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。     

血液透析患者透析前后QT间期及QT离散度变化的临床意义

目的:探讨血液透析对患者QT间期和QT离散度(QTd)的影响.方法:对58例维持性血液透析(MHD)患者行超声心动检查并于透析前、后行心电图检查,测量计算QT间期、校正QT间期、QTd、校正QTd(QTcd).结果:与对照组相比,MHD患者左心室心肌重量指数(LVMI)显著增加(P＜0.01);两组间最大QT间期(QTmax)无明显差异,校正后MHD患者最大QT间期(QTcmax)延长(P＜0.05),QTd及QTcd均较对照组有极为明显的增加(均P＜0.01):透析后QTmax、QTcmax、QTd、QTcd均较透析前明显延长(均P＜0.05);MHD患者透析前QTd与其LVMI、透析前平均动脉压呈正相关(r分别为0.41和0.34,P＜0.05).结论:MHD患者LVMI增加,QTcmax、QTd、QTcd延长,透析后更加显著.血液透析后发生室性心律失常的危险性增大.     

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.     

Relationship of the duration of QT interval and corrected QT interval in patients with coronary heart disease and the cause of the bicycle ergometer test cessation

AIM: To comparatively study Q-T interval duration in groups of patients with coronary heart disease (CHD) identified by the cause of exercise test cessation. MATERIALS AND METHODS: Bicycle ergometric test (BET) was performed in 93 males with CHD (functional class II-III angina pectoris on exertion). During BET, ECG recorded in the leads, as described by Nebu. The QT interval was visually measured in one lead. This interval was determined as a distance between the onset of a Q wave and the end of a T wave (in mlsec). The mean value by 3 cardiac cycles was taken as an actual value of the QT interval. To compare the duration of the QT interval at different rates of cardiac rhythm, its corrected value (QTc) was calculated. RESULTS AND CONCLUSION: In case of positive BET (anginal attack, 1-mm or more depressed ST segment at a distance of 0.8 cm from the joint J), the values of QT and QTc measured at rest and peak exercise were greater than those if the cause of test cessation was the submaximum heart rate or a patient's fatigue. The value of QTc was higher if the cause of BRT cessation was 1-mm or more depressed ST segment preceding an anginal attack or the only cause of test cessation.     

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。     

QT interval dispersion and autonomic modulation in subjects with anxiety

This study was designed to assess Q-T interval dispersion as a marker of electrical instability in subjects with anxiety. Recent observations have shown that the presence of anxiety symptoms increases the risk of sudden death. The Kawachi anxiety questionnaire identified 29 subjects (male/female ratio 13:16) who scored 0, 22 subjects (male/female ratio 14:8) who scored 1, and 37 subjects (male/female ratio 13:24) who scored 2 or more. In all subjects we measured electrocardiographic interlead QT dispersion and autonomic function through spectral analysis of R-R interval and blood pressure variabilities and left ventricular mass. Compared with subjects who scored 0, those reporting 2 or more symptoms showed increased heart rate-corrected QT dispersion (54.9+/-1.7 ms vs. 34.9+/-3.2 ms, P<.001), sympathetic modulation (normal logarithm low-frequency power/high-frequency power 0.59+/-0.1 vs. 0.12+/-0.04, P<.05), and left ventricular mass (120.7+/-3.5 g/m2 vs. 97.9+/-2.8 g/m2, P<.001). Probably because it augments sympathetic activity, anxiety causes left ventricular mass to increase and, like hypertension, increases heart rate-corrected Q-T interval dispersion. The consequent electrical instability could be the substrate responsible for inducing fatal ventricular arrhythmias.     

