QTc interval measurement in patients with right bundle branch block: A practical method

Background and Aim

Prolonging the QT interval in the right bundle branch block (RBBB) can create challenges for electrophysiologists in estimating repolarization time and eliminating the effect of depolarization changes on QT interval. In this study, we aimed to develop a practice formula to eliminate the effect of depolarization changes on QT interval in patients with RBBB.

Methods

This prospective study evaluated accidentally induced RBBB in patients undergoing electrophysiological study. Two expert electrophysiologists recorded the ECG parameters, including QRS duration, QT interval, and cycle length, in the patients. The formula was developed based on QT interval differences (with and without RBBB) and its proportion to QRS. Additionally, the Bazzet, Rautaharju, and Hodge formulas were used to evaluate QTc.

Results

We evaluated 96 patients in this study. The mean QT interval without RBBB was 369.39 ± 37.38, reaching 404.22 ± 39.23 after inducing RBBB. ΔQT was calculated as 34.83 ± 17.61, and the ratio of ΔQT/QRS with RBBB was almost 23%. Our formula is: (QT_{with RBBB} − 23% × QRS). Subtraction of 25% instead of 23% seems more straightforward and practical. Our formula could also predict the QTc interval in RBBB based on the Bazzet, Rautaharju, and Hodge formulas.

Conclusion

Previous formulas for QT correction were hard to apply in the clinical setting or were not specified for RBBB. Our new formula allows a rapid and practical method for QT correction in RBBB in clinical practice.     

Remarkable response to cardiac resynchronization therapy via left bundle branch pacing in patients with true left bundle branch block

BackgroundLeft bundle branch pacing (LBBP) has been suggested as an alternative means to deliver cardiac resynchronization therapy (CRT).HypothesisLBBP may deliver resynchronization therapy along with an advantage over traditional biventricular (BiV) pacing in clinical outcomes.MethodsHeart failure patients who presented LBBB morphology according to Strauss''s criteria and received successful CRT procedure were enrolled in the present study. Propensity score matching was applied to match patients into LBBP‐CRT group and BiV‐CRT group. Then, the electrographic data, the echocardiographic data and New York heart association (NYHA) class were compared between the groups.ResultsTwenty‐one patients with successful LBBP procedure and another 21 matched patients with successful BiV‐CRT procedure were finally enrolled in the study. The QRS duration (QRSd) was narrowed from 167.7 ± 14.9 ms to 111.7 ± 12.3 ms (P < .0001) in the LBBP‐CRT group and from 163.6 ± 13.8 ms to 130.1 ± 14.0 ms (P < .0001) in the BiV‐CRT group. A trend toward better left ventricular ejection fraction (LVEF) was recorded in the LBBP‐CRT group (50.9 ± 10.7% vs 44.4 ± 13.3%, P = .12) compared to that in the BiV‐CRT group at the 6‐month follow‐up. A trend toward better echocardiographic response was documented in patients receiving LBBP‐CRT procedure (90.5% vs 80.9%, P = .43) and more super CRT response was documented in the LBBP‐CRT group (80.9% vs 57.1%, P = .09) compared to that in the BiV‐CRT group.ConclusionsLBBP‐CRT can dramatically improve the electrical synchrony in heart failure patients with LBBB. Meanwhile, compared with the traditional BiV‐CRT, it has a tendency to significantly improve LVEF and enhance the NYHA cardiac function scores.     

完全性左束支阻滞和右束支阻滞心电图结果分析

目的 了解完全性左束支阻滞和右束支阻滞不同性别、不同年龄的发生率情况.方法 分析108 610例常规心电图检测结果,分别统计完全性左束支阻滞和右束支阻滞不同性别、不同年龄的发生率情况.结果 108 610例门诊及住院患者资料,完全性左束支阻滞19例,占0.18％;右束支阻滞3 794例,占3.49％;完全性左束支阻滞发生率在不同性别之间差异无统计学意义（Х^2=1.707,P=0.191）,不同年龄之间比较差异有统计学意义（Х^2=209.874,P＜0.05）;右束支阻滞发生率在不同性别之间、不同年龄之间比较,差异均有统计学意义（Х^2=986.046,P＜0.05;Х^2=1 483.286,P＜0.05）.结论 60岁以上老年人的完全性左束支阻滞和右束支阻滞发生率较高,应定期进行常规心电图检查,及时发现异常情况并进行相应的处理.     

Recovery of complete left bundle branch block following heart failure improvement by left bundle branch pacing in a patient

A 57‐year‐old male presented with symptomatic systolic heart failure and complete left bundle branch block (LBBB). Left bundle branch pacing corrected LBBB at a low capture threshold (0.5V @0.4ms) with right bundle branch conduction delay and paced QRS morphology changed to near‐normal by adjusting AV delay with diminished RBBD. At 1‐year follow‐up, the patient had a significant improvement in heart failure and LBBB automatically resolved with a rate‐dependent pattern. LBBP may be an alternative to conventional cardiac resynchronization therapy with the likelihood of recovery of LBBB. More research is needed to evaluate the potential use of this pacing strategy in patients with LBBB and heart failure.     

