Left Ventricular Activation Time Research Articles

Conduction latency in left bundle branch pacing in heart failure patient

Since the introduction of left bundle branch pacing (LBBP), a search for precise parameters confirming successful capture of conduction system was conducted. Most of the proposed electrocardiographic criteria refer to patients with narrow QRS complexes. We present a patient with heart failure in whom cardiac resynchronization was achieved using conduction system pacing. While measuring left ventricular activation time, an isoelectric interval of 74 ms between stimulus and R-wave appeared resulting in prolongation of V6 RWPT to 124 ms. Considering the immediate narrowing of QRS complexes following LBBP, the observed latency most probably reflects prolonged conduction time through the His-Purkinje system.

Pilot study to evaluate left-to-right ventricular offset in biventricular pacing-comparison of electrocardiographic imaging and ECG.

Biventricular pacing (BiVp) improves outcomes in systolic heart failure patients with electrical dyssynchrony. BiVp is delivered from epicardial left ventricular (LV) and endocardial right ventricular (RV) electrodes. Acute electrical activation changes with different LV-RV stimulation offsets can help guide individually optimized BiVp programming. We sought to study the BiVp ventricular activation with different LV-RV offsets and compare with 12-lead ECG. In five patients with BiVp (63 ± 17-year-old, 80% male, LV ejection fraction 27 ± 6%), we evaluated acute ventricular epicardial activation, varying LV-RV offsets in 20 ms increments from -40 to 80 ms, using electrocardiographic imaging (ECGI) to obtain absolute ventricular electrical uncoupling (VEUabs, absolute difference in average LV and average RV activation time) and total activation time (TAT). For each patient, we calculated the correlation between ECGI and corresponding ECG (3D-QRS-area and QRS duration) with different LV-RV offsets. The LV-RV offset to attain minimum VEUabs in individual patients ranged 20-60 ms. In all patients, a larger LV-RV offset was required to achieve minimum VEUabs (36 ± 17 ms) or 3D-QRS-area (40 ± 14 ms) than that for minimum TAT (-4 ± 9 ms) or QRS duration (-8 ± 11 ms). In individual patients, 3D-QRS-area correlated with VEUabs (r 0.65 ± 0.24) and QRS duration correlated with TAT (r 0.95 ± 0.02). Minimum VEUabs and minimum 3D-QRS-area were obtained by LV-RV offset within 20 ms of each other in all five patients. LV-RV electrical uncoupling, as assessed by ECGI, can be minimized by optimizing LV-RV stimulation offset. 3D-QRS-area is a surrogate to identify LV-RV offset that minimizes LV-RV uncoupling.

Current Role of Electrocardiographic Imaging in Patient Selection for Cardiac Resynchronization Therapy.

Cardiac resynchronization therapy (CRT) is a recognized therapy for heart failure with altered ejection fraction and abnormal left ventricular activation time. Since the introduction of the therapy, a 30% rate of non-responders is observed and unchanged. The 12-lead ECG remains the only recommended tool for patient selection to CRT. The 12-lead ECG is, however, limited in its inability to provide a precise pattern of regional electrical activity. Electrocardiographic imaging (ECGi) provides a non-invasive detailed mapping of cardiac activation and therefore appears as a promising tool for CRT candidates. The non-invasive ventricular activation maps acquired by ECGi have been primarily explored for the diagnosis and guidance of therapy in patients with atrial or ventricular tachyarrhythmia. However, the accuracy of the system in this field is lacking and needs further improvement before considering a clinical application. On the other hand, its use for patient selection for CRT is encouraging. In this review, we introduce the technical considerations and we describe how ECGi can precisely characterize ventricular activation, especially in patients with left bundle branch block, thus identifying the electrical substrate responsive to CRT.

A porcine large animal model of radiofrequency ablation-induced left bundle branch block.

Electrocardiographic (ECG) features of left bundle branch (LBB) block (LBBB) can be observed in up to 20%-30% of patients suffering from heart failure with reduced ejection fraction. However, predicting which LBBB patients will benefit from cardiac resynchronization therapy (CRT) or conduction system pacing remains challenging. This study aimed to establish a translational model of LBBB to enhance our understanding of its pathophysiology and improve therapeutic approaches. Fourteen male pigs underwent radiofrequency catheter ablation of the proximal LBB under fluoroscopy and ECG guidance. Comprehensive clinical assessments (12-lead ECG, bloodsampling, echocardiography, electroanatomical mapping) were conducted before LBBB induction, after 7, and 21days. Three pigs received CRT pacemakers 7days after LBB ablation to assess resynchronization feasibility. Following proximal LBB ablation, ECGs displayed characteristic LBBB features, including QRS widening, slurring in left lateral leads, and QRS axis changes. QRS duration increased from 64.2 ± 4.2ms to 86.6 ± 12.1ms, and R wave peak time in V6 extended from 21.3 ± 3.6ms to 45.7 ± 12.6ms. Echocardiography confirmed cardiac electromechanical dyssynchrony, with septal flash appearance, prolonged septal-to-posterior-wall motion delay, and extended ventricular electromechanical delays. Electroanatomical mapping revealed a left ventricular breakthrough site shift and significantly prolonged left ventricular activation times. RF-induced LBBB persisted for 3weeks. CRT reduced QRS duration to 75.9 ± 8.6ms, demonstrating successful resynchronization. This porcine model accurately replicates the electrical and electromechanical characteristics of LBBB observed in patients. It provides a practical, cost-effective, and reproducible platform to investigate molecular and translational aspects of cardiac electromechanical dyssynchrony in a controlled and clinically relevant setting.

