Predictors of response to cardiac resynchronization therapy in patients with a non-left bundle branch block morphology

Patients with non-left bundle branch block (LBBB) morphologies are thought to derive less benefit from cardiac resynchronization therapy (CRT) than those with LBBB. However, some patients do exhibit improvement. The characteristics associated with a response to CRT in patients with non-LBBB morphologies are unknown. Clinical, electrocardiographic, and echocardiographic data were collected from 850 consecutive patients presenting for a new CRT device. For inclusion, all patients had a left ventricular ejection fraction of ≤35%, a QRS duration of ≥120 ms, and baseline and follow-up echocardiograms available. Patients with a paced rhythm or LBBB were excluded. The response was defined as an absolute decrease in left ventricular end-systolic volume of ≥10% from baseline. Multivariate models were constructed to identify variables significantly associated with the response and long-term outcomes. A total of 99 patients met the inclusion criteria. Of these 99 patients, 22 had right bundle branch block and 77 had nonspecific intraventricular conduction delay; 52.5% met the criteria for response. On multivariate analysis, the QRS duration was the only variable significantly associated with the response (odds ratio per 10-ms increase 1.23, 95% confidence interval 1.01 to 1.52, p = 0.048). During a mean follow-up of 5.4 ± 0.9 years, 65 patients died or underwent heart transplant or left ventricular assist device placement. On multivariate analysis, the QRS duration was inversely associated with poor long-term outcomes (hazard ratio per 10-ms increase 0.79, 95% confidence interval 0.66 to 0.94, p = 0.005). In patients with advanced heart failure and non-LBBB morphologies, a wider baseline QRS duration is an important determinant of enhanced reverse ventricular remodeling and improved long-term outcomes after CRT.     

束支阻滞类型对心脏再同步治疗效果的影响

目的 探讨不同类型束支阻滞对心脏再同步治疗(CRT)效果的影响.方法 159例难治性心力衰竭患者接受CRT治疗,其中6例已植入永久起搏器,其余153例患者根据体表心电图QRS波形态分为左束支阻滞(LBBB)、右束支阻滞(RBBB)、非特异性室内阻滞(IVCD)、右束支伴左侧分支阻滞(RBBB伴LHB)及室内伴左侧分支阻滞(IVCD伴LHB)5组,比较植入术前及术后6个月心功能(NYHA分级)、QRS时限、左心室射血分数(LVEF)、左心室舒张末期内径(LVEDD)、左心室收缩末期内径(LVESD)等指标的差异.结果 153例患者年龄21～ 84(61.43±12.54)岁,其中男118例,女35例.LBBB组治疗后心功能(3.13±0.55对2.84±0.65)、QRS时限[173.37±28.54)ms对(156.29±22.25)ms]及LVEF[(0.31±0.07)对(0.39±0.09)]、LVEDD[(73.09± 10.81) mm对(68.18± 11.36) mm]、LVESD[(61.38±11.60)mm对(55.20±13.25)mm]等均明显改善(P＜0.01).RBBB组治疗后各项指标未得到显著改善(P＞0.05),IVCD组与RBBB伴LHB组治疗后LVEF显著提高,LVEDD缩小(P＜0.05),而IVCD伴LHB组除QRS时限外,心功能、LVEF、LVEDD、LVESD等指标均得以改善(P＜0.05).此外,RBBB组与IVCD组超声心动图指标的改变不及LBBB组(P＜0.05),而RBBB伴LHB组及IVCD组超声心动图指标改善程度与LBBB组相近(P＞0.05).应用Cox回归分析显示LBBB者较其他束支阻滞类型生存期长(风险比0.30,95％可信区间0.12～0.77,P＜0.01).结论 LBBB者对CRT的反应性优于RBBB者,IVCD者疗效可能介于两者之间,而RBBB伴LHB或IVCD者疗效优于单纯RBBB或IVCD者.     

