Right Ventricular Apical Pacing Research Articles

Comparison between left bundle branch area pacing and right ventricular pacing: ventricular electromechanical synchrony and risk of atrial high-rate episodes.

The electromechanical dyssynchrony associated with right ventricular pacing (RVP) has been found to have adverse impact on clinical outcomes. Several studies have shown that left bundle branch area pacing (LBBAP) has superior pacing parameters compared with RVP. We aimed to assess the difference in ventricular electromechanical synchrony and investigate the risk of atrial high-rate episodes (AHREs) in patients with LBBAP and RVP. We consecutively identified 40 patients with atrioventricular block and no prior atrial fibrillation. They were divided according to the ventricular pacing sites: the LBBAP group and the RVP group (including the right ventricular apical pacing (RVA) group and the right side ventricular septal pacing (RVS) group). Evaluation of ventricular electromechanical synchrony was implemented using electrocardiogram and two-dimensional speckle tracking echocardiography (2D-STE). AHRE was defined as event with an atrial frequency of ≥176 bpm lasting for ≥6 min recorded by pacemakers during follow-up. The paced QRS duration of the LBBAP group was significantly shorter than that of the other two groups: LBBAP 113.56 ± 9.66 ms vs. RVA 164.73 ± 14.49 ms, p < 0.001; LBBAP 113.56 ± 9.66 ms vs. RVS 148.23 ± 17.3 ms, p < 0.001. The LBBAP group showed shorter maximum difference (TDmax), and standard deviation (SD) of the time to peak systolic strain among the 18 left ventricular segments, and time of septal-to-posterior wall motion delay (SPWMD) compared with the RVA group (TDmax, 87.56 ± 56.01 ms vs. 189.85 ± 91.88 ms, p = 0.001; SD, 25.40 ± 14.61 ms vs. 67.13 ± 27.40 ms, p < 0.001; SPWMD, 28.75 ± 21.89 ms vs. 99.09 ± 46.56 ms, p < 0.001) and the RVS group (TDmax, 87.56 ± 56.01 ms vs. 156.46 ± 55.54 ms, p = 0.003; SD, 25.40 ± 14.61 ms vs. 49.02 ± 17.85 ms, p = 0.001; SPWMD, 28.75 ± 21.89 ms vs. 91.54 ± 26.67 ms, p < 0.001). The interventricular mechanical delay (IVMD) was shorter in the LBBAP group compared with the RVA group (-5.38 ± 9.31 ms vs. 44.82 ± 16.42 ms, p < 0.001) and the RVS group (-5.38 ± 9.31 ms vs. 25.31 ± 21.36 ms, p < 0.001). Comparing the RVA group and the RVS group, the paced QRS duration and IVMD were significantly shorter in the RVS group (QRS duration, 164.73 ± 14.49 ms vs. 148.23 ± 17.3 ms, p = 0.02; IVMD, 44.82 ± 16.42 ms vs. 25.31 ± 21.36 ms, p = 0.022). During follow-up, 2/16 (12.5%) LBBAP patients, 4/11 (36.4%) RVA patients, and 8/13 (61.5%) RVS patients had recorded novel AHREs. LBBAP was proven to be independently associated with decreased risk of AHREs than RVP (log-rank p = 0.043). LBBAP generates narrower paced QRS and better intro-left ventricular and biventricular contraction synchronization compared with traditional RVP. LBBAP was associated with a decreased risk of AHREs compared with RVP.

Lead performance of stylet-driven leads in left bundle branch area pacing: Results from a large single-center cohort and insights from in vitro bench testing

BackgroundLeft bundle branch area pacing (LBBAP) requires deep septal lead deployment for left-sided conduction stimulation. Advancing leads toward deep septal positions might add mechanical stress on these leads. Concerns about lead performance and reliability remain an unanswered question. ObjectiveThe purpose of this study was to analyze lead performance and integrity of stylet-driven pacing leads (SDLs) for LBBAP. MethodsThis study assessed lead fracture rates of SDL in a large single-center cohort of adult LBBAP patients. Fluoroscopic analysis of lead bending angulations at the septal insertion point and in vitro bench testing of lead preconditioning were performed to simulate clinical use conditions. Lead performance was compared between LBBAP and conventional right ventricular apical pacing (RVp) sites. ResultsThe study included 325 LBBAP patients (66% male; age 71±15 years). During median follow-up of 18 months, 2 patients (0.6%) experienced conductor fracture between tip housing and ring electrode, whereas no such fractures occurred with RVp patients (n = 149; P = .22). X-ray analysis revealed that high lead bending angulations occurred in 1.3% of the patients. Accelerated bench testing of excessive preconditioned leads showcased a higher probability of early conductor fracture compared to standard preconditioned leads. ConclusionThe incidence of early conductor failure in LBBAP seems higher than with conventional RVp sites. The most vulnerable lead part seems to be the interelectrode space between the tip housing and ring electrode. Excessive angulation and preconditioning might contribute to early fatigue fracture.

