Bundle Branch Block Correction Research Articles

Temporal evolution of His bundle pacing thresholds: a sub-study of the PACE-CONDUCT trial

Abstract Background His bundle pacing (HBP) has become a valuable alternative for cardiac resynchronization therapy, offering physiological pacing. This substudy of the PACE-CONDUCT trial aimed to explore the influence selective and non-selective HBP on threshold height. We assessed these parameters in patients with both normal conduction and bundle branch block conduction. Methods Our study included 61 consecutive patients with a median age of 73 years, who underwent a successful HBP implantation for indications such as sick sinus syndrome, AV Block 2 type 2, binodal disease, and ablate and pace therapy prior to AV-node ablation. Among these patients, 18 exhibited QRS durations exceeding 150 ms, indicating a complete and broad bundle branch block which made them candidates for cardiac resynchronization therapy (CRT). All patients received HBP implantation with the assistance of a 3D electroanatomical system. This system allowed for low-fluoroscopic, atraumatic evaluation of the His bundle (HB) area, presenting the His voltage as a color-coded map for precise electrode placement. Results The feasibility of bundle branch correction is generally accepted in selective HBP distal to the site of block, albeit associated with higher threshold values and potentially lower battery duration. Our analysis encompassed 61 patients who underwent HBP implantation, with 23 patients (37,7%) exhibiting selective HBP and 38 (62,3%) non-selective HBP. Remarkably, 10 out of the 23 patients with selective HBP demonstrated a complete bundle branch block correction after HBP implantation even with a basal QRS durations exceeding 150 ms. We evaluated HBP thresholds at implantation, one day post-implantation, and one month post-implantation, correlating these data with selective and non-selective HBP. Threshold values were converted to volts per millisecond (volts × milliseconds) for analysis. Statistical analysis conducted with IBM SPSS 29.0 revealed a significant difference at the day of implantation, indicating higher threshold capture in selective HBP compared to non-selective HBP (one-sided p-value: < 0.01, two sided p value 0.01). However, this difference could not be sustained at the one-day and one-month threshold follow-ups, suggesting normalization of the selective HBP threshold. Conclusion In our study, the initially higher threshold in selective HBP normalized within 24 hours compared to non-selective HBP. Additionally, our study demonstrated the feasibility of selective His pacing in patients with complete bundle branch block and broad QRS durations. These findings provide insights into HBP optimization and encourage further investigations with larger patient cohorts to validate our observations and enhance patient care in the realm of cardiac pacing.Threshold trend

Atrioventricular shortening is the dominant mechanism of benefit of biventricular pacing in left bundle branch block

Abstract Funding Acknowledgements Type of funding sources: Public Institution(s). Main funding source(s): British Heart Foundation Background Cardiac resynchronization therapy delivered via biventricular pacing is thought to improve haemodynamic function through resynchronization of ventricular activation. Biventricular pacing also improves ventricular filling by shortening atrioventricular delay. Quantifying the relative contributions of these two mechanisms requires atrioventricular delay to be altered while left bundle branch block is preserved. This occurs when the His bundle is paced at an output below the left bundle branch block correction threshold. Purpose We performed His bundle pacing with preservation of left bundle branch block to measure the relative contributions of atrioventricular delay shortening and ventricular resynchronisation to the overall haemodynamic benefit of biventricular pacing. Methods Patients with left bundle branch block referred for conventional cardiac resynchronization therapy with biventricular pacing were recruited. Using a high precision, beat-by-beat systolic blood pressure assessment protocol, we assessed the haemodynamic effects of biventricular pacing and temporary His bundle pacing with left bundle branch block preservation at a full range of atrioventricular delays. We used non-invasive epicardial mapping (ECGI) to assess left ventricular activation time. Left bundle branch block preservation was defined as <20ms shortening of the interval between intrinsic His potential to QRS offset to the interval from stimulation to QRS offset in His bundle pacing. Results In 19 patients, His bundle pacing with preservation of left bundle branch block produced a peak systolic blood pressure improvement of 5.1mmHg (95% confidence interval: 2.2 to 8.0, p = 0.0013) compared to AAI pacing. In 16 of these patients, biventricular pacing was performed and produced a peak systolic blood pressure improvement of 7.1mmHg (3.8 to 10.4, p < 0.001) compared to AAI pacing. The mean within-patient improvement in systolic blood pressure from His bundle pacing with preservation of left bundle branch block to biventricular pacing was 2.6mmHg (-0.4 to 5.7, p = 0.053, n = 16). The mean improvement in systolic blood pressure with left bundle branch block-preserved His bundle pacing was 63% of the mean improvement with biventricular pacing. Change in left ventricular activation time from intrinsic rhythm to 12-lead-ECG-defined left bundle branch block preservation was 0.1ms (-6.4 to 6.7, n = 19). Conclusion Biventricular pacing in left bundle branch block improves haemodynamic function through ventricular resynchronization and shortening of atrioventricular delay. The majority of benefit appears to be produced by atrioventricular delay shortening. When left bundle branch block is not corrected, His bundle pacing may still produce considerable haemodynamic improvement through this mechanism. Abstract Figure.