Left bundle branch block: a continuously evolving concept

Eppinger and Rothberger in 1909 and 1910 first acknowledged the importance of the conduction system, yet a confusion of the pattern of left bundle branch block with right bundle branch block resulted which persisted for 25 years. In left bundle branch block, right ventricular endocardial activation begins before, and is often completed before, initiation of left ventricular endocardial activation. Most likely, right to left septal activation then follows, resulting in left ventricular endocardial activation. Although it is hazardous to make definitive diagnoses of infarction in the presence of left bundle branch block, clues do exist. Benign left bundle branch block is rare; usually disease becomes manifest. Electrocardiographic criteria of hypertrophy are not as helpful in older patients with chronic left bundle branch block (mainly because of the very high incidence of left ventricular hypertrophy) as in younger patients with block of nonatherosclerotic origin. Left bundle branch block is often associated with other abnormalities of the conduction system. Fascicular blocks may mask or mimic myocardial infarction. Left posterior fascicular block is most often an indicator of left ventricular myocardial deficit if right ventricular enlargement is eliminated. Mortality is higher in patients with associated left axis deviation than in those with a normal axis, although the incidence of progression of atrioventricular (AV) block is low. In symptomatic patients with prolonged His to ventricular intervals, the incidence of progression of AV block is higher (12%). Preexisting left bundle branch block in the absence of clinical evidence of heart disease is rare, yet carries with it a slightly increased mortality. Newly acquired left bundle branch block carries a 10-fold increase in mortality; the incidence of sudden death as the first manifestation of heart disease is increased 10-fold.     

右束支阻滞患者心脏再同步治疗疗效分析

目的 回顾分析阜外心血管病医院心律失常中心合并右束支阻滞(RBBB)的心力衰竭患者心脏再同步治疗(CRT)疗效.方法 本中心自2008年1月至2010年12月植入CRT-P/D的合并RBBB的心力衰竭患者,接受常规每3～6个月门诊随访,随访内容包括心功能(NYHA分级)、6 min步行距离、Minnesota生活质量评分、超声心动图及程控等指标.结果 共7例合并RBBB心力衰竭患者植入CRT-P/D,其中男6例,女1例,年龄19 ～74(57±19)岁.随访0.3～43.0(17.6±16.7)个月.随访期间发生心力衰竭住院事件7次,3例患者因心力衰竭加重死亡.6例患者为CRT无反应者,1例为CRT反应者.结论 合并RBBB的心力衰竭患者CRT无明显获益.     

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.     

A larger vectorcardiographic QRS area is associated with left bundle branch block and good prognosis in patients with cardiac resynchronization therapy

Background

The association between the vectorcardiographic QRS area, bundle branch pattern and clinical long-term prognosis in patients who have undergone cardiac resynchronization therapy (CRT) has been unclear.

Defining left bundle branch block in the era of cardiac resynchronization therapy

Cardiac resynchronization therapy (CRT) has emerged as an attractive intervention to improve left ventricular mechanical function by changing the sequence of electrical activation. Unfortunately, many patients receiving CRT do not benefit but are subjected to device complications and costs. Thus, there is a need for better selection criteria. Current criteria for CRT eligibility include a QRS duration ≥ 120 ms. However, QRS morphology is not considered, although it can indicate the cause of delayed conduction. Recent studies have suggested that only patients with left bundle branch block (LBBB) benefit from CRT, and not patients with right bundle branch block or nonspecific intraventricular conduction delay. The authors review the pathophysiologic and clinical evidence supporting why only patients with complete LBBB benefit from CRT. Furthermore, they review how the threshold of 120 ms to define LBBB was derived subjectively at a time when criteria for LBBB and right bundle branch block were mistakenly reversed. Three key studies over the past 65 years have suggested that 1/3 of patients diagnosed with LBBB by conventional electrocardiographic criteria may not have true complete LBBB, but likely have a combination of left ventricular hypertrophy and left anterior fascicular block. On the basis of additional insights from computer simulations, the investigators propose stricter criteria for complete LBBB that include a QRS duration ≥ 140 ms for men and ≥ 130 ms for women, along with mid-QRS notching or slurring in ≥ 2 contiguous leads. Further studies are needed to reinvestigate the electrocardiographic criteria for complete LBBB and the implications of these criteria for selecting patients for CRT.     