Outcomes of left bundle branch area pacing compared to His bundle pacing and right ventricular apical pacing in Japanese patients with bradycardia.

His bundle pacing (HBP) and left bundle branch area pacing (LBBAP) emerge as better alternatives to right ventricular apical pacing (RVAP) in patients with bradycardia requiring permanent cardiac pacing. We aimed to compare the clinical outcomes of LBBAP, HBP, and RVAP in Japanese patients with bradycardia. A total of 424 patients who underwent successful pacemaker implantation (HBP, n = 53; LBBAP, n = 75; and RVAP, n = 296) were retrospectively enrolled in this study. The primary study endpoint was the cumulative incidence of heart failure hospitalization (HFH) during the follow-up. The success rate for implantation was higher in the LBBAP group than in the HBP group (94.9% and 81.5%, respectively). Capture threshold increase >1V during the follow-up occurred in the HBP and RVAP groups (9.4% and 5.1%, respectively), while it did not in the LBBAP group. The cumulative incidence of HFH was significantly lower in the LBBAP group than the RVAP (adjusted hazard ratio, 0.12 [95% confidence interval: 0.02-0.86]; p = .034); it did not differ between the HBP and RVAP groups (adjusted hazard ratio, 0.48 [95% confidence interval: 0.17-1.34]; p = .16). Advanced age, mean percent right ventricular pacing (per 10% increase), left ventricular ejection fraction <50%, and RVAP were associated with HFH. Compared to RVAP and HBP, LBBAP appeared more feasible and effective in patients with bradycardia requiring permanent cardiac pacing.

Safety and Efficacy of His Bundle Area (Para-Hisian) Pacing Using a Mathematical Cross-Correlation Cardiac Synchrony Index

Background: The deleterious effects of right ventricular (RV) apical pacing promoted the need for more physiological pacing techniques, such as conduction system, His bundle area, and mid-septal ventricular pacing. We aimed to compare permanent mid-septal and His bundle area pacing (HBAP) vs RV apical pacing to determine which is more physiological and to assess lead stability and pacing thresholds. Methods: We retrospectively analyzed 137 consecutive patients undergoing permanent pacing (63% men, mean age 61 ± 24 years). Seventy-one (52%) had a baseline QRS of &lt; 120 ms, with no evidence of intraventricular conduction abnormalities, 37 (27%) had right bundle branch block, and 29 (21%) had left bundle branch block. The ventricular lead was implanted at the RV apex in 54 patients, at the His bundle area in 66, and at the mid interventricular septum in 17. Twelve-lead electrocardiogram was recorded, and electrical synchrony was assessed using the Synchromax® crosscorrelation cardiac synchrony index (CSI). Results: QRS duration was prolonged in all pacing sites. There was no correlation between QRS duration and the CSI (r = 0.028, p = 0.79). The CSI was significantly improved only in patients undergoing HBAP, despite a slight widening of the QRS complex. There was no difference in pacing thresholds and sensed R wave voltage. Lead dislodgment occurred in only 1 lead implanted at the His bundle area. Conclusions: HBAP successfully captures the conduction system, normalizing the CSI despite producing a wider QRS, meaning that coordination is more important than duration for achieving optimal cardiac synchrony

Loss of capture of conduction system pacemaker caused by fibrosis surrounding the lead: a case report

BackgroundConduction system pacing (CSP) is a novel technique that involves pacing the His-Purkinje system instead of the traditional right ventricular (RV) apex. This technique aims to avoid the adverse effects of RV apical pacing, which can lead to ventricular dyssynchrony and heart failure over time. CSP is gaining popularity but its long-term efficacy and challenges remain uncertain. This report discusses a case where CSP was initially successful but faced complications due to an increasing pacing threshold.Case presentationA 65-year-old female with total atrioventricular block was referred for brady-pacing. Due to the potential for chronic RV pacing, CSP was chosen. The CSP implantation involved subcutaneous device placement, with a CSP lead in the left bundle branch area (LBBA) and an RV backup lead. A year after successful implantation, the LBBA pacing threshold progressively increased. Subsequent efforts to correct it led to anodal capture and battery depletion. Cardiac magnetic resonance imaging (CMR) revealed mid-septal fibrosis at the area of LBBA lead placement and suggested cardiac sarcoidosis as a possible cause.ConclusionCSP is a promising technique for treating bradyarrhythmias, but this case underscores the need for vigilance in monitoring pacing thresholds. Increasing thresholds can render CSP ineffective, necessitating alternative pacing methods. The CMR findings of mid-septal fibrosis and the potential diagnosis of cardiac sarcoidosis emphasize the importance of pre-implantation assessment, as CSP may be compromised by underlying structural abnormalities. This report highlights the complexities of pacing strategy selection and the significance of comprehensive evaluation before adopting CSP.

