Background: The QT interval shortens in response to sympathetic stimulation. Head-up tilt-table (HUT) testing is a straightforward way to achieve brisk sympathetic stimulation. There is not enough information about th...Background: The QT interval shortens in response to sympathetic stimulation. Head-up tilt-table (HUT) testing is a straightforward way to achieve brisk sympathetic stimulation. There is not enough information about the response of the QT interval to HUT, particularly, in patients with orthostatic hypotension (OH). Objective: Analyse the response of the RR, QT and QTc intervals in patients with OH and reflex syncope (NM) during HUT and find differences between groups. Methods: We reviewed the electrocardiograms and compare the RR and QT/QTc intervals during 1) baseline;2) HUT plus hyperventilation;3) positive test. Results: We studied 137 patients, 62 control group (no syncope and negative HUT). On average, the RR HUT interval was shorter than the resting RR by −171 ± 110.4 ms in controls;−228.6 ± 119.4 ms (NM) and −194 ± (OH) (P Conclusion: Significant differences between the reflex group and the OH during a positive test, the QTc decreased in the NM group, but in the OH population increased. This observation has not been described. We hypothesize that QTc prolongation could reflect autonomic nervous system downregulation and could explain to a degree, the increased mortality in this group.展开更多
Background PD(PD)is associated with a twofold increase in the risk of death especially sudden death.A predisposing factor for cardiac sudden death is prolongation of the QT interval.This study evaluated the potential ...Background PD(PD)is associated with a twofold increase in the risk of death especially sudden death.A predisposing factor for cardiac sudden death is prolongation of the QT interval.This study evaluated the potential association between QT interval and PD.Methods A systematic search was conducted of Medline and EMBASE using the search terms“PD”AND“QT interval”OR“Cardiac Repolarization”to identify articles.Results Seven studies with persons with PD(n=981)and control groups were identified.There was a significant difference in QT interval comparing patients with PD and persons without PD.The odds ratio showed a significant(P<0.001)2.6-fold(random effect)greater QTc prolongation in PD compared to control.Overall,there was a significantly longer QT in patients with PD than controls of 10.7±2.8 ms.Data analysis did not show much publication bias.Focusing only on studies that related the QT interval to the severity of PD as assessed by Hoehn–Yahr classification(n=6),there was a significant(P=0.004)overall correlation between QT interval and the severity of PD.There was little publication bias.The data directly examining patients with PD taking any drug than might prolong QT do not support an association between these mediations and QT prolongation.Conclusion Individuals with PD have a longer QT interval than individuals without PD.The QT interval is associated with a greater severity of PD and a greater probability of developing more severe PD.The QT interval should be considered in assessment of PD and possibly as a target for the treatment of PD.展开更多
BACKGROUND: Cirrhotic Cardiomyopathy is a relatively ill-characterized condition, which is often under-diagnosed due to absence of defined diagnostic criteria. ECG showing corrected QT Interval prolongation is the mos...BACKGROUND: Cirrhotic Cardiomyopathy is a relatively ill-characterized condition, which is often under-diagnosed due to absence of defined diagnostic criteria. ECG showing corrected QT Interval prolongation is the most suitable available option for diagnosis of this condition. OBJECTIVE: To determine the frequency of corrected QT interval prolongation in patients with liver cirrhosis. METHODOLOGY: Patients (n = 166) with confirmed cirrhosis, 30 years or older, presented in the outpatient and emergency department of medicine at Capital Hospital Islamabad between 1 October 2011 and 30 September 2012, were enrolled in this cross-sectional study after taking consent. ECG was done using calibrated ECG machine, and the QT Interval was measured. Corrected QT was calculated using Bazett’s formula and a QTc of more than 0.44 seconds was considered as being prolonged. RESULTS: The mean age of the patients was 57.05 ± 12.03 years. The corrected QT Interval varied from 337 ms to 560 ms. The mean QTc Interval was 429.92 ms ± 45.11. QTc was prolonged in 41 out of 166 patients (24.7%). Frequency of QTc prolongation was 4.5% in Child Pugh Grade A, 23.2% in Child Pugh Grade B, and 32.0% in Child Pugh Grade C. Association of Child Pugh Scoring with QTc prolongation was determined and found to be statistically significant (P < 0.05). CONCLUSION: QTc interval was prolonged in 24.7% of cirrhotic patients in our study. There was a significant increase in frequency with worsening of Child Pugh Grade, thereby indicating an association between QTc prolongation and the severity of cirrhosis.展开更多