Visualization of Left Ventricular Endocardium Activation Time during Cardiac Conduction System Pacing

Introduction. Right ventricular myocardial pacing leads to asynchronous contraction of the left ventricle (LV) and can impair its contractility over time. Stimulation of the conduction system of the heart ensures physiological activation of the ventricles.
 The aim. To visualize the pattern of propagation of the electrical front on the activation map of the LV endocardium during conduction system pacing and during right ventricular myocardial pacing.
 Materials and methods. In two patients with the conduction system pacing, who were operated at the National Amosov Institute of Cardiovascular Surgery, invasive LV activation mapping was performed on various options of cardiac pacing using the EnSite Precision TM navigation system. One patient with complete atrioventricular block had nonselective His bundle pacing. The second patient had dilated cardiomyopathy and indications for cardiac resynchronization therapy and ablation of the atrioventricular junction due to chronic tachyform of atrial fibrillation. After an unsuccessful attempt to place LV lead in coronary sinus, a lead for left bundle branch pacing was implanted. Different activation maps of the LV endocardium were built in two patients with two types of cardiac pacing: right ventricular myocardial pacing and cardiac conduction system pacing.
 Results. The total LV endocardial activation time was significantly different in the two studied patients with different pacing options. In a patient with non-selective stimulation of His bundle, the total LV endocardial activation time was 43 ms (QRS width 126 ms, the interval from the stimulus to the peak of the R wave in lead V6 78 ms). After switching to right ventricular myocardial pacing with a decrease in the pacing amplitude, the total LV endocardial activation time prolonged to 90 ms (QRS width 165 ms, the interval from the stimulus to the peak of the R wave in lead V6 117 ms). In a patient with left bundle branch pacing, total LV endocardial activation time was 51 ms (QRS width 160 ms, the interval from the stimulus to the peak of the R wave in lead V6 66 ms). With switching exclusively to right ventricular pacing the total LV endocardial activation time prolonged to 93 ms (stimulated QRS width 180 ms). At the same time, the activation pattern of the LV endocardium was significantly different, since the right ventricular lead was located closer to the apex.
 Conclusions. Conduction system pacing provides rapid physiological LV activation and potentially avoids the negative consequences of asynchronous slow ventricular activation during right ventricular pacing.

Procedure feasibility and mid-term follow-up of left bundle branch area pacing using stylet-driven pacing leads with a fixed-curve delivery sheath in patients with structural heart disease

Abstract Background Recently, left bundle branch area pacing (LBBAP) has been performed using style-driven extendable screw-in leads with newly introduced pre-shaped delivery sheath in South Korea. There are limited data on the feasibility of LBBAP in patients with structural heart disease (SHD). Purpose To evaluate LBBAP procedure feasibility and mid-term follow-up data of LBBAP lead profile in pateints with SHD Methods Patients, in which LBBAP was attempted, were consecutively enrolled at the Seoul National University Hospital from January 2021 to December 2022. LBBAP was performed with stylet-driven lead (Solia S60, Biotronik) delivered through a delivery sheath (Selectra 3D, Biotronik). Procedure feasibility, LBBAP success rate, and mid-term LBBAP lead threshold were evaluated in patients with or without various type of SHD. Results A total of 121 patients were enrolled (mean age 73.5±12.2 years). Atrioventricular block was the most common indication (n=94, 77.7%), followed by atrial fibrillation with slow ventricular rate (n=12, 9.9%), sick sinus syndrome (n=10, 8.3%), and heart failure indicated cardiac resynchronized therapy (n=5, 4.1%). LBBAP success rate was 89.3% of total study population, deep septal pacing was achieved in 4.1%, and right ventricle apex pacing were performed in 6.6%. Fifty-one patients (42.1%) were accompanied by SHD (Figure). Patients with SHD had significantly lower left ventricular ejection fraction than those without SHD (54±13% vs. 62±5%, p<0.001). Baseline QRS duration was longer in patients with SHD (107±26 ms vs. 135±35 ms, p=0.005). Although LBBAP success rate was significantly lower in patients with SHD than those without in total study population (80.4% vs. 95.7%, p=0.007), LBBAP success rate was not differ between two groups after excluding first 30 cases (98.1% in patients without SHD vs. 97.4% in patients with SHD, p=0.811) (Figure). Among patients with successful LBBAP, total procedure time was longer in pateints with SHD, but there was no significant difference of fluoroscopic time, bipolar V sensing, V pacing threshold, and V impedance between the two groups (Figure). Pateints with SHD had longer left ventricular activation time (LVAT) (80±13ms vs. 72±9 msec, p=0.003), but there was no statistically significant difference in the final QRS duration between the two groups (104±14 ms in patients without SHD vs. 111±14 msec in patients with SHD, p=0.955). During mean 19±6 months follow-up, there was no significant V threshold increase in both groups. Conclusion LBBAP using stylet-driven pacing leads in patients with SHD is feasible and safe as in patients without structural heart disease, even by an early experienced operator with LBBAP procedure.

