Electrocardiographic characteristics of distal His bundle pacing in a patient with left bundle branch block

This case demonstrates the feasibility of placing the pacing lead helix at the His bundle distal to the region of left bundle branch block and reveals three types of electrocardiographic characteristics of distal His bundle pacing during correction of left bundle branch block in a patient. As the pacing lead helix was placed distal to the block, left bundle branch block correction was achieved by pacing with a low and stable capture threshold.     

Impact of left bundle branch block and activation pattern on the heart

Left bundle branch block (LBBB) is known to impair the mechanical function of the left ventricle. For a better understanding of the impact of LBBB on the structure and function of the heart and how this influences the management and outcome in patients with heart failure, we reviewed the most pertinent articles published from 1950 to 2007. Epidemiological studies identified LBBB as an independent risk factor for cardiac mortality. It is not only the morphology or duration of QRS but also the underlying myocardial pathology, ejection fraction or New York Heart Association class that may determine the clinical implications of LBBB. Data indicate that LBBB inversely affects the perfusion, systolic, diastolic performance and hemodynamics of the heart. However, there is no solid evidence answering the question of whether LBBB is a predictor, cause or consequence of myocardial dysfunction. Further studies are warranted for better understanding of these relationships, as this will allow better selection of patients and optimal time for resynchronization therapy in patients with LBBB.     

Impact of left bundle branch block and activation pattern on the heart

Left bundle branch block (LBBB) is known to impair the mechanical function of the left ventricle. For a better understanding of the impact of LBBB on the structure and function of the heart and how this influences the management and outcome in patients with heart failure, we reviewed the most pertinent articles published from 1950 to 2007. Epidemiological studies identified LBBB as an independent risk factor for cardiac mortality. It is not only the morphology or duration of QRS but also the underlying myocardial pathology, ejection fraction or New York Heart Association class that may determine the clinical implications of LBBB. Data indicate that LBBB inversely affects the perfusion, systolic, diastolic performance and hemodynamics of the heart. However, there is no solid evidence answering the question of whether LBBB is a predictor, cause or consequence of myocardial dysfunction. Further studies are warranted for better understanding of these relationships, as this will allow better selection of patients and optimal time for resynchronization therapy in patients with LBBB.     

左束支传导阻滞左心室不同步的影像学研究进展

左束支传导阻滞(LBBB)已证实为心力衰竭患者心脏再同步化治疗后的独立预测因素,对LBBB患者左心室不同步病理生理机制的进一步可视化影像学研究将有助于选择治疗方案和评估疗效、预后。本文针对LBBB患者左心室不同步的病理生理学机制、检查方法和疗效预后评估等影像学研究进展进行综述。     

左束支传导阻滞对慢性心衰患者心室间协调性的影响

目的：评价左束支传导阻滞对慢性心衰患者心室间协调性的影响。方法：分3组：对照组、慢性心衰不伴传导异常组及慢性心衰伴左束支传导阻滞组。应用心肌组织多普勒技术（TDI）通过左、右房室环分别测量左、右心室侧壁电机械运动时间，并计算二者差值表示左右心室收缩期电机械运动延迟时间；并应用脉冲多普勒技术（PW）分别测量主动脉、肺动脉射血前期时间，并计算二者差值表示左右心室射血延迟时间。结果：与对照组及心衰不伴传导异常组相比，心衰伴左束支传导阻滞组的左右心室收缩期电机械运动延迟时间和左右心室射血延迟时间均有统计学意义。结论：使用TDI及PW技术可全面评价心室间不同步运动情况，为起搏治疗慢性心衰提供准确的信息。     

Simplifying thrombolysis decisions in patients with left bundle branch block

Objectives: To redesign and simplify an existing decision algorithm for the management of patients who present to the emergency department with chest pain and left bundle branch block (LBBB) based on the Sgarbossa criteria. To compare its reliability with the current algorithm. Methods: A simplified algorithm was created and tested against the existing algorithm. Electrocardiograms (ECGs) of patients with LBBB were presented to 10 emergency department doctors with both old and new algorithms a week apart. Six ECGs displayed the relevant criteria for thrombolysis and had proven acute myocardial infarction (AMI) based on a gold standard of enzyme measurements. Subjects were asked whether or not they would thrombolyse a patient presenting with the given ECG using each of the algorithms as a guide. Results: The new algorithm has demonstrated improvements in terms of an increase in appropriate thrombolysis and a reduction in inappropriate thrombolysis. Specificity for AMI rose from 0.85 to 0.99 and sensitivity from 0.38 to 0.6. κ score showed greater agreement with the gold standard. Conclusion: Patients with AMI and LBBB have a significantly poorer outcome than those without LBBB. Despite this, thrombolysis is less likely to be given to patients with AMI and LBBB. This study demonstrates that in part this is because of cognitive difficulties using the current algorithm. The proposed proforma addresses these issues and provides a simple tool to aid appropriate treatment in this group of patients.     

