Left Bundle Branch Block Criteria Research Articles

Natural History and Clinical Significance of Isolated Complete Left Bundle Brunch Block without Associated Structural Heart Disease

Left bundle branch block (LBBB), which is associated with underlying cardiac disease, is believed to play a role in the pathogenesis of cardiomyopathy through delays in interventricular conduction, leading to dyssynchrony. However, this has not been established in previous studies. It is unclear whether LBBB indicates clinically advanced cardiac disease or is an independent factor responsible for increased mortality and the development of heart failure. We investigated the natural history of isolated LBBB without any associated structural heart disease in order to determine its clinical significance.We performed a retrospective chart review on consecutive patients who fulfilled the 12-lead electrocardiographic (ECG) criteria for complete LBBB and had a normal echocardiogram with no evidence of structural heart disease and left or right ventricular systolic dysfunction within three months of the initial ECG between January 1, 2000 and December 31, 2009. We excluded patients with documented coronary artery disease (CAD) at any time, any structural heart disease, or cardiac devices. We evaluated the primary endpoints of mortality and incidence of cardiomyopathy, as well as any heart failure hospitalizations over a 1- and 10-year period.We identified 2522 eligible patients. The mean follow-up duration was 8.4±3.2 years. The one-year mortality rate was 7.8%, with a 10-year mortality rate of 22.0%. The incidence of cardiomyopathy over one year was 3.2% and over 10 years was 9.1%. There was no significant difference in QRS duration between patients who were alive and those that were deceased at 10 years (141+/-18 vs. 141+/-17 ms; p=0.951) and patients with and without cardiomyopathy at 10 years (142±17 vs. 141±17 ms; p=0.532).Isolated LBBB occurring without structural heart disease, ventricular dysfunction, or CAD is associated with a low mortality rate and incidence of cardiomyopathy.

Typical BBB morphology and implantation depth of 3830 electrode predict QRS correction by left bundle branch area pacing.

Strict criteria of typical left bundle branch block (LBBB) can help with the prediction for cardiac resynchronization therapy response. The aim of this study is to determine whether the use of strict criteria for both LBBB and right bundle branch block (RBBB) predicts successful QRS correction (≤130ms) by left bundle branch area pacing (LBBAP). Consecutive patients with pacemaker indications according to the present guideline who also underwent LBBAP implantation were retrospectively assessed. Inclusion criteria were patients with BBB and the baseline QRSd>130ms. Baseline characteristics and pacing parameters were compared between typical and atypical BBB groups. Multivariate logistic regression was used to adjust for covariates that were found in univariate analyses for successful QRS correction by LBBAP. Seventy-three patients were enrolled. Among them, 10 (13.6%) had atypical BBB (5 LBBB and 5 RBBB) and 63 (86.4%) had typical BBB (30 LBBB and 33 RBBB). The rate of successful QRS correction was higher in typical-BBB patients (52/63; 82.5%) than that in atypical-BBB patients (3/10; 30%), P<.001. Paced QRSd was obviously narrower in patients with typical BBB than that in patients with atypical-BBB (118 ± 14vs 133 ± 14ms, P=.003). In multivariate logistic regression, only typical BBB morphology and the implantation depth of 3830 pacing electrode in the ventricular septum were independent predictors for successful QRS correction. This study demonstrates that patients with typical-BBB morphology benefit more from LBBAP for QRS correction. Typical BBB morphology together with deep penetration of 3830 ventricular electrode in the interventricular septum predicts the success of QRS correction by LBBAP.

P5974Prognostic value of global tangential strain by three-dimensional echocardiography heart failure patients with intermediate ECG criteria for cardiac resynchronization therapy