Comparison of the left ventricular dyssynchrony between stylet-driven and lumen-less lead technique in left bundle branch area pacing using myocardial perfusion scintigraphy.

Left bundle branch area pacing (LBBAP) has emerged as a novel physiological pacing method to reduce left ventricular (LV) dyssynchrony due to ventricular pacing. Only lumen-less pacing leads (LLLs) with fixed helixes could achieve LBBAP previously, but recently, LBBAP has been performed using stylet-driven leads (SDLs). This study aimed to evaluate the LV dyssynchrony between SDLs and LLLs techniques in LBBAP. We retrospectively evaluated patients who underwent LBBAP with either SDLs or LLLs. We compared both groups' electrocardiogram (ECG) findings and LV dyssynchrony parameters derived from myocardial perfusion scintigraphy. LV dyssynchrony parameters consisted of phase analysis and regional wall motion analysis. We evaluated bandwidth, phase standard deviation (PSD), and entropy in the phase analysis. The time to the end-systolic frame (TES) was calculated in regional wall motion analysis using single-photon emission computed tomography (SPECT). We also evaluated the maximum differences between segmental TES (MDTES), the standard deviation of TES (SDTES), and the difference in the TES between the lateral wall and septum (DTES-LS). In total, 97 patients were enrolled. The success rate of LBBAP did not differ between the groups [SDLs: 47/48 patients (98%) vs. LLLs: 47/51 patients (92%), P=0.36]. The paced QRS duration and the stimulus to the peak LV activation time (stim-LVAT) also did not differ between SDL and LLL groups (122±10 vs. 119±12 ms, P=0.206; 69±12 vs. 66±13 ms, P=0.31, respectively). There were no differences in bandwidth, PSD, and entropy between SDL and LLL groups (73°±37° vs. 86°±47°, P=0.18; 19°±8.5° vs. 21°±9.7°, P=0.19; 0.57±0.08 vs. 0.59±0.08, P=0.17, respectively). The regional wall motion analysis parameters MDTES, SDTES, and DTES-LS also did not differ between SDL and LLL groups (19%±10% vs. 20%±10%, P=0.885; 5.0%±2.5% vs. 5.0%±2.5%, P=0.995; 5.0%±3.7% vs. 4.8%±4.2%, P=0.78, respectively). LBBAP using SDLs was comparable to LV electrical and mechanical synchrony with LLLs.

Difference of ventricular synchrony between LBBP, LBFP and LVSP: A speckle tracking echocardiographic study.

Left bundle branch area pacing (LBBAP) has emerged as a physiological and stable form of pacing. We aim to compare the mechanical ventricular synchrony of LBBP, LBFP, and LVSP. Proximal Left bundle branch pacing (LBBP), left bundle fascicular pacing (LBFP) and left ventricular septal pacing (LVSP) were identified in patients with bradycardia who successfully underwent LBBAP. Patients with left ventricular ejection fraction (LVEF) < 50% or QRS duration (QRSd) ≥ 120ms were excluded. By using electrocardiograms, the left ventricular activation time (LVAT) and QRS duration (QRSd) were measured to examine electrophysiological synchrony. As indications of mechanical synchrony, global longitudinal strain (GLS), global circumferential strain (GCS), global radial strain (GRS), and peak strain dispersion (PSD) were evaluated by using 2-dimensional speckle tracking echocardiography (2D-STE). In 56 patients, data were collected during LBBP (n = 18), LBFP (n = 16), and LVSP (n = 22). LVSP resulted in a longer LVAT (91.3 ± 14.9ms) than LBBP (77.1 ± 10.8ms, P < 0.05) and LBFP (72.1 ± 9.6ms, P < 0.05), but all three groups had similar QRSd. There were no differences in GLS, GCS, GRS, or PSD between LBBP, LBFP, and LVSP. In patients with normal cardiac function and narrow QRS, though LBBAP with LBB capture resulted in better electrophysiological synchrony than without, the mechanical synchrony of the three groups was comparable.

Predictors of implantation failure in left bundle branch area pacing using a lumenless lead in patients with bradycardia.

Left bundle branch area pacing (LBBAP) is a novel conduction system pacing technique. In this multicenter study, we aimed to evaluate the procedural success, safety, and preoperative predictors of procedural failure of LBBAP. LBBAP was attempted in 285 patients with pacemaker indications for bradyarrhythmia, which were mainly atrioventricular block (AVB) (68.1%) and sick sinus syndrome (26.7%). Procedural success and electrophysiological and echocardiographic parameters were evaluated. LBBAP was successful in 247 (86.7%) patients. Left bundle branch (LBB) capture was confirmed in 54.7% of the population. The primary reasons for procedural failure were the inability of the pacemaker lead to penetrate deep into the septum (76.3%) and failure to achieve shortening of stimulus to left ventricular (LV) activation time in lead V6 (18.4%). Thickened interventricular septum (odds ratio [OR], 2.48; 95% confidence interval [CI], 1.15-5.35), severe tricuspid regurgitation (OR, 8.84; 95% CI, 1.22-64.06), and intraventricular conduction delay (OR, 8.16; 95% CI, 2.32-28.75) were preoperative predictors of procedural failure. The capture threshold and ventricular amplitude remained stable, and no major complications occurred throughout the 2-year follow-up. In patients with ventricular pacing burden >40%, the LV ejection fraction remained high regardless of LBB capture. Successful LBBAP was affected by abnormal cardiac anatomy and intraventricular conduction. LBBAP is feasible and safe as a primary strategy for patients with AVB, depending on ventricular pacing.