超声心动图定位评价左束支区域起搏电极的可行性研究

目的总结左束支区域起搏（LBBP）电极的超声心动图表现,探讨电极距三尖瓣隔瓣距离（D_TV-L）等指标定量评价起搏电极位置的可行性。 方法选取2019年3月至12月在首都医科大学附属北京安贞医院行LBBP术的患者49例,其中男性28例,女性21例,年龄19~89岁,平均年龄（65±16）岁。总结患者的超声心动图表现,根据术中起搏电极的植入位置将病例分为高位间隔组（14例）、中位间隔组（17例）和低位间隔组（18例）,采用单因素方差分析比较3组病例电极植入位置（D_TV-L）及植入深度的差异。 结果所有病例均可在超声心动图中显示电极尖端位置,LBBP电极植入室间隔的深度平均为（8.13±2.10）mm,距左心室面距离平均为（2.25±1.79）mm,不同组间电极植入深度及距左心室面距离比较,差异均无统计学意义（P均>0.05）。3组病例D_TV-L结果比较,高位间隔组电极明显小于中位间隔组[（10.79±6.62）mm vs（17.59±5.23）mm,P<0.05],中位间隔组则明显小于低位间隔组[（17.59±5.23）mm vs（32.83±8.99）mm,P<0.001],3组间比较,差异有统计学意义（F=40.273,P<0.001）。 结论超声心动图可用于LBBP电极的定位评价,D_TV-L等参数可作为LBBP电极定位评价的量化指标,为临床提供更有价值的信息。     

难治性心衰伴左束支传导阻滞患者心室运动的研究

目的 定量组织多普勒成像技术分析完全性左束支传导阻滞(CLBBB)患者心室运动的同步性.方法 超声定量组织多普勒测量CLBBB伴左室射血分数正常的患者17例、CLBBB伴左室射血分数减低的患者20例和健康者为对照组20例,分别测量二尖瓣瓣环纵向运动的峰值速度、达峰时间,并使用脉冲多普勒测量主动脉瓣和肺动脉瓣开放及关闭时间等.结果 CLBBB患者二尖瓣瓣环部等容收缩期时间延长,射血时间、充盈时间及收缩时间缩短;主动脉瓣开放时间较对照组明显延迟,射血期峰值速度、舒张早期及晚期峰值速度减低,且CLBBB伴射血分数减低组的各项指标改变尤为明显.结论 定量组织多普勒成像能够准确、客观地评价心室运动的同步性,从而提高同步化治疗的应答率.     

Circumferential myocardial strain in cardiomyopathy with and without left bundle branch block

Background

Cardiac resynchronization therapy (CRT) has been shown to decrease mortality in 60-70% of advanced heart failure patients with left bundle branch block (LBBB) and QRS duration > 120 ms. There have been intense efforts to find reproducible non-invasive parameters to predict CRT response. We hypothesized that different left ventricular contraction patterns may exist in LBBB patients with depressed systolic function and applied tagged cardiovascular magnetic resonance (CMR) to assess circumferential strain in this population.

Methods

We determined myocardial circumferential strain at the basal, mid, and apical ventricular level in 35 subjects (10 with ischemic cardiomyopathy, 15 with non-ischemic cardiomyopathy, and 10 healthy controls). Patterns of circumferential strain were analyzed. Time to peak systolic circumferential strain in each of the 6 segments in all three ventricular slices and the standard deviation of time to peak strain in the basal and mid ventricular slices were determined.

Results

Dyskinesis of the anterior septum and the inferior septum in at least two ventricular levels was seen in 50% (5 out of 10) of LBBB patients while 30% had isolated dyskinesis of the anteroseptum, and 20% had no dyskinesis in any segments, similar to all of the non-LBBB patients and healthy controls. Peak circumferential strain shortening was significantly reduced in all cardiomyopathy patients at the mid-ventricular level (LBBB 9 ± 6%, non-LBBB 10 ± 4% vs. healthy 19 ± 4%; both p < 0.0001 compared to healthy), but was similar among the LBBB and non-LBBB groups (p = 0.20). The LBBB group had significantly greater dyssynchrony compared to the non-LBBB group and healthy controls assessed by opposing wall delays and 12-segment standard deviation (LBBB 164 ± 30 ms vs. non-LBBB 70 ± 17 ms (p < 0.0001), non-LBBB vs. healthy 65 ± 17 ms (p = 0.47)).

Conclusions

Septal dyskinesis exists in some patients with LBBB. Myocardial circumferential strain analysis enables detailed characterization of contraction patterns, strengths, and timing in cardiomyopathy patients with and without LBBB.