QT Interval Prolongation with Global T‐Wave Inversion: A Novel ECG Finding in Acute Pulmonary Embolism

Objective: The purpose of this study was to report a novel electrocardiographic (ECG) phenomenon in acute pulmonary embolism characterized by QT interval prolongation with global T‐wave inversion. Methods: Among a total of 140 study patients with a confirmed diagnosis of acute pulmonary embolism, patients who fulfilled the inclusion criteria for QT interval prolongation with global T‐wave inversion were examined. Each of these patients had undergone a detailed clinical evaluation including testing for myocardial injury and echocardiography. Results: QT interval prolongation with global T‐wave inversion was found in five patients (age 51–68 years) with acute pulmonary embolism. Four were women. Acute pulmonary embolism was diagnosed by ventilation‐perfusion scan in three patients and by spiral computed tomography in other two patients. None of the patients had any right or left ventricular regional wall motion abnormalities on echocardiography. All patients had changes characteristic of hemodynamically significant pulmonary embolism, including right ventricular stunning or hypokinesis and dilatation in five patients with paradoxical septal motion in four. Acute coronary syndrome was ruled out in each patient by clinical evaluation, serial ECGs and cardiac markers, and lack of regional wall motion abnormalities on echocardiography. Prolongation of QT intervals (QTc 456–521 ms) with global T‐wave inversion was noted on presentation. The ECG changes gradually resolved in 1 week in all patients with appropriate treatment of acute pulmonary embolism. One patient died. None of the patients developed torsade de pointes. Conclusions: Acute pulmonary embolism may occasionally result in reversible QT interval prolongation with deep T‐wave inversion, and, thus should be considered among the acquired causes of the long QT syndrome.     

心得安试验QT离散度变化与QTd本质的研究

目的：研究心得安试验前后QT离散度(QTd)变化，探讨QTd的本质及评价其临床应用价值。方法：于经冠脉造影及其他检查除排除器质性心脏病，静息心电图有T波低平、双向、倒置或有u波的186例思考，观察心得安试验前、后QTd的变化。结果：(假定QTd＞50ms为异常)78例心得安试验阳性QTd异常率试验前、后分别为83．3％，11．5％，有显差异(P＜0．01)；108例心得安试验阴性QTd异常率试验前、后依次为77．8％，74、1％，无显差异(P＞0．05)。两组QTd异常率试验前无显差异，试验后有显差异(P＜0．01)。结论：非器质性心脏病心得安试验QTd变化提示QTd异常不能作为反映心肌复极的不均一性指标，预测恶性心律失常或心脏猝死，而只是反映T波非特异性异常的一个粗浅的量化指标，对QTd的临床应用宜慎重。     

运动试验QT离散度变化与心肌缺血或T波改变相关性的研究

目的 :探讨运动试验QT离散度 (QTd)变化与心肌缺血和T波变化的相关性及评价QTd的临床应用价值。方法 :2 4 2例经冠脉造影证实冠心病而静息心电图正常 ,平板运动试验阳性 (冠心病组 )和 16 8例静息心电图有T波低平、双向、倒置或有u波 ,平板运动试验心电图正常 ,并经冠脉造影及其他检查排除器质性心脏病 (非器质性心脏病组 )。观察两组平板运动试验QTd的变化与心肌缺血和T波变化的相关性。结果 :设QTd >5 0ms为异常 ,冠心病组运动前QTd异常率为18% ,运动后为 80 % ;非器质性心脏病组运动前QTd异常率为 84 % ,运动后为 12 %。QTd的变化与T波改变相关 ,r=0 .86 ,P <0 .0 1;与冠心病运动后单纯缺血性ST段下移无相关性。结论 :运动试验QTd变化与心肌缺血无相关性 ,QTd异常不能判断心肌复极不均一性进而预测恶性心律失常或心脏猝死 ,而只是反映T波非特异性异常的一个粗浅的量化指标     

