A shorter R wave peak time in left bundle branch pacing may not be a marker of more physiological ventricular activation: A case report.

Left bundle branch pacing (LBBp) is a promising alternative to conventional biventricular pacing cardiac resynchronization therapy. The left anterior fascicle (LAF) is adjacent to the left ventricular outflow tract, while the left posterior fascicle (LPF) dominates a broader area of the left ventricle. Whether LAF or LPF dominates ventricular activation has not been determined. We present the case of a 76-year-old man who underwent LBBp implantation and propose the left ventricular activation domination in LPF pacing, an alternative when LBBp is unavailable.

Corrigendum: Guidance on left bundle branch pacing using continuous pacing technique and changes in lead V1 characteristics under real-time monitoring.

[This corrects the article DOI: 10.3389/fcvm.2023.1195509.].

Guidance on left bundle branch pacing using continuous pacing technique and changes in lead V1 characteristics under real-time monitoring.

Background: The changes in the morphology and characteristics of the V1 leads during left bundle branch capturing still need to be fully understood. Objective: This study aims to provide some suggestions about the LBB capture process through the morphology and characteristics of the V1 lead. Method: LBBP using the continuous pacing and morphology monitoring technique during screw-in using a revolving connector (John Jiang's connecting cable). The morphology and features of V1 leads are recorded by continuous monitoring technology. Results: The most common morphology in the LVSP stage is QR, while in the NS-LBBP (low output) stage and the NS-LBBP (lower output) stage, it is rSR. In the S-LBBP stage, it is rsR. The predominant morphology is with r/R waves in S-LBBP, which includes variations like rSR, rsR, rSr, rsr, rR, rs, rS, and R type, making up 96.7% of the total. The r waves in lead V1 are associated with agitated myocardium conducted from the left bundle branch. Conclusion: The initial r-wave in lead V1 may be a marker during the follow-up of patients with selective LBB capture.

2:1 Intrahisian block with Wenckebach phenomenon during his bundle pacing.

BACKGROUND: Intrahisian blocks with split His bundle (HB) potentials are occasionally observed in practice with intrahisian Wenckebach phenomenon being rare. CASE PRESENTATION: We report a case of an 85c and third-degree atrioventricular block. Some electrophysiological phenomena were recorded which serve as evidence of second-degree block intrahisian within the HB. During HB pacing (HBP) lead deployment, widening and splitting of HB potential and intrahisian Wenckebach phenomenon were recorded in intracardiac electrogram. Then, we began unipolar HBP at 2 V/0.5 ms. The paced QRS exhibited morphology identical to that during intrinsic rhythm, indicating selective capture of the HB. Notably, pacing the H1 potential at 750 ms results in 2:1 intrahisian block with intrahisian Wenckebach phenomenon. CONCLUSION: The case highlights the interesting finding of second-degree block intrahisian block in the HBP.

Interesting phenomena during threshold testing of conduction system pacing: What is the mechanism?

BACKGROUND: Although the interest in conduction system pacing is increasing, the data on longitudinal dissociation in the literature is still limited. METHODS AND RESULTS: We performed left bundle branch (LBB) pacing on a patient with sick sinus syndrome and atrioventricular block. The transition of QRS morphology can be observed during the threshold testing. The main findings were different left ventricular activation times when selective LBB capture was performed at different outputs. CONCLUSIONS: This phenomenon may be due to the anatomical basis of longitudinal dissociation of the His-Purkinje system, which allows pacing stimulation at different thresholds to excite different portions of the conduction system.

Premature beat of selective left bundle branch: a novel marker for reaching and capturing the left bundle branch.

BACKGROUND: It was recently shown that template beats and fixation beats of the premature ventricular contractions (PVCs) were generated during lead deployment. These could be exploited to guide the left bundle branch (LBB) pacing (LBBP) procedure. However, lack of a revolving connector that can continuously record and pace during lead rotations has been a limitation when using the traditional implant technique. Here, we report ten cases in which a revolving connector was used and showed that the premature beats of selective left bundle branch (SLBB-PBs) were generated as the lead was reached and the electrical stimulus selectively captured the LBB. METHODS AND RESULTS: Ten patients who underwent the transseptal placement of the pacing lead using a revolving connector were included in the study. We aimed to examine whether the SLBB-PB was a marker of LBB capture during LBBP and the clinical significance of SLBB-PB. LBBP was performed and data of these cases were analyzed to show the characteristics of the electrocardiogram and the intracardiac electrogram of SLBB-PBs. CONCLUSIONS: This is the first case series on SLBB-PBs in LBBP. The presence of SLBB-PBs suggested that the LBB was reached and selectively captured and possibly increased the safety of lead implantation.

A Continuous Pacing and Recording Technique for Differentiating Left Bundle Branch Pacing From Left Ventricular Septal Pacing: Electrophysiologic Evidence From an Intrapatient-Controlled Study.