Background Haloperidol is the most frequently prescribed antipsycbotic for delirium symptoms. The risk of QTc prolongation often raises concerns, although the effect of haloperidol on QTc interval has not yet been inv...Background Haloperidol is the most frequently prescribed antipsycbotic for delirium symptoms. The risk of QTc prolongation often raises concerns, although the effect of haloperidol on QTc interval has not yet been investigated in a randomised placebo-controlled fixed-dose study. Methods A subanalysis of a randomised double-blind placebo-controlled study was conducted to evaluate the effect of prophylactic haloperidol 1 mg or placebo 1 mg orally twice-daily （maximum of 14 doses） on QTc interval in patients aged 70 years and over. Bedside, 12-lead ECGs were recorded before, during and after the one-week intervention period. Automatic QTc measurements were ob- tained in addition to manual measurements of QT and RR intervals, blinded for treatment status. Manual measurements were corrected （QTc） using Bazett （QTc-B）, Framingham （QTc-Fa）, Fridericia （QTc-Fi） and Hodges （QTc-H） methods. Mixed model analyses were used to test for differences in longitudinal course of QTc between patients receiving haloperidol and placebo. Results ECG recordings of 72 patients （haloperidol n = 38） were analysed, 45.8% male. Median （range） haloperidol serum concentration on day 4 was 0.71 （0.32-1.82） μg/L （n = 23）. Longitudinal course of mean QTc did not significantly differ between treatment arms for any of the automatic or manually derived QTc values. Conclusions Low dose oral haloperidol did not result in QTc prolongation in older acutely hospitalised patients. Results may not be generalizable to patients with existing ECG abnormalities such as atrial fibrillation.展开更多
目的观察氨磺必利与齐拉西酮治疗精神分裂症的临床疗效及对心电图QTC间期的影响。方法选取2020年5月至2022年8月吉安市第三人民医院收治的76例精神分裂症患者作为研究对象,采用随机数字表法分为常规组与研究组,各38例。常规组服用盐酸...目的观察氨磺必利与齐拉西酮治疗精神分裂症的临床疗效及对心电图QTC间期的影响。方法选取2020年5月至2022年8月吉安市第三人民医院收治的76例精神分裂症患者作为研究对象,采用随机数字表法分为常规组与研究组,各38例。常规组服用盐酸齐拉西酮胶囊,研究组服用氨磺必利。比较两组临床疗效、阳性和阴性症状量表(positive and negative syndrome scale,PANSS)评分、记忆功能[韦氏记忆量表中国修订版(Wechsler memory scale-revised Chinese version,WMS-RC)评分]、认知功能[简易智能精神状态检查量表(mini-mental state examination,MMSE)评分]、QTC间期及不良反应发生情况。结果两组治疗总有效率比较差异无统计学意义。用药后,两组一般精神病理、阳性症状、阴性症状评分及总分均低于用药前,差异有统计学意义(P<0.05),但组间比较差异无统计学意义。用药后,两组WMS-RC、MMSE评分均高于用药前,差异有统计学意义(P<0.05),但组间比较差异无统计学意义。用药后2、4、8周,研究组QTC间期均短于常规组,差异有统计学意义(P<0.05)。两组不良反应发生率比较差异无统计学意义。结论氨磺必利、齐拉西酮治疗精神分裂症临床疗效及安全性相当,均可减轻患者阳性及阴性症状,改善患者记忆功能与认知功能,但氨磺必利对心电图QTC间期的影响更小,值得临床推广应用。展开更多
Objective： To evaluate the changes in Tp-e interval （an interval from the peak to the end of the T wave）, QT interval and Tp-e/QT ratio of the body surface ECG in patients with left ventricular hypertrophy （LVH）....Objective： To evaluate the changes in Tp-e interval （an interval from the peak to the end of the T wave）, QT interval and Tp-e/QT ratio of the body surface ECG in patients with left ventricular hypertrophy （LVH）. Methods： The Tp-e interval and QT interval were measured on body surface ECGs in 42 patients without either hypertension or LVH （control group）, 41 patients having hypertension but not LVH （non-LVH group）, and 38 patients with both hypertension and LVH （LVH group）. Results： The mean corrected QT （QTc） interval, and mean corrected Tp-e[T（p-e）c] interval were significantly longer in the LVH group （0.430±0.021s vs. 0.409±0.019s, p 〈 0.01; 0.098±0.013s vs. 0.088±0.011s, respectively） than those in the control group. The Tp-e/QT ratio was also amplified in LVH group （0.232± 0.028 vs.0.218± 0.027） （p 〈 0.05）. Conclusion： LVH increased the QT interval, Tp-e interval and Tp-e/QT ratio of the body surface ECG.展开更多
Assessment of the QT interval on a standard 12 lead electrocardiogram is of value in the recognition of a number of conditions. A critical part of its use is the adjustment for the effect of heart rate on QT interval....Assessment of the QT interval on a standard 12 lead electrocardiogram is of value in the recognition of a number of conditions. A critical part of its use is the adjustment for the effect of heart rate on QT interval. A systematic search was conducted to identify studiesthat proposed formulae to standardize the QT interval by heart rate. A nomenclature was developed for current and subsequent equations based on whether they are corrective(QTc) or predictive(QTp). QTc formulae attempt to separate the dependence of the length of the QT interval from the length of the RR interval. QTp formulae utilize heart rate and the output QTp is compared to the uncorrected QT interval. The nomenclature consists of the first letter of the first author's name followed by the next two consonance(whenever possible) in capital letters; with subscripts in lower case alphabetical letter if the first author develops more than one equation. The single exception was the Framingham equation,because this cohort has developed its own "name" amongst cardiovascular studies. Equations were further categorized according to whether they were linear,rational,exponential,logarithmic,or power based. Data show that a person's QT interval adjusted for heart rate can vary dramatically with the different QTc and QTp formulae depending on the person's heart rate and QT interval. The differences in the QT interval adjustment equations encompasses values that are considered normal or significant prolonged. To further compare the equations,we considered that the slope of QTc versus heart rate should be zero if there was no correlation between QT and heart rate. Reviewing a sample of 107 patient ECGs from a hospital setting,the rank order of the slope- from best(closest to zero) to worst was QTc DMT,QTc RTHa,QTc HDG,QTc GOT,QTcF RM,QTcF RD,QTcB ZT and QTcM YD. For two recent formulae based on large data sets specifically QTcD MT and QTcR THa,there was no significant deviation of the slope from zero. In summary a nomenclature permits easy reference to QT formulae that adjust for heart rate. Twenty different formulae can produce discordant calculations of an adjusted QT interval. While the formulae developed by Bazett and Fridericia(QTc BZT and QTc FRD respectively) may continue to be used clinically,recent formulae from large population studies specifically QTcD MT and QTcR THa appear to be betterto adjust QT for heart rate in clinical practice.展开更多