Time-related factors predicting a positive response to cardiac resynchronisation therapy in patients with heart failure

This study aimed to identify time parameters predicting favourable CRT response. A total of 38 patients with ischemic cardiomyopathy, qualified for CRT implantation, were enrolled in the study. A 15% reduction in indexed end-systolic volume after 6 months was a criterion for a positive response to CRT. We evaluated QRS duration, measured from a standard ECG before and after CRT implantation and obtained from mapping with NOGA XP system (AEMM); and the delay, measured with the implanted device algorithm (DCD) and its change after 6 months (ΔDCD); and selected delay parameters between the left and right ventricles based on AEMM data. A total of 24 patients presented with a positive response to CRT versus 9 non-responders. After CRT implantation, we observed differences between responders and non-responders group in the reduction of QRS duration (31 ms vs. 16 ms), duration of paced QRS (123 ms vs. 142 ms), and the change of ΔDCDMaximum (4.9 ms vs. 0.44 ms) and ΔDCDMean (7.7 ms vs. 0.9 ms). The difference in selected parameters obtained during AEMM in both groups was related to interventricular delay (40.3 ms vs. 18.6 ms). Concerning local activation time and left ventricular activation time, we analysed the delays in individual left ventricular segments. Predominant activation delay of the posterior wall middle segment was associated with a better response to CRT. Some AEMM parameters, paced QRS time of less than 120 ms and reduction of QRS duration greater than 20 ms predict the response to CRT. ΔDCD is associated with favourable electrical and structural remodelling.Clinical trial registration: SUM No. KNW/0022/KB1/17/15.

Conduction system pacing guided by 3d-electroanatomic mapping system preserves systolic function in paediatric patients

Abstract Funding Acknowledgements Type of funding sources: None. Background/Introduction Paediatric transvenous permanent pacing from alternative ventricular sites including conduction system pacing may prevent ventricular dyssynchrony and systolic dysfunction. These procedures may be difficult and require higher fluoroscopic exposures. The use of three-dimensional-electroanatomic mapping system (3D-EAM) may guide lead implantation toward these alternative sites and reduce fluoroscopic exposure. Purpose of this study is the outcome of 3D-EAM-guided alternative sites pacing in paediatric patients. Methods Retrospective analysis of children and young patients with congenital or acquired complete atrioventricular block (CAVB) with or without other congenital heart disease (CHD) who underwent 3D-EAM-guided transvenous pacing in alternative sites of the subpulmonary ventricle, to perform non-selective His bundle pacing (NSHBP), pacing of ventricular septum close to conduction system (VS-CSP) or outflow tract (OT). 3D-pacing map guided stylet-directed screw-in lead implantation toward septal sites with narrower paced QRS. Procedure and follow-up data were recorded. Parameters of ECG (QRS duration, left ventricular activation time, LVAT), echocardiogram (3D ejection fraction, EF, global longitudinal strain, GLS, of the systemic ventricle) and lead (threshold, sensing) were registered and compared at baseline (pre-implantation) and during follow-up (1-3-year). Data are reported as median (25th-75th centiles). P&amp;lt;0.05 was significant. Results 64 patients (47 females) with CAVB, of whom 11 with CHD, underwent 3D EAM-guided pacing (31 VVIR, 33 DDD) at age 12 (8-15) years, weight 44 (27-57) kg. Prior pacing (RV apex, RV and LV free wall, also biventricular) was present in 27 patients. Pacing sites were: 10 NSHBP, 5 RVOT, 49 VS-CSP (Figure 1). Procedure time was 175 (146-200) min, fluoroscopy exposure was: 3.0 (1.2-5.0) mGy and 90 (33-146) microGy/m2. Echographic parameters at baseline and follow-up are reported in Table 1. Baseline QRS duration 85 (80-130) ms, increased after implantation, 115 (100-120) ms (P=0.002), with LVAT 80 (70-81) ms (Figure 1). In patients with prior pacing, QRS shortened post-implantation: QRS 130 (120-160) vs. 120 (110-125)ms (P=0.004). Lead parameters were good post-implantation and at 3-year follow-up: threshold 0.5 (0.4-0.7) vs. 0.9 (0.7-1.2)V/0.5 ms; R-wave sensing 9 (6-12) vs. 7 (4-9)mV. Four NSHBP patients showed lead dislodgement requiring lead repositioning. Conclusions 3D-EAM-guided alternative site pacing was accomplished with low fluoroscopic exposure. Paced QRS duration was significantly broader than in junctional rhythm but it was significantly narrower than prior epi/conventional site endo pacing. This pacing approach preserved ventricular systolic function in paediatric patients with CAVB at mid-term follow-up.

