Left Bundle Branch Block Research Articles

Clinical significance and prognostic value of right bundle branch block in permanent pacemaker patients.

In patients undergoing pacemaker implantation with no prior history of heart failure (HF), the presence of left bundle branch block (LBBB) has been identified as an independent predictor of HF-related death or hospitalization, while the prognostic significance of right bundle branch block (RBBB) remains uncertain. We aimed to assess the long-term risk of all-cause mortality in patients with a standard indication for permanent pacing and normal or moderately depressed left ventricular function when RBBB is detected at the time of implantation. We retrospectively enrolled 1348 consecutive patients who had undergone single- or dual-chamber pacemaker implantation at the study center, from January 1990 to December 2022. Patients with a left ventricular ejection fraction ≤35% or a prior diagnosis of HF were excluded. The baseline 12-lead electrocardiogram revealed an RBBB in 241 (18%) and an LBBB in 98 (7%) patients. During a median follow-up of 65 [25th-75th percentile: 32-117] months, 704 (52%) patients died. The combined endpoint of cardiovascular death or HF hospitalization was reached by 173 (13%) patients. On multivariate analysis, RBBB was confirmed as an independent predictor of death [hazard ratio, 1.33; 95% confidence interval (CI), 1.09-1.63; P = 0.005]. However, when considering the combined endpoint of cardiovascular death and HF hospitalization, this endpoint was independently associated with LBBB (hazard ratio, 2.13; 95% CI, 1.38-3.29; P < 0.001), but not with RBBB. In patients with standard pacemaker indications and normal or moderately depressed left ventricular function, the presence of basal RBBB was an independent predictor of mortality. However, it was not associated with the combined endpoint of cardiovascular death and HF hospitalization.

Impact of left bundle branch block morphology in predicting response to left bundle branch area pacing for cardiac resynchronization therapy

Abstract Background Left bundle branch area pacing (LBBAP) is a novel pacing technique with an emerging role in resynchronization therapy [1-4]. QRS morphology has shown to significantly influence cardiac resynchronization therapy (CRT) response [5-6]. Purpose The aim of this study was to assess whether different left bundle branch block (LBBB) definitions are associated with response to LBBAP resynchronization therapy. Methods 40 consecutive CRT candidates with previously unsuccessful biventricular (BiV) pacing or in which effective CRT could not be achieved with BiV pacing based on anatomical or functional criteria were selected for this study. Both ischemic and non-ischemic heart failure (HF) patients were included. Patients were divided into two groups according to LBBB morphology. Group 1 included 20 patients (45% ischemic HF) with strict LBBB definition according to Strauss criteria [7], while 20 patients in Group 2 (55% ischemic HF) had conventional LBBB morphology. Response to CRT was defined for (1) reduction in QRS duration; (2) increase in left ventricular ejection fraction (LVEF) ≥ 5% and (3) decrease in left ventricular end systolic volume (LVESV) ≥ 15%. Results LBBAP was successfully achieved in all patients (mean age: 72.0 years; male: 29). The mean baseline QRS duration before implantation was 178.6±13.8 in the Group 1 and 170.8±29.4 in the Group 2, without a statistically significant difference. Over a mean follow-up of 5.6 months, LBBAP resulted in QRS narrowing in both groups, with a greater reduction in Group 1 (-40.6 ms) compared to Group 2 (-15.1 ms), (p 0.002). Pre-implantation ventricular systolic function did not show significant differences between the two groups, with a mean of 30.1±3.5% in the Strauss LBBB group and 31.0±6.0% in the conventional LBBB group. After implantation LVEF was 42.1±8.5 % in the true LBBB patients and 33.2±7.5 in the conventional LBBB group. Echocardiographic response was observed in 65% of patients with a statistically significant difference between Group 1 (90% of responders) and Group 2 (40% of responders), (p 0,001). HF etiology did not impact the response to LBBAP CRT. Conclusions Strict LBBB definition is associated to a greater electrocardiographic and echocardiographic response in patients receiving LBBAP CRT compared to conventional LBBB criteria.\

Retrograde Conduction in Left Bundle Branch Block: Insights From Left Bundle Branch Pacing.

Biventricular pacing is a well-established therapy for patients with heart failure (HF), left bundle branch block (LBBB) and left ventricular (LV) dysfunction. Left bundle branch pacing (LBBP) has emerged as an alternative to biventricular pacing. The aim of this study was to assess the retrograde conduction properties of the left bundle branch in patients with nonischemic cardiomyopathy and LBBB during LBBP and its clinical implications. Patients undergoing successful LBBP for nonischemic cardiomyopathy with LV ejection fraction (LVEF)≤35% and LBBB were included. Continuous recording of His potential was performed using a quadripolar catheter. Unidirectional block was defined as retrograde His bundle activation during LBBP with stimulus to His potential (SH) duration less than or equal to antegrade HV interval and bidirectional block as VH dissociation or SH duration greater than HV interval. HF hospitalization, ventricular arrhythmias, and mortality were documented. A total of 165 patients were included. The mean follow-up duration was 21.8 ± 13.1months. Bidirectional block (group I) was observed in 82% (n=136), and these patients were noted to have advanced HF stage and prolonged baseline QRS duration. Unidirectional block (group II) with intact retrograde conduction was observed in 18% (n=29) and was associated with narrow paced QRS duration and higher LVEF during follow-up. Super-response (LVEF≥50%) was observed in 54.4% (n=74) in group I compared with 73.3% (n=22) in group II (P=0.03). The OR for LVEF normalization was 4.1 (95%CI: 1.26-13.97; P=0.02), with unidirectional block compared with bidirectional block in patients with LBBB and LV dysfunction. Adverse clinical outcomes as measured by a composite of HF hospitalization, ventricular arrhythmias, and mortality were significantly higher in group I compared with group II (12.5% vs 0%; P=0.04). Bidirectional block in LBBB was characterized by advanced HF symptoms, while unidirectional block was associated with better clinical outcomes after cardiac resynchronization therapy by LBBP.