Left ventricular anterolateral site is the preferable left ventricular lead position for an upgrade to biventricular pacing

Abstract Background Cardiac resynchronization therapy (CRT) is a well-established treatment for symptomatic heart failure with electrical dyssynchrony. The LV lead position in patients with left bundle branch block is usually recommended at the LV posterolateral to the lateral site, which is the latest electrical activation site. In contrast, the preferable LV lead position in patients who plan to upgrade from conventional RV apical pacing to CRT remains unclear. Purpose This study aimed to identify the preferable LV lead position for upgrading to CRT from conventional RV apical pacing. Methods An electrophysiological study was performed on patients who underwent ablation for atrial fibrillation. The electrode catheters were positioned at the RV apex, LV anterolateral, and LV posterolateral sites via the coronary sinus branches. During RV apical pacing, the activation time from the RV apex to the LV anterolateral and posterolateral sites was measured, and the activation time ratio to QRS duration was calculated. Biventricular pacing from both the RV apex and LV anterolateral or LV posterolateral sites was performed, and the difference in QRS duration and LV dP/dt compared to only the RV apical pacing state was measured. Results We enrolled 37 patients who exhibited anterolateral and posterolateral LV coronary sinus branches. During RV apical pacing, the average activation time ratio to QRS duration was higher at the LV anterolateral site than at the LV posterolateral site (0.89±0.07 vs. 0.71±0.11, P &amp;lt;0.001). The shortening ratio of QRS duration during biventricular pacing compared to baseline RV apical pacing was greater at LV anterolateral site than at the LV posterolateral site (45.7±18.0% vs. 32.0±17.6%, P &amp;lt;0.001). The improvement ratio of LV dP/dt during biventricular pacing was also better from the LV anterolateral site than from the LV posterolateral site (12.7±8.9% vs. 3.7±8.2%, P &amp;lt;0.001). Conclusion LV lead position in patients who plan to upgrade to CRT from conventional RV apical pacing is preferably at the LV anterolateral site.

Abstract 18100: Comparative Analysis of Right Ventricular (RV) Apical Pacing versus Physiologic Left Bundle Branch Area Pacing (LBBAP) in Hypertrophic Cardiomyopathy With Left Ventricular Outflow Tract Obstruction (LVOTO): A Case Study

Introduction: AV dyssynchrony is considered advantageous in HoCM patients requiring pacemaker therapy. The impact of physiologic pacing, particularly LBBAP, on LVOTO in HoCM remains unexplored. We present a patient highlighting the effect of LBBAP on LVOTO. Case: A 69-year-old female with HoCM (resting gradient ~130mmHg) and asymmetric septal hypertrophy (17mm), managed conservatively due to high surgical risk. She had persistent AF, accompanied by debilitating fatigue and palpitations. Due to unsuccessful treatment with sotalol, dofetilide, and 5 DCCV procedures, other treatment options were discussed. She opted for LBBA pacing and AV node ablation. Dual chamber device was implanted utilizing a Medtronic 3830 lead. Within 48 hours of discharge, she came to the ER with exertional dyspnea and lightheadedness, indicating ambulatory cardiogenic shock (BP: 78/66 mmHg). A stat echo showed LVEF of 75%, severe SAM, LVOT gradient of 179 mmHg, and severe MR. No pericardial effusion. Phenylephrine was initiated, and VVIR rate was decreased from 90 bpm to 60 bpm, but no BP improvement. Obstructive cardiogenic shock from worsened LVOTO was likely caused by physiologic LBBAP. To objectively demonstrate this, she underwent a brief study in the lab after informed consent. We inserted a temporary RV apical pacing lead and assessed LVOT gradients at rest and during exercise for both physiologic pacing and RV apical pacing. RV apical pacing had lower LVOT gradient at rest and exercise compared to LBBA pacing (Figure 1). LBBA lead was extracted and a CRT-P device implanted and programmed for optimal dyssynchrony. Discussion: Traditional RV apical pacing is superior to physiologic LBBAP in HoCM. Limited studies suggest biventricular pacing reduces LVOT gradient, but CRT is not superior to RV pacing. LBBA pacing may be contraindicated in LVOTO patients. Conclusion: In HCM patients with LVOTO, RV apical pacing appears superior to LBBAP, reducing LVOT gradient at rest and during exercise.

Pacemaker-induced cardiomyopathy.

Chronic right ventricular (RV) pacing is an often-unrecognized cause of cardiomyopathy, despite research that has revealed that chronic RV pacing can cause significant cardiomyopathy and heart failure, leading causes of hospitalization in the United States. Studies have found that chronic RV apical pacing results in ventricular dyssynchrony, reduced cardiac function, and heart failure. This article describes the deleterious effects of permanent cardiac pacemakers and their association with cardiomyopathy and heart failure. More research is needed to investigate other forms of pacing and treatment to prevent ventricular dyssynchrony and myocardial remodeling.