Earliest time of change in QT dispersion after stenting in patients with single vessel coronary artery disease

Dispersion of the QT interval (QTd) is a measure of inhomogeneity of ventricular repolarization, and its prolongation may provide a suitable substrate for life-threatening ventricular arrhythmias. The present study was performed to determine the onset time of change in the corrected QT (QTc) interval and QTd in patients with stable angina and single vessel coronary artery disease. Electrocardiograms of 60 patients with successful stenting, obtained 1 h before and 1 h, 6 h, 12 h and 24 h after the procedure were analyzed. The QTc interval, QTc maximum, QTc minimum and QTd were measured. All electrocardiograms were scanned, and then underwent computer-based analysis. There was a significant reduction in the mean QTc interval as early as 12 h after the procedure (from 474±41 ms to 460±31 ms; P<0.001), which persisted to the 24 h follow-up. This was associated with a significant reduction in mean QT maximum (from 496±31 ms to 418±66 ms; P<0.001) and a significant prolongation in mean QT minimum (from 403±21 ms to 444±12 ms; P<0.001) at the same time intervals. Therefore, successful stenting of coronary arteries in patients with single vessel coronary artery disease and stable angina decreases QTd as early as 12 h after the procedure. This phenomenon may be the result of improved regional myocardial circulation, and reduced ischemia. A persistently low QTd in the following months may therefore have prognostic significance, and can be used as a noninvasive marker of stent patency. Further studies are necessary to define the clinical applicability of QTd in the assessment of long-term stent patency in such patients.     

QT Interval in Patients with Unstable Angina and Non‐Q Wave Myocardial Infarction

Background: Non‐Q wave mvocardial infarction (NQMI) and unstable angina (UAP) have similar clinical presentations and similar ST‐T changes on the electrocardiogram. The purpose of this study was to assess whether changes in QT interval might help differentiating between these entities. Methods: The QT intervals of 52 patients hospitalized with NQMI were compared to those of 52 patients hospitalized for UAP. All patients had repeated ECG for at least 4 days. Results: Maximal QTc in patients with NQMI was significantly longer than in patients with UAP (475 vs 439 ms, P < 0.0001). QTc on the admission ECG was 450 ms in patients with NQMI compared to 417 ms in UAP P < 0.005). QTc > 460 ms was present in 48% patients with NQMI and in 19% of UAP patients. Maximal QT prolongation was observed within 36 hours of admission with return to normal within 96 hours. QT dispersion was within normal range, being longer in patients with NQMI than patients with UAP (55 vs 43 ms, P < 0.003). QT prolongation was not associated with increased frequency of arrhythmia. The cause of QT prolongation in NQMI may be related to the damage of subendocardial layer exposing the M cells layer which markedly prolong action potential duration. Conclusion: Transient QT prolongation is observed in about half of patients with NQMI. These ECG changes may help differentiating between patients with NQMI and UAP already on admission. A.N.E. 2002;7(4):343–348     

Dispersion of the QT Interval in Subjects with Frequent Nonsustained Ventricular Arrhythmias and No Underlying Heart Disease: Arrhythmogenic Substrate or Mechanoelectrical Feedback of Arrhythmias?