AIM To examine the impact of liver cirrhosis on QT interval and cardiac autonomic neuropathy(CAN). METHODS A total of 51 patients with cirrhosis and 51 controls were examined. Standard 12-lead electrocardiogram record...AIM To examine the impact of liver cirrhosis on QT interval and cardiac autonomic neuropathy(CAN). METHODS A total of 51 patients with cirrhosis and 51 controls were examined. Standard 12-lead electrocardiogram recordings were obtained and QT as well as corrected QT interval(QTc) and their dispersions(dQT, dQTc) were measured and calculated using a computer-based program. The diagnosis of CAN was based upon the battery of the tests proposed by Ewing and Clarke and the consensus statements of the American Diabetes Association. CAN was diagnosed when two out of the four classical Ewing tests were abnormal. RESULTS QT, QTc and their dispersions were significantly longer(P < 0.01) in patients with cirrhosis than in controls. No significant differences in QT interval were found among the subgroups according to the etiology of cirrhosis. Multivariate regression analysis after controlling for age, gender and duration of cirrhosis demonstrated significant association between QT and presence of diabetes mellitus [standardized regression coefficient(beta) = 0.45, P = 0.02] and treatment with diuretics(beta = 0.55, P = 0.03), but not with the Child-Pugh score(P = 0.54). Prevalence of CAN was common(54.9%) among patients with cirrhosis and its severity was associated with the Child-Pugh score(r = 0.33, P = 0.02). Moreover, patients with decompensated cirrhosis had more severe CAN that those with compensated cirrhosis(P = 0.03). No significant association was found between severity of CAN and QT interval duration.CONCLUSION Patients with cirrhosis have QT prolongation. Treatment with diuretics is associated with longer QT. CAN is common in patients with cirrhosis and its severity is associated with severity of the disease.展开更多
Objective To analyze the effect of age on the ECG QT interval, an important predictor of cardiovascular mortality and drug-induced cardiac arrhythmias, and determine whether QT-heart rate correction formulae （QTc） h...Objective To analyze the effect of age on the ECG QT interval, an important predictor of cardiovascular mortality and drug-induced cardiac arrhythmias, and determine whether QT-heart rate correction formulae （QTc） have differential relationships with age and sex. Methods Data were examined from the US National Health and Nutrition Examination Survey （NHANES） II and III, civilian population aged 25 to 90 years. QT weighted means and standard deviations were calculated for all ages. The QTc were evaluated for six QTc： proposed by Bazett （QTcBZT）, Fridericia （QTcFRD）, Hodges （QTcHDG）, Dmitrienko （QTcDMT）, Rautaharju （QTcRTHa） and Framingham （QTcFRM）. Results QTc was strongly related to age and gender, for all formulae except for QTcBZT for women. The relationship between QTc and age was significant regardless of whether the relationship was approximated by a linear or non-linear （quadratic or cubic spline） model. QTc increased more dramatically with age in men. There was a significant （P 〈 0.001） positive relationship between QTc variance and age for each QTc formula for both men and women. There were a greater proportion of individuals with longer QTc with older ages especially age 80 years and above. Conclusion QTc and its variance increase with age. Prolonged QTc is more prevalent in older individuals, especially men.展开更多
许多广泛使用的药物都可能导致QT间期/QTc延长,继而引起尖端扭转型室性心动过速(torsade de pointes,TdP)等心律失常,后者可能会进一步恶化为心室颤动,甚至造成心脏性猝死。因此,为了预防和降低药源性QT间期延长和TdP的风险,对危险因素...许多广泛使用的药物都可能导致QT间期/QTc延长,继而引起尖端扭转型室性心动过速(torsade de pointes,TdP)等心律失常,后者可能会进一步恶化为心室颤动,甚至造成心脏性猝死。因此,为了预防和降低药源性QT间期延长和TdP的风险,对危险因素的发现、预警和纠正至关重要。近年来,临床已开始应用决策支持系统等预警策略,通过识别多种风险因素预测QT间期/QTc延长和警示TdP高风险人群。本文总结了可引起长QT间期和TdP风险的药物及相关危险因素,并归纳现有的预警措施,期望为暴露于相关风险的患者管理提供参考。展开更多
Objectives To explore the effect of aging on cardiac toxicity specifically the interaction of age and antipsychotic drugs to alter the QT interval. Methods The Medline databases were searched using the OvidSP platform...Objectives To explore the effect of aging on cardiac toxicity specifically the interaction of age and antipsychotic drugs to alter the QT interval. Methods The Medline databases were searched using the OvidSP platforms with the search strategy： ＂QT interval＂ or ＂QT＂ and ＂age＂ or ＂aging＂. The entry criteria were： over 10,000 apparently healthy individuals with data on both sexes; QT interval corrected for heart rate （QTc） and an expression of its variance for multiple age decades extending into the older ages. Results QTc increased in duration with increasing age. Considering a modest one SD increment in QTc in the normal population, the addition of Chlorpromazine produced a QTc on average greater than 450 ms for ages 70 years and older. Risperidone, that did not on average alter QTc, would be expected to produce a QTc of 450 ms in persons in their mid 70 years under some circumstances. QTc prolongation 〉 500 ms with antipsychotic drugs is more likely for persons with QTc initially at the 99th percentile. It may occur with Haloperidol which does not on average alter QTc. Conclusions The range of values for the QT interval in apparently normal older men or women, when combined with the range of expected QT interval changes induced by antipsychotic drugs, can readily be associated with prolonged QTc. Individuals with QTc at the 99th percentile may have serious QTc prolongation with antipsychotic drugs even those that are not usually associated with QTc prolongation.展开更多