间歇性左束支阻滞时QRS波形态特点的分析

目的观察12导联动态心电图间歇性完全性左束支阻滞出现前后心电图QRS波群形态改变特点。方法选择2005年1月至2009年3月住院的16158例患者的12导联动态心电图,检出间歇性完全性左束支阻滞16例,占0.9‰,并对完全性左束支阻滞时心电图QRS波群形态改变的特点进行分析。结果①平均QRS电轴:完全性左束支阻滞时33.64±59.77°,正常室内传导时68.36±13.70°,二者比较,p=0.038;②QT间期:完全性左束支阻滞时0.44±0.07s,正常室内传导时0.40±0.08s,二者比较,p<0.001;③V2导联r波振幅:完全性左束支阻滞时0.13±0.08mV,正常室内传导时0.41±0.28mV,p=0.02。结论间歇性完全性左束支阻滞发生率较低,心电图主要特点为QRS电轴左偏,QT间期延长,V2导联r波振幅明显降低或消失,QRS波群总振幅无明显改变,上述特点有助于识别动态心电图中的间歇性完全性左束支阻滞。     

The ability of QRST isointegral maps to detect myocardial infarction in the presence of simulated left bundle branch block

The clinical value of QRST isointegral maps (I-maps) for thedetection of myocardial infarction (MI) in the presence of leftbundle branch block (LBBB) was investigated. We recorded I-mapsduring sinus rhythm and right ventricular (RV) pacing, whichsimulated LBBB, in 62 patients with MI (42 patients had at leastone akinetic segment and the remaining 20 patients had onlyhypokinesis or normal contraction) and 26 patients without MI.An abnormal decrease in the QRST value of the I-map was assessedby the difference map (D-map), which indicated a ‘–2SDarea’, where the QRST integral value was less than thelower limit of the normal range (mean –2SD) calculatedfrom 608 normal individuals. The I-maps recorded during thetwo activation sequences were similar to each other in patientswith and without MI (r = 0.87 and 0.92, respectively). The ‘–2SDarea’ was located over the left anterior chest in patientswith an anterior MI and over the lower torso in patients withan inferior MI during each activation sequence. We were ableto diagnose MI during simulated LBBB with a sensitivity of 84%,a specificity of 81% and a diagnostic accuracy of 83% when weused the criterion that MI is present if the sum of QRST integralvalues below the normal range (DM) exceeds 100 mV.ms. We wereable to diagnose an akinesis with a sensitivity of 81%, a specficityof 85% and a diagnostic accuracy of 83% when we used the criterionthat akinesis is present DM exceeds 500 mV .ms during simulatedLBBB. These findings demonstrate that I-maps may be useful indetecting the presence of MI and estimating severity of asynergyin patients with LBBB.     

完全性左束支阻滞81例临床分析

目的分析完全性左束支阻滞(CLBBB)病例的临床特点。方法回顾性分析81例完全性左束支阻滞患者的病因、动态心电图、超声心动图、冠状动脉造影结果。结果60岁以上男性43例,占53%。病因以冠心病、高血压、心功能不全多见。本组冠脉造影的28例完全性左束支阻滞患者中确诊为冠心病者16例,占57.14%。超声心动图结果:55%患者心房、心室增大或心房心室同时增大。左室射血分数(LVEF)<50%者22例,占33.8%。动态心电图检查可见左束支阻滞常合并各种类型心律失常。结论完全性左束支阻滞常发生在老年男性患者,常见于器质性心脏病,尤其是冠心病、高血压、扩张型心肌病。完全性左束支阻滞可导致不良的心脏血流动力学效应,导致左心室功能受损。     

完全性左束支阻滞的发生率及心电图特点

目的 观察受检者完全性左束支阻滞的发生率及心电图特点.方法 记录和分析86621例常规12导联同步心电图,分别统计完全性左束支阻滞(CLBBB)及右束支阻滞(RBBB)的发生情况及心电图特点.结果 检出完全性左束支阻滞(CLBBB) 170例,占0.19％;检出RBBB3243例(男2252例,年龄4～98岁;女991...     