Abstract Background In the current clinical guidelines, cardiac resynchronization therapy (CRT) is recommended in heart failure (HF) patients with left bundle branch block (LBBB) with QRS width ≥150ms as Class I indication. In terms of HF patients with intermediate ECG criteria, prediction for benefit of CRT is still controversial in routine echocardiography. Purpose The aim was to assess whether three-dimensional (3D) echocardiographic indexes of global LV function at baseline has a prognostic value following CRT implantation in patients who fulfilled with intermediate ECG criteria. Methods We studied 62 HF patients who fulfilled with the indication criteria of CRT implantation according to current the clinical guidelines. In addition to routine two-dimensional echo, 3D echo dataset was acquired for determination of 3D global tangential strain (GTS) and 3D global longitudinal strain (GLS). We tracked predefined unfavorable outcomes for 3 years after CRT implantation: death, hospitalization due to worsening HF. Results LBBB with QRS width ≥150ms was evident in 26 of 62 patients (aged 68±11 years with 160±26 ms of QRS duration and 29±7% of LV ejection fraction), and the other 36 patients only fulfilled intermediate ECG criteria (QRS width 120–149ms or non-LBBB). Unfavorable events occurred in 21 patients (34%). The median GTS was −15.4%. Although GLS was not predictive, GTS greater than −15.4% had high probability of unfavorable outcomes over 3 years (Log-rank, p&lt;0.05). There is no difference in the probability of unfavorable outcomes between LBBB and intermediate ECG criteria. Baseline GTS in patients with intermediate ECG criteria was associated with unfavorable outcomes: −12.6±2.6% vs. −17.3±3.8% (p&lt;0.05). Outcome was better in the intermediate ECG criteria patients with GTS ≤−15.4% than in those with LBBB and in those with intermediate ECG criteria patients with GTS &gt;−15.4% (Log-rank: p&lt;0.05, p&lt;0.0001, respectively). Conclusions Baseline GTS by 3D echocardiography is useful for predicting outcome over 3 years after CRT implantation regardless of the ECG criteria for CRT indication.

P5429Mechanical dyssynchrony has a higher predictive value for CRT response than different ECG-based definitions of LBBB

Abstract Background/Aim To investigate the value of baseline assessment of mechanical dyssynchrony (Dyss) in predicting response to cardiac resynchronization therapy (CRT) in comparison to the classic ECG definition of left bundle branch block (LBBB) (Classic-def) as well as the recently proposed Sex- based definition (Sex-def.). Methods The baseline ECGs of 194 patients (31% females, 39% with ischemic cardiomyopathy, mean QRS width 159±25 ms and mean LVEF 29±8%) were investigated for identifying the criteria of LBBB before CRT implantation. Classic-def., defined as notched or slurred QRS complex in at least two of the leads I, aVL, V1, V2, V5 and V6 with a total width of at least 120 ms in addition to the absence of Q wave in lead I, V5 and V6 was identified in 74% of the study population. Sex-def. was identified in 69%, which is a QRS duration of at least 140 and 130 ms for men and women respectively with otherwise the same criteria of the Classic definition. Dyss was defined as the presence of either apical rocking and/or septal flash in 2D echocardiography prior to implantation. Volumetric response to CRT was defined as a reduction of at least 15% of the LV-end systolic volume (ESV) at follow up echocardiography (12±6 months after device implantation). Results Patient with baseline Dyss showed the highest response rates (76%) with a sensitivity of 88%, a specificity of 63% and an area under the curve (AUC) of 0.76 (P&lt;0.001) compared to 70% (sensitivity 82%, specificity 47%, AUC 0.65, P&lt;0.01) in patients with Sex-def. and 65% (sensitivity 84%, specificity 40%, AUC 0.62, P=0.01) in patients with Classic-def. (Figure A). Pairwise comparisons showed that the accuracy of the Sex-def. did not differ significantly from the Classic-def. in response prediction (AUC=0.65 vs. 0.62 for Sex-def. vs. Classic-def. respectively, P=0.27). Alternatively, Dyss showed a significantly higher accuracy in predicting response to therapy (AUC=0.76) as compared to Sex-def. and Classic-def. (P=0.02 and &lt;0.01 respectively, Figure B). Mech. dyssynchrony vs. ECG-based LBBB Conclusion The presence of Apical rocking and/or septal flash before CRT is associated with better response to CRT as compared to various ECG definitions of LBBB. Although a Sex-based definition of LBBB showed a trend of better response to CRT as compared to the Classic definition, it was not statistically significant.