Comparison of myocardial depolarization spreading after resynchronization with left bundle branch area pacing versus biventricular pacing

Abstract Funding Acknowledgements Type of funding sources: None. Introduction Left bundle branch area pacing (LBBAP) is an emerging new method of cardiac resynchronization therapy (CRT) in patients with left bundle branch block (LBBB). Studies comparing LBBAP with standard biventricular pacing (BiV) have shown similar post-operative shortening of QRS duration and left ventricular activation times. Calculation of equivalent dipole (ED) trajectories from 12-lead high-resolution ECG (hrECG) provides additional insight into myocardial depolarization and may be used for further assessment of left ventricular activation. Purpose The aim of this study was to determine myocardial depolarization patterns with assessment of ED trajectories in patients undergoing CRT with LBBAP or BiV and to compare them to myocardial depolarization patterns of healthy controls. Methods Twenty-five heart failure patients in sinus rhythm and LBBB with indication for CRT were randomized in LBBAP or BiV pacing group. Five-minute supine 12-lead hrECG recordings before and one month after implantation were assessed. LBBAP group was compared to BiV group and both groups were compared to the control of healthy subjects with normal surface ECG. The QRS duration was measured manually by two independent electrophysiologists and averaged. ED trajectories were constructed with the use of inverse algorithm method. The length of ED trajectory was defined as a line between the start and the end of the ED trajectory and its orientation with azimuth and elevation angles. (Figure 1). Results Eleven patients received LBBAP and 14 BiV. There were no differences in baseline characteristics (72% male, 64% non-ischemic cardiomyopathy) between groups. The average baseline QRS duration was 174±20 ms in LBBAP and 180±17 ms in BiV group (p=0.42). QRS duration decreased to 134±14 ms after LBBAP (p&amp;lt;0.01) and 137±11 ms after BiV pacing (p&amp;lt;0.01) and was comparable in both groups (p=0.59). There was also no difference in absolute (p=0.72) or relative (p=0.72) QRS shortening. The absolute and relative ED shortening did not differ (p=0.43 and p=0.38, respectively). At follow-up, analysis of ED trajectories showed a significant difference in elevation angle in both groups (p&amp;lt;0.01). The elevation angle in LBBAP group (6±30°) was significantly different from the angle in BiV group (-44±33°) (p &amp;lt; 0.01), pointing more toward apex of the heart (Figure 2). Furthermore, elevation angle in LBBAP was more similar (absolute difference 49°) to healthy subjects than the elevation angle in BiV group (absolute difference 103°) (p&amp;lt;0.01). There was no intergroup difference in azimuth angle (p=0.07). Conclusion Compared to BiV pacing, resynchronization with LBBAP produces significantly different ED trajectory orientation, which was more comparable to orientation in healthy controls. While both resynchronization methods result in similar QRS narrowing, LBBAP may provide more physiological depolarization of the left ventricle in comparison to BiV.

Impact of left ventricular scar burden on response to two different modalities of conduction system CRT

Abstract Funding Acknowledgements Type of funding sources: Foundation. Main funding source(s): British Heart Foundation Introduction Cardiac resynchronisation therapy (CRT) in the form of His bundle CRT and left bundle area CRT can be more effective than the gold standard, biventricular pacing (BVP). In BVP scar burden is known to predict response whether this is true for these novel modalities is not known. Purpose The purpose of this study was to determine whether left ventricular scar burden assessed using cardiac MRI can be used to predict the electrical and acute haemodynamic response to two novel CRT modalities. Methods Patients with standard CRT indications were recruited. They underwent a pre-procedure cardiac MRI, with late gadolinium enhancement (LGE) to quantify scar. His bundle CRT (His CRT) and left bundle area CRT (LBA CRT) were attempted. The electrical response was measured using high precision non-invasive mapping ECGi (CardioInsight, Medtronic). The haemodynamic response was measured with a high precision protocol. We investigated the impact of scar and baseline electrical characteristic on ECGi and haemodynamic response. Results 26 patients were recruited (85% male, mean age 69 ± 10, with ischaemic cardiomyopathy in 35%). LGE was observed in 96% of cases and the mean (range 1-39%). We found a significant correlation between scar extent and the electrical response with both modalities. There was a significant correlation between a lower scar burden and better electrical response. For His CRT the reduction in left ventricular activation time was better with lower scar burden (R= 0.77, p &amp;lt; 0.01, Picture 1), for LBA CRT for reduction in left ventricular activation was also better with lower scar burden (R = 0.53, p = 0.05, Picture 2). With His CRT there was also a significant correlation between lower scar extent and better acute haemodynamic response ( R = 0.6, p = 0.002) but this was not observed with LBA CRT (R = 0.07, p = 0.77). Conclusion Left ventricular myocardial scar can be used to predict the electrical response to two different conduction system CRT modalities.