BACKGROUND Corrected QT(QTc)interval is prolonged in patients with liver cirrhosis and has been proposed to correlate with the severity of the disease.However,the effects of sex,age,severity,and etiology of cirrhosis ...BACKGROUND Corrected QT(QTc)interval is prolonged in patients with liver cirrhosis and has been proposed to correlate with the severity of the disease.However,the effects of sex,age,severity,and etiology of cirrhosis on QTc have not been elucidated.At the same time,the role of treatment,acute illness,and liver transplantation(Tx)remains largely unknown.AIM To determine the mean QTc in patients with cirrhosis,assess whether QTc is prolonged in patients with cirrhosis,and investigate whether QTc is affected by factors such as sex,age,severity,etiology,treatment,acute illness,and liver Tx.METHODS In the present systematic review and meta-analysis,the searching protocol“{[QTc]OR[QT interval]OR[QT-interval]OR[Q-T syndrome]}AND{[cirrhosis]OR[Child-Pugh]OR[MELD]}”was applied in PubMed,EMBASE,and Google Scholar databases to identify studies that reported QTc in patients with cirrhosis and published after 1998.Seventy-three studies were considered eligible.Data concerning first author,year of publication,type of study,method used,sample size,mean age,female ratio,alcoholic etiology of cirrhosis ratio,Child-Pugh A/B/C ratio,mean model for end-stage liver disease(MELD)score,treatment withβ-blockers,episode of acute gastrointestinal bleeding,formula for QT correction,mean pulse rate,QTc in patients with cirrhosis and controls,and QTc according to etiology of cirrhosis,sex,Child-Pugh stage,MELD score,and liver Tx status(pre-Tx/post-Tx)were retrieved.The Newcastle-Ottawa quality assessment scale appraised the quality of the eligible studies.Effect estimates,expressed as proportions or standardized mean differences,were combined using the randomeffects,generic inverse variance method of DerSimonian and Laird.Subgroup,sensitivity analysis,and meta-regressions were applied to assess heterogeneity.RESULTS QTc combined mean in patients with cirrhosis was 444.8 ms[95%confidence interval(CI):440.4-449.2;P<0.001 when compared with the upper normal limit of 440 ms],presenting high heterogeneity(I2=97.5%;95%CI:97.2%-97.8%);both Egger’s and Begg’s tests showed non-significance.QTc was elongated in patients with cirrhosis compared with controls(P<0.001).QTc was longer in patients with Child-Pugh C cirrhosis when compared with Child-Pugh B and A(P<0.001);Child-Pugh B patients presented longer QTc when compared with Child-Pugh A patients(P=0.003).The MELD score was higher in patients with cirrhosis with QTc>440 ms when compared with QTc≤440 ms(P<0.001).No correlation of QTc with age(P=0.693),sex(P=0.753),or etiology(P=0.418)was detected.β-blockers shortened QTc(P<0.001).QTc was prolonged during acute gastrointestinal bleeding(P=0.020).Tx tended to improve QTc(P<0.001).No other sources of QTc heterogeneity were revealed.CONCLUSION QTc is prolonged in cirrhosis independently of sex,age,and etiology but is correlated with severity and affected byβ-blockers and acute gastrointestinal bleeding.QTc is improved after liver Tx.展开更多
Objective To investigate therapeutic action of verapamil on QT prolongation induced by arsenic trioxide (As2O3) in guinea pig and to further explore its possible mechanism. Methods Different doses of As2O3 was infused...Objective To investigate therapeutic action of verapamil on QT prolongation induced by arsenic trioxide (As2O3) in guinea pig and to further explore its possible mechanism. Methods Different doses of As2O3 was infused intravenously to observe the changes of QT interval on the electrocardiogram (ECG) at different times in guinea pig.Patch clamp technique and laser scanning confocal microscopy were utilized to study the action of As2O3 on action potential duration (APD),L-type calcium current (ICa-L), rapid delayed rectifier potassium current (IKr) and intracellular calcium concentration ([Ca2+]i) of guinea pig myocytes. At the same time, verapamil was applied preliminarily to evaluate effects of verapamil on changes of the above index induced by AS2O3 . Results Intravenous administration of As2O3 at the dose of 1.6mg/kg and 0.8mg/kg prolonged QT interval on ECG obviously in guinea pig hearts dose dependently and time de pendently. QTc (corrected QT interval) was progressively prolonged in the 2-hour period of intravenous infusion of 1.6mg/ kg As2O3 from (328 .5±30.9)ms of control to (388 .4±31. 3)ms at 2h following As2O3 (P < 0.01). When verapamil was pretreated for 5min,then 1.6mg/kg As2O3 was added,the results showed that QTc was shorter in verapamil-treatment group (357 .3±21 .4)ms than that in As2O3 group (388 .4±31.3)ms (P<0.05) at 2h.Confocal experiments showed that in normal Tyrode solution, As2O3 (1μmol/L and 10/μmol/L) had no obvious effects on resting [Ca2+ ]i( P > 0 .05) in guinea pig cardiomyoeytes,however, 10μmol/L As2O3 could markedly enhance [Ca2+ ]. increase induced by KCl 60mmol/ L and the peak value increased from 903 .4±369.4 to 1674. 6±563 .2 ( P < 0.05 ) . The action of elevating [ Ca2+ ]i could be blocked by 10μmol/L verapamil incompletely. The patch-clamp studies indicated that As2O3 at concentration of 10μmol/L prolonged APD50 from (263 .6±75 .2)ms to (523.9±47 .8)ms (P<0.01) and APD90 from (277.5±77.5) ms to (536.3±49.6)ms (P<0.01),and increased ICa-L from ( -6.0±1.5)pA/pF to ( -8.7±2.0)pA/pF (P < 0.01) at 0mV and also reduced IKr from (6.7±1.8)pA/pF to (4.5±1 .8)pA/pF ( P < 0.05) .However,10μmol/L verapamil could modulate prolonging APD50 from (523 . 9±47 . 8 ) ms to (340.4±83 . 8 ) ms ( P < 0.01) and APD90 from (536.3±49.6) ms to (348.9±85.5)ms (P < 0.01) and correct increasing ICa-L induced by 10μmol/L As2O3 from ( - 8 .7±2.0) pA/pF to ( - 6.6±1.4) pA/pF ( P < 0.05) at 0mV. Conclusion As2O3 could induce prolongation of the QT interval on the ECG in guinea pig hearts and the ionic mechanism is associated with increasing ICa-L and inhibiting IKr/HERG. Verapamil may be useful in normalizing QT prolongation during As2O3 therapy by decreasing ICa-L and [Ca2+]i of ventricular myocytes in guinea pig.展开更多