An S wave in ECG lead V6 predicts poor response to cardiac resynchronization therapy and long-term outcome

Cardiac resynchronization therapy (CRT) is a standard treatment for selected patients with chronic heart failure(HF). However, up to 30%-50% of patients still do not respond to CRT. Our aim was to identify the predictive value of an S wave in lead V6 in CRT response in patients with complete left bundle branch block (CLBBB). The CLBBB definition included the Strauss left bundle branch block criteria and the absence of q waves in leads I, V5, and V6. According to the electrocardiogram at baseline, CLBBB patients were divided into 3 groups: T-CLBBB group (CLBBB without an S wave in lead V5 or V6), V5S group (CLBBB with an S wave in lead V5 and no S wave in lead V6), and V5&V6S group (CLBBB with S waves in leads V5 and V6). CRT response was defined as left ventricular end-systolic volume reduction ≥ 15% at 6-month follow-up. The combined end point included HF rehospitalization or all-cause death. Of 181 patients with left bundle branch block-like pattern, 112 patients with CLBBB were included into 3 groups: 54 in the T-CLBBB group, 32 in the V5S group, and 26 in the V5&V6S group. The CRT response rate was 85.2% (46), 65.6% (21), and 38.5% (10), respectively (P < .001). Kaplan-Meier curves demonstrated that patients in the V5&V6S group had a higher incidence of HF rehospitalization or all-cause death than those in the other 2 groups (P < .001). In a multivariate logistic regression model analysis, an S wave in lead V6 was significantly associated with CRT nonresponse (hazard ratio 0.33; 95% confidence interval 0.11-0.96; P = .042). An S wave in lead V6 can predict poor response to CRT and long-term outcome.

Relationships between electrical and mechanical dyssynchrony in patients with left bundle branch block and healthy controls

BackgroundAbnormal electrical activation may cause dyssynchronous left ventricular (LV) contraction. In this study, we characterized and analyzed electrical and mechanical dyssynchrony in patient with left bundle branch block (LBBB) and healthy controls. MethodsMyocardial perfusion imaging (MPI) data from 994 patients were analyzed. Forty-three patient fulfilled criteria for LBBB and 24 for controls. Electrical activation was characterized with vector electrocardiography (VECG) and LV function including mechanical dyssynchrony with ECG-gated MPI phase analysis. ResultsQRS duration (QRSd; r = 0.69, P < .001) and a few other VECG parameters correlated significantly with phase bandwidth (phaseBW) representing mechanical dyssynchrony. End-diastolic volume (EDV; r = 0.59, P < .001), ejection fraction and end-systolic volume correlated also with phaseBW. QRSd (β = 0.47, P < .001) and EDV (β = 0.36, P = .001) were independently associated with phaseBW explaining 55% of its variation. Sixty percent of patients with LBBB had significant mechanical dyssynchrony. Those patients had wider QRSd (159 vs 147 ms, P = .013) and larger EDV (144 vs 94 mL, P = .008) than those with synchronous LV contraction. Cut-off values for mechanical dyssynchrony seen in patients with LBBB were QRSd ≥ 165 ms and EDV ≥ 109 mL. ConclusionsDespite obvious conduction abnormality, LBBB is not always accompanied by mechanical dyssynchrony. QRSd and EDV explained 55% of variation seen in phaseBW. These two parameters were statistically different between LBBB cases with and without mechanical dyssynchrony.

Intracardiac Delineation of Septal Conduction in Left Bundle-Branch Block Patterns.

Septal activation in patients with left bundle-branch block (LBBB) patterns has not been described previously. We performed detailed intracardiac mapping of left septal conduction to assess for the presence and level of complete conduction block (CCB) in the His-Purkinje system. Response to His bundle pacing was assessed in patients with and without CCB in the left bundle. Left septal mapping was performed with a linear multielectrode catheter in consecutive patients with LBBB pattern referred for device implantation (n=38) or substrate mapping (n=47). QRS width, His duration, His-ventricular (HV) intervals, and septal conduction patterns were analyzed. The site of CCB was localized to the level of the left-sided His fibers (left intrahisian) or left bundle branch. Patients with ventricular activation preceded by Purkinje potentials were categorized as having intact Purkinje activation. A total of 88 left septal conduction recordings were analyzed in 85 patients: 72 LBBB block pattern and 16 controls (narrow QRS, n=11; right bundle-branch block, n=5). Among patients with LBB block pattern, CCB within the proximal left conduction system was observed in 64% (n=46) and intact Purkinje activation in the remaining 36% (n=26). Intact Purkinje activation was observed in all controls. The site of block in patients with CCB was at the level of the left His bundle in 72% and in the proximal left bundle branch in 28%. His bundle pacing corrected wide QRS in 54% of all patients with LBBB pattern and 85% of those with CCB (94% left intrahisian, 62% proximal left bundle-branch). No patients with intact Purkinje activation demonstrated correction of QRS with His bundle pacing. CCB showed better predictive value (positive predictive value 85%, negative predictive value 100%, sensitivity 100%) than surface ECG criteria for correction with His bundle pacing. Heterogeneous septal conduction was observed in patients with surface LBBB pattern, ranging from no discrete block to CCB. When block was present, we observed pathology localized within the left-sided His fibers (left intrahisian block), which was most amenable to corrective His bundle pacing by recruitment of latent Purkinje fibers. ECG criteria for LBBB incompletely predicted CCB, and intracardiac data might be useful in refining patient selection for resynchronization therapy.