Electrophysiology-guided algorithm for patients with conduction abnormalities post TAVR: one-year follow-up

Abstract Introduction Transcatheter aortic valve replacement (TAVR) revolutionized the treatment of aortic stenosis [1]. Although TAVR is an effective treatment for AS patients, it is associated with high incidence of new-onset conduction disturbances and pacemaker implantations. The two most common conduction disturbances after TAVR are new onset left bundle branch block (LBBB) and high-degree atrioventricular block (HDAVB) [2]. While patients with HDAVB require a permanent pacemaker implantation (PPM), the management of LBBB is not completely established yet. According to the ESC 2021 guidelines, a PPM is indicated in patients with persistent HDAVB or new onset alternating BBB after TAVR. Yet, the recommendations regarding other conduction abnormalities are not well defined. In patients with persistent new onset LBBB, ambulatory continuous ECG monitoring or electrophysiology study (EPS) are recommended [3]. Purpose To evaluate the clinical outcomes of patients with conduction disorders after TAVR who were managed according to electrophysiology-guided algorithm (Figure 1), including mortality, late pacemaker’s implantations, and heart failure hospitalizations. Predictors of periprocedural LBBB and HDAVB were also assessed. Methods Retrospective population-based cohort study including all patients who developed new onset LBBB after TAVR at a tertiary University Medical Center from October 1, 2018, to December 31, 2022, and were managed according to specific electrophysiology-guided algorithm. Results The study cohort included 230 consecutive patients who underwent TAVR. Mean age was 80.3 and 56.5% were females (Figure 2). Twenty patients (8.7%) developed HDAVB and required a PPM, whereas 40 patients (17.4%) developed persistent LBBB. According to the algorithm, 8 patients (20%) with a QRS&amp;lt;130ms were discharged without PPM [group A], 20 patients (50%) with a QRS of 130-160ms underwent EPS, and 12 patients (30%) with a QRS&amp;gt;160ms [Group C] received a PPM. Among the EPS group: 9 patients (22.5%) with HV&amp;gt;65ms underwent PPM [group B2], while 11 patients with HV&amp;lt;65ms (27.5%) were discharged without PPM [group B1]. During a one-year follow-up only one patient required late PPM [group B1]. Mortality was higher among the subgroups with PPM [B2 and C] compared to the subgroups without a PPM [A and B1]: 4 vs. 1 patient accordingly. Conclusions The presented electrophysiology-guided algorithm for patients with persistent LBBB after TAVR appears safe and efficient, with a modest incidence of PPM (17.6% of the total cohort) during hospitalization and a minimal need for late PPM at one year follow-up. Importantly, there was no excess of mortality among patients who were discharged without a pacemaker implantation. Thus, we suggest that the presented algorithm may serve as a reliable strategy to distinguish between individuals with new onset persistent LBBB after TAVR who require PPM compared to those in whom a PPM can be safely avoided.

Predictors of responders to cardiac resynchronization therapy in patients with non-left bundle branch block with mid-wide QRS duration

Abstract Background Cardiac resynchronization therapy (CRT) is useful for patients with severe heart failure with dyssynchrony of left ventricular contraction, significantly reducing total mortality or heart failure rehospitalization. In patient with left bundle branch block (LBBB) or QRS duration (QRSd) ≥ 150 ms, CRT is a well-established therapy at guidelines in Japan and other countries. However, CRT may be more useful and effective in Asian patients with middle range wide QRSd, because of smaller body size than in the West. Few reports have shown the usefulness and efficacy of CRT in patients with non-LBBB and middle range wide QRS duration (mid-wide QRSd). Purpose To evaluate the predictors of CRT responders in heart failure patients with non LBBB and mid wide QRSd. Methods We retrospectively studied 174 consecutive patients who underwent a denovo CRT device implantation at two institutions between September 2013 and March 2023. Follow up echocardiography examination could be performed after 150 days postoperatively. CRT responders were defined as a decrease in left ventricular end systolic volume ≥15% on echocardiography. We plotted thereceiver operating characteristic (ROC) curve for predicting CRT responders. The area under the curve (AUC) was calculated to determine the best cut off value. Results A total of 34 patients with non LBBB and 120≤ QRSd &amp;lt;150 ms were enrolled in this study. Sixteen of 34 (47%) patients were the responders for CRT. There was no significant difference in gender between the responder and non responder groups (p=0.274). Non ischemic cardiomyopathy was more prevalent in the responder group (p=0.046). The ROC curve analysis confirmed that 0.809 was the better optimal cut off value of QRSd/left ventricular end diastolic volume (LVEDV) for predicting CRT responders (AUC = 0.688). The multivariate analysis demonstrated that QRSd/LVEDV was significantly associated with CRT responders [odds ratio (OR) 9.88, 95% confidence interval 1.51 64.90, p = 0.017]. Conclusion The corrected QRSd for heart size using LVEDV could be the independent predictor of CRT responders in Japanese patients with non LBBB and mid wide QRSd.

Feasibility and effectiveness of left bundle branch area pacing after TAVR: the single center experience