BACKGROUND: Left bundle branch pacing (LBBP) is a promising approach for achieving near-physiologic pacing. However, differentiating LBBP from left ventricular septal endocardial pacing (LVS(e)P) remains a challenge. This study aimed to establish a simple and effective method for differentiating LBBP from LVS(e)P and to evaluate their electrophysiologic characteristics. METHODS: LBBP, using continuous uninterrupted pacing and real-time monitoring of electrocardiograms along with intracardiac electrograms, was performed in 97 consecutive patients. We evaluated the electrophysiologic characteristics observed during LBBP using 6 modalities: right ventricular septal pacing (RVSP), intraventricular septal pacing (IVSP 1 and 2), LVS(e)P, nonselective LBBP (NSLBBP), and selective LBBP (SLBBP). RESULTS: Of the 97 patients, 87 (89.7%) met the criteria (abrupt change in paced QRS morphology with a transition from Qr to QR/qR in lead V1 and shortening of stimulus to V6 R-wave peak time [Stim-V6RWPT] of ≥ 10 ms with constant output while rather than after lead screwing) for nonselective left bundle branch (LBB) capture. Selective LBB capture was observed in 82 patients (84.5%). The Stim-V6RWPT of NSLBBP and SLBBP were significantly shorter than LVS(e)P (respectively, 67.1 ± 8.7 ms, 67.0 ± 9.3 ms, and 82.1 ± 10.9 ms). Stim-QRSend was the narrowest in IVSP2 (136.6 ± 15.2 ms) instead of NSLBBP (140.0 ± 17.1 ms). CONCLUSIONS: The uninterrupted pacing technique for differentiating LBBP from LVS(e)P in the same group of patients is feasible. Electrophysiologic evidence from our intrapatient-controlled study shows that LBBP and LVS(e)P differ in ventricular electrical synchronization.

Case report: Left bundle branch pacing guided by real-time monitoring of current of injury and electrocardiography.

Background: Left bundle branch (LBB) pacing (LBBP) has recently emerged as a physiological pacing mode. Current of injury (COI) can be used as the basis for electrode fixation position and detection of perforation. However, because the intermittent pacing method cannot monitor the changes in COI in real time, it cannot obtain information about the entire COI change process during implantation. Case summary: Left bundle branch pacing was achieved for treatment of atrioventricular block in a 76-year-old female. Uninterrupted electrocardiogram and electrogram were recorded on an electrophysiology system. In contrast to the interrupted pacing method, this continuous pacing and recording technique enables real-time monitoring of the change in ventricular COI and the paced QRS complex as the lead advances into the interventricular septum. During the entire screw-in process, the COI amplitude increased and then decreased gradually after reaching the peak, followed by a small but significant, rather than dramatic, decrease. Conclusion: This case report aims to demonstrate the clinical significance of changes in COI and QRS morphology for LBBP using real-time electrocardiographic monitoring and filtered and unfiltered electrograms when the lead is deployed using a continuous pacing technique. The technique could be used to confirm LBB capture and avoid perforation.

The left bundle branch has been captured but shows the left ventricular septal pacing:What is the mechanism?

It was shown that V6 R-wave peak time (V6 RWPT) prolongs with transition form non-selective left bundle branch pacing (ns-LBBP) to left ventricular septal pacing (LVSP) but remains constant or slightly prolongs with transition to selective left bundle branch pacing (sel-LBBP) [1,2]. Here, we report on a patient who was observed with a LBB potential, isoelectric interval, where the V6 RWPT substantially prolonged with transition from ns-LBBP to sel-LBBP at near threshold output.

Electrophysiological characteristics and possible mechanism of bipolar pacing in left bundle branch pacing.

BACKGROUND: Left bundle branch pacing is a physiological pacing modality with a low and stable threshold. The electrophysiological characteristics and mechanisms of bipolar pacing remain unclear. OBJECTIVES: This study aimed to assess the electrophysiological characteristics of bipolar pacing of left bundle branch pacing and to infer the mechanisms underlying each electrocardiogram and electrogram waveform morphology. METHODS: A total of 65 patients who strictly met the criteria for left bundle branch capture were enrolled. The changes in the morphology of the electrocardiogram and electrogram during the threshold testing with different outputs on unipolar and bipolar pacing were recorded. The electrophysiological characteristics were then analyzed. RESULTS: Four distinct morphologies and 3 different types of transitions during bipolar pacing threshold testing were identified; we labeled the 4 types of morphologies as nonselective (NS)-bipolar-left bundle (LB), NS-cathodal-LB, selective (S)-cathodal-LB, and left ventricular septal-cathodal. Except left ventricular septal-cathodal, the other 3 types (NS-bipolar-LB, NS-cathodal-LB, and S-cathodal-L) had a short and constant V6 R-wave peak time (RWPT) (64.8 ± 7.7 ms vs 65.7 ± 7.8 ms vs 65.7 ± 7.3 ms). The paced QRS (P-QRS) complex was the narrowest in NS-bipolar-LB rather than in NS-cathodal-LB (118.2 ± 14.2 ms vs 133.8 ± 15.8 ms; P < .001). NS-bipolar-LB had a higher threshold than did NS-cathodal-LB (2.5 ± 1.2 V vs 0.8 ± 0.4 V; P < .001). CONCLUSION: With a higher output on bipolar pacing, NS-bipolar-LB capture had the shortest V6 RWPT, V1 RWPT, and P-QRS. S-cathodal-LB capture had the longest V1 RWPT and P-QRS complex.