Impact of electrocardiogram recording format on QT interval measurement and QT dispersion assessment

The aim of this study was to determine the effect of recording conditions on the operator dependent measures of QT dispersion in patients with known and/or suspected repolarization abnormalities. Among several methods for risk stratification, QT dispersion has been suggested as a simple estimate of repolarization abnormalities. In a cohort of high and low risk patients, different components of the repolarization process were assessed in the 12-lead ECG using three different paper speeds and amplifier gains. To assess measurement error and reproducibility, a straight line was repeatedly measured. The operator error was 0.675 +/- 0.02 mm and the repeatability of the measurement error was 31 +/- 6%. The QT interval was most frequently measurable in V2-V5. Depending on the lead selected for analysis, the incidence of visible U waves was greatest in the precordial leads with high amplifier gain and low paper speed, strongly affecting QT interval measurement. The timing of the onset of the QRS complex (QRS onset dispersion) or offset of the T wave was strongly dependent on the paper speed. Paper speed, but not amplifier gain, had a significant shortening effect on the measurement of the maximum QT interval. As QT interval measurement in each ECG lead incorporates QRS onset and T wave offset (depending on the number of visible U waves), the dispersion of each of these parameters significantly affected QT dispersion. Thus, QT dispersion appears to reflect merely the presence of more complex repolarization patterns in patients at risk of arrhythmias.     

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。     

Effect of angiotensin-converting enzyme therapy on QT interval dispersion

Patients with chronic heart failure (CHF) have an increased risk for sudden death. This increased risk has been associated with increased QT dispersion (QTd), a reflection of the heterogeneity in ventricular repolarization. Angiotensin-converting enzyme (ACE) inhibitors have been reported to decrease heart size as well as decreasing morbidity and mortality in moderate-to-severe CHF. The aim of this study was to determine if ACE therapy is associated with a decrease in QTd, a marker for increased electrical instability. Ninety-seven patients were evaluated. The normalized QTd after 2 months of ACE therapy decreased from 16 +/- 4 to 12 +/- 3, a 25% reduction in dispersions. QTd also decreased from 61 +/- 14 to 47 +/- 12 (P < .001) and QTc dispersions decreased from 71 +/- 18 to 52 +/- 14 (P < .001). After 2 months of ACE inhibitor therapy, heart rate slowed significantly (RR intervals 765 +/- 198 before and 838 +/- 186 after ACE). There was a negative correlation between ejection fraction and QTd (r = -0.8; P < .001). The study also found no correlation between ACE level, percent converting enzyme inhibition, and QTd. The effects of ACE therapy appear early on in terms of repolarization changes. The reduction in QTd may explain the reduced sudden death mortality in patients with heart failure who are treated with ACE inhibitor therapy.     

Serum quinidine concentrations and effect on QT dispersion and interval

OBJECTIVE: To establish a relationship between serum quinidine concentrations (SQCs) and QT interval dispersion, compared with corresponding QT intervals, in order to identify a reason why many reports describe torsade de pointes as occurring at subtherapeutic concentrations. DESIGN: Retrospective study. SETTING: University teaching hospital. PARTICIPANTS: Eleven patients with atrial arrhythmias managed with quinidine therapy. MAIN OUTCOME MEASURES: Patients with subtherapeutic (<2 microg/mL) and therapeutic (2-5 microg/mL) SQCs with corresponding 12-lead electrocardiograms (ECGs) (25 mm/sec) and baseline ECG were evaluated for QT interval dispersion, calculated as the maximum minus the minimum QT interval on the 12-lead ECG. RESULTS: Mean +/- SD subtherapeutic and therapeutic SQCs were 1.48 +/- 0.39 microg/mL and 3.78 +/- 0.88 microg/mL (p < 0.001). Baseline values for QT/QTc intervals were 376.4 +/- 59.2/429.5 +/- 57.3 msec. At subtherapeutic and therapeutic SQCs, mean QT/QTc intervals were 403.6 +/- 59.9/450.5 +/- 38.5 msec and 439.1 +/- 48.9/472.4 +/- 44.6 msec, respectively. Mean QT dispersion was 47 +/- 16.2 msec at baseline, 98.2 +/- 27.5 msec at subtherapeutic SQC, and 70.9 +/- 33.9 msec at therapeutic SQCs (p = 0.001 for overall analysis; p < 0.001 for baseline vs. subtherapeutic concentrations; p = NS for therapeutic vs. subtherapeutic in post hoc comparison). CONCLUSIONS: Despite QT interval lengthening with increasing SQCs, QT dispersion was numerically greatest at subtherapeutic SQCs. Further study is required to determine the value of QT dispersion as a tool for identifying proarrhythmic risk with drugs that prolong the QT interval.     