Background: QT dispersion (QTd) on the ECG is thought to reflect the temporal and spatial inhomogeneity of repolarization in the underlying myocardium. In myocardial infarction, ischemia, and long QT syndromes, an increased QTd is associated with a propensity for malignant ventricular arrhythmias and sudden cardiac death. We investigated this feature of the repolarization process in subjects with frequent ventricular arrhythmias and structurally normal hearts. Methods: Forty‐nine patients referred for frequent, nonsustained ventricular arrhythmias (45 ± 14 years, ×± SD, 61% female) had normal ventricular dimensions and function, no late potentials, and normal ECG. They were compared with 30 controls (42 ± 13 years, 50% female). QTd was measured as the difference between the longest and the shortest QT in the six precordial leads at a paper speed of 50 mm/s. Results: In patients, QTc was similar to that of controls: 395 ± 21 versus 386 ± 20. However, QTd was greater: 49 ± 20 ms versus 32 ± 14 ms, P < 001. Moreover, 18 patients (36%) had QTd exceeding 60 ms—a value superior to the mean normal value of 2 SD—compared to only 1 control (3%) (P < 0.01). Finally, patients with more frequent ventricular arrhythmias had larger QTd. Conclusions: In patients with frequent nonsustained ventricular arrhythmias and otherwise normal hearts, QT interval dispersion is increased. We speculate that, instead of representing a specific electrophysiological substrate of arrhythmias, QT dispersion in this specific population could result from arrhythmias themselves through a possible mechanoelectrical feedback.     

Effect of amiodarone on qt dispersion in the 12-lead standard electrocardiogram and its significance for subsequent arrhythmic events

Background and hypothesis: QT dispersion, measured as interlead variability of QT intervals in the surface electrocardiogram, has been demonstrated to provide an indirect measurement of the inhomogeneity of myocardial repolarization. The purpose of the present study was twofold: (1) to analyze the effect of amiodarone on QT dispersion measured in the 12-lead standard ECG, and (2) to examine the association between QT dispersion on amiodarone and subsequent arrhythmic events. Methods: To determine the effect of amiodarone on QT dispersion and its clinical significance for subsequent arrhythmic events, QT dispersion was measured in the 12-lead standard electrocardiogram (ECG) in 52 patients before and after administration of empiric amiodarone for ventricular tachyarrhythmias. Results: QT intervals increased from 401 ± 44 ms before amiodarone to 442 ± 53 ms after amiodarone therapy, and rate corrected QT intervals (QTc) increased from 452 ± 43 ms to 477 ± 37 ms, respectively (p<0.01). QT dispersion, QTc dispersion, and adjusted QTc dispersion, which take account of the number of leads measured, were not significantly different before and after initiation of amiodarone therapy (58 ± 24 ms vs. 61 ± 26 ms, 68 ± 29 vs. 66 ± 26 ms, and 22 ± 8 vs. 22 ± 8 ms, respectively, p = NS). During 31 ± 25 months follow-up after initiation of amiodarone therapy, arrhythmic events defined as sustained ventricular tachycardia, ventricular fibrillation, or sudden death occurred in 11 of 52 study patients (21%). QT dispersion, QTc dispersion, and adjusted QTc dispersion on amiodarone were not different between patients with and without arrhythmic events during follow-up (65 ± 14 vs. 59 ± 29 ms, 73 ± 15 vs. 64 ± 28 ms, and 25 ± 6 vs. 21 ± 8 ms, respectively, p=NS). Conclusions: We conclude that (1) amiodarone increases QT intervals and QTc intervals during sinus rhythm but does not significantly change measures of QT dispersion; and (2) QT dispersion measured in the 12-lead standard ECG after initiation of amiodarone therapy does not appear to be a useful marker for subsequent arrhythmic events.     

QT间期及其离散度测定的方法学研究和正常值

报告１００例健康成人同步体表１２导联心电图的ＱＴ间期和ＱＴ间期离散度（ＱＴｄ）：（１）各参数测量结果（±ｓ）：ＱＴｄ、ＱＴｃｄ（矫正ＱＴｄ）、ＪＴｄ（ＪＴ离散度）、ＱＴｐｄ（ＱＴ顶点离散度）、ＪＴｐｄ（ＪＴｐ离散度）、Ｔｐ－ＴＥｄ（Ｔ波顶点至Ｔ波终点间期离散度）、ＱＲＳｄ（ＱＲＳ间期离散度）和Ｏ－Ｑｄ（ＱＲＳ起始时间离散度）分别为２５．６±１１．２，２６．８±１２．６，２６．１±１２．５，２４．６±１４．７，３２．０±１５．６，３１．０±１４．６，２０．６±８．８和１２．５±７．３ｍｓ，其范围均在５～５０ｍｓ以内，与国际上研究结果一致。笔者认为ＱＴｄ的正常值可暂定为＜５０ｍｓ；（２）体表１２导联心电图同步记录方法，比常规非同步记录更能反映ＱＴｄ的实际情况，并且可测量同步１２导联ＱＲＳ起始部时间（Ｑ－ＱＴ）及其离散度（Ｑ－ＱＴｄ）；（３）本文资料由国内和国外三组不同人员测量结果相同，表明ＱＴ、ＱＴｄ测定的可重复性好；（４）性别差异，ＱＴ间期女性比男性长，而ＱＲＳ间期男性比女性长，其机理尚待进一步研究探讨。     