Interesting electrophysiological phenomenon during positioning of the lead deep inside the septum.

Left bundle branch pacing (LBBP) is a developing physiological pacing technique. Wu et al. proposed that direct LBB capture could be confirmed by recording retrograde His potential (PoReHis ) and mapping of the left conduction system potential. The transventricular-septal electrophysiological phenomena deserve further study. Here, we used a continuous uninterrupted pacing technique to confirm the LBB capture by dynamically observing changes in PoReHis and stimulus to left ventricular activation time.

Recording an isoelectric interval as an endpoint of left bundle branch pacing with continuous paced intracardiac electrogram monitoring.

BACKGROUND: The present study aimed to evaluate the feasibility and safety of the novel left bundle branch pacing (LBBP) procedure that uses isoelectric interval as an endpoint for lead implantation. METHODS: A total of 41 patients with indications for pacing were enrolled. All patients underwent a novel LBBP procedure guided by recording an isoelectric interval as an endpoint for lead implantation. The procedural details and electrophysiological characteristics were then analyzed. RESULTS: A total of 38/41 (92.7%) cases were confirmed of left bundle branch (LBB) capture. An isoelectric interval was observed in 36/41 cases (87.8%). A total of 36/41 (87.8%) cases with LBB potential were observed. The mean unipolar LBBP threshold at the implant was 0.5 ± 0.2 V. The mean sensed amplitude of the R wave and the pacing impedance at the implant were 12.9 ± 5.0 mV and 723.5 ± 117.1 Ω. During the final threshold testing, a transition from non-selective to selective LBBP (S-LBBP) was demonstrated in 26 patients. A transition from non-selective LBBP (NS-LBBP) to left ventricular septal myocardial capture was observed in 12 patients. CONCLUSION: Using an isoelectric interval as an endpoint to guide the LBBP was feasible in a high proportion of captured LBB cases.

High-pass filter settings and the role and mechanism of discrete ventricular electrograms in left bundle branch pacing.

Objective: The characteristics of discrete intracardiac electrogram (EGM) in selective left bundle branch (SLBB) pacing (SLBBP) have not been described in detail previously. This study aimed to examine the effect of different high-pass filter (HPF) settings on discrete local ventricular components in an intracardiac EGM and to analyze its possible mechanisms. Methods: This study included 144 patients with indications of permanent cardiac pacing. EGMs were collected at four different HPF settings (30, 60, 100, and 200 Hz) with a low-pass filter at 500 Hz, and their possible mechanisms were analyzed. Results: LBBP was successfully achieved in 91.0% (131/144) of patients. SLBBP was achieved in 123 patients. The occurrence rates of discrete local ventricular EGM were 16.7, 33.3, 72.9, and 85.4% for HPF settings of 30, 60, 100, and 200 Hz, respectively. The analysis of discrete EGM detection showed significant differences between the different HPF settings. By using the discrete local ventricular component and isoelectric interval as the SLBB capture golden standard, the results of EGMs revealed that the 30 Hz HPF has a sensitivity of 19% and specificity of 100%. The 60 Hz HPF had a sensitivity of 39% and a specificity of 100%. The 100 Hz HPF had a sensitivity of 85% and a specificity of 100%. The 200 Hz HPF had a sensitivity of 100% and specificity of 100%. Conclusion: An optimal HPF setting of 200 Hz is recommended for discrete local ventricular EGM detection. A discrete local ventricular EGM should exhibit an isoelectric interval. A steep deflection and high-frequency ventricular EGM morphology nearly identify an intrinsic EGM morphology.

Association between chymase gene polymorphisms and atrial fibrillation in Chinese Han population.

BACKGROUND: Chymase is the major angiotensin II (Ang II)-forming enzyme in cardiovascular tissue, with an important role in atrial remodeling. This study aimed to examine the association between chymase 1 gene (CMA1) polymorphisms and atrial fibrillation (AF) in a Chinese Han population. METHODS: This case-control study enrolled 126 patients with lone AF and 120 age- and sex-matched healthy controls, all from a Chinese Han population. Five CMA1 polymorphisms were genotyped. RESULTS: The CMA1 polymorphism rs1800875 (G-1903A) was associated with AF. The frequency of the GG genotype was significantly higher in AF patients compared with controls (p = 0.009). Haplotype analysis further demonstrated an increased risk of AF associated with the rs1800875-G haplotype (Hap8 TGTTG, odds ratio (OR) = 1.668, 95% CI 1.132-2.458, p = 0.009), and a decreased risk for the rs1800875-A haplotype (Hap5 TATTG, OR = 0.178, 95% CI 0.042-0.749, p = 0.008). CONCLUSIONS: CMA1 polymorphisms may be associated with AF, and the rs1800875 GG genotype might be a susceptibility factor for AF in the Chinese Han population.