Paradoxical correction of bundle branch block-What is the mechanism?

A 14-year-old boy with recurrent palpitations and no preexcitation in the electrocardiogram (ECG) was taken up for an electrophysiology study. This article is protected by copyright. All rights reserved.

His-Optimized Cardiac Resynchronization Therapy With Ventricular Fusion Pacing for Electrical Resynchronization in Heart Failure

This study sought to evaluate the effectiveness of His-optimized cardiac resynchronization therapy (HOT-CRT) for reducing left ventricular activation time (LVAT) compared to His bundle pacing (HBP) and biventricular(BiV) pacing (including multipoint pacing [MPP]), using electrocardiographic (ECG) imaging. HBP may correct bundle branch block (BBB) and has shown encouraging results for providing CRT. However, HBP does not correct BBB in all patients and may be combined with univentricular or BiV fusion pacing to deliver HOT-CRT to maximize resynchronization. Nineteen patients with a standard indication for CRT, implanted with HBP without correction of BBB and BiV (n=14) or right ventricular (n=5) leads, were prospectively enrolled. Patients underwent ECG imaging while pacing in different configurations using different LV electrodes and at different HBP ventricular pacing (VP) delays. The primary endpoint was reduction in LVAT with HOT-CRT, and the secondary endpoints included various other dys-synchrony measurements including right ventricular activation time (RVAT). Compared to HBP, HOT-CRT reduced LVAT by 21% (-17ms [95% confidence interval [CI]:-25 to-9ms]; p<0.001) and outperformed BiV by 24% (-22ms [95%CI:-33 to-10ms]; p=0.002) and MPP by 13% (-11ms[95%CI:-21 to-1ms]; p=0.035). Relative to HBP, HOT-CRT also reduced RVAT by 7% (-5ms[95%CI:-9to-1ms; p=0.035) in patients with right BBB, whereas RVAT was increased by BiV. Theotherelectrical dyssynchrony measurements also improved with HOT-CRT. HOT-CRT acutely improves ventricular electrical synchrony beyond BiV and MPP. The impact of this finding needs to be evaluated further in studies with clinical follow-up. (Electrical Resynchronization and Acute Hemodynamic Effects of Direct His Bundle Pacing Compared to Biventricular Pacing; NCT03452462).

Bundle Branch Block Pattern Resolution in Non-Selective His Bundle Pacing: Effect of Programmed AV Delays