Differential effect of glyburide (glibenclamide) and metformin on QT dispersion: a potential adenosine triphosphate sensitive K+ channel effect

Glyburide (glibenclamide) is a specific blocker of the adenosine triphosphate (ATP) sensitive potassium (K+) channel. It has been reported to result in prolongation of the QT interval. QT interval dispersion (QTd) is a potentially sensitive marker for increased risk of arrhythmia and sudden cardiac death. The aim of the present study was to evaluate the effect of glyburide on QTd and compare it with that of metformin, a hypoglycemic agent that does not block the adenosine triphosphate sensitive K+ channel. Thirty patients with type 2 diabetes were randomized to glyburide and metformin groups. A 12-lead electrocardiogram was obtained before and at 2 months after being on glyburide or metformin. Therapy with QT and QTd were measured and QT corrected for rate (QTc). There was no significant difference between the glyburide and metformin groups in age (62 +/- 9 vs 59 +/- 10 years), baseline RR interval (819 +/- 86 vs 753 +/- 100 ms), QT (387 +/- 28 vs 383 +/- 27 ms), and QTc (433 +/- 25 vs 444 +/- 15 ms). Glyburide was associated with a significant increase in QTc (433 +/- 24 to 467 +/- 24 ms, p <0.001), QTd (24 +/- 16 to 60 +/- 22 ms, p <0.001), and QTc dispersion (QTcd) (35 +/- 18 to 68 +/- 21 ms, p <0.001). In contrast, metformin was associated with a decrease in QTc (444 +/- 15 to 432 +/- 15 ms, p <0.01) and did not affect QTd (14 +/- 5 to 12 +/- 6 ms, p = NS) and QTcd (23 +/- 9 to 22 +/- 10 ms, p = NS). Glyburide, unlike metformin, causes an increase in QT dispersion. Increased dispersion may be a factor underlying an increased risk of arrhythmias and sudden cardiac death.     

QT dispersion and late potentials during doxorubicin therapy for non-Hodgkin's lymphoma

OBJECTIVES: To investigate effects of doxorubicin therapy on cardiac electrophysiology, with special emphasis on QT dispersion and late potentials, in lymphoma patients. DESIGN: Prospective study. SETTING: University hospital. SUBJECTS: Twenty-eight adult non-Hodgkin's lymphoma patients who received doxorubicin to a cumulative dose of 400-500 mg m-2. MAIN OUTCOME MEASURES: Standard 12-lead electrocardiogram (ECG) and signal-averaged ECG (SAECG) recordings were performed at baseline and after cumulative doxorubicin doses of 200, 400 and 500 mg m-2. RESULTS: Heart rate-corrected QT interval (QTc) increased from 402 +/- 4 to 416 +/- 5 ms (P = 0.002) during the study period. QT dispersion (variability in QT interval duration amongst the different leads of the standard 12-lead ECG) increased from 24.1 +/- 2.5 to 35.0 +/- 2.8 ms (P = 0.041) and QTc dispersion increased from 26.5 +/- 2.5 to 39.0 +/- 3.5 ms (P = 0.039). Five patients (18%) developed QT dispersion exceeding 50 ms. In addition, two patients (7%) developed late potentials during doxorubicin therapy. The changes in QTc duration, QT dispersion and late potentials occurred independently of the impairment of left ventricular function. CONCLUSIONS: Prolongation of QTc, increased QT dispersion and development of late potentials are indicative of doxorubicin-induced abnormal ventricular depolarization and repolarization. QT dispersion and late potentials are both known to be associated with increased risk of serious ventricular dysrhythmias and sudden death in various cardiac diseases. Thus, follow-up of these parameters might also be useful in assessing the risk of late cardiovascular events in cancer patients treated with anthracyclines.     