Predicting response to cardiac resynchronization therapy: Use of strict left bundle branch block criteria.

Cardiac resynchronization therapy (CRT) reduces morbidity and mortality in heart failure with reduced ejection fraction (HFrEF). CRT efficacy is greater in left bundle branch block (LBBB). This study aimed to determine if strict LBBB criteria predict an improved QRS duration and left ventricular ejection fraction (LVEF) response after CRT. HFrEF patients who received a CRT device at a single quaternary center were included. Patients were divided into three groups based on baseline QRS morphology. Group 1 consisted of patients with strict LBBB. Group 2 had conventional LBBB, and group 3 had non-LBBB morphology. Outcomes assessed included change in QRS duration after CRT, change in LVEF, and all-cause mortality. In 231 patients, 56% of patients were in group 1, 29% were in group 2, and 15% were in group 3. Patients with strict LBBB had a significant reduction in QRS duration (-20.9±12.4ms) compared to conventional LBBB (6.7±19.4ms; P<0.0001) and non-LBBB (3.9±29.3ms; P<0.0001). Patients with strict LBBB had a significant increase in LVEF (19.5±10.2) compared to conventional LBBB (5.3±12.6; P<0.0001) and non-LBBB (-1.3±10.9; P<0.0001). There was moderate negative correlation between changes in QRS duration and LVEF (correlation coefficient=-0.63, P<0.0001). Strict LBBB criteria were associated with a significant reduction in mortality compared to conventional LBBB (odds ratio 0.49, 95% confidence interval 0.24 to 0.99; P=0.046). Strict LBBB predicted a reduction in QRS duration and an increase in LVEF compared to conventional LBBB and non-LBBB morphology in patients with HFrEF who received CRT.

Automatic diagnosis of strict left bundle branch block using a wavelet-based approach.

Patients with left bundle branch block (LBBB) are known to have a good clinical response to cardiac resynchronization therapy. However, the high number of false positive diagnosis obtained with the conventional LBBB criteria limits the effectiveness of this therapy, which has yielded to the definition of new stricter criteria. They require prolonged QRS duration, a QS or rS pattern in the QRS complexes at leads V1 and V2 and the presence of mid-QRS notch/slurs in 2 leads within V1, V2, V5, V6, I and aVL. The aim of this work was to develop and assess a fully-automatic algorithm for strict LBBB diagnosis based on the wavelet transform. Twelve-lead, high-resolution, 10-second ECGs from 602 patients enrolled in the MADIT-CRT trial were available. Data were labelled for strict LBBB by 2 independent experts and divided into training (n = 300) and validation sets (n = 302) for assessing algorithm performance. After QRS detection, a wavelet-based delineator was used to detect individual QRS waves (Q, R, S), QRS onsets and ends, and to identify the morphological QRS pattern on each standard lead. Then, multilead QRS boundaries were defined in order to compute the global QRS duration. Finally, an automatic algorithm for notch/slur detection within the QRS complex was applied based on the same wavelet approach used for delineation. In the validation set, LBBB was diagnosed with a sensitivity and specificity of Se = 92.9% and Sp = 65.1% (Acc = 79.5%, PPV = 74% and NPV = 89.6%). The results confirmed that diagnosis of strict LBBB can be done based on a fully automatic extraction of temporal and morphological QRS features. However, it became evident that consensus in the definition of QRS duration as well as notch and slurs definitions is necessary in order to guarantee accurate and repeatable diagnosis of complete LBBB.