Stepwise application of ECG and electrogram based criteria to ensure left bundle branch pacing

Abstract Funding Acknowledgements Type of funding sources: Public Institution(s). Main funding source(s): MPL received the Catalan Society of Cardiology Research Grant in 2019 and 2020 (Catalonia, Spain); the Josep Font Grant (2019-2022) from Hospital Clínic Barcelona (Catalonia, Spain). Background Left bundle branch pacing (LBBP) has emerged as an alternative to biventricular pacing. However, lack of a systematic stepwise application of the left bundle branch (LBB) capture criteria complicates implantation. Objective To define a stepwise application of LBBP capture criteria that will simplify implantation and ensure LBB capture. Methods A cohort of 24 patients from the LEVEL-AT trial who received LBBP and had electrocardiographic imaging (ECGI) at 45 days post-implant were included. The usefulness of ECG and electrogram based criteria to predict accurate LBB capture were analyzed. A two-step approach was developed to ensure LBB capture. The gold standard used to confirm LBB capture was the change in ventricular activation pattern and shortening in left ventricular activation time, assessed by ECGI. Results Twenty-two (91.6%) patients showed LBBP capture on ECGI. All patients fulfilled pre-screwing requisites: lead in septal position in left-oblique projection and W paced morphology in V1. In the first step, presence of either right bundle branch conduction delay pattern (qR or rSR in V1) or left bundle branch capture Plus (QRS ≤120ms) resulted in 95% sensitivity and 100% specificity to predict LBB capture, with an accuracy of 95.8%. In the second step, the presence of selective capture (100% specificity, only 41% sensitivity) or a spike-R&amp;lt;80ms (100% specificity, sensitivity 46%) ensured 100% accuracy to predict LBBP capture. Conclusions Stepwise application of ECG and electrogram criteria ensured an accurate assessment of left conduction system capture.

Left bundle branch area pacing versus biventricular pacing for cardiac resynchronisation therapy

Abstract Funding Acknowledgements Type of funding sources: None. Background Conventional right ventricular pacing induces dyssynchrony and 20% of patients may need upgrade for resynchronisation therapy (CRT). Currently, left bundle branch area pacing (LBBAP) is growing as an alternative for conventional pacing, preserving left ventricular function. Purpose We aimed to describe procedural characteristics of a group of consecutive patients submitted to LBBAP, and to compare the final QRS duration to a group of consecutive idiopathic LBB patients submitted to conventional CRT. Methods Single-centre cohort including consecutive patients submitted to LBBAP or CRT since November 2021. Feasibility, procedure and fluoroscopy times, final QRS duration during pacing immediately after implantation, and periprocedural complications were assessed. Successful implantation of LBBA pacing was defined as a left ventricular activation time (LVAT) &amp;lt; 90ms plus right bundle branch block pattern in V1. Results A total of 91 patients (mean age 75±11 years, 70.3% male, and 43 [47.3%] with LBBAP) were included. Total procedure (63min [50-76] vs. 91min [71-131], p&amp;lt;0.001) and fluoroscopy times (4.1min [2.4-6.4] vs. 13.4min [8.3-23.1], p&amp;lt;0.001) were significantly lower in the LBBAP vs. CRT group, respectively. In the LBBA pacing group, median LVAT was 86ms (IQR 81-94) and no cases of electrode dislocation or perforation at discharge were reported. Final QRS duration was 112ms (IQR 105-125) vs 127ms (IQR 115-143) in the LBBAP vs CRT groups respectively (p&amp;lt;0.001). Conclusion When compared to a group of idiopathic LBB block patients submitted to CRT, LBBAP was faster, required less fluoroscopy time and was associated with final narrower QRS. Further studies are necessary to understand its role in patients with LV dysfunction and indication for resynchronisation therapy.

PO-02-013 EFFICACY OF LEFT BUNDLE BRANCH PACING IN PATIENTS WITH DIFFERENT LEFT BUNDLE BRANCH BLOCK MORPHOLOGIES

Left bundle branch pacing (LBBP) is a novel technique to deliver cardiac resynchronization therapy (CRT) by correcting intrinsic LBBB to achieve electrical and mechanical resynchrony. Whether the efficacy of LBBP is different across different LBBB morphologies has not been reported. To explore the efficacy of LBBP in patients with different LBBB morphologies. Consecutive patients who received LBBP due to either heart failure (HF) with LBBB or atrioventricular block accompanied with a LBBB pattern escape rhythm were recruited. The changes of QRS duration (ΔQRSd) and left ventricular activation time (ΔLVAT) were compared before and after LBBP. Relationships of ΔQRSd and ΔLVAT with cardiac function in HF patients were also explored. HF patients were followed up for at least 6 months. Electrical resynchrony and cardiac function were compared based on 4 major LBBB morphological criteria. Comparison 1: LBBB meeting Strauss criteria vs not; Comparison 2: presence of q wave in lead I and aVL vs not; Comparison 3: presence of QS vs rS morphology of QRS in lead V1; and Comparison 4: presence of S wave in lead V6 vs not. A total of 82 patients were enrolled from January 2018 to August 2022. In Comparison 1, 59 patients had LBBB meeting Strauss criteria vs 23 not meeting criteria. Patients with LBBB meeting Strauss criteria had greater reduction in QRSd (56.95±24.10ms vs 36.83±32.16ms, P<0.05) and LVAT (56.47±14.90ms vs 41.52±17.13ms, P<0.001). Forty-two HF patients met the Strauss criteria had greater LVEF improvement (19.92±6.89% vs 12.41±13.10%, P<0.05) compared to those not meeting the criteria. Comparison 4 included 61 patients without S wave in lead V6 and these patients exhibited better electrical synchrony after LBBP (ΔQRSd: -55.18±24.79ms vs -40.05±33.67ms, P<0.05; ΔLVAT: -55.74±14.70ms vs -41.67±18.55ms, P<0.05) than patients with S wave in V6. Among them, 51 patients without S wave in V6 had HF and showed greater LVEF improvements than those with S wave in V6 (ΔLVEF: 18.65±10.13% vs 6.61±7.78%, P<0.05). Correlation analyses showed significant associations between both ΔQRSd (R=0.55, P <0.001) and ΔLVAT (R=0.39, P <0.01) with LVEF improvement. In multivariate analysis, ΔQRSd>53 ms is an independent predictor of cardiac super response (LVEF improvement>15%). LBBB pattern meeting the Strauss criteria and absence of S wave in lead V6 can predict better electrical resynchrony and LVEF improvement by LBBP.