Impact of Right Ventricle Lead Position on Left Ventricular Function in Permanent Single and Dual Chamber Pacemakers

Abstract Aim and objectives To identify the short term effect of the pacemaker RV lead position related electric remodeling on LV systolic function Patients and Methods The study included 30 patients who presented with an indication of permanent pacing to the cardiology department of Ain Shams university hospitals and underwent permanent single or dual-chamber pacemaker insertion, 15 patients each with right ventricular (RV) apical pacing (RV apex), and 15 patients nonapical pacing (mid septal). 2D speckle tracking imaging technique was used for quantification of global longitudinal function of the left ventricle and dyssynchrony evaluation before pacemaker implantation and after a 3-month follow-up. Results 2D speckle tracking echocardiography 3 months follow up post pacing revealed impairment of global longitudinal strain in all patients and Intraventricular dyssynchrony was significantly more in apical location compared to a non-apical location (radial dyssynchrony: 108.67 ± 11.68 msec vs. 80.53 ± 8.17 msec, p-value &amp;lt; 0.001) with more difference (50.53 ± 13.30 msec) in apical location compared to non-apical location difference (29.87 ± 6.64 msec), p-value &amp;lt; 0.001. Conclusion By the analysis of 2D speckle tracking echocardiography, In the short-term follow-up, we found that radial dyssynchrony was more in apical location when compared to the non-apical location of RV lead. The RV septal pacing is a better alternative in terms of less dyssynchrony compared to RV apical pacing. Older age, the higher percentage of pacing, and device type are prognostic factors for the development of pacemaker-induced cardiomyopathy.

Assessment of Extent of Myocardial Injury in Patients Undergoing Transvenous Implantation of Pacemaker Using Cardiac Troponin I (cTnI) as a Marker of Structural Heart Damage and It’s Relation to Different Sites of RV Implantation

Abstract Aim and objectives The aim of the study is to assess the extent of myocardial injury in patients undergoing trans-venous implantation of pacemaker using cardiac troponin I (cTnI) as a marker of myocardial injury and it’s relation to different sites of RV pacing and number of screwing. Patients and Methods This study included 50 patients undergoing Trans-venous Implantation of single or dual chamber permanent pacemakers at Ain Shams University Hospitals during the period from February 2020 to August 2020, divided into 2 equal groups according to the site of RV lead implantation, 25 patients RV lead implanted in the Apex and 25 patients RV lead implanted in the Septum. Results All patients had rise in Troponin I after implantation of pacemaker indicating that there is significant relationship between trans-venous implantation of permanent pacemaker and incidence of myocardial injury. Comparing the RV septal pacing group to the RV apical pacing group, results showed that septal RV pacing caused more rise in cardiac troponin I after implantation than in apical pacing group indicating that there is a significant relationship between site of RV pacing and extent of myocardial injury being more in septal RV pacing than apical RV pacing. Furthermore, our study showed that regarding active fixation of RV lead into the myocardium, increasing number of trials of screwing the lead in different sites to achieve the best pacing threshold causes more rise in cardiac troponin I. So, there is a significant relationship between number of screwing and extent of myocardial injury. Conclusion We conclude that trans-venous implantation of permanent pacemakers is associated with an increased incidence of myocardial injury and septal RV pacing is associated with more extent of myocardial injury than apical RV pacing. Also, increasing number of trials of active fixation by screwing the RV leads into the myocardium is associated with more extent of myocardial injury.

Association of Sinus Wavefront Activation and Ventricular Extrastimuli Mapping With Ventricular Tachycardia Re-Entrant Circuits

BackgroundSubstrate-based ablation targets areas of delayed and fractionated electrograms during sinus rhythm, which are sensitive for identifying the ventricular tachycardia (VT) isthmus but is influenced by the activation wavefront direction and decremental pacing. ObjectivesThe aim of this study was to correlate the areas of latest activation during varying wavefront activation mapping and decremental pacing mapping with sites critical to the VT isthmus. MethodsThree high-density electroanatomical substrate maps were created in patients presenting for ablation of monomorphic VT: 1) native sinus rhythm; 2) right ventricular (RV) apical pacing; and 3) an RV apical S2 map following the S1 drive train at 20 ms above the ventricular effective refractory period. Areas corresponding to the latest activation were compared with the VT isthmus identified by conventional mapping. ResultsTwenty patients with structural heart disease with a mean age of 55.6 ± 16.9 years were included. The majority of the cohort consisted of patients with ischemic heart disease (50%) and arrhythmogenic RV cardiomyopathy (35%). Epicardial ablation was performed in 45% of patients. The concordance of the site of latest activation in sinus rhythm with the VT isthmus was 75%. The location of the latest activation during RV apical pacing corresponded with the VT isthmus in 85% of cases. However, in 95% of cases, the site of the latest activation following the S2 stimulus colocalized to the VT isthmus. ConclusionsIn a mix of underlying myocardial substrates, regions of conduction slowing during decremental pacing colocalize with the VT isthmus more frequently than sinus rhythm activation mapping and may have a role in substrate-based ablation where VT induction is undesirable.

Preferred left ventricular lead position for upgrade from right ventricular pacing to cardiac resynchronization therapy.

