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

Electrocardiographic predictors of echocardiographic response in cardiac resynchronization therapy: Update of an old story

BACKGROUND

A better selection of patients with left bundle branch block (LBBB) might increase the response to cardiac resynchronization therapy (CRT). The aim of the study was to investigate the association between the Strauss criteria, absence of S wave in V₅-V_6, the Selvester score and response to CRT.

METHODS AND RESULTS

The retrospective analysis included all consecutive patients having undergone implantation of biventricular defibrillators in primary prevention between 2018 and 2020. The final analysis included 236 patients (mean age 69.7 ± 9.9; 77.5% of males). The Strauss criteria were significantly associated with CRT response (p < 0.01) with a sensitivity of 71.3% and specificity of 64.1%. The Strauss criteria along with the absence of S wave in V₅ and V₆ showed a sensitivity of 56.7%, a specificity of 82.6% and a positive predictive value of 90.5%. The Selvester score was significantly and inversely associated with CRT response (OR 0.818, 95% CI 0.75-0.89; p < 0.001). The multivariable model showed that left ventricular ejection fraction (LVEF) and QRS duration (≥140 ms in males and ≥ 130 ms in females) were independently associated with CRT response (respectively OR 0.92, CI 95% 0.86-0.98, p = 0.01 and OR 3.70, CI 95% 1.12-12.21, p = 0.03).

CONCLUSIONS

Strauss criteria, especially in association with absence of S wave in V₅ and V₆, were able to increase specificity and positive predictive value for predicting CRT response. The Selvester score was inversely associated with CRT response. Finally, LVEF and QRS duration were independently associated with echocardiographic response to CRT.

Prevention of non-response to cardiac resynchronization therapy: points to remember

Cardiac resynchronization therapy (CRT) is an important and effective therapy for end-stage heart failure. Non-response to CRT is one of the main obstacles to its application in clinical practice. There is no uniform consensus or definition of CRT “response.” Clinical symptoms, ventricular remodeling indices, and cardiovascular events have been reported to be associated with non-responders. To prevent non-response to CRT, three aspects should be thoroughly considered: preoperative patient selection, electrode implantation, and postoperative management. Preoperative selection of appropriate patients for CRT treatment is an important step in preventing non-response. Currently, the CRT inclusion criteria are mainly based on the morphology of QRS waves in deciding ventricular dyssynchrony. Echocardiography and cardiac magnetic resonance are being explored to predict nonresponse to CRT. The location of left ventricular electrode implantation is a current hot spot of research; it is important to identify the location of the latest exciting ventricular segment and avoid scars. Cardiac magnetic resonance and ultrasonic spot tracking are being progressively developed in this field. Some new techniques such as His Bundle pacing, endocardial electrodes, and novel sensors are also being investigated. Postoperative management of patients is another essential step towards preventing non-response; it mainly focuses on the treatment of the disease itself and CRT program control optimization. CRT treatment is just one part of the overall treatment of heart failure, and multidisciplinary efforts are needed to improve the overall outcome.

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

BACKGROUND

Left bundle branch pacing (LBBP) has been suggested as an alternative means to deliver cardiac resynchronization therapy (CRT).

HYPOTHESIS

LBBP may deliver resynchronization therapy along with an advantage over traditional biventricular (BiV) pacing in clinical outcomes.

METHODS

Heart 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.

RESULTS

Twenty-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.

CONCLUSIONS

LBBP-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.

Role of electrocardiographic and echocardiographic types of left bundle branch block in prediction of response to cardiac resynchronization therapy

AIM

To assess the value of the complex analysis of electrocardiographic (ECG) variants and echocardiographic (echo) manifestation of left bundle branch block (LBBB) in predicting the success of cardiac resynchronization therapy (CRT).

MATERIALS AND METHODS

The study included 39 patients (mean age 61.49±9.0 years) on sinus rhythm with LBBB, QRS duration ≥130 ms, left ventricular ejection fraction (LVEF) ≤35%, heart failure (HF) NYHA II-IV despite optimal pharmacological therapy during 3 month. All patients had undergone CRT-D implantation. Depending on presence or absence of ECG-criteria, proposed by D.G. Strauss et al., patients were divided into 2 groups: 1 group - strict LBBB, proposed by D.G. Strauss et al. (n=29) and 2 group - other patients (n=10). In addition to standard echocardiography, global longitudinal 2-dimensional strain (GLS) and LBBB contraction pattern have been performed initially and in 6 months after implantation. Response to CRT was defined as decrease in LV end-systolic volume by &gt;15% after 6 months of follow-up.