PO-03-012 STEPWISE APPLICATION OF ECG AND ELECTROGRAM BASED CRITERIA TO ENSURE ELECTRICAL RESYNCHRONIZATION WITH LEFT BUNDLE BRANCH PACING

Left bundle branch pacing (LBBP) has emerged as an alternative to biventricular pacing. However, a systematic stepwise approach to ensure electrical resynchronization is lacking. To define a stepwise application of LBBP criteria that will simplify implantation and guarantee electrical resynchronization. A cohort of 24 patients from the LEVEL-AT trial (NCT04054895) who received LBBP and had electrocardiographic imaging (ECGI) (CardioinsightTM Medtronic, USA) at 45 days post-implant were included. The usefulness of ECG and electrogram based criteria to predict accurate electrical resynchronization with LBBP were analyzed. A two-step approach was developed. The gold standard used to confirm resynchronization was the change in ventricular activation pattern and shortening in left ventricular activation time, assessed by ECGI. Twenty-two (91.6%) patients showed electrical resynchronization on ECGI. All patients fulfilled pre-screwing requisites: lead in septal position in left-oblique projection and W paced morphology in V1. In the first step, presence of either right bundle branch conduction delay pattern (qR or rSR in V1) or left bundle branch capture Plus (QRS ≤120ms) resulted in 95% sensitivity and 100% specificity to predict LBBP resynchronization, with an accuracy of 95.8%. In the second step, the presence of selective capture (100% specificity, only 41% sensitivity) or a spike-R<80ms (100% specificity, sensitivity 46%) ensured 100% accuracy to predict resynchronization by LBBP. Stepwise application of ECG and electrogram criteria ensured accurate assessment of electrical resynchronization with left bundle branch pacing.

PO-03-023 OUTCOMES OF LEFT BUNDLE BRANCH AREA PACING AND ATRIOVENTRICULAR NODE ABLATION IN PATIENTS WITH GROUP III PULMONARY HYPERTENSION AND ATRIAL FIBRILLATION IN REDUCING RECURRENT HOSPITALIZATION

Data on the feasibility of left bundle branch area pacing (LBBAP) and atrioventricular node (AVN) ablation in patients with pulmonary hypertension (PH) are limited. This study investigated the characteristics and outcomes of LBBAP and AVN ablation in patients with PH. This is a retrospective study of patients with PH and AF who underwent LBBAP and AVN ablation at the Cleveland Clinic between January 1, 2019 and August 1, 2022. Pre-procedural, post-procedural, and follow-up patient data were obtained. A total of 11 patients (mean age 74±10 years old, 100% female) with PH and AF who underwent concomitant LBBAP and AVN ablation were included. The etiology of PH was Group III PH in all patients (55% had COPD and 91% had restrictive lung disease), with the average pulmonary arterial systolic pressure (PASP) of 42 mmHg by echocardiogram, FEV1 of 61.9±17.4% predicted, and FVC of 59.9±7.8% predicted. Baseline ejection fraction was 57±10%, QRS duration was 96±20 ms. Concomitant LBBAP and AVN ablation was successful in all patients. Final implant characteristics included: QRS duration was 124±8 ms, left ventricular activation time was 73.7±5.4 ms; threshold 0.6±0.2 mV @ 0.4 ms and was 0.7±0.2 mV @ 0.4 ms on follow-up; impedance was 618±119 ohms and was 545±145 ohms on follow-up. Prior to the LBBAP and AVN ablation procedure, the average number of AF or heart failure (HF) hospitalizations 24 months prior to the procedure was 4.9±5.3, 64% of patients were on antiarrhythmic drugs, and 100% were on either beta-blockers or calcium channel blockers. During a mean follow-up of 21.9±15.3 months after the LBBAP and AVN ablation procedure, the average AF or HF hospitalization was 0.4±0.9, and all patients were no longer on any antiarrhythmic drugs, beta-blockers, or calcium channel blockers. There were no cases of lead dislodgement. In patients with elevated PA systolic pressure, successful LBBAP and AVN ablation with good two-year outcomes are achievable.Tabled 1Pre LBBAP and AVN ablation*Post LBBAP and AVN ablation**P-valueAF or HF hospitalizations4.9 ± 5.30.4 ± 0.9P<0.01On antiarrhythmic drugs7 (63.6%)0 (0%)P<0.01On rate control drugs11 (100%)0 (0%)NALead dislodgement-0 (0%)NALead capture threshold, mV-0.7 ± 0.2NAValues are mean ± SD or n (%) *24 months prior to LBBAP and AVN ablation **Average follow-up of 22±15 months after LBBAP and AVN ablation Open table in a new tab