QT interval is prolonged but QT dispersion is maintained in patients with primary aldosteronism

The relationship between QT duration and its dispersion in patients with primary hyperaldosteronism is not clearly known. We studied 26 patients (nine males and 17 females) with primary hyperaldosteronism. The serum potassium levels were low (2.32 +/- 0.52 mmol/l), did not correlate with serum renin or aldosterone levels, or aldosterone/renin ratio (ARR). The maximum QT intervals (QTmax) were prolonged (502 +/- 62 ms), correlated well with ARRs (p = 0.005) and aldosterone levels (p = 0.019), but not to renin (p = 0.517) or potassium levels (p = 0.196). The QT dispersions (QTd) were small (60 +/- 28.8 ms) and did not correlate with potassium, renin or aldosterone levels. QTmax but not QTd correlate with aldosterone levels in patients with primary aldosteronism. The maintenance of repolarisation homogeneity with relatively unchanged QT dispersion may contribute to our understanding of the clinical observation that ventricular tachydysrhythmia is rare among patients with primary aldosteronism.     

The effect of altitude on P-wave and QT duration and dispersion

Background: Short-term and long-term exposure to high altitude has been reported to change the surface electrocardiogram. We aimed to compare P-wave and QT parameters between healthy people living at high altitude and sea level.
Methods: Twelve-lead electrocardiographies of 38 healthy people living at sea level (Antalya,Turkey) and 38 healthy people living at high altitude (Van, Turkey; 1,700–1,800 m) were obtained. Minimum and maximum P-wave durations, P-wave dispersion, minimum and maximum corrected QT intervals, and corrected QT dispersion were calculated.
Results: There was no significant difference between the two groups in respect to heart rate and QT variables. Mean Pminimum values were slightly but significantly lower in the high altitude group (P = 0.029). Mean Pmaximum values tended to be lower at high altitude but did not reach statistical significance (P = 0.085). However, there was no significant difference in respect to P-wave dispersion values.
Conclusions: In a sample of men and women living at high altitude in Turkey, significant reduction of Pminimum and borderline reduction of Pmaximum duration, but no significant change of P-wave and QT dispersion, were observed.     

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.     

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     

Effects of adrenaline and potassium on QTc interval and QT dispersion in man

BACKGROUND: Hypoglycaemia alters cardiac repolarization acutely, with increases in rate-corrected QT (QTc) interval and QT dispersion (QTd) on the electrocardiogram (ECG); such changes are related to the counterregulatory sympatho-adrenal response. Adrenaline produces both QTc lengthening and a fall in plasma potassium (K+) when infused into healthy volunteers. Hypokalaemia prolongs cardiac repolarization independently however, and therefore our aim was to determine whether adrenaline-induced repolarization changes are mediated directly or through lowered plasma K+. MATERIALS AND METHODS: Ten healthy males were studied on two occasions. At both visits they received similar l-adrenaline infusions but on one occasion potassium was also administered; infusion rates were adjusted to maintain circulating K+ at baseline. The QTc interval, QTd, peripheral physiological responses and plasma adrenaline and potassium concentrations were measured during both visits. RESULTS: The QTc interval and QTd increased both with and without potassium clamping. Without K+ replacement, mean (SE) QTc lengthened from 378 (5) ms to a final maximum value of 433 (10) ms, and QTd increased from 36 (5) ms to 69 (8) ms (both P < 0.001). During K+ replacement, QTc duration at baseline and study end was 385 (7) ms and 423 (11) ms, respectively (P < 0.001), and QTd 38 was (4) ms and 63 (5) ms (P = 0.001). CONCLUSIONS: These data suggest that disturbed cardiac repolarization as a result of increases in circulating adrenaline occurs independently of extracellular potassium. A direct effect of adrenaline upon the myocardium appears the most likely mechanism.     