The 43rd International Society for Computerized Electrocardiology ECG initiative for the automated detection of strict left bundle branch block

The presence of left bundle branch block (LBBB) is an important predictor of benefit from cardiac resynchronization therapy (CRT). New “strict” electrocardiographic (ECG) criteria for LBBB have been shown to better predict benefit from CRT. The “strict” LBBB criteria include: QRS duration ≥140 ms (men) or ≥130 ms (women), QS- or rS-configurations of the QRS complex in leads V1 and V2, and mid-QRS notching or slurring in ≥2 of leads V1, V2, V5, V6, I and aVL. The “strict” LBBB criteria are not regularly used and most hospital automated ECG systems and physicians still use more conventional LBBB criteria. As part of the 43rd International Society for Computerized Electrocardiology (ISCE) meeting, we conducted an initiative on the automated detection of “strict” LBBB where industry and academic investigators could present their algorithm results on digital 12-lead ECGs with varying QRS morphologies from the MADIT-CRT trial (300 training and 302 test set ECGs that were manually adjudicated for “strict” LBBB presence). The results revealed a 64–82% accuracy, 48–76% sensitivity and 46–87% specificity for automated “strict” LBBB detection from 7 participants. Most mismatches were likely attributed to differences in detection and absence of specific definitions for notches and slurs while differences in QRS duration and S-waves in leads V1 and V2 were less problematic. The full unblinded training and test datasets including all ECG signals are being made available through the Telemetric and Holter ECG Warehouse (THEW) for further exploration.

Cardiac resynchronization therapy response in heart failure patients with different subtypes of true left bundle branch block

Left bundle branch block (LBBB) configuration has been described as a predictor of response to cardiac resynchronization therapy (CRT). We investigated whether different subtypes of true LBBB configuration could help select patients with better response and clinical outcome. This retrospective study included 198 consecutive LBBB patients implanted with a CRT. True LBBB was defined using the Strauss and the Predict study criteria. Echocardiographic response was evaluated by the reduction in left ventricular end-systolic volume (LVESV) and the increase in left ventricular ejection fraction (LVEF). Clinical response was defined as an improvement in one category of the NYHA functional class. Patients with true LBBB had a greater improvement in both LVESV reduction (median = - 27.6%, interquartile range = [- 4.9, - 50.1]) and LVEF increase (median 10.8 ± 10) than those with non-true LBBB (- 19.7%, [16.7, - 48.0]) p = 0.04 and 5.1 ± 10, p = 0.03, respectively. No differences were exhibited between true LBBB Strauss group (- 26.7%, [- 11.0, - 46.9]) and true LBBB Predict group (- 26.6%, [- 15.9, - 39.4]). There were no statistically significant differences in the percentage of patients with clinical response, assessed by NYHA improvement, among all groups. In the Cox model for death, age, ischemic etiology, and ΔLVESV were independent predictors of mortality. True LBBB (Strauss + Predict) patients had a trend towards lower mortality than non-true LBBB [HR = 0.55, 95% CI = (0.22-1.15)], p = 0.08. In the Cox model for HF hospitalization, age, sex male, prior LVEF, and ΔLVESV were independent predictors. True LBBB (Strauss + Predict) patients had a significantly lower risk of developing HF hospitalization than those with non-true LBBB [0.45 (0.21-0.90)], p = 0.029. Patients with true LBBB, either Strauss or Predict criteria, had greater echocardiographic response and lower incidence of HF hospitalization than non-true LBBB when implanted with CRT.

Validation of an automatic diagnosis of strict left bundle branch block criteria using 12-lead electrocardiograms.

Strict left bundle branch block (LBBB) criteria were recently proposed to identify LBBB patients to benefit most from cardiac resynchronization therapy (CRT). The aim of our study was to automate identification of strict LBBB in order to facilitate its broader application. We developed a series of algorithms to automatically detect and measure parameters required for strict LBBB criteria and proposed a definition of QRS notch detection. The algorithms were developed using training (n=20) and validation (n=592) sets consisting of signal-averaged 12-lead ECGs (1,000Hz sampling) recorded from 612 LBBB patients from Multicenter Automatic Defibrillator Implantation Trial-CRT. Four trained clinicians independently performed adjudication on 148 different ECGs for comparing automatic and manually adjudicated results, in addition to 13 ECGs for evaluation of intraobserver variability and 32 ECGs for interobserver variability. We assessed the performance of the automated algorithms using manually adjudicated ECGs as references. Overall sensitivity and specificity for detecting strict LBBB were 95% and 86%, respectively. The mean absolute deviation (MAD) of QRS duration and notch/slur locations for the automated method versus the manual method was below 1ms, and MAD values were lower than 2ms for interobserver and intraobserver variability. Sensitivity and specificity for detecting notch and slur locations were 87% and 96% for notches and 78% and 90% for slurs using the automatic method. In addition 95% and 93% agreements for notches and 90% and 88% agreements for slurs were reached for intra- and interobserver. The proposed algorithms automatically measure QRS features for the diagnosis of strict LBBB. Our study shows good performance in reference to manual results.