Cardiac resynchronization therapy (CRT) is well-established for treating symptomatic heart failure with electrical dyssynchrony. The left ventricular (LV) lead position is recommended at LV posterolateral to lateral sites in patients with left bundle branch block; however, its preferred region remains unclear in patients being upgraded from right ventricular (RV) apical pacing to CRT. This study aimed to identify the preferred LV lead position for upgrading conventional RV apical pacing to CRT. We used electrode catheters positioned at the RV apex and LV anterolateral and posterolateral sites via the coronary sinus (CS) branches to measure the ratio of activation time to QRS duration from the RV apex to the LV anterolateral and posterolateral sites during RV apical pacing. Simultaneous biventricular pacing was performed at the RV apex and each LV site, and the differences in QRS duration and LV dP/dtmax from those of RV apical pacing were measured. Thirty-seven patients with anterolateral and posterolateral LV CS branches were included. During RV apical pacing, the average ratio of activation time to QRS duration was higher at the LV anterolateral site than at the LV posterolateral site (0.90 ± 0.06 vs. 0.71 ± 0.11, p < .001). The decreasing ratio of QRS duration and the increasing ratio of LV dP/dtmax were higher at the LV anterolateral site than at the posterolateral site (45.7 ± 18.0% vs. 32.0 ± 17.6%, p < .001; 12.7 ± 2.9% vs. 3.7 ± 8.2%, p < .001, respectively) during biventricular pacing compared with RV apical pacing. The LV anterolateral site is the preferred LV lead position in patients being upgraded from conventional RV apical pacing to CRT.

Myocardial work by speckle-tracking echocardiography in pacemaker patients according to pacing site: a prospective study

Abstract Funding Acknowledgements Type of funding sources: None. Introduction The optimal lead position for right ventricle (RV) pacing is still a matter of debate. Several studies compared 2D-echocardiography left ventricle ejection fraction (LVEF) and LV global longitudinal strain (LVGLS) by speckle-tracking imaging (STI). However, these parameters present limitations, such as load dependency. Recently, myocardial work (MW) has emerged as an alternative tool for myocardial systolic function assessment. Purpose To compare LV MW and LVGLS between patients with RV outflow tract/septum pacing (Group1) and RV apical pacing (Group2). Methods Prospective single-center study of patients with permanent pacemaker (PMK) followed at our cardiac device’s outpatient clinic between july and november of 2022. Patients were divided into two groups according to RV pacing site. Moderate/severe valvular disease, LVEF&amp;lt;50%, segmental wall-motion abnormalities, pulmonary hypertension, cardiomyopathies, or RV dysfunction were exclusion criteria. STI-based LVGLS analysis and MW parameters were obtained (GWI:Global Work Index; GCW:Global Constructive Work; GWW:Global Wasted Work; GWE:Global Work Efficiency). RV pacing was required at the moment of imaging. A 12-lead ECG was also performed. Blood pressure (BP) was simultaneously measured. Results Our cohort comprised 30 patients in group 1 and 25 patients in group 2. The 2 groups were well-matched, except for the median time since PMK implantation, which was significantly higher in Group2 (5.3years vs 0.9years, p&amp;lt;0.001). The QRS was significantly narrower in Group1 (Group1:129ms±9 vs Group2:165ms±15, p&amp;lt;0.001). LVEF was similar in both groups (Group1:58%±7.5 vs Group2:60%±7.5, p = NS). Likewise, both systolic and diastolic BP were comparable (p = NS), but LVGLS was significantly higher in Group1 (15±3.3 vs 13±3.7, p = 0.043). Except for GWI which was also significantly higher in Group1 (1553mmHg%±581 vs 1238mmHg%±516, p = 0.040), no significant differences were found in the other parameters of MW among the groups (all p = NS). Conclusion Our results point to LVGLS being significantly lower in the group of RV apical pacing. Despite most parameters of MW didn’t differ between groups, GWI also showed significant impairment. These findings should be regarded as preliminary and further larger studies are needed to ascertain the value of this new tool in understanding the impact of pacing depolarization site on LV mechanics.

Both LBBP and LVSP significantly improve ventricular dyssynchrony and effectivity of LV performance compared to RV apical pacing in heart failure patients with LBBB and an indication to CRT