Prolongation of the QT interval is associated with adverse cardiac events specifically Torsades de pointes(TdP).There are multiple mediations that have a known,possible,or conditional risk for prolonged QT interval,bu...Prolongation of the QT interval is associated with adverse cardiac events specifically Torsades de pointes(TdP).There are multiple mediations that have a known,possible,or conditional risk for prolonged QT interval,but general practitioners’knowledge of these medications is unknown.We conducted a survey to assess internal medicine(IM)providers’knowledge of risk factors and medications associated with prolonged QT as well as provider experience and comfort when treating patients with prolonged QT.A 17-question,anonymous survey was constructed in 2019 and distributed to IM providers and residents at a tertiary care center.Questions included demographic information,6 Likert-scale questions gauging provider experience with prolonged QT,and 10 multiple choice clinical vignettes to assess clinical knowledge.Data was analyzed descriptively.Knowledge was assessed via clinical vignettes and compared by level of training.Forty-one responses were received out of a total of 87 possible respondents(47.1%response rate).About 70%of respondents see patients with acquired prolonged QT once monthly or more.95%rarely see congenital prolonged QT.When presented with QTc drug issues,73%of providers seldom or sometimes consulted pharmacy,but about half used online resources.The average correct score on the clinical vignettes was 5.59/10,with the highest scores seen in attending physicians in their first five years of practice(6.96/10).Our survey suggests that IM providers commonly encounter QT prolonging drugs.Educational efforts to improve knowledge of drug and patient risk factors for TdP may be needed.展开更多
文摘Background: The QT interval shortens in response to sympathetic stimulation. Head-up tilt-table (HUT) testing is a straightforward way to achieve brisk sympathetic stimulation. There is not enough information about the response of the QT interval to HUT, particularly, in patients with orthostatic hypotension (OH). Objective: Analyse the response of the RR, QT and QTc intervals in patients with OH and reflex syncope (NM) during HUT and find differences between groups. Methods: We reviewed the electrocardiograms and compare the RR and QT/QTc intervals during 1) baseline;2) HUT plus hyperventilation;3) positive test. Results: We studied 137 patients, 62 control group (no syncope and negative HUT). On average, the RR HUT interval was shorter than the resting RR by −171 ± 110.4 ms in controls;−228.6 ± 119.4 ms (NM) and −194 ± (OH) (P Conclusion: Significant differences between the reflex group and the OH during a positive test, the QTc decreased in the NM group, but in the OH population increased. This observation has not been described. We hypothesize that QTc prolongation could reflect autonomic nervous system downregulation and could explain to a degree, the increased mortality in this group.
文摘Background PD(PD)is associated with a twofold increase in the risk of death especially sudden death.A predisposing factor for cardiac sudden death is prolongation of the QT interval.This study evaluated the potential association between QT interval and PD.Methods A systematic search was conducted of Medline and EMBASE using the search terms“PD”AND“QT interval”OR“Cardiac Repolarization”to identify articles.Results Seven studies with persons with PD(n=981)and control groups were identified.There was a significant difference in QT interval comparing patients with PD and persons without PD.The odds ratio showed a significant(P<0.001)2.6-fold(random effect)greater QTc prolongation in PD compared to control.Overall,there was a significantly longer QT in patients with PD than controls of 10.7±2.8 ms.Data analysis did not show much publication bias.Focusing only on studies that related the QT interval to the severity of PD as assessed by Hoehn–Yahr classification(n=6),there was a significant(P=0.004)overall correlation between QT interval and the severity of PD.There was little publication bias.The data directly examining patients with PD taking any drug than might prolong QT do not support an association between these mediations and QT prolongation.Conclusion Individuals with PD have a longer QT interval than individuals without PD.The QT interval is associated with a greater severity of PD and a greater probability of developing more severe PD.The QT interval should be considered in assessment of PD and possibly as a target for the treatment of PD.
文摘BACKGROUND: Cirrhotic Cardiomyopathy is a relatively ill-characterized condition, which is often under-diagnosed due to absence of defined diagnostic criteria. ECG showing corrected QT Interval prolongation is the most suitable available option for diagnosis of this condition. OBJECTIVE: To determine the frequency of corrected QT interval prolongation in patients with liver cirrhosis. METHODOLOGY: Patients (n = 166) with confirmed cirrhosis, 30 years or older, presented in the outpatient and emergency department of medicine at Capital Hospital Islamabad between 1 October 2011 and 30 September 2012, were enrolled in this cross-sectional study after taking consent. ECG was done using calibrated ECG machine, and the QT Interval was measured. Corrected QT was calculated using Bazett’s formula and a QTc of more than 0.44 seconds was considered as being prolonged. RESULTS: The mean age of the patients was 57.05 ± 12.03 years. The corrected QT Interval varied from 337 ms to 560 ms. The mean QTc Interval was 429.92 ms ± 45.11. QTc was prolonged in 41 out of 166 patients (24.7%). Frequency of QTc prolongation was 4.5% in Child Pugh Grade A, 23.2% in Child Pugh Grade B, and 32.0% in Child Pugh Grade C. Association of Child Pugh Scoring with QTc prolongation was determined and found to be statistically significant (P < 0.05). CONCLUSION: QTc interval was prolonged in 24.7% of cirrhotic patients in our study. There was a significant increase in frequency with worsening of Child Pugh Grade, thereby indicating an association between QTc prolongation and the severity of cirrhosis.