Abstract Introduction Transcatheter aortic valve replacement (TAVR) is a safe alternative to open-heart surgery in patients with symptomatic severe aortic stenosis and high surgical risk due to multiple comorbidities, advanced age, and severe left ventricle dysfunction. Due to anatomical considerations of the atrioventricular node, conduction abnormalities requiring the implantation of a pacemaker are common findings after TAVR. High-grade atrioventricular block and new-onset left bundle branch block (LBBB) are the most commonly reported conduction abnormalities after TAVR. Purpose The aim of our study was to assess the feasibility, success rates, and effectiveness of LBBAP in patients requiring pacing after TAVR. Methods A total of 302 patients underwent the TAVR procedure in our institution in the period from January 2022 to November 2023. In this cohort, 38 patients required ventricular pacing in the postoperative period. 16 patients who underwent permanent pacing using LBBAP were included in this observational study. Patients undergoing traditional right ventricular pacing biventricular pacing or leadless pacemaker implantation were excluded from the study. Results LBBAP was successfully performed in 16 patients (89%). 2 patients underwent conventional CRT implantation (1 cardiac resynchronization therapy pacemaker and 1 cardiac resynchronization therapy defibrillator) in order to severe calcification and presence of fibrotic tissue in the target area. The mean age was 60.5±2.74 years, and 10 patients (62.5%) were women. According to the patient’s medical history, 14 patients (84%) had hypertension; coronary artery disease – 2 (12.5%), 2 (12.5%) patients had atrial fibrillation and atrial flutter, and 7 (43.5%) patients had diabetes mellitus. The mean left ventricle ejection fraction (LVEF) was 46.2±14.7%. Interventricular septal thickness 11.8 ± 1.9 mm. Type of conduction diseases: Infranodal AV block and LBBB were present in 9 (56.5%) patients. 5 (31,25%) patients had persistent complete AV block and 2 (12,25%) had Mobitz II AV block. In 2 patients we observed congestive heart failure combined with LBBB. Pre-TAVR QRS morphology was normal in 15 (93%), and RBBB morphology in 1 (7%). The mean QRS duration at baseline was 105±20 ms. Pre-implant QRS duration 135±52 ms. The single-chamber pacemaker was implanted in 1 patient, dual-chamber pacemaker - 13 patients, and cardiac resynchronization therapy defibrillators in 2 patients. Procedural duration and fluoroscopy times were 105. ± 31.9 min and 18 ± 11 min, respectively. Conclusion Complete AV block and new-onset LBBB after TAVR is still an important issue. LBBB correction using conduction system pacing technology is an effective strategy for this type of patient. LBBAP is one of the most exciting developments in pacing therapy over the last few years. Long-term clinical outcomes and safety of physiological pacing data are limited and require further investigations

Impact of non-typical LBBB on CRT response

Abstract Introduction Cardiac resynchronization therapy (CRT) benefits have been established in patients with heart failure and reduced left ventricular ejection fraction (HFrEF) who have a broad QRS and remain symptomatic despite optimized medical therapy. Responders typically are female, with LBBB and broader QRS. It remains uncertain to what extent do patients with non-LBBB QRS complex morphology respond to CRT and also if there are differences among various types of intraventricular conduction delays. Purpose To evaluate the impact of non-typical left bundle branch block (LBBB) on reverser remodeling and clinical events. Methods Single center, observational, retrospective study including patients (pts) who implanted CRT in the context of HFrEF, from 2015 to 2020. Evaluation of QRS morphology analysis was conducted. CRT response was defined by a reduction of LVESV≥15% or an increase in LVEF≥10%. Predictors of CRT response were evaluated with Chi-square and Mann- Whitney analysis. Impact on reverse remodeling and clinical outcomes was performed with Kaplan-Meyer analysis. Results A total of 361 pts were included for analysis, of which 184 had non-typical LBBB. Pts had a mean age of 71±9years old, the majority of pts were female (61%), and almost half were ischemic (47.8%). EGC evaluation prior to CRT implantation, revealed an atypical LBBB in 83 (45.1%) pts, typical RBBB in 23 (12.5%) pts, atypical RBBB 94.(9%) pts and nonspecific intraventricular conduction delay in 69 (37.5%) pts. During a mean time of follow-up of 2.9 ±2.4years, 33 pts (18%) had hospitalizations due to HF and 68 (37%) died. In this cohort, 78 pts (42.4%) were deemed as responders, who presented a better clinical outcome when compared to non-responders (p &amp;lt; 0.001, HR 2.629 [95% CI 1.635-4.225]. There was no difference among the four types of intraventricular conduction analyzed in respect to degree of CRT response – figure 1. Regarding clinical events during follow-up, there was once again no significant difference among the different patterns of non-typical LBBB– figure 2. In this subset population we found no independent predictors of CRT response, although non-responders were significantly older than responders (72±8 vs 69±10 years-old (p=0.016). Conclusion Although pts with non-typical LBBB morphology display a lower therapy response to CRT than reported for LBBB pts, the rate of response is not negligible and represents a protective factor for clinical outcomes. Different types of intraventricular conduction delay present no difference regarding long- term prognosis or reverse remodeling.Survival according to CRT response

Clinical significance and prognostic value of right bundle branch block in permanent pacemaker patients

Abstract Aim In patients undergoing pacemaker implantation with no prior history of heart failure (HF), the presence of left bundle branch block (LBBB) has been identified as an independent predictor of HF-related death or hospitalization, while the prognostic significance of right bundle branch block (RBBB) remains uncertain. We aimed to assess the long-term risk of all-cause mortality in patients with a standard indication for permanent pacing and normal or moderately depressed left ventricular function when RBBB is detected at the time of implantation. Methods We retrospectively enrolled 1348 consecutive patients who had undergone single- or dual-chamber pacemaker implantation at the study center, from January 1990 to December 2022. Patients with a left ventricular ejection fraction ≤35% or a prior diagnosis of HF were excluded. Results The baseline 12-lead electrocardiogram revealed an RBBB in 241 (18%) and an LBBB in 98 (7%) patients. During a median follow-up of 65 [25th-75th percentile: 32-117] months, 704 (52%) patients died. The combined endpoint of cardiovascular death or HF hospitalization was reached by 173 (13%) patients. On multivariate analysis, RBBB was confirmed as independent predictor of death (Hazard Ratio, 1.33; 95% CI, 1.09–1.63; P=0.005). However, when considering the combined endpoint of cardiovascular death and HF hospitalization, this endpoint was independently associated with LBBB (Hazard Ratio, 2.13; 95% CI, 1.38–3.29; P&amp;lt;0.001), but not with RBBB. Conclusions In patients with standard pacemaker indications and normal or moderately depressed LV function the presence of basal RBBB was an independent predictor of mortality. However, it was not associated with the combined endpoint of cardiovascular death and HF hospitalization.Time to event