Abstract Funding Acknowledgements Type of funding sources: Public grant(s) – EU funding. Main funding source(s): Supported by the Ministry of Health of the Czech Republic, grant number NU21-02-00584 and by the project National Institute for Research of Metabolic and Cardiovascular Diseases (Programme EXCELES, ID Project No. LX22NPO5104) - Funded by the European Union – Next Generation EU. Background Left bundle branch pacing and left septal myocardial pacing (LVSP) are novel methods of CRT in patients with heart failure. However, their exact impact on ventricular synchrony visualized by noninvasive assessment and the LV performance effectivity is unknown. Aims To compare ventricular synchrony and a change in blood pressure values between nonselective left bundle branch pacing (nsLBBP), LVSP, and RV apical pacing (RVAP) in heart failure patients. Methods In patients with CRT indication and LBBB, a lead was placed in the left septal area, where the transition between nsLBBP and LVSP was observed during decremental output pacing. Another lead was placed in the RV apex. UHF-ECG was used to assess ventricular synchrony during RVAP, nsLBBP, and LVSP. Dyssynchrony parameter e-DYS was calculated as an absolute value of the time difference between the first and last activation. Systolic blood pressure measurements were obtained invasively from the radial artery during VVI pacing at rates ten beats/minute higher than spontaneous rhythm. The protocol included multiple transitions between RVAP, nsLBBP, and LVSP. Results The study protocol was finalized in six patients; mean age 67 years, LVEF 33%, 3 had ischemic cardiomyopathy, and QRSd during spontaneous LBBB was 172±8 ms. QRSd was prolonged to 182±10ms during RVAP and shortened to 145±12 ms and 149±13 ms during nsLBBP and LVSP, respectively. The dyssynchrony parameter e-DYS shortened from 46±18 ms during RVAP to 1±16 ms during nsLBBP and 12±13 ms during LVSP, p &amp;lt; 0.05 for RVAP vs. nsLBBP and LVSP, and p = 0.4 for nsLBBP vs. LVSP. Both nsLBBP and LVSP led to a significant increase in the systolic blood pressure compared to RVAP (9±1 mmHg and 10±1 mmHg for nsLBBp and LVSP vs. RVAP, p &amp;lt; 0.001, respectively. nsLBBP produced slightly higher systolic blood pressure than LVSP (mean difference 2±1 mmHg, p = 0.005. Conclusion In patients with LBBB and CRT indication, both nsLBBp and LVSP significantly reduce ventricular dyssynchrony and lead to better effectivity of the LV performance compared to RV apical pacing.

Feasibility and short-term outcomes of left bundle pacing in paediatric patients: a case series

Abstract Funding Acknowledgements Type of funding sources: Other. Main funding source(s): Government Background Chronic RV apical pacing in pediatric patients can lead to LV dysfunction. Left bundle pacing has been shown to preserve LV function in adults. The feasibility and outcomes of left bundle pacing in pediatric patients are unknown. Objectives To study the feasibility, safety, and short-term outcomes of pediatric left bundle branch pacing (LBBp). Methods Patients &amp;lt; 18 years with class I or II indication for pacing were the study subjects. All patients had dual-chamber pacemaker implantation from the right or left side. We did the device implantation either under conscious sedation, or general anesthesia, after 6 hours of fasting and intravenous hydration with normal saline at 1 ml/kg/min. A venogram was performed on the ipsilateral to the implantation site from the cubital venous access with 5-10 ml of non-ionic contrast side to delineate the venous anatomy before the procedure. Venous access was obtained through two separate punctures of the extrathoracic axillary vein using an 18 G puncture needle and a 0.025 glide wire. The vein was sequentially SelectSecure 3830 4F lead, and C315HIS sheath was used for LBBp. An additional loop was added to the ventricular lead to account for the growth of the patient. The primary outcomes were successful, stable LBBp. The secondary outcomes were lead stability over three months with no implant-related complications or death. Result This case series has six patients of whom 2 were males and with a mean age of 9.5 years, and a mean body weight of 25.5 Kgs. All patients but one had undergone intracardiac repair (4 VSD, 1 ASD). The pacing indication was symptomatic AV block in five and sick sinus syndrome in one patient. At implant, the mean R wave was 12.83±4.8 mV, mean ventricular threshold was 0.6 ± 0.1 V at 0.5 ms pulse width, mean ventricular impedance of 737.3W ±131.5 ohms. The mean procedure time was 65± 20min, the mean fluoroscopy time was 14.63±13.3 min and the mean contrast volume was 30±20ml and the mean paced QRS duration was 98.5±16.5 ms and V5 LVAT 62.66±22.33ms. During follow follow-up of 4±3 months, the lead parameters were stable with a ventricular threshold of 0.8±0.1V at 0.5ms pulse width impedance of 689±130.2 ohms. There was no lead perforation, dislodgement, or death. Conclusion LBBp in the pediatric population is feasible and safe with good -lead stability and no complications in the near term.

PO-03-088 TWO-DIMENSIONAL SPECKLE TRACKING ECHOCARDIOGRAPHY SHOWS THAT LEFT BUNDLE BRANCH PACING MAINTAINS LEFT VENTRICULAR GLOBAL LONGITUDINAL STRAIN AND CONTRACTILITY COMPARED TO RIGHT VENTRICULAR APICAL PACING