We have reported that non-selective but not selective His-bundle pacing (HBP) resolves bundle branch block (BBB) pattern. Characterized by ventricular pre-excitation, the mechanism by which nonselective-HBP resolves BBB is unknown. As A-V delays may determine both duration and timing of ventricular pre-excitation, it was hypothesized that an analysis of P-wave to HBP interval in relation to P-wave to His-bundle electrogram (HBE), may yield further insights into resolution of BBB pattern in NS-HBP. Methods: In 27 patients with RBBB+LAD (n=11) and LBBB (n=16), QRS parameters at AV delays resulting in P-HBP interval P-HBE. Results: At P-33 HBP< P-HBE, the pre-excitation duration was longest (63±13ms), and a more normal pre-excited complex replaced the RBBB, LAD, or LBBB pattern. In addition, the QRS-voltage in L1 was restored (LAD and LBBB), QRS-axis normalized (LAD), ventricular activation times decreased (LBBB) and rightward delay (S wave in L1) resolved (RBBB) (p<0.01). At longer A-V delays with P-HBP interval prolonging incrementally beyond P-HBE interval, underlying BBB emerged progressively, and correlated with both delayed pre-excitation and decrease in pre-excitation duration. Conclusion: The resolution of BBB pattern is associated with maximal pre-excitation in NS-HBP. Delayed ventricular pre-excitation and decreased pre-42 excitation duration, caused by with longer AV delays, result in progressive fusion complexes with increasing BBB pattern. Thus, our data is most consistent with a bundle branch pattern being replaced by a more normal pre-excited QRS pattern, and less consistent with correction of BBB itself.

Electrocardiographic patterns predictive of left bundle branch block correction with His bundle pacing.

Permanent His bundle pacing (p-HBP) could be an alternative for traditional cardiac resynchronization therapy (CRT), but an important limitation is that p-HBP cannot always correct the left bundle branch block (LBBB). The purpose of this article is to assess electrocardiographic patterns of LBBB that can predict electrocardiographic response (QRS narrowing) to His bundle pacing. We designed a prospective descriptive study of patients with LBBB and CRT indication proposed for CRT by p-HBP. We analyzed the correlation between the different electrocardiographic patterns and the correction of conduction disturbance (LBBB). We included 70 patients. Pacing at the location where His bundle electrogram was recorded narrowed the QRS in 81.4% (n=57). Basically, we identified two electrocardiographic patterns in lead V1: QS or rS. The QS pattern was a sensitivity of 56%, a specificity of 84.6%, and a positive predictive value (PPV) of 94.1% to predict the correction of the LBBB (area under the curve [AUC] = .70). In patients with rS pattern, a ratio between the descending and the ascending S wave component duration ≥0.64 was a very good predictor of the correction of the LBBB (AUC = .968); with a value ≥0.64, the sensitivity, specificity, and PPV was 92%, 100%, and 100%, respectively. In patients with LBBB and CRT indication, the QS pattern in lead V1 predicts the correction of the QRS with HBP. In the case of rS pattern in lead V1, the ratio descending/ascending S wave component duration has a strong correlation with the LBBB correction.

P1487Cardiac resynchronization through His bundle pacing in patients with heart failure

Abstract Introduction and purpose Permanent His bundle pacing (p-HBP) can correct intraventricular conduction disorders and could be a physiological alternative for traditional cardiac resynchronization therapy (CRT) via the coronary sinus: our aim was to describe our results in patients with heart failure and ventricular dysfunction who were resynchronized by p-HBP. Methods Prospective descriptive study of patients with CRT indication and who were resynchronized by p-HBP, using the specific tools. The correction of bundle branch block (BBB) by His bundle pacing (HBP) has been previously checked. We analyzed: the global success of the implant, the His thresholds, and the improvement in left ventricular ejection fraction (LVEF) at one month of follow-up. Results We included 54 patients (median age 66 (56-72)) with an indication for CRT: 89% (n = 48) with heart failure (HF), left bundle block branch (LBBB) and LVEF &amp;lt;35%; 3% (n = 2) with HF, right bundle block branch (RBBB) and LVEF &amp;lt;35%; 2% (n = 1) with permanent pacemaker, ventricular dysfunction and ventricular pacing &amp;gt;40%; and 6 % (n = 3) with complete AV block, LBBB and ventricular dysfunction. With HBP we corrected the BBB in 83% of patients (n = 45), and we achieved cardiac resynchronization through p-HBP in 93% of this patients (n = 42), with a global success (including those in whom HBP did not correct the BBB) of 78% (n = 42). The basal QRS was 160 ms (151-162) and the paced QRS was 132 ms (125-145). The median of His acute threshold was 1.6 volts (0.9-1.9), stable at one month of follow-up, excluding one patient whose His threshold progressively increased to 5.5 volts. There was no dislocation of leads in the follow-up. LVEF improved in all patients: basal 30% (27-35) and at one month follow-up 52% (48-64). Median fluoroscopy times of device implantation including the time taken for temporary HBP were 8.1 minutes (range 6.1-9.9). There were no relevant complications during the implant or follow-up; all patients showed clinical subjective improvement. Conclusions CRT by p-HBP is feasible and safe in a high percentage of patients, with reasonable times of fluoroscopy, acceptable capture thresholds, and an early improvement in LVEF in patients with HF and an indication for CRT.