ECG imaging as a real time tool to guide left bundle branch pacing implant in patients with left bundle branch block and resynchronization therapy indication

Abstract Background Left bundle branch pacing (LBBP) has emerged as a promising alternative technique for cardiac resynchronization therapy (CRT). ECG imaging (ECGI) may provide an accurate assessment of electrical resynchronization using real-time maps during LBBP implant. Purpose To evaluate the usefulness of ECGI to guide LBBP implant, by analyzing the ventricular activation times and the degree of resynchronization at each screwing step during the lead implant. Methods Four patients with CRT indication and left bundle branch block (LBBB) referred for LBBP were prospectively enrolled. ECGI was performed during the implant procedure. Cardiac signals were recorded using ECGI and projected into an artificial intelligence-derived geometric model. Thus, generating imageless and non-invasive activation maps at defined stages during lead screwing: basal rhythm (LBBB), right ventricular (RV) septum, mid-septal, deep-septal, and finally pacing from the left bundle branch (according with guidelines ECG criteria). The following parameters were measured: a) total activation time (TAT); b) left ventricular activation time (LVAT); c) left ventricular dyssynchrony index (LVDI) (as a quantifier of intraventricular dyssynchrony); d) ventricular electrical uncoupling (VEU); and e) histogram overlap between LV and RV distribution (the last 2 markers of interventricular dyssynchrony). Results The study cohort comprised men with a median age of 68 [Q1 59- Q3 79], with a median basal LBBB QRS duration of 175 ms [160-188] and a median LVEF of 32% [28-39]. A shortening of the activation times and a decrease in intra and interventricular dyssynchrony was achieved when the final lead position was reached. See the results in Figure 2. Conclusion Real-time and imageless ECGI system may offer a novel approach for guiding LBBP and it is useful to ensure left ventricular resynchronization.ECGI to guide LBBP implantActivation and dyssynchrony measurements

Left bundle branch vs biventricular pacing for cardiac resynchronization therapy

Abstract Background/Introduction Left bundle branch pacing (LBBP) has emerged as a predominant conduction system pacing technique for reducing QRS duration in patients with intrinsic left bundle branch block (LBBB). It represents a potentially optimal alternative to cardiac resynchronization therapy (CRT) through biventricular pacing (BiVP). Purpose This study aims to compare the efficacy of LBBP-CRT with BiVP-CRT in patients experiencing heart failure with reduced left ventricular ejection fraction. Methods This single-center prospective study involved patients with heart failure and reduced ventricular ejection fraction, encompassing both ischemic and nonischemic cardiomyopathy. LBBP-CRT was employed when BiVP was unsuccessful for any reason, with LBBP-CRT implanted during the same procedure. After 3 and 6 months of preplanned follow-up, comparisons were made between the New York Heart Association (NYHA) functional class and QRS duration in the BiVP-CRT and LBBP-CRT groups. Results Sixty consecutive patients were included in the study (39 males, mean age 64.1 ± 10.6 years, LVEF 29.6% ± 5.6%). All patients completed follow-up, with 32 receiving LBBP-CRT and 28 receiving BiVP-CRT. All 32 LBBP-CRT patients achieved LBB capture, with 14 undergoing selective LBBP and 18 undergoing nonselective LBBP. The LBBP-CRT group exhibited shorter procedure and x-ray exposure times ((11.95 ± 5.77 vs 18.66 ± 10.12). The LBBP lead demonstrated a lower LBB capture threshold at implantation (0.7 ± 0.26 V vs. 1.1 ± 0.40 V; p= 0.039) compared to the CS LV lead in the BiVP-CRT group. Pacing parameters remained stable at the 6-month follow-up (0.72 ± 0.20 V vs. 1.1 ± 0.57 V; p=0.07). During the 3 and 6-month follow-up, pacing parameters remained stable in both groups. Only one patient in the LBBP-CRT group experienced dislodgment of the CS LV lead two days after the procedure, while no patients in the LBBP-CRT group had lead dislodgment. QRS duration significantly shortened in LBBP (171.6 ± 14.3 ms to 131.5 ± 12.5 ms; p=0.047) and remained not significantly shortened in BiVP (174.7 ± 14.1 ms to 150.6 ± 12.9 ms; p=0.06). Both LBBP and BiVP demonstrated improvement in NYHA functional class at the 3 and 6-month follow-up, with statistically significant differences observed between the two groups (change in NYHA functional class from baseline to 6 months -1.2 ± 0.1 vs -0.94 ± 0.11 p=0.047). Throughout the 6-month follow-up, neither the LBBP-CRT nor BiVP-CRT groups experienced rehospitalizations for heart failure, ventricular arrhythmia events, or all-cause death. Conclusions In this series, LBBP-CRT exhibited improvements in NYHA functional class and significantly shortened QRS duration when compared to BiVP-CRT in patients with reduced left ventricular ejection fraction and LBBB.

Electrocardiographic predictors of haemodynamic benefit from biventricular pacing: the role of atrioventricular timing measures