Distinct left bundle branch block pattern in ischemic and non-ischemic dilated cardiomyopathy

BACKGROUND: A high percentage of patients with dilated cardiomyopathy have the electrocardiographic (ECG) pattern of advanced left bundle branch block (LBBB). In the present study we sought to investigate whether patients with dilated cardiomyopathy of ischemic or non-ischemic etiology can be differentiated on the basis of LBBB pattern. METHODS AND RESULTS: The study population included 41 patients with dilated cardiomyopathy of non-ischemic (NIC) (n=26) or ischemic origin (IC) (n=15) and LBBB on surface ECG. ECG duration and voltage were digitally measured. The presence of notching of S wave in right precordial leads (V1-V3) was not statistically different between the groups. The voltages of precordial leads V2, V3 and the Sigma(V1+V2+V3 voltages) were significantly more prominent in patients with NIC (P=0.002, P<0.001 and P=0.002, respectively). The discriminative power of receiver operating characteristic analysis was best at voltages of V3 of 2100 microV (area under the curve, 0.805; standard error, 0.001). The sensitivity and specificity of V3 voltage >2100 microV on surface ECG in the presence of LBBB to identify a cardiomyopathy of non-ischemic origin were 85 and 73%, respectively. CONCLUSIONS: A single ECG criteria, voltage of lead V3, appears to be a useful parameter to identify patients with dilated cardiomyopathy of ischemic or non-ischemic origin in the presence of advanced LBBB.     

真性完全性左束支阻滞与心脏再同步化治疗超反应的研究进展

真性完全性左束支阻滞作为一个新概念被提出,不仅促进了心电学的发展,而且也丰富了心脏再同步化治疗心力衰竭的内容,并成为慢性心力衰竭伴真性完全性左束支阻滞的患者对心脏再同步化治疗获超反应的一个新的预测因子.     

QT interval effects of cisapride in the clinical setting

Purpose: The clinical effect of cisapride on QT intervals was prospectively studied. Subjects: Consecutive adult patients were recruited in whom cisapride was indicated for gastroesophogeal reflux, gastric ulcer, duodenal ulcer, diabetic gastroparesis or chronic constipation refractory to laxatives. Exclusion criteria included disorders and medications affecting cardiac conduction, electrolyte homeostasis, drug clearance and membrane stability. Methods: Seventy-five patients were included and followed at 1 to 2 week intervals. Patients took cisapride 5 mg thrice daily for 1 to 4 weeks (lower dose stage), followed by 10 mg thrice daily for another 1 to 4 weeks (higher dose stage). Twelve-lead ECGs were performed before commencing cisapride (group B), at completion of the lower dose stage (group L) and at completion of the higher dose stage (group H). Results: No patients experienced presyncope or syncope. Seventeen patients failing to comply, and 7 complaining of abdominal discomfort or diarrhea were excluded, leaving 51 participants. Group H’s corrected QT interval (QTc) was longer than group B’s by 13±15 ms (P<0.001), and longer than group L’s by 7±11 ms (P<0.001). Group L’s QTc was longer than group B’s by 7±21 ms (P<0.05). QT dispersion did not differ significantly among groups. Neither torsade de pointe nor ventricular tachycardia were noted in Holter monitoring of 33 patients during the higher dose stage. Conclusion: cisapride dose-dependently prolongs the QT interval. Further study is needed to examine the arrhythmogenicity of cisapride in higher doses and for longer durations.     

Association between C-reactive protein,corrected QT interval and presence of QT prolongation in hypertensive patients

C-reactive protein (CRP) and corrected QT (QTc) interval are predictors of cardiovascular disease. Whether CRP is associated with QTc interval and QT prolongation is unknown in hypertensive patients. We recruited hypertensive patients from a cardiovascular clinic in a tertiary medical center in Taiwan. All received standard 12-lead electrocardiogram examination. QT prolongation was defined as QTc interval ≥440 ms in men or ≥450 ms in women. High-sensitive CRP kits were used for the measurement of the CRP levels. A total of 466 consecutive patients were finally enrolled. Mean age was 60.6 ± 12.0 years. CRP level was correlated with QTc interval (p < 0.001) and presence of QT prolongation (p = 0.014). Multivariate regression analysis showed that CRP level (p = 0.001), age (p = 0.004), sex (p < 0.001), height (p = 0.001), low-density lipoprotein (p = 0.041), and QRS interval (p < 0.001) were associated with QTc interval. Furthermore, CRP level [odds ratio (OR) = 1.203, 95% confidence interval (CI) = 1.027–1.410, p = 0.022], age (OR = 1.040, 95% CI = 1.010–1.071, p = 0.009), waist (OR = 1.033, 95% CI = 1.000–1.066, p = 0.047), triglyceride (OR = 0.993, 95% CI = 0.987–0.999, p = 0.021) and QRS interval (OR = 1.046, 95% CI = 1.028–1.065, p < 0.001) independently predicted the presence of QT prolongation. Because CRP is an independent predictor of QTc interval and presence of QT prolongation, it could be considered in the risk assessment for hypertensive patients.     

孤立性左束支传导阻滞的多普勒超声频谱改变

目的:观察孤立性左束支传导阻滞(LBBB)患者左室舒张期的充盈方式。方法:比较LBBB组与正常心脏传导组的超声多普勒参数。结果:发现两组二尖瓣血流频谱的E峰、E／A、E峰减速时间(DT)、E峰下降速率、二尖瓣环的组织多普勒运动频谱e及e／a存在显著差异(P<0.05~<0.01)。结论:与正常心脏传导比较,孤立性左束支传导阻滞患者的左室舒张充盈方式异常。