His bundle pacing for newly acquired pacing needs in patients implanted with a subcutaneous implantable cardioverter defibrillator: A feasibility study based on the automated screening score and clinical cases.

Management of subcutaneous implantable cardioverter defibrillator (S-ICD) patients with newly acquired pacing needs remains problematic. His bundle pacing (HBP) allows for cardiac pacing without significant changes in the QRS morphology. We hypothesized that HBP does not alter S-ICD sensing and functions. Twenty consecutive patients were implanted with a HB pacemaker. Among them, 17 demonstrated successful His recruitment and were prospectively screened with the automated screening tool (AST). Results of screenings performed immediately after implant and during follow-up, during intrinsic rhythm and while pacing from all available pacing configurations, were compared using the AST score. Positive-screening tests were defined by greater than or equal to 1 positive vector. Among the 17 patients successfully implanted (male: 41%; mean age: 73), 13 presented an indication of ventricular pacing and four of cardiac resynchronization. Absolute AST scores during both HBP (all configurations) and intrinsic rhythm were similar (p: NS). Due to left bundle branch block correction, HBP resulted in higher number of positive vectors (AST ≥ 100). AST scores were higher during HBP when compared with right ventricular pacing (RVP) (primary vector: 272 [16; 648] vs 4.6 [0.8; 16.2]; P = .003; secondary vector: 569 [183; 1186] vs 1.5 [0.7; 8.3]; P < .0001; alternate vector: 44 [2;125] vs 4.8 [0.9; 9.3]; P = .02) and resulted in a much higher number of positive vectors. Up to 90% of the patients had a positive-screening test during HBP. This passing rate was higher when compared RVP (17%; P < .0001). HBP restores normal intrinsic conduction and minimally modifies the surface electrocardiograph and subcutaneous electrograms. When ventricular pacing is needed, HBP might represent an ideal pacing option for patients implanted with a S-ICD.

P6018Can chronic his bundle pacing be safely started in centers with lack of experience of this technique? Data from a multicentric registry

Abstract Introduction Right ventricular pacing (RVP) induces ventricular asynchrony in patients with normal QRS and increases the risk of heart failure and atrial fibrillation on long term. His bundle pacing (HBP) is a physiological alternative to RVP. Interest in HBP has been hampered in part by technical challenges and limited implantation tool set. Recent studies assessed feasibility and safety in expert centers with a vast experience of HBP. These results may not apply to less experienced centers. Purpose To evaluate feasibility and safety of permanent his bundle pacing in hospitals with limited technical training to this technique and to evaluate stability of his bundle capture thresholds at 3 months follow up. Methods We included all patients who underwent pacemaker implantation with attempt of HBP in three hospitals between September 2017 and December 2018. All the 5 operators were novice for HBP at the beginning of the study. Selective his bundle capture (HBC) was defined as concordance of QRS and T waves complexes with the native ECG (patients with underlying bundle branch block may normalize), presence of a delay between spike and QRS complex, absence of widening of the QRS at a low pacing output, and recordable his bundle electrogram. At 3 months follow-up, his bundle capture thresholds, R-wave amplitudes and pacing impedances were recorded. Results HPB was successful in 51 of 58 patients (87.9%); selective HBC was obtained in 40 patients while nonselective HBC occurred in 11 patients. Indication for pacemaker implantation was atrioventricular conduction disease in 31 patients (53%), sinus node dysfunction in 5 patients (9%) and AV nodal ablation for non-controlled atrial arrhythmias in 22 patients (38%). AV nodal ablation was performed during the same procedure in 14 patients. The mean procedure duration was 75±8 min, and mean fluoroscopy duration was 10±2 min. The mean HBP threshold was 1.47±0.27 V and did not increase after a 3 months follow-up (1.12±0.18 V). Only 7 patients (14%) had HBP threshold &gt;2V/0.5ms. The mean impedance was 477±37 Ω and slightly decreased at 3 months (364±24Ω). The mean R-wave amplitude was 4.1±1 mV at implantation and 3.2±0.6 mV at 3 months. Bundle branch block correction was achieved in 5 of 7 patients with underlying left bundle branch block. There was no pericardial effusion, no pneumothorax and no device infection. Ventricular lead revision was required at 3 months in one patient for sudden threshold increase, without obvious dislodgement. LBBB correction after HBP Conclusion His bundle pacing performed by novice operators to this technique appeared feasible and safe. The mean HBP threshold did not increase at 3 months follow-up.