Abstract Background Patients with heart failure (HF) and left bundle branch block (LBBB) are selected for biventricular pacing (BVP) cardiac resynchronisation therapy (CRT) based on their 12-lead ECG QRS complex duration (QRSd). This is due to the long-held belief that BVP delivers its beneficial effects almost exclusively by reducing ventricular dyssynchrony. Recent work (1) suggests that atrioventricular delay (AVD) shortening is another key mechanism of benefit and, therefore, that atrioventricular timing may be an important CRT substrate. The ideal 12-lead ECG measure to facilitate patient selection that yields benefits from this mechanism is yet to be elucidated. Purpose We set out to establish whether incorporating a measure of AV delay provides additional benefit over and above using QRSd when using the 12-lead ECG to select patients who are likely to obtain haemodynamic benefit from BVP. Methods We identified patients in sinus rhythm with HF and LBBB meeting clinical criteria for CRT who had undergone implantation of a BVP device and had also undergone high-precision haemodynamic assessment of BVP. This is where pacing is alternated between atrium-only pacing (AAI) and DDD pacing using BVP multiple times for each of a full range of AVDs during continuous beat-by-beat blood pressure recording to determine the peak haemodynamic benefit of BVP in each patient. We extracted potentially predictive, pre-specified intrinsic (unpaced) ECG features that incorporated left or right AV timing to varying extents: PR interval (PR), end-of-p-wave-to-R-wave-peak-time-V6 (Pend-RWPTV6), start-of-p-wave-to-end-of-QRS (P-QRSend) as well as conventional QRSd. Pearson's test assessed the unadjusted correlation between intrinsic ECG intervals and BVP haemodynamic benefit(∆SBP). A multiparametric regression analysis model was constructed to account for confounders and interactions between different ECG features. Results 53 eligible patients were identified. 39 were male (73.6%), 31 had non-ischaemic aetiology (58.5%), mean LVEF was 27.6% ± SD 4.79 and mean LVEDD was 57.9± SD 9.4mm. Unadjusted correlations between intrinsic ECG features were not strong but favoured P-QRSend as a potentially predictive feature; R2 values: PR 0.28 (p=0.04), Pend-RWPTV6 0.19 (p=0.18), P-QRSend 0.27 (p=0.054), QRSd 0.045 (p=0.75). However, the multiparametric model revealed that utilising both PR interval and Pend-RWPTV6 in a predictive model showed better-adjusted correlation with BVP haemodynamic benefit (R2 0.54, p=0.04). Conclusion ECG features that incorporate either right (PR interval) or left (Pend-RWPTV6) AVD or both (P-QRSend) are superior to QRSd for predicting haemodynamic benefit from BVP in patients with HF and LBBB. This further reinforces the role of AVD shortening as a mechanism of benefit of BVP and suggests that selecting patients on the basis of AV timing may yield more overall benefit from CRT delivered by BVP or potentially conduction system pacing.ECG interval measurementCorrelation Graphs

Left bundle branch area pacing in the setting of cardiac amyloidosis: a case series

Abstract Background Cardiac amyloidosis (CA) is a highly prevalent cause of congestive heart failure. It often requires cardiac pacing due atrioventricular conduction (AV) system disorders, often with cardiac resynchronization (CRT) to prevent development/deterioration of left ventricular (LV) dysfunction. Left bundle branch area pacing (LBBAP) is an emerging alternative to CRT, offering a strict physiological LV activation and very limited use of iodinated contrast. The feasibility of LBBAP in CA is considered limited due to the presence of septal pseudohypertrophy which theoretically limits left-sided conduction system engagement. Purpose To evaluate the feasibility and effectiveness of LBBAP in cardiac amyloidosis. Methods Consecutive patients with CA (both light-chain -AL- or wild-type transtiretin -wtATTr) with a pacing indication for AV conduction disorders were enrolled. Patients underwent baseline echocardiographic examination. LBBAP was achieved by means of stylet-driven leads advanced transeptally (right ventricle (RV) to LV) via dedicated delivery systems, with continuous monitoring of 12-lead electrocardiographic morphology and impedance until a typical QRS morphology in V1 was obtained (usually rSr’ or Sr’). Standard measures for left bundle (LB) capture were used (stimulus to peak R in V6 – S-RV6, V6-V1 interpeak interval, presence of transition in these measures during threshold testing, presence of fascicular signal during spontaneous QRS). Results Between January 2022 and June 2023, among 63 patients undergoing LBBAP, 7 patients (11%) had CA, 2 AL (28%) and 5 (72%) wtATTR. Patients were prevalently old (78±7 y) males (6, 85%); LV mean septal thickness was 17±2 mm (min 16, max 20 mm) and mean LV ejection fraction (LVEF) was 45±6%. Indications were PR prolongation in 3, bradycardic atrial fibrillation and LB branch block (LBBB) in 2, primary LBBB in 1 and chronic RV pacing in 1. Baseline QRS duration was 145±47 ms (QRS&amp;lt;120 ms: 97±15 ms, QRS&amp;gt;120 ms: 182±13 ms). LBBAP success was 100%. Fascicular electrograms were observed in ¾ of patients without LBBB; S-RV6 interval was 74 ±11 ms (³70 ms in 3), RV6-RV1 interpeak interval was 47±9 ms (³ 30 ms in 6 patients). DQRS in baseline broad QRS was -52 ms and +32 ms in narrow. No complications were observed. Over a short follow up of 6 months, an increase in average LVEF was observed (LVEF at 6 months: 51±3%, p&amp;lt;0.05). Conclusions In patients with CA, LBBAP is easily achievable with stylet-driven systems with frequent selective engagement of conduction system. QRS narrowing in baseline broad QRS is significant while QRS broadening in baseline narrow QRS is limited. Early results regarding follow-up of surrogate endpoint such as LVEF are promising.

Left bundle branch area pacing optimized cardiac resynchronization therapy (LOT CRT) -comparative results to a CRT implanted patient population

Abstract Background Cardiac resynchronization therapy (CRT) is gold standard treatment option among patients with symptomatic heart failure with reduced left ventricular ejection fraction (LVEF) and intraventricular conduction delay of left bundle branch block (LBBB) morphology. Purpose Left bundle branch area pacing optimized cardiac resynchronization therapy (LOT CRT) is a novel and promising approach for CRT candidate patients even in advanced intraventricular conduction delay, however convincing follow-up data regarding this patient group is still lacking. Methods In our observational registry 35 LOT CRT vs. 35 conventional CRT patients were consecutively implanted according to current guidelines. All the patients had LBBB morphology QRS width of &amp;gt;150 ms. The two compared patient group did not show significant difference in age, gender, baseline non-ischemic etiology, LVEF, NYHA functional class, LBBB QRS width. Results Immediate postoperative results showed significantly increased QRS width reduction (p=.028) and at 6 months of follow-up a significantly greater improvement in LVEF(p=.031), NYHA functional class (p=.04) and Nt-ProBNP levels (p=0.043) were seen in LOT CRT patient group compared to conventional CRT patients. Conclusion Our single center observational study showed significant improvement in prompt postoperative QRS width and clinical follow-up parameters in LOT CRT implanted patients compared to conventional CRT implanted patients.LOTCRTvs.CRTQRSwidthreductionLOTCRTXray