T wave peak-to-end interval and QT dispersion in acquired long QT syndrome: a new index for arrhythmogenicity

QT dispersion (QTD) on 12-lead ECGs has been proposed as a marker of malignant ventricular tachyarrhythmias, and increased QTD has been reported in long QT syndrome (LQTS). On the other hand, it has been demonstrated that transmural dispersion is associated with ventricular tachyarrhythmias in an experimental model. However, the precise type of QTD or transmural dispersion that contributes most to ventricular tachyarrhythmias in patients with LQTS remains unclear. We evaluated 27 patients with acquired LQTS. These patients were divided into two groups: group A (n =12), patients with polymorphic ventricular tachycardia [torsades de pointes (TdP)], and group B (n =15), patients without TdP. The QT intervals were corrected using Bazett's formula. QTD was measured as the difference between the maximum and the minimum QT intervals, and T wave peak-to-end interval divided by the QT interval (Tpe) in the V5 lead was measured as a new index. Both the corrected QTD (QTDc) and Tpe were significantly larger in group A than in group B. Logistic regression analysis revealed that a reliable predictor for TdP in the QT variables in these patients was not QTDc but Tpe. Cumulative frequency distributions revealed that a Tpe of 0.28 is a good cut-off point for TdP. Tpe did not correlate with the corrected maximum QT interval, whereas the QTDc did correlate with this parameter. In conclusion, Tpe may be the best predictor for TdP in patients with acquired LQTS.     

Effects of sevoflurane on QT dispersion and heart rate variability

The purpose of this study was to use estimates of corrected QT dispersion (QTcd) and heart rate variability (HRV) to assess the effects of sevoflurane, an inhalation agent used frequently in clinical practice, on autonomic cardiac function. This study was conducted prospectively and in a blind manner on 20 women between 38 and 51 y of age who were classified as American Society of Anesthesiologists stage I–II and whose treatment required total abdominal hysterectomy. Electrocardiograms were recorded by 12-lead Holter monitor for 5 min before sevoflurane induction and again for 5 min at 10 min after tracheal intubation. Data on the first recording were considered as baseline; those on the second recording were viewed as final data. The study was terminated at this point, and surgery was allowed to proceed. QTcd and HRV values were assessed by a cardiologist, who was blinded to all data. All parameters were expressed as a mean value ± standard deviation. Wilcoxon’s test was used to compare baseline and final data. Statistical significance was considered asP< .05. No significant changes were observed between baseline and final QTcd values and between low and high-frequency components (LF and HF) of HRV; nor were changes seen in the LF/HF ratio. With the patient under sevoflurane/nitrous oxide anesthesia, no significant changes were detected in QTcd, LF, and HF values, and in the LF/HF ratio, whereas a significant increase (P=.001) was seen in standard deviation of the R-R interval, which was used as a measure of cardiac autonomic tone.     

逆转高血压左心室肥厚对QT间期离散度的影响

目的：研究左心室肥厚与ＱＴ间期离散度相互关系。方法：４６ 例服卡托普利２５～５０ ｍｇ／ｄ,２／ｄ,平均２１ 个月。结果：用药后室间隔、左室后壁厚度变薄,左室重量指数明显下降;ＱＴｃ 离散度明显减小。结论： 高血压病左室肥厚的逆转, 可明显缩短ＱＴ离散度,减少心血管事件的发生率和病死率。