文摘Background Haloperidol is the most frequently prescribed antipsycbotic for delirium symptoms. The risk of QTc prolongation often raises concerns, although the effect of haloperidol on QTc interval has not yet been investigated in a randomised placebo-controlled fixed-dose study. Methods A subanalysis of a randomised double-blind placebo-controlled study was conducted to evaluate the effect of prophylactic haloperidol 1 mg or placebo 1 mg orally twice-daily （maximum of 14 doses） on QTc interval in patients aged 70 years and over. Bedside, 12-lead ECGs were recorded before, during and after the one-week intervention period. Automatic QTc measurements were ob- tained in addition to manual measurements of QT and RR intervals, blinded for treatment status. Manual measurements were corrected （QTc） using Bazett （QTc-B）, Framingham （QTc-Fa）, Fridericia （QTc-Fi） and Hodges （QTc-H） methods. Mixed model analyses were used to test for differences in longitudinal course of QTc between patients receiving haloperidol and placebo. Results ECG recordings of 72 patients （haloperidol n = 38） were analysed, 45.8% male. Median （range） haloperidol serum concentration on day 4 was 0.71 （0.32-1.82） μg/L （n = 23）. Longitudinal course of mean QTc did not significantly differ between treatment arms for any of the automatic or manually derived QTc values. Conclusions Low dose oral haloperidol did not result in QTc prolongation in older acutely hospitalised patients. Results may not be generalizable to patients with existing ECG abnormalities such as atrial fibrillation.
文摘目的观察氨磺必利与齐拉西酮治疗精神分裂症的临床疗效及对心电图QTC间期的影响。方法选取2020年5月至2022年8月吉安市第三人民医院收治的76例精神分裂症患者作为研究对象,采用随机数字表法分为常规组与研究组,各38例。常规组服用盐酸齐拉西酮胶囊,研究组服用氨磺必利。比较两组临床疗效、阳性和阴性症状量表(positive and negative syndrome scale,PANSS)评分、记忆功能[韦氏记忆量表中国修订版(Wechsler memory scale-revised Chinese version,WMS-RC)评分]、认知功能[简易智能精神状态检查量表(mini-mental state examination,MMSE)评分]、QTC间期及不良反应发生情况。结果两组治疗总有效率比较差异无统计学意义。用药后,两组一般精神病理、阳性症状、阴性症状评分及总分均低于用药前,差异有统计学意义(P<0.05),但组间比较差异无统计学意义。用药后,两组WMS-RC、MMSE评分均高于用药前,差异有统计学意义(P<0.05),但组间比较差异无统计学意义。用药后2、4、8周,研究组QTC间期均短于常规组,差异有统计学意义(P<0.05)。两组不良反应发生率比较差异无统计学意义。结论氨磺必利、齐拉西酮治疗精神分裂症临床疗效及安全性相当,均可减轻患者阳性及阴性症状,改善患者记忆功能与认知功能,但氨磺必利对心电图QTC间期的影响更小,值得临床推广应用。
文摘Objective： To evaluate the changes in Tp-e interval （an interval from the peak to the end of the T wave）, QT interval and Tp-e/QT ratio of the body surface ECG in patients with left ventricular hypertrophy （LVH）. Methods： The Tp-e interval and QT interval were measured on body surface ECGs in 42 patients without either hypertension or LVH （control group）, 41 patients having hypertension but not LVH （non-LVH group）, and 38 patients with both hypertension and LVH （LVH group）. Results： The mean corrected QT （QTc） interval, and mean corrected Tp-e[T（p-e）c] interval were significantly longer in the LVH group （0.430±0.021s vs. 0.409±0.019s, p 〈 0.01; 0.098±0.013s vs. 0.088±0.011s, respectively） than those in the control group. The Tp-e/QT ratio was also amplified in LVH group （0.232± 0.028 vs.0.218± 0.027） （p 〈 0.05）. Conclusion： LVH increased the QT interval, Tp-e interval and Tp-e/QT ratio of the body surface ECG.
文摘Assessment of the QT interval on a standard 12 lead electrocardiogram is of value in the recognition of a number of conditions. A critical part of its use is the adjustment for the effect of heart rate on QT interval. A systematic search was conducted to identify studiesthat proposed formulae to standardize the QT interval by heart rate. A nomenclature was developed for current and subsequent equations based on whether they are corrective(QTc) or predictive(QTp). QTc formulae attempt to separate the dependence of the length of the QT interval from the length of the RR interval. QTp formulae utilize heart rate and the output QTp is compared to the uncorrected QT interval. The nomenclature consists of the first letter of the first author's name followed by the next two consonance(whenever possible) in capital letters; with subscripts in lower case alphabetical letter if the first author develops more than one equation. The single exception was the Framingham equation,because this cohort has developed its own "name" amongst cardiovascular studies. Equations were further categorized according to whether they were linear,rational,exponential,logarithmic,or power based. Data show that a person's QT interval adjusted for heart rate can vary dramatically with the different QTc and QTp formulae depending on the person's heart rate and QT interval. The differences in the QT interval adjustment equations encompasses values that are considered normal or significant prolonged. To further compare the equations,we considered that the slope of QTc versus heart rate should be zero if there was no correlation between QT and heart rate. Reviewing a sample of 107 patient ECGs from a hospital setting,the rank order of the slope- from best(closest to zero) to worst was QTc DMT,QTc RTHa,QTc HDG,QTc GOT,QTcF RM,QTcF RD,QTcB ZT and QTcM YD. For two recent formulae based on large data sets specifically QTcD MT and QTcR THa,there was no significant deviation of the slope from zero. In summary a nomenclature permits easy reference to QT formulae that adjust for heart rate. Twenty different formulae can produce discordant calculations of an adjusted QT interval. While the formulae developed by Bazett and Fridericia(QTc BZT and QTc FRD respectively) may continue to be used clinically,recent formulae from large population studies specifically QTcD MT and QTcR THa appear to be betterto adjust QT for heart rate in clinical practice.
