Transseptal Transition Patterns During Left Bundle Branch Area Lead Implantation.

Continuous deep septal pacing and signal recording during implantation of left bundle branch pacing (LBBP) lead enables to monitor beat-to-beat changes of electrocardiogram (ECG) and myocardial current of injury (COI) as the lead crosses the septum. This study aimed to characterize patterns of continuous QRS, ST-T, and COI change for monitoring of the lead depth and instantaneous determination of the obtained capture type (LBBP vs left ventricular septal pacing [LVSP]). The ECG and COI during lead implantation were scrutinized for sudden changes of V6 R-wave peak time, V1 initial and terminal R-wave amplitude, V3-V6 R-wave amplitude, repolarization pattern and S-wave amplitude in I, V5-V6, and COI drop. The sudden and gradual transition patterns were diagnosed depending on the presence or absence of the above beat-to-beat ECG phenomena, respectively. A total of 212 pacemaker recipients were analyzed; LBBP and LVSP were obtained in 77.4% and 22.6%, respectively. There were 4.7 ± 2.1 and 0.2 ± 0.6 beat-to-beat phenomena in LBBP and LVSP patients, respectively. The sudden transition pattern, recognized in 80.7%, had sensitivity and specificity for LBBP diagnosis of 98.8% and 81.2%, respectively. A sudden drop of COI (29.4 ± 8.5 mV to 12.8 ± 4.9 mV) was observed in 53.9% patients (LBBP was simultaneously obtained in 92.7%). Capture of left bundle branch during lead penetration is a beat-to-beat phenomenon. Two transseptal transition patterns were identified: 1) sudden, which is typical for obtaining LBBP; and 2) gradual, which is typical for obtaining LVSP. A sudden COI drop, a very observable phenomenon, also identified reaching the left subendocardial area.

Jastrzębski M ，Kiełbasa G ，Moskal P ，Bednarek A ，Rajzer M ，Burri H ，Curila K ，Vijayaraman P ... -  《-》

Electrophysiological characteristics of lead position-dependent electrogram uninterrupted transition during left bundle branch pacing.

The interrupted technique of left bundle branch pacing (LBBP) limits the continuous monitoring of paced electrocardiogram and intracardiac electrogram (EGM) transitions, which may result in overlooked or misinterpreted subtle transitions. This study aimed to explore the electrophysiological characteristics of lead position-dependent EGM continuous transitions to evaluate lead depth and to investigate the clinical significance of transseptal pacing modalities. A continuous pacing and recording technique enabled by a rotatable connector was used to allow the real-time monitoring of progressive changes in paced EGM and electrocardiographic morphology. Careful observations were conducted to evaluate whether there were significant changes in the amplitude and morphology of the ventricular current of injury (COI), R-wave peak times in leads V1 and V6, QRS duration, and impedance at different interventricular septal depths. The study included 105 patients. Nonselective LBBP was achieved in 94 patients (89.5%), of whom 88 (83.8%) achieved selective LBBP (SLBBP). Left ventricular septal pacing was confirmed in 11 patients (11.5%). The amplitude of ventricular EGM predictably changed with radial septum depth and peaked in the interventricular septum (26.3±11.3 mV). As the lead was inserted into the left ventricular subendocardium, the ventricular COI declined to a level approximating that of the right septum (11.7 ± 6.3 mV for SLBBP vs 10.4 ± 5.8 mV for right ventricular septal pacing). When selective left bundle branch capture occurred, significant morphological transitions in the ventricular COI were observed in the unfiltered EGM. The continuous recording technique provides a more detailed understanding of pacing lead radial depth throughout implantation. COI amplitude and morphology variations can identify different pacing modalities, particularly in recognizing SLBBP.

Shen J ，Jiang L ，Wu H ，Zhang L ，Li H ，Pan L ... -  《-》

Predictors of failed left bundle branch pacing implant in heart failure with reduced ejection fraction: Importance of left ventricular diameter and QRS morphology.

Left bundle branch pacing (LBBP) is considered an alternative to cardiac resynchronization therapy (CRT). However, LBBP is not suitable for all patients with heart failure. The aim of our study was to identify predictors of unsuccessful LBBP implantation in CRT candidates. A cohort of consecutive patients with indications for CRT were included. Clinical, echocardiographic, and electrocardiographic variables were prospectively recorded. A total of 187 patients were included in the analysis. LBBP implantation was successful in 152 of 187 patients (81.2%) and failed in 35 of 187 patients (18.7%). The causes of unsuccessful implantation were unsatisfactory paced QRS morphology (28 of 35 [80%]), inability to screw the helix (4 of 35 [11.4%]), lead instability (2 of 35 [5.7%]), and high pacing thresholds (1 of 35 [2.8%]). The left ventricular end-diastolic diameter (LVEDD), non-LBBB (left bundle branch block) QRS morphology, and QRS width were predictors of failed implantation according to the univariate analysis. According to the multivariate regression analysis, LVEDD (odds ratio 1.31 per 5-mm increase; 95% confidence interval 1.05-1.63 per 5-mm increase; P = .02) and non-LBBB (odds ratio 3.07; 95% confidence interval 1.08-8.72; P = .03) were found to be independent predictors of unsuccessful LBBP implantation. An LVEDD of 60 mm has 60% sensitivity and 71% specificity for predicting LBBP implant failure. When LBBP was used as CRT, LVEDD and non-LBBB QRS morphology predicted unsuccessful implantation. Non-LBBB triples the likelihood of failed implantation independent of LVEDD. Caution should be taken when considering these parameters to plan the best pacing strategy for patients.