RESULTS

Typical LBBB echo contraction pattern was detected in 25 patients (64% of all included). These patients had more pronounced longitudinal dissynchrony and a more expressed global longitudinal strain before CPT-D implantation (p&lt;0.05). 27 patients (69% of all included) were included in the &quot;response&quot; group, the remaining 12 patients (31% of all included) - the &quot;non-response&quot; group. In the &quot;response&quot; group the morphology of the QRS complex was significantly more likely to meet the criteria, proposed by D.G. Strauss et al., than other variants (23 vs. 6, respectively, p=0.02), and the echo contraction pattern of this patients more often corresponded to &quot;typical&quot; LBBB (24 vs. 1, p=0.001). All patients, who had the ECG criteria, proposed by D.G. Strauss et al., and echo &quot;typical&quot; LBBB contraction pattern, responded on CPT. Moreover, the proportion of these patients in the &quot;response&quot; group was rather high - 81.5% (22 of 27 patients).

CONCLUSION

ECG criteria LBBB, proposed by D.G. Strauss et al., identify patients with delayed transseptal interventricular conduction due to complete LBBB, what is a good target for CPT. Evaluation of the echo contraction pattern based on the definition of longitudinal myocardial deformation by means of a two-dimensional strand technology allows predicting the success of CPT in patients with LBBB. Patients with «typical» LBBB contraction pattern show more pronounced global longitudinal strain and larger longitudinal dissynchrony compared with other patients, and it explains their better response to CPT. Complex analysis of strict LBBB ECG criteria and echo contraction pattern are promising parameters in predicting beneficial response to CRT in patients with HF.

Improved patient selection for cardiac resynchronization therapy by normalization of QRS duration to left ventricular dimension

Aims

This study evaluates the relative importance of two components of QRS prolongation, myocardial conduction velocity and travel distance of the electrical wave front (i.e. path length), for the prediction of acute response to cardiac resynchronization therapy (CRT) in left bundle branch block (LBBB) patients.

Methods and results

Thirty-two CRT candidates (ejection fraction <35%, LBBB) underwent cardiac magnetic resonance (CMR) imaging to provide detailed information on left ventricular (LV) dimensions. Left ventricular end-diastolic volume (LVEDV) was used as a primary measure for path length, subsequently QRSd was normalized to LV dimension (i.e. QRSd divided by LVEDV) to adjust for conduction path length. Invasive pressure-volume loop analysis at baseline and during CRT was used to assess acute pump function improvement, expressed as LV stroke work (SW) change. During CRT, SW improved by +38 ± 46% (P < 0.001). The baseline LVEDV was positively related to QRSd (R = 0.36, P = 0.044). Despite this association, a paradoxical inverse relation was found between LVEDV and SW improvement during CRT (R = -0.40; P = 0.025). Baseline unadjusted QRSd was found to be unrelated to SW changes during CRT (R = 0.16; P = 0.383), whereas normalized QRSd (QRSd/LVEDV) yielded a strong correlation with CRT response (R = 0.49; P = 0.005). Other measures of LV dimension, including LV length, LV diameter, and LV end-systolic volume, showed similar relations with normalized QRSd and SW improvement.

Conclusion

Since normalized QRSd reflects myocardial conduction properties, these findings suggest that myocardial conduction velocity rather than increased path length mainly determines response to CRT. Normalizing QRSd to LV dimension might provide a relatively simple method to improve patient selection for CRT.

Optimizing Cardiac Resynchronization Therapy: an Update on New Insights and Advancements

PURPOSE OF REVIEW

This review focuses on the current advancements in optimizing patient response to cardiac resynchronization therapy (CRT).

RECENT FINDINGS

It has been well known that not every patient will derive benefit from CRT, and of those that do, there are varying levels of response. Optimizing CRT begins well before device implant and involves appropriate patient selection and an understanding of the underlying substrate. After implant, there are different CRT device programming options that can be enabled to help overcome barriers as to why a patient may not respond. Given the multifaceted components of optimizing CRT and the complex patient population, multi-subspecialty clinics have been developed bringing together specialists in heart failure, electrophysiology, and imaging. Data as to whether this results in better response rates and outcomes shows promise.