文摘AIM To examine the impact of liver cirrhosis on QT interval and cardiac autonomic neuropathy(CAN). METHODS A total of 51 patients with cirrhosis and 51 controls were examined. Standard 12-lead electrocardiogram recordings were obtained and QT as well as corrected QT interval(QTc) and their dispersions(dQT, dQTc) were measured and calculated using a computer-based program. The diagnosis of CAN was based upon the battery of the tests proposed by Ewing and Clarke and the consensus statements of the American Diabetes Association. CAN was diagnosed when two out of the four classical Ewing tests were abnormal. RESULTS QT, QTc and their dispersions were significantly longer(P < 0.01) in patients with cirrhosis than in controls. No significant differences in QT interval were found among the subgroups according to the etiology of cirrhosis. Multivariate regression analysis after controlling for age, gender and duration of cirrhosis demonstrated significant association between QT and presence of diabetes mellitus [standardized regression coefficient(beta) = 0.45, P = 0.02] and treatment with diuretics(beta = 0.55, P = 0.03), but not with the Child-Pugh score(P = 0.54). Prevalence of CAN was common(54.9%) among patients with cirrhosis and its severity was associated with the Child-Pugh score(r = 0.33, P = 0.02). Moreover, patients with decompensated cirrhosis had more severe CAN that those with compensated cirrhosis(P = 0.03). No significant association was found between severity of CAN and QT interval duration.CONCLUSION Patients with cirrhosis have QT prolongation. Treatment with diuretics is associated with longer QT. CAN is common in patients with cirrhosis and its severity is associated with severity of the disease.
文摘Objective To analyze the effect of age on the ECG QT interval, an important predictor of cardiovascular mortality and drug-induced cardiac arrhythmias, and determine whether QT-heart rate correction formulae （QTc） have differential relationships with age and sex. Methods Data were examined from the US National Health and Nutrition Examination Survey （NHANES） II and III, civilian population aged 25 to 90 years. QT weighted means and standard deviations were calculated for all ages. The QTc were evaluated for six QTc： proposed by Bazett （QTcBZT）, Fridericia （QTcFRD）, Hodges （QTcHDG）, Dmitrienko （QTcDMT）, Rautaharju （QTcRTHa） and Framingham （QTcFRM）. Results QTc was strongly related to age and gender, for all formulae except for QTcBZT for women. The relationship between QTc and age was significant regardless of whether the relationship was approximated by a linear or non-linear （quadratic or cubic spline） model. QTc increased more dramatically with age in men. There was a significant （P 〈 0.001） positive relationship between QTc variance and age for each QTc formula for both men and women. There were a greater proportion of individuals with longer QTc with older ages especially age 80 years and above. Conclusion QTc and its variance increase with age. Prolonged QTc is more prevalent in older individuals, especially men.
文摘许多广泛使用的药物都可能导致QT间期/QTc延长,继而引起尖端扭转型室性心动过速(torsade de pointes,TdP)等心律失常,后者可能会进一步恶化为心室颤动,甚至造成心脏性猝死。因此,为了预防和降低药源性QT间期延长和TdP的风险,对危险因素的发现、预警和纠正至关重要。近年来,临床已开始应用决策支持系统等预警策略,通过识别多种风险因素预测QT间期/QTc延长和警示TdP高风险人群。本文总结了可引起长QT间期和TdP风险的药物及相关危险因素,并归纳现有的预警措施,期望为暴露于相关风险的患者管理提供参考。
文摘Objectives To explore the effect of aging on cardiac toxicity specifically the interaction of age and antipsychotic drugs to alter the QT interval. Methods The Medline databases were searched using the OvidSP platforms with the search strategy： ＂QT interval＂ or ＂QT＂ and ＂age＂ or ＂aging＂. The entry criteria were： over 10,000 apparently healthy individuals with data on both sexes; QT interval corrected for heart rate （QTc） and an expression of its variance for multiple age decades extending into the older ages. Results QTc increased in duration with increasing age. Considering a modest one SD increment in QTc in the normal population, the addition of Chlorpromazine produced a QTc on average greater than 450 ms for ages 70 years and older. Risperidone, that did not on average alter QTc, would be expected to produce a QTc of 450 ms in persons in their mid 70 years under some circumstances. QTc prolongation 〉 500 ms with antipsychotic drugs is more likely for persons with QTc initially at the 99th percentile. It may occur with Haloperidol which does not on average alter QTc. Conclusions The range of values for the QT interval in apparently normal older men or women, when combined with the range of expected QT interval changes induced by antipsychotic drugs, can readily be associated with prolonged QTc. Individuals with QTc at the 99th percentile may have serious QTc prolongation with antipsychotic drugs even those that are not usually associated with QTc prolongation.
文摘BACKGROUND Corrected QT(QTc)interval is prolonged in patients with liver cirrhosis and has been proposed to correlate with the severity of the disease.However,the effects of sex,age,severity,and etiology of cirrhosis on QTc have not been elucidated.At the same time,the role of treatment,acute illness,and liver transplantation(Tx)remains largely unknown.AIM To determine the mean QTc in patients with cirrhosis,assess whether QTc is prolonged in patients with cirrhosis,and investigate whether QTc is affected by factors such as sex,age,severity,etiology,treatment,acute illness,and liver Tx.METHODS In the present systematic review and meta-analysis,the searching protocol“{[QTc]OR[QT interval]OR[QT-interval]OR[Q-T syndrome]}AND{[cirrhosis]OR[Child-Pugh]OR[MELD]}”was applied in PubMed,EMBASE,and Google Scholar databases to identify studies that reported QTc in patients with cirrhosis and published after 1998.Seventy-three studies were considered eligible.Data concerning first author,year of publication,type of study,method used,sample size,mean age,female ratio,alcoholic etiology of cirrhosis ratio,Child-Pugh A/B/C ratio,mean model for end-stage liver disease(MELD)score,treatment withβ-blockers,episode of acute gastrointestinal bleeding,formula for QT correction,mean pulse rate,QTc in patients with cirrhosis and controls,and QTc according to etiology of cirrhosis,sex,Child-Pugh stage,MELD score,and liver Tx status(pre-Tx/post-Tx)were retrieved.The Newcastle-Ottawa quality assessment scale appraised the quality of the eligible studies.Effect estimates,expressed as proportions or standardized mean differences,were combined using the randomeffects,generic inverse variance method of DerSimonian and Laird.Subgroup,sensitivity analysis,and meta-regressions were applied to assess heterogeneity.RESULTS QTc combined mean in patients with cirrhosis was 444.8 ms[95%confidence interval(CI):440.4-449.2;P<0.001 when compared with the upper normal limit of 440 ms],presenting high heterogeneity(I2=97.5%;95%CI:97.2%-97.8%);both Egger’s and Begg’s tests showed non-significance.QTc was elongated in patients with cirrhosis compared with controls(P<0.001).QTc was longer in patients with Child-Pugh C cirrhosis when compared with Child-Pugh B and A(P<0.001);Child-Pugh B patients presented longer QTc when compared with Child-Pugh A patients(P=0.003).The MELD score was higher in patients with cirrhosis with QTc>440 ms when compared with QTc≤440 ms(P<0.001).No correlation of QTc with age(P=0.693),sex(P=0.753),or etiology(P=0.418)was detected.β-blockers shortened QTc(P<0.001).QTc was prolonged during acute gastrointestinal bleeding(P=0.020).Tx tended to improve QTc(P<0.001).No other sources of QTc heterogeneity were revealed.CONCLUSION QTc is prolonged in cirrhosis independently of sex,age,and etiology but is correlated with severity and affected byβ-blockers and acute gastrointestinal bleeding.QTc is improved after liver Tx.