Pacemaker-dependent patients with right ventricular (RV) apical pacing are at increased risk for reduced left ventricular function, ventricular dyssynchrony, and the development of pacing-induced heart failure. Physiological pacing of the conduction system through the left bundle branch (LBB) has been shown to have improved synchrony of the ventricles and a more physiological activation sequence. Direct comparison of left ventricular (LV) strain using LBB and RVAP in paired experiments in the same animals or patients has not been published. Evaluate the changes to the left ventricular mechanics (global longitudinal strain (GLS), global circumferential strain (GCS), global radial strain (GRS), and left ventricular ejection fraction (LVEF) through LBB pacing compared to RV pacing using two-dimensional speckle tracking echocardiography. Under anesthesia, six mixed breed hounds had pacing leads from two ICDs (CobaltTM XT DR, Medtronic, Inc) implanted at the RV apex (6947 Sprint Quattro SecureTM, Medtronic, Inc) and the LBB (3830 SelectSecureTM, Medtronic, Inc). Echocardiographic measurements were taken for sinus rhythm, LBB pacing, and RV pacing to evaluate the LV strain, and contractility. Two-dimensional speckle tracking was performed following the pacing procedure to determine GLS, and LVEF from the four-chamber apical views, GCS, and GRS from the short-axis views. In our study, LV GLS was maintained better during LBB pacing when compared to LV GLS during RV pacing. The magnitude of GLS was not significantly different between sinus and LBB pacing, but was significantly lower for RV pacing than both sinus and LBB pacing (Fig. A). GCS only showed a significant difference between sinus and RV pacing (Fig. B), while GRS did not show differences between any of the groups (Fig. C). Results for the LV ejection fraction followed a similar pattern as the GLS. There was not a significant difference in LVEF for sinus and LBB pacing, but LVEF was significantly lower for RV pacing compared to both sinus and LBB pacing (Fig. D). LBB pacing preserves GLS, and the LVEF better than RV apical pacing and is similar to sinus beats. This further supports LBB pacing as a preferred method of pacing for preserving contractility for patients with pacemakers.

PO-03-109 RIGHT VENTRICULAR PACING EXACERBATE ELECTRICAL DYSSYNCHRONY BEYOND INTRINSIC LEFT BUNDLE BRANCH BLOCK

Right ventricular (RV) pacing produces an iatrogenic form of left bundle branch block (LBBB). Intrinsic LBBB (I-LBBB) can cause adverse hemodynamic effects due to ventricular dyssynchrony, mainly in patients with heart failure and reduced ejection fraction (HFrEF). Although RV pacing is thought to create a similar activation pattern as LBBB, some studies suggest RV apical pacing can be harmful even in patients with I-LBBB. Currently, the mechanism responsible for this harm is not fully understood. We aimed to quantify and compare the degree of ventricular electrical dyssynchrony, as measured on the surface ECG, during I-LBBB, and RV pacing in patients with HFrEF (left ventricular EF ≤40%) and I-LBBB. Patients with HFrEF and prophylactic defibrillator therapy were prospectively recruited. For each patient, 3-minute, high-resolution (1024 Hz), digital 12-lead ECGs were recorded during I-LBBB rhythm and then RV pacing at 60 bpm or intrinsic heart rate (whichever was higher). High-resolution ECGs were analyzed to quantify abnormal intra-QRS peaks (QRSp) as a measure of ventricular electrical dyssynchrony. QRSp was defined as the mean number of peaks detected in the QRS complex that deviated from a smoothing-filtered version of the QRS. QRSp was automatically quantified for each precordial lead using validated custom software. Mean QRSp was defined as the average of QRSp in precordial leads. Thirty patients with HFrEF (66±9 yrs, 50% male, LVEF 30±8%) and I-LBBB (QRS duration [QRSd]: 172±22 ms) were included. Changes in mean QRSp between I-LBBB and RV apical pacing are shown in (Figure1A). RV pacing increased the mean QRSp in 27 patients (90%) as compared to I-LBBB, suggesting overall more electrical dyssynchrony during RV pacing. Changes in QRSd between I-LBBB and RV pacing are shown in (Figure 1B). RV pacing resulted in QRSd widening beyond I-LBBB QRSd in 18 patients (60%), while QRSd did not change in the remaining patients. During RV pacing (versus I-LBBB), Mean QRSp changed in more patients as compared to QRSd (27 patients versus 18 patients; p = 0.007). Although RV pacing produces an iatrogenic form of LBBB, ventricular electrical activation is more dyssynchronous during RV pacing as measured by changes in mean QRSp and QRSd. Compared to QRSd, mean QRSp is a more sensitive marker of change in ventricular electrical dyssynchrony between RV pacing and I-LBBB. Our results suggest RV pacing can exacerbate ventricular electrical dyssynchrony in those with I-LBBB.