Dynamics of Ventricular Repolarization in Patients with Dilated Cardiomyopathy Versus Healthy Subjects

Background: Patients with impaired left ventricular function have a high risk of developing ventricular arrhythmias and sudden death. Among different markers of risk, the prolongation and regional heterogeneity of repolarization are of increasing interest. However, there are limited data regarding feasibility of analyzing repolarization parameters and their dynamics in 24‐hour Holter ECG recordings. Methods: Dynamic behavior of repolarization parameters was studied with a new automatic algorithm in digital 24‐hour Holter recordings of 60 healthy subjects and 55 patients with idiopathic dilated cardiomyopathy (IDC). Repolarization parameters included the mean value of QT and QTc durations, QT dispersion, and peaks of QT duration and QT dispersion above prespecified thresholds. Results: In comparison to healthy subjects, patients with IDC had lower heart rate variability, longer mean QT and QTc durations, higher content of QTc peaks >500 ms, longer QT dispersion and its standard deviation, and a higher content of peaks >100 ms of QT dispersion (P < 0.01 for all comparisons). These repolarization parameters were significantly higher in IDC patients after adjustment for age, sex, and heart rate variability. The parameters of repolarization dynamics correlated with SDNN in healthy subjects but not in dilated cardiomyopathy patients. Conclusions: The automatic assessment of repolarization parameters in 24‐hour digital ECG recordings is feasible and differentiates dilated cardiomyopathy patients from healthy subjects. Patients with dilated cardiomyopathy have increased QT duration, QT dispersion, and increased variability of QT dispersion reflecting variations in T‐wave morphology, the factors which might predispose them to the development of arrhythmic events.     

Nifekalant Enlarged the Transmural Activation-Recovery Interval Difference as Well as the Peak-to-End Interval on Surface ECG in a Patient with Short-QT Syndrome

Transmural ARI Dispersion in SQTS. A 38-year-old woman with type 1 short-QT syndrome (SQTS) was referred to our hospital. Her ECG showed short QT/QTc interval and peaked T wave. Activation-recovery intervals (ARIs) were calculated from the intracardiac endocardial and epicardial electrode catheters placed in the left ventricle (LV). Intravenous administration of nifekalant prolonged effective refractory period at multiple ventricular sites as well as the QT/QTc interval (from 260/300 to 364/419 ms) on the surface ECG. Nifekalant also enlarged the transmural ARI dispersion of the ventricular repolarization, which was measured by the difference between the longest endocardial ARI and the shortest epicardial ARI during atrial pacing at 90 bpm, from 73 to 103-105 ms. These values corresponded to the intervals between the peak and end of the T wave on the surface ECG. Nifekalant-induced QT interval prolongation on the surface ECG may not indicate attenuation of the arrhythmogenic potential in the heart of SQTS patients. (J Cardiovasc Electrophysiol, Vol. 23, pp. 877-880, August 2012).     