Impact of myocardial phenotype on atrioventricular delay optimization at rest and during exercise: insights from a virtual patient study

Abstract Background The usefulness of atrioventricular delay (AVD) optimization in cardiac resynchronization therapy (CRT) for heart failure (HF) patients with left bundle branch block (LBBB) and reduced left ventricular ejection fraction (LVEF) is still debated. Yet, studies have not explored the role of non-electrical myocardial disease substrates in determining optimal AVD settings among patients. Purpose We first hypothesized that acute response to AVD optimization might be modulated by various myocardial disease substrates. Furthermore, we hypothesized that cardiac function is more sensitive to changes in AV coupling during exercise and that this sensitivity is also modulated by underlying myocardial disease substrates. Methods We used the CircAdapt model of the human heart and circulation to simulate different types of LV remodeling that can be found in CRT candidates. First, an LBBB-like pattern of mechanical activation was imposed by delaying LV free wall (LVFW) and interventricular septal (IVS) activation relative to right ventricular free wall activation. Then, two types of LV remodeling were simulated by LV dilation with preserved or impaired myocardial contractility, resulting in LVEF &amp;lt;35%. To investigate the effect of diastolic dysfunction, we increased passive myocardial stiffness of the IVS and LVFW on both substrates with LV remodeling until a mean left atrial pressure (mLAP) of 14 mmHg was reached. CRT was simulated by resynchronizing IVS and LVFW. AVD optimization was conducted by gradually reducing the paced AVD from 220 ms to 40 ms in steps of 20 ms. In each simulation, the optimal paced AVD at rest (cardiac output (CO) and heart rate (HR) of 4.2 L/min and 80 bpm, respectively) was assessed using stroke volume (SV) and mLAP which is used as a measure of LV filling pressure. To investigate the relative effect of these myocardial phenotypes during AVD optimization under exercise, CO and HR were increased step-wise. Results The gain in SV by AVD optimization was larger in the simulations with healthy myocardium than in those with hypo-contractile and stiff myocardium (Figure 1: top-row). However, mLAP was comparably decreased by AVD optimization in healthy and diseased myocardium (Figure 1: bottom row). During exercise, the optimum AVD shifted to shorter values (Figure 2: top-row), and mLAP was much more sensitive to AVD, particularly in the presence of hypo-contractile and stiff myocardium (Figure 2: bottom row). Conclusion Virtual patient simulations show that both myocardial hypocontractility and stiffness dampen the effect of AVD optimization on SV. Furthermore, simulations suggest that patients benefit more from AVD optimization during exercise than during resting conditions. These mechanistic insights may help to gain more benefit from AVD optimization for patients undergoing CRT.AVD optimization at restAVD optimization during exercise

Which paced QRS duration can be achieved in selective and non-selective His bundle pacing?

Abstract Background The paced QRS duration (pQRS) is associated with the risk of developing a pacing-induced cardiomyopathy. His bundle pacing (HBP), either selective (sHBP) or non-selective (nsHBP) can achieve a rather narrow pQRSd in patients with a narrow intrinsic QRS (iQRS) or right bundle branch block (RBBB). We prospectively analyzed the pQRS in sHBP and nsHBP and correlated it with the iQRS. Patients and Methods All consecutive patients who received an implantation with sHBP or nsHBP were enrolled and received a 12-lead ECG before and after implantation (digital recording, 25 mm/s). Measurements of the pQRS after implantation were performed in unipolar VVI 100 bpm mode to exclude fusion beats. QRS duration was measured in 6fold magnification of the digital ECG (600%) 1) for the iQRS, 2) from the beginning to the end of the QRS in sHBP, 3) from the end of the pacing artifact to the end of the QRS in nsHBP, and 4) from the end of the pseudo-delta wave to the end of the QRS in nsHBP (see Fig.). Results In 388 patients (78±11 years, 38% female, 18% RBBB, 9% left bundle branch block) with an iQRS of 110±28 ms before implantation, sHBP was achieved in 206 patients (53%), nsHBP in 182 (47%). In sHBP, the pQRS was 88±18 ms, in nsHBP 123±18 ms including the pseudo-delta wave, 83±14 ms excluding the pseudo delta-wave. In sHBP, the pQRS was on average 15 ms shorter than the iQRS. In nsHBP, the pQRS was 9 ms longer than the iQRS when the pseudo-delta wave was included, and 31 ms shorter if it was excluded, the latter mostly due to correction of a RBBB by nsHBP. Conclusions In sHBP and nsHBP, very narrow pQRS durations of 80-90 ms can be achieved. The pQRS is frequently shorter than the iQRS, mostly by correction of a RBBB.QRS measurements in sHBP and nsHBP

Optimising electrical performance of leadless cardiac resynchronisation therapy and leadless LV septal pacing