Permanent His bundle pacing in heart failure patients: A systematic review and meta-analysis.

Cardiac resynchronization therapy (CRT) is the standard-of-care therapy for the patients with heart failure and left ventricular (LV) dyssynchrony. However, approximately 30% of the patients show no response. Recent studies have shown that His bundle pacing (HBP) could be an alternative for the patients with CRT indications. The purpose of this study was to evaluate the efficacy of HBP in patients with heart failure. We searched PubMed and Embase databases for studies evaluating HBP in patients with heart failure and LV dyssynchrony. The successful rate of implantation, QRS duration, pacing threshold, LV function at baseline and follow-up, and mortality rates were extracted and summarized. Eleven studies including 494 patients were included in this analysis. The overall successful rate for implantation was 82.4%. The main indications for HBP were CRT candidates and cardiomyopathy with atrial fibrillation undergoing atrioventricular node ablation. Permanent HBP resulted in narrow QRS duration of 116.3±13.9ms after implantation. LV functions, including echocardiographic parameters and clinical outcomes, significantly improved at follow-up (P<0.001). However, there was a trend of increased capture and bundle branch block correction thresholds at follow-up compared to baseline (P=0.01 and 0.02, respectively). During a mean follow-up of 23.7months, 5.9% of the patients experienced heart failure-related hospitalization and the mortality rate was 9.1%. Permanent HBP has shown promising results for heart failure patients in small observational studies. Randomized controlled trials are needed to assess the efficacy of HBP in these patients.

Permanent His Bundle Pacing for Cardiac Resynchronization Therapy in Patients With Heart Failure and Right Bundle Branch Block.

Background Cardiac resynchronization therapy utilizing biventricular pacing is an effective therapy for patients with left ventricular (LV) systolic dysfunction, left bundle branch block, and heart failure. Benefits of biventricular pacing may be limited in patients with right bundle branch block (RBBB). Permanent His bundle pacing (HBP) has recently been reported as an option for cardiac resynchronization therapy. The aim of the study was to assess the feasibility and outcomes of HBP in patients with RBBB and heart failure. Methods HBP was attempted as a primary or rescue (failed LV lead implant) strategy in patients with reduced LV ejection fraction, RBBB, QRS duration ≥120 ms, and New York Heart Association class II to IV heart failure. Implant characteristics, New York Heart Association functional class, and echocardiographic data were assessed in follow-up. Results Mean age was 72±10 years, female 15%, with an average LV ejection fraction of 31±10%. HBP was successful in 37 of 39 patients (95%) with narrowing of RBBB in 78% cases. His capture and bundle branch block correction thresholds were 1.1±0.6 V and 1.4±0.7 V at 1 ms, respectively. During a mean follow-up of 15±23 months, there was a significant narrowing of QRS from 158±24 to 127±17 ms ( P=0.0001), increase in LV ejection fraction from 31±10% to 39±13% ( P=0.004), and improvement in New York Heart Association functional class from 2.8±0.6 to 2±0.7 ( P=0.0001) with HBP. Increase in capture threshold occurred in 3 patients. Conclusions Permanent HBP was associated with significant narrowing of QRS duration and improvement in LV function in patients with RBBB and reduced LV ejection fraction. Permanent HBP is a promising option for cardiac resynchronization therapy in patients with RBBB and reduced LV ejection fraction.