An Evaluation of the Impact of Gender and Age on QT Dispersion in Healthy Subjects

Objectives: To determine if gender, age, and gender per age category, have an impact on QT and QTc dispersion in healthy volunteers. Methods: This study was undertaken in 150 patients (50 per age group, 75 males, 75 females). The age groups included young (20–40 years), middle‐aged (41–69 years) and elderly (> 70 years) subjects. The QT intervals on a 12 lead ECG were determined and Bazett's formula was used to derive the QTc intervals. The QT and QTc dispersion were determined by subtracting the shortest QTc interval from the longest on each 12‐lead recording. Results: Males had higher QT dispersion than females (50 ± 22 vs 42 ± 18 ms, P = 0.017) but QTc dispersion was not significantly changed. No significant differences were seen among the different age categories for QT or QTc dispersion. In elderly subjects, males had higher QT and QTc dispersion than females (54 ± 23 vs 42 ±15 ms, P = 0.039 and 63 ± 23.7 vs 48 ± 21 ms, P = 0.032, respectively). Conclusions: When evaluating the effect of gender in different age categories, elderly males have significantly greater QT and QTc dispersion than elderly female subjects. No other gender differences were noted for QT or QTc dispersion in the other two age categories. When evaluating a population of healthy volunteers, regardless of age, gender has an impact on QT dispersion but no significant interaction with QTc dispersion. Evaluating age without dividing the data by gender yields no significant differences in QT or QTc dispersion. A.N.E. 2001;6(2):129–133     

Is myocardial repolarization duration associated with repolarization heterogeneity?

Background

Dispersion of repolarization is theorized as one mechanism by which myocardial repolarization prolongation causes lethal torsades de pointes, (TdP). Our primary purpose was to determine whether prolongation of myocardial repolarization as measured by the heart rate‐corrected J‐to‐T peak interval (JTpkc), is associated with repolarization heterogeneity as measured by transmural dispersion, defined as the median duration from the peak to the end of the T wave (TpTe).

Methods

A retrospective cohort study was performed at a single urban tertiary ED from July 2011–September 2012. Inclusion criteria included all consecutive ED patients with ECG based on QTc and QRS intervals. Automated measurements of all intervals were performed. The association of JTpkc with the dependent variable TpTe was assessed after adjustment for QRS and RR interval durations with a multiple linear regression model. A secondary analysis included a similar adjusted assessment of the association of JTpkc with QT dispersion, QTd. Finally, we constructed two multiple regression models to assess the association of clinical causative factors of TdP with TpTe and JTpkc.

Results

Eight hundred seventy‐four cases were included: 186 with QTc <500 ms, 118 with QTc ≥500 and QRS ≥120 ms, and 570 with QTc ≥500 and QRS <120 ms. The coefficient for association of JTpkc with TpTe was ?0.10 (95%CI ?0.15 to ?0.05), and for JTpkc with QTd was 0.03 (95% CI ?0.01 to 0.06). Clinical causative TdP factors were associated more with JTpkc than TpTe.

Conclusion

Repolarization duration as measured by JTpkc is not positively associated with dispersion of repolarization as measured by TpTe or QTd. Dispersion of repolarization may not be a critical mechanistic link between QTc prolongation and TdP.

     

QT离散度对心衰患者心脏事件的预测价值

目的探讨QT离散度(QTd)、校正QT离散度(QTcd)及心率校正QT间期(QTc)对心衰患者心脏事件的预测价值。方法回顾性研究了106例充血性心力衰竭(CHF)患者QTd、QTcd、及QTc的资料。结果心脏事件发生组CHF病人(Ⅰ组)QTd、QTcd、QTc、QTcd/QTc与无心脏事件发生组(Ⅱ组)比较有显著的统计学差异(P<0.05、<0.01、<0.05、<0.001)。结论QTd、QTcd、QTc、QTcd/QTc是心衰病人心脏事件独立预测因子,QTcd/QTc准确性最高。     