不同左束支阻滞型态的心力衰竭患者心脏再同步治疗效果比较

目的 验证符合左束支阻滞(LBBB)新诊断标准的慢性心力衰竭患者是否能从心脏再同步治疗(CRT)中更显著地获益.方法 入选2007年5月至2012年6月符合传统LBBB诊断标准且植入CRT患者,根据术前体表心电图形态分为“真性”LBBB组(真LBBB组:V1、V2导联负向波为主(QS或rS);V1、V2、V5、V6、I、aVL导联中至少有2个以上的导联QRS波中间有切迹或顿挫;QRS时限,男≥140 ms、女≥130ms)和“假性”LBBB组(假LBBB组:符合传统的LBBB标准,但尚未达到“真性”LBBB诊断标准,具体包括上述6个导联中仅有1个或没有导联出现切迹或者顿挫,QRS时限,男＜140 ms、女＜130 ms).术后定期随访,比较两组患者QRS时限、左心室舒张末期内径(LVEDD)、左心室射血分数(LVEF)及心功能(NYHA分级)变化.结果 共入选32例患者(男13例),真LBBB组23例,假LBBB组9例,术前两组患者间性别、年龄、基础疾病、LVEF及心功能等基本情况差异无统计学意义.术后随访显示真LBBB组较假LBBB组LVEF增加显著(0.39±0.11对0.27±0.07,P=0.006),LVEDD缩小明显[(6.3±1.0)cm对(7.6±1.0) cm,P=0.003],提示真LBBB组对CRT治疗反应更佳.结论 符合LBBB新诊断标准的慢性心力衰竭患者从CRT中更显著获益.     

Left bundle branch block and mechanical events of the cardiac cycle

Left bundle branch block (LBBB) is associated with a prolongation of the interval from the QRS onset to the onset of left ventricular (LV) ejection. The locus and prevalence of specific sites of delay were examined in 56 patients with complete LBBB using echocardiography, phonocardiography and external pulse recordings. The results were compared with those in 52 control subjects without LBBB. The onset of the QRS complex was used as the initial reference point of measurement of time intervals. The following abnormalities were found in patients with LBBB: (1) delayed mitral valve closure (Q-MC greater than 0.08 second) was the major site of delay in 23% of patients; (2) prolongation of the LV isovolumetric contraction time (greater than 0.06 second) was the major site of delay in 41%; (3) both Q-MC and LV isovolumetric contraction time were prolonged in 18%; and (4) in 26% of patients the onset of ventricular contraction determined by the onset of the increase of the apex impulse was delayed (Q-VC greater than 0.07 second). The most common cause of delayed ejection was a prolonged LV isovolumetric contraction time, which occurred in 59% of patients. A control group of 20 patients with abnormal LV function but without LBBB had a low incidence of the 3 types of delay in LV ejection (0 to 15%). Thus, the major abnormalities in the cardiac cycle in LBBB are due to the conduction defect and not to LV dysfunction. The results of this study suggest the presence of variable abnormalities of conduction in complete LBBB.     

Cardiac resynchronization performed by LBBaP-CRT in patients with cardiac insufficiency and left bundle branch block

Objective

To evaluate the efficacy and safety of left bundle branch area pacing (LBBaP) in patients with heart failure and left bundle branch block (LBBB), and to compare the clinical effects with traditional cardiac resynchronization therapy (CRT).

Methods

Thirty-two patients with dilated cardiomyopathy complicated by cardiac insufficiency and left bundle branch block were divided into CRT group and LBBaP group. Parameters including pacing threshold, R-wave amplitude, pacing impedance and operation time, and X-ray exposure time were recorded. The left ventricular ejection fraction (LVEF), left ventricular end-diastolic diameter (LVEDD), and left ventricular end-systolic diameter (LVESD) were examined by echocardiography. The changes of QRS complex before and after operation were compared.