Magnetic Resonance Imaging Correlates of Left Bundle Branch Disease in Patients With Nonischemic Cardiomyopathy

The pathologic correlates of intraventricular conduction delays in patients with nonischemic cardiomyopathy (NIC) have been scarcely investigated. We assessed left ventricular (LV) structural, functional, and tissue abnormalities associated with intraventricular conduction left bundle disease (LBD), including left anterior hemiblock or complete left bundle branch block, in a cohort of patients with NIC submitted to cardiovascular magnetic resonance. Twelve-lead electrocardiogram and cardiovascular magnetic resonance were performed in 196 consecutive patients with NIC. The presence and extent of myocardial fibrosis was evaluated with late gadolinium enhancement (LGE) technique. Compared with normal intraventricular conduction patients, those with LBD were older (66 vs 59 years, p = 0.001), had greater LV volumes (p = 0.035 for end-diastolic and p = 0.009 for end-systolic volume) and mass (p = 0.034), and showed lower LV ejection fraction (33% vs 40%, p = 0.008). LGE was observed more commonly in LBD than in normal intraventricular conduction patients and was more often located in the ventricular septum (p < 0.001). On multivariate analysis, septal LGE was independently associated with a higher likelihood of LBD (odds ratio 6.1, 95% confidence interval 2.9 to 12.7, p < 0.001), even after correction for LV volumes, mass, and ejection fraction. In conclusion, in NIC, the presence of LBD is associated with worse LV remodeling and dysfunction than normal intraventricular conduction. Septal fibrosis yielded a 6-fold greater likelihood of LBD, independently of the degree of LV dilatation and systolic dysfunction.

Stricter criteria for left bundle branch block diagnosis do not improve response to CRT

BACKGROUND

Cardiac resynchronization therapy (CRT) has proved to be effective in patients with heart failure and left bundle branch block (LBBB). Recently, new electrocardiography criteria have been proposed for the diagnosis of LBBB. These criteria are stricter than the current American Heart Association (AHA) criteria. We assessed the rate of echocardiographic response to CRT in patients with traditional LBBB versus patients who met the new criteria (strict LBBB).

METHODS

Consecutive patients undergoing CRT were enrolled in the CRT MORE registry. Patients with no-LBBB QRS morphology according to AHA criteria, atrial fibrillation, right bundle branch block, and right ventricular pacing were excluded. Strict LBBB was defined as: QRS ≥ 140 ms for men and ≥130 ms for women, QS or rS in V1-V2, mid-QRS notching or slurring in ≥2 contiguous leads. Patients showing a relative decrease of ≥15% in left ventricular end-systolic volume (LVESV) at 12 months were defined as responders.

RESULTS

Among 335 patients with LBBB, 131 (39%) had strict LBBB. Patients with and without strict LBBB showed comparable baseline characteristics, except for QRS duration (166 ± 20 ms vs 152 ± 25 ms, P < 0.001). On 12-month evaluation, 205 patients (61%) were responders; 85 of 131 (65%) had strict LBBB and 120 of 204 (59%) had traditional LBBB (P = 0.267). On multivariate analysis, a history of atrial fibrillation, larger LVESV, and the presence of mid-QRS notching in ≥1 lead (odds ratio 2.099; 95% confidence interval 1.061-4.152, P = 0.033) were independently associated with echocardiographic response.

CONCLUSION

Stricter definition of LBBB did not improve response to CRT in comparison to the current AHA definition.

Coronary sinus activation patterns in patients with and without left bundle branch block undergoing electroanatomic mapping system-guided cardiac resynchronization therapy device implantation

BACKGROUND

Implantation of the left ventricular (LV) lead in segments with delayed electrical activation may improve response to cardiac resynchronization therapy (CRT).

OBJECTIVE

The purpose of this study was to evaluate the amount and regional distribution of LV electrical delay (LVED) in patients with or without left bundle branch block (LBBB).

METHODS

We enrolled 60 patients who underwent electroanatomic mapping system-guided CRT device implantation. Activation mapping of the coronary sinus (CS) branches was performed using an insulated guidewire. LVED was defined as the interval between the beginning of the QRS complex on the surface electrocardiogram (ECG) and the local electrogram and expressed in milliseconds or as percentage of the total QRS duration (LVED%).

RESULTS

Forty-three patients showed a LBBB and 17 a non-LBBB electrocardiographic pattern. A total of 148 CS branches (mean 2.5 per patient; range 2-4 per patient) were mapped. Patients with LBBB showed higher maximum LVED (135 ms [108-150 ms] vs 100 ms [103-110 ms]; P < .001) and LVED% (86% [79%-89%] vs 72% [54%-80%]; P < .001) than did patients without LBBB. The maximum LVED was recorded in mid-basal anterolateral or inferolateral LV segments (traditional CRT targets), significantly more often in patients with LBBB than in patients without LBBB (85% vs 59%; P = .02). The number of CS branches showing LVED >50% of the total QRS duration, >75% of the total QRS duration, and >85 ms was significantly higher in patients with LBBB than in patients without LBBB.

CONCLUSION

Patients without LBBB showed lower LVED and more heterogeneous electrical activation of the CS than did patients with LBBB. This finding may contribute to a lower rate of response to CRT of patients without LBBB and suggests the use of activation mapping to guide LV lead placement.