Prevalence of true left bundle branch block in current practice of cardiac resynchronization therapy implantation.

Accurate selection of patients with left bundle branch block (LBBB) may help increasing response to cardiac resynchronization therapy (CRT). There is no agreement on LBBB definition. The aim of the study was to investigate the prevalence of 'true-LBBB' according to Strauss in patients undergoing CRT. The study population included 414 consecutive patients (71.9% men; mean age 69.7 ± 9.6 years), who underwent CRT according to 2010 European Society of Cardiology (ESC) guidelines. Patients were classified into three groups: traditional LBBB according to American Heart Association, LBBB according to Strauss and intraventricular conduction delay (IVCD). Subsequently, they were re-classified into classes of recommendations, according to the current 2013 ESC Guidelines. Traditional LBBB was recorded in 229 patients (55%), an LBBB according to Strauss in 153 (37%) and an IVCD in 32 (8%). Patients with an LBBB according to Strauss showed a significantly more prolonged QRS duration (P < 0.001), greater baseline end-systolic and end-diastolic volumes (P = 0.011 and P = 0.013, respectively) compared with those with IVCD. The prevalence of mid-QRS notching in at least two contiguous leads was 100% in LBBB according to Strauss; 24% in traditional LBBB and 21.9% in IVCD (P < 0.001). At multivariate analysis, PR interval less than 200 ms and QRS of at least 150 ms were independent predictors of mid-QRS notching [odds ratio (OR) 1.78; 95% confidence interval (95% CI) 1.10-2.88; P = 0.02 and OR 2.88; 95% CI 1.80-4.62;P < 0.0001]. Applying stricter criteria for LBBB according to Strauss, a significant reduction in Class I recommendation and an increase in Class II was observed (90.1 vs. 37%; P < 0.0001 and 9.9 vs. 63%; P < 0.0001). Applying stricter criteria, only 37% of patients undergoing CRT showed a true-LBBB according to Strauss. Accurate identification of true-LBBB may have a potential additional value in better selecting patients.

The electrocardiographic characteristics of septal flash in patients with left bundle branch block.

In patients with systolic heart failure and left bundle branch block (LBBB), septal flash (SF) movement has been described by echocardiography. We evaluated the prevalence of SF in LBBB and non-LBBB patients and evaluated whether specific electrocardiographic (ECG) characteristics within LBBB are associated with the presence of SF on echocardiography. One hundred and four patients with probable LBBB on standard 12-lead ECG were selected, 40 patients with non-LBBB served as controls. Left bundle branch block and non-LBBB were defined, according to the most recent guidelines. The presence of SF was assessed by echocardiography. Strict LBBB criteria were met in 93.3% of the patients. Septal flash was present in 45.2% of LBBB patients and was not present in non-LBBB patients. This was more prevalent in patients without anterior ischaemic cardiomyopathy (ICMP) compared with those with anterior ICMP (P = 0.008). The duration of QRS was longer in SF patients compared with that of non-SF patients (P < 0.05). The presence of a mid-QRS notching inmore than two consecutive leads was a good predictor for the presence of SF (P = 0.01), and when combined with an absent R-wave in lead V1, the presence of SF is very likely (P = 0.001). Our data show that SF is present in 45.2% of LBBB patients, whereas it was absent in patients with non-LBBB. Patients with SF fulfilled more LBBB criteria compared with LBBB patients without SF. Our findings raise the provocative question of whether the presence of SF identifies patients with 'true LBBB' and whether this echocardiographic finding might be considered as a selection parameter in cardiac resynchronization therapy.