文摘Objective To investigate therapeutic action of verapamil on QT prolongation induced by arsenic trioxide (As2O3) in guinea pig and to further explore its possible mechanism. Methods Different doses of As2O3 was infused intravenously to observe the changes of QT interval on the electrocardiogram (ECG) at different times in guinea pig.Patch clamp technique and laser scanning confocal microscopy were utilized to study the action of As2O3 on action potential duration (APD),L-type calcium current (ICa-L), rapid delayed rectifier potassium current (IKr) and intracellular calcium concentration ([Ca2+]i) of guinea pig myocytes. At the same time, verapamil was applied preliminarily to evaluate effects of verapamil on changes of the above index induced by AS2O3 . Results Intravenous administration of As2O3 at the dose of 1.6mg/kg and 0.8mg/kg prolonged QT interval on ECG obviously in guinea pig hearts dose dependently and time de pendently. QTc (corrected QT interval) was progressively prolonged in the 2-hour period of intravenous infusion of 1.6mg/ kg As2O3 from (328 .5±30.9)ms of control to (388 .4±31. 3)ms at 2h following As2O3 (P < 0.01). When verapamil was pretreated for 5min,then 1.6mg/kg As2O3 was added,the results showed that QTc was shorter in verapamil-treatment group (357 .3±21 .4)ms than that in As2O3 group (388 .4±31.3)ms (P<0.05) at 2h.Confocal experiments showed that in normal Tyrode solution, As2O3 (1μmol/L and 10/μmol/L) had no obvious effects on resting [Ca2+ ]i( P > 0 .05) in guinea pig cardiomyoeytes,however, 10μmol/L As2O3 could markedly enhance [Ca2+ ]. increase induced by KCl 60mmol/ L and the peak value increased from 903 .4±369.4 to 1674. 6±563 .2 ( P < 0.05 ) . The action of elevating [ Ca2+ ]i could be blocked by 10μmol/L verapamil incompletely. The patch-clamp studies indicated that As2O3 at concentration of 10μmol/L prolonged APD50 from (263 .6±75 .2)ms to (523.9±47 .8)ms (P<0.01) and APD90 from (277.5±77.5) ms to (536.3±49.6)ms (P<0.01),and increased ICa-L from ( -6.0±1.5)pA/pF to ( -8.7±2.0)pA/pF (P < 0.01) at 0mV and also reduced IKr from (6.7±1.8)pA/pF to (4.5±1 .8)pA/pF ( P < 0.05) .However,10μmol/L verapamil could modulate prolonging APD50 from (523 . 9±47 . 8 ) ms to (340.4±83 . 8 ) ms ( P < 0.01) and APD90 from (536.3±49.6) ms to (348.9±85.5)ms (P < 0.01) and correct increasing ICa-L induced by 10μmol/L As2O3 from ( - 8 .7±2.0) pA/pF to ( - 6.6±1.4) pA/pF ( P < 0.05) at 0mV. Conclusion As2O3 could induce prolongation of the QT interval on the ECG in guinea pig hearts and the ionic mechanism is associated with increasing ICa-L and inhibiting IKr/HERG. Verapamil may be useful in normalizing QT prolongation during As2O3 therapy by decreasing ICa-L and [Ca2+]i of ventricular myocytes in guinea pig.
文摘Prolongation of the QT interval is associated with adverse cardiac events specifically Torsades de pointes(TdP).There are multiple mediations that have a known,possible,or conditional risk for prolonged QT interval,but general practitioners’knowledge of these medications is unknown.We conducted a survey to assess internal medicine(IM)providers’knowledge of risk factors and medications associated with prolonged QT as well as provider experience and comfort when treating patients with prolonged QT.A 17-question,anonymous survey was constructed in 2019 and distributed to IM providers and residents at a tertiary care center.Questions included demographic information,6 Likert-scale questions gauging provider experience with prolonged QT,and 10 multiple choice clinical vignettes to assess clinical knowledge.Data was analyzed descriptively.Knowledge was assessed via clinical vignettes and compared by level of training.Forty-one responses were received out of a total of 87 possible respondents(47.1%response rate).About 70%of respondents see patients with acquired prolonged QT once monthly or more.95%rarely see congenital prolonged QT.When presented with QTc drug issues,73%of providers seldom or sometimes consulted pharmacy,but about half used online resources.The average correct score on the clinical vignettes was 5.59/10,with the highest scores seen in attending physicians in their first five years of practice(6.96/10).Our survey suggests that IM providers commonly encounter QT prolonging drugs.Educational efforts to improve knowledge of drug and patient risk factors for TdP may be needed.