Graterol FR ，Pujol-López M ，Borràs R ，Ayala B ，Uribe L ，Guasch E ，Regany-Closa M ，Niebla M ，Carro E ，Guichard JB ，Castel MÁ ，Arbelo E ，Porta-Sánchez A ，Sitges M ，Brugada J ，Roca-Luque I ，Doltra A ，Mont L ，Tolosana JM ... -  《-》

New-Onset Left Ventricular Dysfunction After Left Bundle Branch Pacing.

Left bundle branch pacing (LBBP) provides stable pacing parameters and has been suggested as an alternative for right ventricular pacing and cardiac resynchronization therapy. The aim of the study was to assess the incidence and etiology of new-onset left ventricular dysfunction (NOLVD) following LBBP in patients with baseline normal left ventricular (LV) function and cardiomyopathy patients with normalized LV function. Patients undergoing successful LBBP for symptomatic bradyarrhythmia or as an alternative to cardiac resynchronization therapy were included. Normalization of LV function was defined as improvement in LV ejection fraction to ≥50%. Patients with baseline normal LV function and those with recovered LV function after LBBP constituted the study group. Loss of conduction system capture (LOCSC) was defined as complete or partial loss of right bundle branch delay pattern along with inability to demonstrate capture transition during threshold assessment. A total of 426 patients were included; 59% (n = 250) had baseline normal LV function (group I) and 41% (n = 176) had recovered LV function after LBBP (group II). Mean follow-up duration of 28.3 ± 16.7 months. NOLVD was noted in 3.75% (n = 16; group I, n = 5, and group II, n = 11) of patients. The etiologies for NOLVD were LOCSC in 62.5% (n = 10), suboptimal atrioventricular (AV) delay in 18.7% (n = 3), atrial fibrillation in 6.3% (n = 1), and idiopathic in 12.5% (n = 2). LOCSC occurred at a mean interval of 9.2 ± 6.4 months after the initial implantation. Reinterventions (n = 6) including lead repositioning, AV delay optimization, and AV junction ablation resulted in renormalization of LV function in all 6 patients. Periodic assessment in device clinic is required because NOLVD from reversible causes can occur during follow-up in patients after LBBP.

Ponnusamy SS ，Ganesan V ，Nagalingam S ，Ramalingam V ，Mariappan S ，Moghal H ，Murugan S ，Kumar M ，Joseph R ，Vijayaraman P ... -  《-》

Safety assessment of coronary arteries during left bundle branch area pacing.

This study aimed to assess the safety of left bundle branch area pacing (LBBAP) by measuring the distance from the tip of the electrode to the nearby coronary artery with a nine-partition grid method. From January 2019 to October 2020, patients who underwent LBBAP and postoperative coronary angiography in the Second Affiliated Hospital of Nanchang University were included in the study. The patients' fluoroscopic images of LBBAP and coronary angiography were collected and analyzed. Changes in the ST‑T segment in the electrocardiogram (ECG), serum troponin, and myocardial enzyme profiles were observed before and after the LBBAP procedure. A total of 50 patients were included in this study, of whom 46 patients underwent implantation with a pacemaker and 4 patients received an implantable cardioverter defibrillator (ICD). The pacing electrodes were confined to the posterior-middle (PM), median (M), Posterior inferior (PI), and middle inferior (MI) positions of the two-dimensional nine-square grid or in the junction area of the above positions, and were concentrated in the rectangle formed by the line of the center points of the four positions. The average vertical distances from the electrode tip to the left anterior descending branch artery (LAD), posterior descending branches (PD) and the left posterior ventricular branches (PL) were 19.69 ± 8.72 mm, 26.09 ± 8.02 mm, and 21.11 ± 7.86 mm, respectively; the minimum was 5.28 mm, 9.51 mm, and 8.69 mm, respectively. Coronary angiography in all patients showed no significant injury to the ventricular septal branch; however, we observed elevated serum troponin and changes in ST‑T segment in ECG. The study demonstrates that pacing electrodes in LBBAP can be safely implanted over a wide range. Coronary arteries are likely to be safe when the pacing electrodes are located within the rectangle formed by the line connecting the PM, M, PI, and MI zone centroids. The left bundle branch can be quickly captured and the safety of the coronary artery can be improved by locating the electrode in the posterior-mid zone. The potential risk of injury to the LAD from the electrode is greater compared with the PD.

Kong Q ，Chen H ，Hua J ，Xiong Z ，Le S ，Liu J ，Wang D ，Chen Q ... -  《-》