Abstract Introduction Leadless left ventricular (LV) endocardial pacing with the WiSE-CRT System is an emerging form of cardiac resynchronisation therapy (CRT). The system was designed to provide lateral wall LV pacing (LVP) via an endocardial receiver electrode in response to detection of a right ventricular pacing (RVP) stimulus from a co-implanted device, thereby delivering near-simultaneous biventricular pacing (BiVP). However, it is unclear whether BiVP generates the optimal electrical performance in this system, particularly in the context of leadless LV septal pacing, a novel use for leadless CRT. Aim We aimed to characterise the acute performance of leadless CRT at different pacing modalities using electrocardiographic imaging (ECGi). Methods Patients with the leadless CRT underwent an acute ECGi study. The following pacing modalities were tested: RVP; BiVP; LVP; and LVP with an electrically optimised atrioventricular delay (LV-OPT) in patients with sinus rhythm (SR). Reconstructed epicardial electrograms (Figure 1) were used to calculate BiV activation time (BIVAT-90), LV activation time (LVAT-90), RV activation time (RVAT-90), LV dyssynchrony index (LVDI), and BiV dyssynchrony index (BIVDI). For each metric, the improvement compared to baseline rhythm was calculated, and the optimal pacing modality (OPM) in each patient was determined. Results Ten patients were studied, 5 receiving septal LVP, and 5 receiving lateral LVP. The underlying rhythm in 4 patients was SR with left bundle branch block (LBBB), and atrial fibrillation (AF) with complete heart block (CHB) in the remaining 6. BiVP generated a 23.7% improvement in BiVAT-90 compared to baseline (p=0.002). An individualised OPM resulted in a 43.3% BiVAT-90 improvement compared to baseline (p=0.0001), thus a 19.6% improvement compared to BiVP (p=0.02, Figure 2A). Using an OPM, BiVAT-90 was significantly improved in both patients with lateral (43.3%, p=0.0001) and septal LVP (42.4%, p=0.009). The BiVAT-90 OPM varied between patients (Figure 2B). BiVP was the OPM in 4/10 patients, all of whom had AF with CHB. BiVP was the OPM in 1/5 patients receiving LV septal pacing, with LVP or LV-OPT performing best in the remaining 4. In 3/4 patients in SR, LV-OPT was the OPM. Choosing the OPM increased performance primarily through significant improvements in RVAT-90 compared to BiVP (36.5% versus -8.2%, p =0.002). Conclusion Leadless CRT, both with lateral and septal LVP, significantly reduces electrical activation times and improves electrical dyssynchrony. Individualised selection of the OPM may be required with leadless CRT to accommodate for varying conduction disease phenotypes and implant locations.

Clinical characteristics of patients with better ejection fraction recovery after upgrading to cardiac resynchronization therapy

Abstract Background Chronic right ventricular (RV) pacing can cause cardiac systolic dysfunction and heart failure (HF), increased risk of HF hospitalization and adverse outcomes. In these patients upgrading to cardiac resynchronization therapy (CRT) may improve left ventricular function. Purpose We aimed to identify the profile of patients (their clinical, electrical and echocardiographic characteristics) who are more likely to make a significant change in left ventricular ejection fraction (LVEF) one year after revision of the RV pacing system to CRT. Methods This was a retrospective, observational, single-center study. We included patients with a permanent antibradycardia pacemaker who had no systolic dysfunction and HF symptoms at the time of pacemaker implantation and who experienced a drop in LVEF below 35% during follow-up, with development of HF symptoms and with at least 20% of ventricular pacing. In all patient's revision to CRT was performed at our center between January 2014 and December 2019. We excluded patients who were indicated for a system upgrade regardless of the percentage of ventricular pacing and those in whom the drop in LVEF is due to a new coronary event. We used patients’ medical records to collect data on baseline characteristics. LVEF was measured pre-revision and 12 months after upgrade. To examine the difference in LVEF change between specified subgroups of patients we used a t-test. Results During the defined period, 82 upgrade procedures from conventional pacemaker to CRT were done in our center. We excluded 12 patients with left bundle branch block (LBBB) QRS morphology, 4 with non-LBBB QRS morphology but with QRS duration over 150ms and 4 patients who died within a year after revision to CRT. Therefore, we analyzed 62 patients (20.9% female, mean age 66.9 ± 11.2 years, mean LVEF 25.9 ± 6.8). After 12 months, 58.1% of patients had an increase in EF above 5%, and the mean change in LVEF (ΔLVEF) was 7.8 ± 11.8. Compared to those with non-ischemic cardiomyopathy (NICMP), patients with ischemic etiology had statistically significantly less improvement in LVEF (ΔLVEF 1.8 ± 6.8 vs 13.1 ± 12.7, p &amp;lt; 0.01), as well as patients with an RV apical pacing compared to those with a septal lead position (ΔLVEF 5.1 ± 9.1 vs 14.1 ± 14.7, p = 0.021). Patients with narrower paced QRS complex (&amp;lt;150ms) before upgrade had a significantly greater improvement in LVEF compared to those with a wider paced QRS complex (≥150ms) (ΔLVEF 10.9 ± 12.2 vs 4.8 ± 10.7, p = 0.04), and those with post-revision paced QRS width above 150ms had significantly lower change in LVEF compared to those with a narrower paced QRS (ΔLVEF 4.6 ± 9.8 vs 11.1 ± 12.8, p = 0.028). Conclusion Patients with NICMP and with width of the paced QRS complex before and after revision to CRT below 150ms had significantly greater improvement in LVEF 12 months after the upgrade. The position of RV lead significantly affects the success of the upgrade procedure.

Unsupervised machine learning defines subgroups in ischemic heart disease patients presenting with ventricular tachycardia

