相比无明显变化 ( P值均 >0 .0 5 )。消融前的预激 QRS波群导致消融前后 QTd和 QTcd的差别。由于消融前后 JTd和 JTcd并无差异 ,表明心室偏心除极不导致复极离散度异常。结论　在显性预激存在时 ,测定心室复极离散度使用 JTd和 JTcd优于 QTd和 QTcd;同时 ,预激时的心室偏心除极不导致复极离散度异常 ,即心室偏心除极不是导致复极离散度异常的机制。     

导管射频消融对QT、JT离散度的影响

目的研究导管射频消融术（ＲＦＣＡ）对ＱＴ、ＪＴ离散度（ＱＴｄ、ＪＴｄ）的影响。方法测量６２例阵发性室上性心动过速和４例特发性室速患者ＲＦＣＡ术前、术后的ＱＴｄ、ＪＴｄ。结果所有患者术前、术后ＱＴｄ、ＪＴｄ无显著差异（Ｐ均＞０．０５），三组不同电生理机制的室上速患者之间术后ＱＴｄ、ＪＴｄ差异无显著性（Ｐ均＞０．０５）。结论ＰＦＣＡ不影响正常心室肌复极离散度。     

急性缺氧对飞行员QTc和JTc间期的影响

目的　旨在探讨急性缺氧对飞行员心室肌细胞除复极的影响。方法　现役男性飞行员 50人 ,年龄平均 2 5± 2 .3 6岁。采用经面罩吸入低氧 (含氧量仅 7.1 % )混合气体的方法模拟 750 0m高空急性缺氧。分别于缺氧前和缺氧后 4min时记录标准 1 2导联心电图 ,供测算QTc和JTc间期。结果　急性缺氧可使飞行员体表心电图QTc和JTc间期显著延长。结论　急性缺氧可增加飞行员心肌复极不均一性。     

Effect of Weight Loss following Bariatric Surgery on Myocardial Dispersion of Repolarization in Morbidly Obese Patients

Background Weight-stable obese subjects have an increased risk of arrhythmias and sudden death, even in the absence of cardiac dysfunction, and the risk of sudden cardiac death (SCD) with increasing weight is seen in both genders. The mechanism of unexplained deaths in obese patients is still unclear and may be related to ventricular repolarization abnormalities. The aim of this study is to determine the effect of severe obesity on spatial and transmural ventricular repolarization and to clarify the influence of bariatric surgery with a consequent substantial weight loss on arrhythmogenic substrate in the morbidly obese population. Methods For the study, we enrolled 100 severely obese patients; 50 age-matched non-obese healthy subjects were also recruited as controls. All subjects underwent conventional 12-lead electrocardiography for analysis of spatial and transmural ventricular repolarization assessed by corrected QT dispersion (QTcd), corrected JT dispersion (JTc-d) and transmural dispersion of repolarization, (TDR). All subjects underwent bariatric surgery and were resubmitted to electrocardiographic, biochemical and anthropometric examination 12 months postoperatively. Results Severely obese patients had greater values in QTc-d, JTc-d and TDR than the normal-weight controls. Bariatric surgery reduced significantly the QTcd value, JTc-d value and TDR value. There was a significant correlation between decrease of heterogeneity of repolarization indexes (QTd, JTd and TDR) and bariatric surgery-induced weight loss. Conclusions In severely obese patients, surgicallyinduced weight loss is associated with significant decrease in the heterogeneity of ventricular repolarization. The reduction of spatial (QTc-d, JTc-d) and transmural dispersion of repolarization (TDR) may be of clinical significance, by reducing the risk of potentially fatal arrhythmias in morbidly obese subjects.     

The effects of long-term physical training in patients with coronary heart disease

A previous trial was completed in 24 patients with coronary heart disease, randomly assigned to a group who undertook a 6-month exercise training programme (5BX/XBX) and a control (no training) group. It was shown that the patients in the training group were able to achieve during exercise a higher heart rate at ST segment depression of 0.1 mV (HR/ST threshold) and that the patients in the control group showed a reduction in the threshold as well as symptomatic deterioration; the results indicated that the training programme had resulted in a reduction in the severity of myocardial ischaemia. In the present trial 9 patients of the previous training group were followed up to examine the effect of long-term maintenance training (up to 4.5 years). The same methods were used to examine the effect of maintenance training in a further group of 8 patients with coronary heart disease, 6 of whom were on beta-blocker therapy. By the end of the study, the heart rate achieved during exercise in the 17 patients was still significantly greater (P less than 0.0004) by 12.1 +/- 2.85 beats/min (mean +/- SEM) than that at the beginning of the trial; similar results were obtained in the 6 patients on beta-blocker therapy. Therefore a maintenance exercise training programme in patients with coronary heart disease can result in a sustained improvement in the form of a reduction in the severity of myocardial ischaemia, and this can occur in patients on beta-blocker therapy.