A study of clinical profile and etiology of left bundle branch block

Background: Left bundle branch block (LBBB) is a quite common disorder associated with a three to four fold increase in cumulative cardiovascular mortality. Although risk is especially increased for LBBB when accompanied an organic heart disease, it has been reported that mortality is also high in isolated LBBB. Objective: To study clinical profile and etiology of left bundle branch block Methods: The present cross sectional analytical study was carried out among 100 cases of left bundle branch block attending the outpatient department. All cases fulfilling ECG criteria of LBBB were included in the present study. The various criteria for LBBB were QRS duration > 120 msec, broad, notched R waves in lateral precordial leads (V5 and V6) and usually leads I and AVL, Small or absent r waves in right precordial leads (V1 and V2) followed by deep S waves, Absent septal q waves in left sided leads and prolonged intrinsicoid deflection (> 60 msec) in V5 and V6. Results: Mean age in low LVEF group was 56.6+9.92 years and in the normal LVEF group it was 53.27+10.71 years. Males predominated in both the groups. In cases of LBBB with valvular heart disease there was no significant difference between two groups of LVEF Conclusion: Hypertension and ischemic heart disease contributed to maximum cases of LBBB. Patient of LBBB with coronary artery disease and dilated cardiomyopathy have low LVEF while the patients of idiopathic LBBB had normal ejection fraction.

Mechanistic insights into the benefits of multisite pacing in cardiac resynchronization therapy: The importance of electrical substrate and rate of left ventricular activation

Multisite pacing (MSP) of the left ventricle is proposed as an alternative to conventional single-site LV pacing in cardiac resynchronization therapy (CRT). Reports on the benefits of MSP have been conflicting. A paradigm whereby not all patients derive benefit from MSP is emerging. We sought to compare the hemodynamic and electrical effects of MSP with the aim of identifying a subgroup of patients more likely to derive benefit from MSP. Sixteen patients with implanted CRT systems incorporating a quadripolar LV pacing lead were studied. Invasive hemodynamic and electroanatomic assessment was performed during the following rhythms: baseline (non-CRT); biventricular (BIV) pacing delivered via the implanted CRT system (BIV(implanted)); BIV pacing delivered via an alternative temporary LV lead (BIV(alternative)); dual-vein MSP delivered via 2 LV leads; MultiPoint Pacing delivered via 2 vectors of the quadripolar LV lead. Seven patients had an acute hemodynamic response (AHR) of <10% over baseline rhythm with BIV(implanted) and were deemed nonresponders. AHR in responders vs nonresponders was 21.4% ± 10.4% vs 2.0% ± 5.2% (P < .001). In responders, neither form of MSP provided incremental hemodynamic benefit over BIV(implanted). Dual-vein MSP (8.8% ± 5.7%; P = .036 vs BIV(implanted)) and MultiPoint Pacing (10.0% ± 12.2%; P = .064 vs BIV(implanted)) both improved AHR in nonresponders. Seven of 9 responders to BIV(implanted) had LV endocardial activation characterized by a functional line of block during intrinsic rhythm that was abolished with BIV pacing. All these patients met strict criteria for left bundle branch block (LBBB). No nonresponders exhibited this line of block or met strict criteria for LBBB. Patients not meeting strict criteria for LBBB appear most likely to derive benefit from MSP.

New strict left bundle branch block criteria reflect left ventricular activation differences

AimsPacing lead electrical delays and strict left bundle branch block (LBBB) criteria were assessed against cardiac resynchronization therapy (CRT) outcome. MethodsForty-nine patients with LBBB and QRS duration >130 milliseconds underwent CRT-implantation. Sensed right ventricular to left ventricular electrical delay (RV-LV-IED) was measured. Response to CRT was defined as ≥15% decrease in left ventricular end-systolic volume. ResultsEighteen of 20 (90%) patients with non-ischemic dilated cardiomyopathy (DCM) and 18 of 29 (62%) with ischemic heart disease (IHD) responded to CRT, p<0.01. When applying new strict ECG criteria subsequent rates of response in DCM were 18/19 (95%) and in IHD of 18/23 (78%) respectively, p<0.05 between IHD groups. Correspondingly, RV-LV-IED was longer in DCM compared to IHD patients and in responders compared to non-responders, p=0.017 and p<0.001, respectively. ConclusionInterventricular electrical delay predicts left ventricular remodeling after CRT and new, strict ECG criteria of LBBB are superior in predicting remodeling.

Electrocardiographic markers of left ventricular systolic dysfunction in patients with left bundle branch block.