Abstract Background Ventricular tachycardia (VT) in ischemic heart disease (IHD) is the leading cause of sudden cardiac death (SCD). Despite the well-defined recommendations, tailoring therapies individually is often a challenge owing to the great heterogeneity in this population. We hypothesized that unsupervised machine learning can uncover hidden patterns to identify patient subgroups with similar characteristics. Aims To use unsupervised machine learning methods on a database of patients with ischemic VT, to discover subgroups with similar characteristics and compare the survival of the identified groups. Methods We collected the data of 566 patients with IHD hospitalized for sustained monomorphic VT, excluding those with acute coronary syndrome. The 17 recorded features included medical history and echocardiography. All-cause mortality was registered with one-year follow-up. We performed dimension reduction using T-distributed Stochastic Neighbor Embedding (TSNE) to produce 3 dimensions of the data. Then, we applied spectral clustering to create three groups within the population. Each group was compared to the rest of the population for each variable. Finally, we compared the survival across the three groups using Kaplan-Meyer analysis, univariate Cox-regression, and Log-rank test. Results We identified three groups with distinct characteristics. Group 1 represented the healthiest population; patients had no previous VT hospitalizations, and none of HD instability, LBBB, SCD, diabetes, VT storm or ICD shocks; additionally, they always had a single VT episode at presentation. They showed better left ventricular ejection fraction (LVEF) (38% vs. 33%, p&amp;lt;0.001) and TAPSE (20 mm vs. 18 mm, p=0.01), less severe mitral and tricuspid regurgitation (MR, TR), smaller left ventricular end-systolic diameter, and longer DT. Conversely, patients in Group 2 (n=349) had more previous VT hospitalizations (30% vs. 18%, p=0,003), more often had diabetes (46% vs. 18%, p&amp;lt;0.001), left bundle branch block (23% vs. 13%, p=0.006), and more often presented with HD instability (47% vs. 28%, p&amp;lt;0.001). Group 3 contained all seriously ill patients with VT storm or incessant VT, more commonly presenting with ICD shocks (34% vs. 21%, p=0.004), SCD (24% vs. 15%, p=0.004), hemodynamic instability (50% vs. 37%, p=0.01). This group had the poorest LVEF (30% vs. 35%, &amp;lt;0.001) and TAPSE (17 mm vs. 19 mm p=0.001), more severe MR and TR, and the shortest DT (140 ms vs. 173 ms p&amp;lt;0.001). Finally, we compared survival across the three groups. Significantly better survival was found in Group 1 (HR: 0.52 CI [0.28 - 0.98]) and Group 2 (HR: 0.61 CI [0.42 - 0.88]), while Group 3 had higher mortality (HR: 2.7 CI [1.83 - 3.97]). Conclusions Using spectral clustering we identified three groups in our cohort of ischemic VT patients. This method delineates the group of ischemic VT patients with the highest risk of mortality who might need more aggressive treatment and closer follow-up.

Conduction system pacing improved cardiac functions and functional capacity in heart failure with reduced ejection fraction and right bundle branch block

Abstract Conduction system pacing (CSP) is increasingly accepted as an alternative to biventricular pacing in heart failure (HF) patients with left bundle branch block (LBBB) and non-LBBB. However, its efficiency in right bundle branch block (RBBB) is ill-defined. Herein, we report on the clinical outcomes of CSP in HFrEF patients with wide QRS complex and RBBB morphology. His-bundle (HBP) or LBB-area pacing (LBBAP) was attempted as a primary strategy in patients with RBBB, QRS duration ≥130 ms and left ventricular ejection fraction (LV EF) &amp;lt;35% and NYHA class II to IV HF despite optimized medical treatment for at least 6 months. Data on functional status, NT-pro-BNP levels and echocardiographic parameters were collected during follow-up and expressed as mean ± SEM, Statistical significance was calculated with Student’s paired t-test and chi square distribution. CSP was performed in 12 RBBB-HF patients (age 64.3±2.9 years) with mean QRS duration of 150±4 msec and baseline LV EF of 25.4±2.3%. The aetiology of HF was ischaemic (6 patients) and non-ischaemic cardiomyopathy (6 patients). During the procedure, HBP was achieved in 7 and LBBAP in 5 patients, resulting in a significant reduction in the QRS-duration (115±2.6 msec, P&amp;lt;0.0001) as compared with baseline value. CSP improved LV function (LV EF= 31.8±2.8%, P=0.009) as well as NYHA functional class (25% of the patients with NYHA II and 75% with NYHA III before vs. 33% with NYHA I, 33% with NYHA II and 33% with NYHA III after CSP, P=0.048) as compared to what was obtained prior to the procedure. A numerical decrease was also found in NT-proBNP levels (4735±2606 ng/ml before CSP vs. 3972±1883 ng/ml after CSP) which did not reach the level of statistical significance (P=0.45). In conclusion, CSP improved both quality of life and LV function in HFrEF patients with RBBB. Our results support the use of CSP in HFrEF patients with QRS width&amp;gt;130msec and RBBB morphology.

Effectiveness of left bundle branch area pacing to restore narrow QRS in patients with right bundle branch block

Abstract Background/Introduction Left bundle branch area pacing (LBBaP) is an innovative technique used to capture conduction tissue and maintain ventricular synchrony during pacing. There are few data about the efficacy of LBBaP in right bundle branch block (RBBB). Purpose To compare the response to LBBaP, evaluated by the change in QRS duration (QRSd) after pacing, in patients with RBBB, left bundle branch block (LBBB) or without conduction disorder. Methods A total of 162 patients with pacemaker indication underwent LBBaP with stylet driven lead with dedicated sheaths, between November 2020 and April 2023. ECG characteristics were evaluated. Data are presented in mean ± standard deviation (SD) or n (%). Paired sample t-test was used to compare QRSd before and after pacing. Results Indications for pacing were atrioventricular block (AVB) 48,4 %, sinus node dysfunction (SND) 37,7 %, AVB and SND 10,7 % and cardiac resynchronization therapy 3,1 %. LBBaP was successfully performed in 98 % (159/162) of patients (78 ± 10 years, 62 % male). Overall, baseline QRSd was 113,2 ± 26,7 ms and paced QRSd was 112,3 ± 14,8 ms (p = 0,662), with left ventricular activation time (LVAT) of 69 ± 14 ms (table 1). Baseline ECG showed 18 LBBB, 29 RBBB and 11 undetermined conduction disorder. In every kind of conduction disorder, paced QRSd was reduced to &amp;lt; 120 ms (table 2). Notably, paced QRSd was &amp;lt; 120 ms, regardless of baseline QRSd. In patients with most important pre-existing conduction disorder (QRS ≥ 145 ms), an impressive reduction in QRSd was observed (Delta = -40,8 ms , table 1). Conclusion LBBaP with stylet driven lead is an effective approach to obtain short paced QRS regardless of baseline QRSd and of the nature of the initial conduction disorder. This opens new perspectives for cardiac resynchronization in patients with RBBB.