心肌梗死患者QTd、Tp-Te和Tp-Te/QT的观察

目的观察心肌梗死后3~6个月患者心电图QTd、Tp-Te和Tp-Te/QT与对照组之间有无差异。方法选取自2011年1月至9月行心电图检查的心梗后3~6个月患者30例,男14例,女16例,平均年龄(51.2±11.94)岁;收集年龄、性别相匹配的对照组30例,男15例,女15例,平均年龄(50.4±9.45)岁,测量各组心电图QTd、Tp-Te间期并计算Tp-Te/QT值。结果心梗组Tp-Te和Tp-Te/QT比值均大于对照组,差异具有统计学意义(心梗组Tp-Te:101.9±14.5ms;Tp-Te/QT:0.287±0.04;对照组Tp-Te:75.7±12.4ms;Tp-Te/QT:0.193±0.03;p<0.05);QTd在两组之间无差异(心梗组:40.5±3.9ms;对照组:37.9±3.8ms;p>0.05)。结论心梗患者Tp-Te,Tp-Te/QT比值增高,可反映跨室壁复极离散度的变化,与心律失常的发生关系密切。     

Changes in QT dispersion during adenosine infusion

BACKGROUND: QT dispersion (QTd) measurement during treadmill stress testing has been to shown to improve the accuracy of exercise electrocardiogram (ECG) in the detection of significant coronary artery disease (CAD). HYPOTHESIS: The aim of this study was to determine whether adenosine-induced changes in QTd could predict significant CAD and to assess its efficacy as a diagnostic index in patients undergoing adenosine stress test. METHODS: QT interval measurements were made in 57 consecutive patients undergoing adenosine sestamibi stress test. Patients with an abnormal stress test underwent coronary angiography. Patients with significant disease by coronary angiography (> 70% stenosis) were classified as having CAD (Group 1), and those with normal stress images and/or normal coronaries by angiography were classified as having no CAD (Group 2). RESULTS: QT dispersion increased from 28.2 +/- 4.5 to 43.8 +/- 4.5 ms with a delta QTd of 15.53 +/- 3.68 in Group 1 (p = 0.001) and from 28.4 +/- 2.6 to 34.8 +/- 2.8 ms with a delta QTd of 6.58 +/- 2.21 ms in Group 2 (p = 0.006). Patients in Group 1 had a significantly higher increase in QTd (delta QTd) than the patients in Group 2 (p < 0.03). Addition of delta QTd (> 10 ms) to the ST depression during adenosine infusion would increase the sensitivity of the ECG from 23 to 65% and decrease the specificity from 91 to 70% for diagnosis of significant CAD. CONCLUSIONS: delta QTd is significantly more prolonged in patients with CAD during adenosine infusion. It increases the sensitivity of the stress ECG in diagnosis of CAD during adenosine infusion when used as an adjuvant index.     

获得性QT间期延长伴尖端扭转型室性心动过速52例临床分析

目的 总结获得性QT间期延长伴尖端扭转型室性心动过速(扭转型室速)患者的危险因素、心电图特征、治疗方法,为临床医生正确识别和处理提供帮助.方法以"扭转型室速"及"QT间期延长"检索阜外心血管病医院1990至2010年病历库,统计获得性扭转型室速患者的临床资料.结果总计52例获得性扭转型室速,其中67.3%有基础心脏病,59.6%存在电解质紊乱,36.5%应用利尿剂,28.8%应用延长QT间期的抗心律失常药.治疗前后平均QTc分别为(571±93)ms及(456±50)ms,所有患者均经补钾、补镁治疗,32.7%应用异丙肾上腺素,13.5%接受临时起搏治疗.结论获得性扭转型室速多发生于电解质紊乱及应用延长QT间期药物的患者.高危患者应监测心电图及QTc变化,注意有预警价值的表现,有助于早期识别并正确治疗.