Estimation of left ventricular activation sequence in patients with heart failure using two-dimensional speckle tracking echocardiography

Evaluation of longitudinal strain (LS) from two-dimensional echocardiography is useful for global and regional left ventricular (LV) dysfunction assessment. We determined whether the LS reflects contraction process in patients with asynchronous LV activation. We studied 144 patients with an ejection fraction ≤ 35%, who had left bundle branch block (LBBB, n = 42), right ventricular apical (RVA) pacing (n = 34), LV basal- or mid-lateral pacing (n = 23), and no conduction block (Narrow-QRS, n = 45). LS distribution maps were constructed using 3 standard apical views. The times from the QRS onset-to-early systolic positive peak (Q-EPpeak) and late systolic negative peak (Q-LNpeak) were measured to determine the beginning and end of contractions in each segment. Negative strain in LBBB initially appeared in the septum and basal-lateral contracted late. In RVA and LV pacing, the contracted area enlarged centrifugally from the pacing site. Narrow-QRS showed few regional differences in strain during the systolic period. The Q-EPpeak and Q-LNpeak exhibited similar sequences characterized by septum to basal-lateral via the apical regions in LBBB, apical to basal regions in RVA pacing, and lateral to a relatively large delayed contracted area between the apical- and basal-septum in LV pacing. Differences in Q-LNpeaks between the apical and basal segments in delayed contracted wall were 107 ± 30 ms in LBBB, 133 ± 46 ms in RVA pacing, and 37 ± 20 ms in LV pacing (p < 0.05, between QRS groups). Specific LV contraction processes were demonstrated by evaluating the LS distribution and time-to-peak strain. These evaluations may have potential to estimate the activation sequence in patients with asynchronous LV activation.

Strain echocardiography in predicting LV dysfunction in RV apical pacing

Right ventricular (RV) pacing is associated with a reduction in left ventricular (LV) systolic function, thought to be mediated by pacing-induced ventricular dyssynchrony. The prevalence of heart failure after RV pacing is reported to range from 31±3%. We studied 60 subjects with high-grade atrioventricular block and Complete Heart Block (CHB) scheduled to undergo right ventricular apical pacing. 2D echocardiography was done at baseline, 1 month and 12 months. Pacing-induced cardiomyopathy was defined as a reduction in LVEF to <45%. Strain was evaluated off-line from digitally stored images using all advanced software package (cardiac wall motion quantification (CMQ); Toshiba Medical Systems). Longitudinal strain for individual myocardial segments was measured from the apical four-chamber, two-chamber and long axis views (16 segment AHA/ASE model). None had LV dysfunction at baseline based on 2D and strain echo imaging. Subsequently 18 patients were detected to develop low GLS score (less than -14.5) at 1 month. On subsequent follow up at 1 year, all 18 patients developed LV dysfunction on 2D Echocardiography. Thus Strain imaging with GLS score helped in early detection of LV dysfunction in RV apical pacing subjects. Pacing-induced cardiomyopathy had significant association with high grade AV block with pacemaker dependency. It had no significant associations with other comorbidities like diabetes, hypertension, ischemic heart disease or with the type of medication intake. However there was a statistically significant association with heart failure.

Leadless biventricular left bundle and endocardial lateral wall pacing versus left bundle only pacing in left bundle branch block patients.

Biventricular endocardial (BIV-endo) pacing and left bundle pacing (LBP) are novel delivery methods for cardiac resynchronization therapy (CRT). Both pacing methods can be delivered through leadless pacing, to avoid risks associated with endocardial or transvenous leads. We used computational modelling to quantify synchrony induced by BIV-endo pacing and LBP through a leadless pacing system, and to investigate how the right-left ventricle (RV-LV) delay, RV lead location and type of left bundle capture affect response. We simulated ventricular activation on twenty-four four-chamber heart meshes inclusive of His-Purkinje networks with left bundle branch block (LBBB). Leadless biventricular (BIV) pacing was simulated by adding an RV apical stimulus and an LV lateral wall stimulus (BIV-endo lateral) or targeting the left bundle (BIV-LBP), with an RV-LV delay set to 5ms. To test effect of prolonged RV-LV delays and RV pacing location, the RV-LV delay was increased to 35ms and/or the RV stimulus was moved to the RV septum. BIV-endo lateral pacing was less sensitive to increased RV-LV delays, while RV septal pacing worsened response compared to RV apical pacing, especially for long RV-LV delays. To investigate how left bundle capture affects response, we computed 90% BIV activation times (BIVAT-90) during BIV-LBP with selective and non-selective capture, and left bundle branch area pacing (LBBAP), simulated by pacing 1cm below the left bundle. Non-selective LBP was comparable to selective LBP. LBBAP was worse than selective LBP (BIVAT-90: 54.2 ± 5.7ms vs. 62.7 ± 6.5, p < 0.01), but it still significantly reduced activation times from baseline. Finally, we compared leadless LBP with RV pacing against optimal LBP delivery through a standard lead system by simulating BIV-LBP and selective LBP alone with and without optimized atrioventricular delay (AVD). Although LBP alone with optimized AVD was better than BIV-LBP, when AVD optimization was not possible BIV-LBP outperformed LBP alone, because the RV pacing stimulus shortened RV activation (BIVAT-90: 54.2 ± 5.7ms vs. 66.9 ± 5.1ms, p < 0.01). BIV-endo lateral pacing or LBP delivered through a leadless system could potentially become an alternative to standard CRT. RV-LV delay, RV lead location and type of left bundle capture affect leadless pacing efficacy and should be considered in future trial designs.