Results

Compared with CRT group, the LBBaP group spent less time on total operation time and X-ray exposure time and had stable electrode parameters including pacing threshold, R-wave amplitude, and lead impedance after 12-month follow-up. In addition, LBBaP can achieve narrow QRS complex (117.15 ± 9.91) ms immediately than that in CRT group (130.32 ± 12.41) ms. The change of QRS between LBBaP is (50.30 ± 23.79) ms and CRT group is (33.15 ± 20.22) ms. After 6 months' follow-up in LBBaP group, EF was higher than that before operation. Followed up for 12 months after operation, EF and LVEDD in LBBaP group were significantly improved compared with those before operation.

Conclusion

Left bundle branch area pacing is a safe and effective resynchronization method for patients with cardiac insufficiency and asynchronization, which can achieve same clinical effects to CRT.

     

心力衰竭伴不同宽度左束支传导阻滞患者对心脏再同步治疗反应的分析

目的:分析左束支传导阻滞(left bundle branch block,LBBB)心力衰竭患者对心脏再同步(cardiac resynchronization therapy,CRT)治疗的疗效反应情况。方法:回顾性分析在本院成功置入CRT伴LBBB的心力衰竭患者。所有患者术前、术后1w及最终随访均行12导联心电图、超声心动图、组织多普勒。均对比术前、术后左心室大小、射血分数及生存现状。结果:共44例完成随访,随访6~61个月,平均27.12个月,4例再同步治疗后仍反复出现心力衰竭并因此再入院治疗,无死亡病例。共有38例(86.4%)患者对CRT治疗有反应,真性LBBB亚组中29例(93.5%)有反应,非真性LBBB亚组中9例(69.2%)有反应。真性LBBB亚组左心室射血分数绝对值、左心室舒张末径(left ventricular end diastolic diameter,LVEDD)及左心室射血分数的改善程度更显著,差异有统计学意义。结论:CRT治疗可使大部分患者获益,真性LBBB患者心功能改善更为显著,但终末期心脏失代偿严重者难于从中获益。     

His束起搏治疗扩张型心肌病伴完全性左束支阻滞患者的心力衰竭(附二例报道)

2例均为扩张型心肌病合并完全性左束支传导阻滞(CLBBB),NYHA心功能Ⅲ级,在接受心脏再同步化过程中,左室电极不能到达靶静脉,改用His束起搏治疗。1例57岁男性患者,随访10个月,临床症状明显改善,QRS波恢复正常,左室及左室射血分数恢复正常。另1例50岁的男性患者,随访12个月,临床症状明显改善,QRS波恢复正常,左室及左室射血分数恢复正常。     

Optimizing the programation of cardiac resynchronization therapy devices in patients with heart failure and left bundle branch block

This study was conducted to investigate the clinical impact of cardiac resynchronization device optimization. A series of 100 consecutive patients received cardiac resynchronization therapy. In the first 49 patients, an empirical atrioventricular delay of 120 ms was set, with simultaneous biventricular stimulation (interventricular [VV] interval=0 ms). In the next 51 patients, systematic atrioventricular optimization was performed. VV optimization was also performed, selecting 1 VV delay: right or left ventricular preactivation (+30 or -30 ms) or simultaneous (VV interval=0 ms), according to the best synchrony obtained by tissue Doppler-derived wall displacement. At follow-up, patients who were alive without cardiac transplantation and showed improvement of >or=10% in the distance walked in the 6-minute walking test were considered responders. There were no differences between the 2 groups at baseline. Left ventricular ejection fraction improved in the 2 groups, but left ventricular cardiac output improved only in the optimized group. At 6 months, patients with optimized devices walked slightly further in the 6-minute walking test (497+/-167 vs 393+/-123 m, p<0.01), with no differences in New York Heart Association functional class or quality of life compared with nonoptimized patients. Overall, the number of nonresponders were similar in the 2 groups (27% vs 23%, p=NS). In conclusion, the echocardiographic optimization of cardiac resynchronization devices provided a slight incremental clinical benefit at midterm follow-up. Simple and rapid methods to routinely optimize the devices are warranted.