Abstract：

Objective Risk factors, ECG characteristics and treatment options of patients with Torsade de Points associated with acquired QT prolongation are summarized in this study. Method Using "torsade de points" and "QT prolongation" as the keywords to search the inpatients database from 1990 -2010 of Fuwai hospital, 52 eligible patients were included in this analysis. Results Structural heart diseases were found in 67.3% and electrolyte disorders in 59. 6% patients, 36. 5% patients received diuretic therapy and 28. 8% received antiarrhythmic drugs which might induce prolonged QT interval The mean QTc was (571 ±93)ms and (456 ±50)ms before and after treatment. All patients received potassium and magnesium supplement. Isoproterenol was used in 32. 7% patients. 13.5% patients received temporary pacing therapy. Conclusions Torsade de points and acquired QT interval prolongation was often associated with electrolyte disorders and drugs causing QT prolongation. ECG and QTc should be intensively monitored for high risk patients. Early awareness of the warning signs might contribute to early recognition and proper treatment of patients with Torsade de Points associated with acquired QT prolongation.     

Effects of Three Fluoroquinolones on QT Analysis After Standard Treatment Courses

Background: Fluoroquinolone (FQ) agents have been speculated to influence the risk of Torsades de pointes (Tdp). Methods of evaluating this risk are varied and not systematic. QTc interval (QTc) prolongation is the most commonly used marker of Tdp, but has questionable utility. QT dispersion (QTd) may be a more selective marker of Tdp. No assessment of QTd for FQs has been reported. The current study evaluates the effects of three commonly prescribed FQs by comprehensive QT analysis. Methods: In an open‐label crossover study, 13 healthy participants received 3 treatments in random order: ciprofloxacin 500 mg twice daily, levofloxacin 500 mg once daily, and moxifloxacin 400 mg once daily. Each treatment was given for 7 days with a 1‐week washout period. Twelve‐lead electrocardiographic measurements were performed prior to the first dose, 2 hours after the first dose, and following the 7‐day medication course. QTc prolongation was determined by measurement of lead II, and QTd from the difference between the maximum and minimum QTc intervals among the 12 leads. The data were analyzed using Friedman ANOVA, with the Wilcoxon signed rank test post hoc analysis, with P < 0.05 significance. Results and Conclusions: No difference was seen in baseline QTc (P = 0.48) or QTd (P = 0.92). Following 7 days of moxifloxacin, the QTc was prolonged by 6 ms relative to baseline (408 ms, P = 0.022), and 11 ms from the 2‐hour measurement (403 ms, P = 0.003). Ciprofloxacin and levofloxacin had no effect on QTc, and no FQ changed the QTd. Within our study population, ciprofloxacin and levofloxacin did not display an increased risk for Tdp. Moxifloxacin, while showing QTc prolongation, did not affect QTd, and an increased Tdp risk is questionable.     

QT离散度测定的重复性和正常值的研究

为评价ＱＴ离散度（ＱＴｄ）测定的重复性和制定正常值范围,采用同步十二导联心电图机测量１００例正常人和５０例心肌梗死患者的ＱＴｄ,分析ＱＴｄ在不同纸速时测量的重复性情况,以及测量ＱＴｄ正常值范围。结果：正常人心电图以同步５０ｍｍ／ｓ纸速记录时ＱＴｄ的重复性较好,此时一人两次（Ｉｎｔｒａｏｂｓｅｒｖｅｒ）和两人一次（Ｉｎｔｅｒｏｂｓｅｒｖ－ｅｒ）测量的相关系数分别为０．８５,０．７５（Ｐ均＜０．０５）。心肌梗死患者的ＱＴｄ重复性以同步２５ｍｍ／ｓ纸速记录时为佳,在Ｉｎｔｒａｏｂｓｅｒｖｅｒ和Ｉｎｔｅｒｏｂｓｅｒｖｅｒ的相关系数分别为０．７５,０．６８（Ｐ均＜０．０５）。１００例正常人在同步５０ｍｍ／ｓ纸速下记录心电图测定的ＱＴｄ为２７±１２ｍｓ,９５％分布范围为３～５１ｍｓ。ＱＴｄ在男、女性别及各年龄段之间差异无显著性。结果提示用不同走纸速度测量正常和异常心电图的ＱＴｄ有助于提高其重复性。ＱＴｄ＜５０ｍｓ为正常范围。