Although some patients with left bundle branch block (LBBB) have structural heart diseases, some patients with LBBB have "normal hearts". The electrocardiography (ECG) criteria of LBBB in reduced left ventricular ejection fraction (LVEF) have not been defined completely. The main purpose of this study was to differentiate patients with reduced LVEF from patients with normal left ventricular systolic function simply by analysing 12-lead ECG. Subjects admitted to our hospital with LBBB in their ECG were included in the study. The patients were categorised according to their left ventricular systolic function as group 1 (LVEF ≥ 50%) and group 2 (LVEF < 50%). Duration of the QRS complex, residual conduction of left bundle branch, and concordance/discordance of T waves in leads V5, V6, or D1 were recorded. The ECG findings of the two groups were compared. One hundred consecutive patients with LBBB were included in the study (male/female: 56/44, age: 66 ± 15 years). In the whole group, there were 35 patients with normal left ventricular systolic function (LVEF ≥ 50%), and 65 patients had LVEF below 50%. 80% of male patients with LBBB and 45% of female patients with LBBB had their LVEF below 50% (p < 0.001). Mean QRS durations of group 1 and group 2 were 132 ± 10 ms vs. 152 ± 22 ms, respectively (p < 0.001). The QRS duration of 140 ms was found to be the cut-off value to differentiate group 1 from group 2, with sensitivity and specificity of 72% and 75%, respectively. Twenty-one per cent of patients in group 1 and 69% in group 2 had discordant LBBB (p < 0.001). Residual conduction of left bundle branch was more frequent in group 2 (29% in group 1 vs. 52% in group 2, p = 0.03). Male gender, QRS duration greater than 140 ms, discordant LBBB, and residual conduction in the left bundle branch seem to be markers of reduced LVEF in patients with LBBB.

Prevalence of manual Strauss LBBB criteria in patients diagnosed with the automated Glasgow LBBB criteria

IntroductionAbout one-third of patients undergoing cardiac resynchronization therapy because of left bundle branch block (LBBB) and heart failure do not improve. Strauss et al. have developed strict criteria to more accurately define complete LBBB in this patient group. The aim of this study was to investigate the prevalence of the manual application of the Strauss criteria for LBBB (QRS≥140ms in men, ≥130ms in women, along with mid-QRS notching/slurring) in consecutive patients who have been diagnosed with LBBB by the automated Glasgow criteria (QRS≥120ms). MethodIn 158 consecutive patients (78 females) diagnosed with LBBB according to the automated Glasgow criteria, the manual Strauss criteria were applied. Results & conclusionA majority of patients (87%) diagnosed with LBBB using the Glasgow criteria were positive for the Strauss criteria. In 70% (13/20) of the cases of disagreement the reason for disagreement was short QRS duration.

Vectorcardiographic QRS area as a novel predictor of response to cardiac resynchronization therapy

BackgroundQRS duration and left bundle branch block (LBBB) morphology are used to select patients for cardiac resynchronization therapy (CRT). We investigated whether the area of the QRS complex (QRSAREA) on the 3-dimensional vectorcardiogram (VCG) can improve patient selection. MethodsVCG (Frank orthogonal lead system) was recorded prior to CRT device implantation in 81 consecutive patients. VCG parameters, including QRSAREA, were assessed, and compared to QRS duration and morphology. Three LBBB definitions were used, differing in requirement of mid-QRS notching. Responders to CRT (CRT-R) were defined as patients with ≥15% reduction in left ventricular end systolic volume after 6months of CRT. ResultsFifty-seven patients (70%) were CRT-R. QRSAREA was larger in CRT-R than in CRT non-responders (140±42 vs 100±40 μVs, p<0.001) and predicted CRT response better than QRS duration (AUC 0.78 vs 0.62, p=0.030). With a 98μVs cutoff value, QRSAREA identified CRT-R with an odds ratio (OR) of 10.2 and a 95% confidence interval (CI) of 3.4 to 31.1. This OR was higher than that for QRS duration >156ms (OR=2.5; 95% CI 0.9 to 6.6), conventional LBBB classification (OR=5.5; 95% CI 0.9 to 32.4) or LBBB classification according to American guidelines (OR=4.5; 95% CI 1.6 to 12.6) or Strauss (OR=10.0; 95% CI 3.2 to 31.1). ConclusionQRSAREA is an objective electrophysiological predictor of CRT response that performs at least as good as the most refined definition of LBBB. Condensed abstractIn 81 candidates for cardiac resynchronization therapy (CRT) we measured the area of the QRS complex (QRSAREA) using 3-dimensional vectorcardiography. QRSAREA was larger in echocardiographic responders than in non-responders and predicted CRT response better than QRS duration and than simple LBBB criteria. QRSAREA is a promising electrophysiological predictor of CRT response.