PO-03-009 3830 LEAD TIP POSITION ON COMPUTED TOMOGRAPHY AND ELECTROPHYSIOLOGIC OUTCOMES IN LEFT BUNDLE BRANCH AREA PACING

Prior studies have evaluated the impact of lead tip distance from the LV blood pool on pacing parameters during left bundle branch area pacing (LBBAP). Few studies to date have evaluated lead tip angulation within the interventricular septum (IVS) in relation to pacing morphology on surface 12-lead ECG. To establish the observed lead tip trajectories within the interventricular septum encountered during LBBAP. Patients who underwent LBBAP implantation between 02/2019-07/2022 were retrospectively analyzed. Patients who underwent computed tomography (CT) of the chest or thorax post-implantation for any indication were included for analysis. Lead distance from the mitral annulus, lead tip distance from LV blood pool (DEBP), lead tip angle of incidence (AOI), and post-implantation electrocardiographic and pacing parameters were analyzed (Figure 1a). 38 pts were identified, out of whom 37 pts had CT images available for analysis. In the 20 pts with contrast enhanced imaging, DEBP was 2.1±1.8mm. Average observed AOI was 10.9±20.6 degrees in the axial plane (long axis; Figure 1b) and 12.4±22.2 degrees in the saggital plane (short axis; Figure 1c). Lead impedance at time of implant did not correlate strongly with axial or sagittal angle of incidence (R2=0.01 and 0.03 respectively) or with distance from LV endocardial blood pool (R2=0.04). The most commonly encountered lead insertion locations included the mid-septal (22, 59.5%), basal septal (4, 10.8%), and mid antero-septal (3, 8.1%) positions (Figure 1d). Average lead tip distance from the AV annulus was 36.6±8.2mm. Mean paced QRSd for the basal, mid, and apical cohorts were 122.5±8.1ms, 118.5±10.7ms, and 120±15.9ms, respectively. Left ventricular activation time in lead V6 numerically decreased for more apical positions, with basal, mid and apical values of 84.4±11.9ms, 73.9±10.6ms, and 69.5±6.0ms, respectively. Lead threshold, impedance, and sensed R waves were stable at time of 2 year follow-up. No analyzed patients underwent lead revision. Multiple lead tip orientations are observed in relation to the IVS during successful LBBAP. More apical lead tip positioning may result in numerically lower LVAT values, despite similar overall QRS duration.

PO-01-182 CONDUCTION SYSTEM PACING REMAINS EFFECTIVE IN PATIENTS WITH NON-CONDUCTIVE SEPTAL SCAR BUT SURVIVING PURKINJE

Conduction system pacing (CSP), delivered through His bundle (HBP) or left bundle pacing (LBP), is a novel effective treatment for patients with proximal left bundle branch block (LBBB). The presence of septal scar is known to affect response to CSP, but the effect of scar conduction properties on response to CSP has never been investigated. To quantify the effect of scarred myocardium and Purkinje conduction velocity (CV) on response to CSP using computational modelling. We computed ventricular activation on 24 four-chamber heart geometries generated from heart failure patients, inclusive of septal scar and His-Purkinje networks with proximal LBBB. We simulated LBBB baseline, selective HBP and selective LBP with optimized atrioventricular delay (AVD) with the following myocardium and Purkinje conduction properties within the scar: A) non-conductive myocardium and Purkinje; B) slow conductive myocardium and Purkinje (10% CV compared to healthy tissue); C) non-conductive myocardium and slow conductive Purkinje. Response was quantified with 90% biventricular (BIVAT90) and 95% left ventricular (LV) activation times. HBP and LBP were ineffective in the presence of non-conductive septal myocardium and Purkinje (LVAT95: baseline 130.9±11.2ms vs HBP 129.4±13.9ms vs LBP: 130.2±11.6, P=0.9, Fig A,D). CSP reduced BIVAT90 and LVAT95 compared to baseline when the myocardium and the Purkinje within the scar were slow but conductive (BIVAT90: baseline 120.7±9.5ms, HBP: 98.1±11.2ms, LBP: 82.9±9.4ms, P<0.01 vs baseline, Fig B,D). CSP remained effective when the scarred myocardium was non-conductive and the Purkinje was slow but conductive (BIVAT90: baseline 115.7±11.2ms, HBP: 84.4±7.6ms, LBP: 64.3±8.6ms, P<0.01 vs baseline, Fig C,D). The presence of septal scar does not necessarily make CSP ineffective. CSP remains effective in patients with LBBB and septal scar if the Purkinje within the scar is still conductive.