Pacing Strategy Research Articles

Consecutive Experience with Left Bundle Branch Area Pacing in a High-Volume Australian Centre.

Left-bundle branch area pacing (LBBAP) is a relatively new technique for conduction system pacing. Australian safety and efficacy data is currently lacking. We aim to evaluate the learning curve, medium-term safety, and lead performance in a high-volume Australian setting. We performed a retrospective cohort study of 200 consecutive LBBAP procedures performed by a single operator at two centres between January 2019 and May 2020. Left bundle branch area pacing was performed predominantly via left subclavian access using a 69 cm Medtronic SelectSecure 3830 pacing lead and a preformed non-steerable C315-His sheath. Procedural success was defined as evidence of left septal or left bundle branch area capture as evidenced by a right bundle branch block-like paced morphology. Procedural characteristics, and follow-up (including lead performance) data were collected. Procedural efficiency over time, as well as safety data, were collected. Median age was 78.26 years (interquartile range [IQR] 71-85), 37% were female. Atrial fibrillation was present in 22%. The left ventricular ejection fraction <50% in 24%, atrioventricular (AV) block was present in 43.5%, left bundle branch block in 22.5% and right bundle branch block in 24.5%. Acute procedural success was 91.5%. Implant threshold was 0.6V @ 0.5 ms, and 0.75V @ 0.5 ms at 11.9 months of follow-up. The QRS was significant reduced (baseline 134 ms vs implant 114 ms, p<0.001) There was a reduction in procedural time and X-ray dose over the course of the study. There were no complications specific toLBBAP. LBBAP appears to be a safe and effective pacing strategy. The QRS duration was significantly reduced compared to baseline. There appears to be an early learning curve with LBBAP.

Safety and efficacy of left bundle branch area pacing compared with right ventricular pacing in patients with bradyarrhythmia and conduction system disorders: Systematic review and meta-analysis

BackgroundRight Ventricular Pacing (RVP) may have detrimental effects in ventricular function. Left Bundle Branch Area Pacing (LBBAP) is a new pacing strategy that appears to have better results. The aim of this systematic review and meta-analysis is to compare the safety and efficacy of LBBAP vs RVP in patients with bradyarrhythmia and conduction system disorders. MethodsMEDLINE, EMBASE and Pubmed databases were searched for studies comparing LBBAP with RVP. Outcomes were all-cause mortality, atrial fibrillation (AF) occurrence, heart failure hospitalizations (HFH) and complications. QRS duration, mechanical synchrony and LVEF changes were also assessed. Pairwise meta-analysis was conducted using random and fixed effects models. ResultsTwenty-five trials with 4250 patients (2127 LBBAP) were included in the analysis. LBBAP was associated with lower risk for HFH (RR:0.33, CI 95%:0.21 to 0.50; p < 0.001), all-cause mortality (RR:0.52 CI 95%:0.34 to 0.80; p = 0.003), and AF occurrence (RR:0.43 CI 95%:0.27 to 0.68; p < 0.001) than RVP. Lead related complications were not different between the two groups (p = 0.780). QRSd was shorter in the LBBAP group at follow-up (WMD: −32.20 msec, CI 95%: −40.70 to −23.71; p < 0.001) and LBBAP achieved better intraventricular mechanical synchrony than RVP (SMD: -1.77, CI 95%: −2.45 to −1.09; p < 0.001). LBBAP had similar pacing thresholds (p = 0.860) and higher R wave amplitudes (p = 0.009) than RVP. ConclusionsLBBAP has better clinical outcomes, preserves ventricular electrical and mechanical synchrony and has excellent pacing parameters, with no difference in complications compared to RVP.

Identifying Pacing Profiles in 2000 Metre World Championship Rowing

The pacing strategy adopted by athletes is a major determinants of success during timed competition. Various pacing profiles are reported in the literature and its importance depends on the mode of sport. However, in 2000 metre rowing, the definition of these pacing profiles has been limited by the minimal availability of data. Purpose: Our aim is to objectively identify pacing profiles used in World Championship 2000 metre rowing races using reproducible methods. Methods: We use the average speed for each 50 metre split for each available boat in every race of the Rowing World Championships from 2010-2017. This data was scraped from www.worldrowing.com. This data set is publicly available (https://github.com/danichusfu/rowing_pacing_profiles) to help the field of rowing research. Pacing profiles are determined by using k-shape clustering, a time series clustering method. A multinomial logistic regression is then fit to test whether variables such as boat size, gender, round, or rank are associated with pacing profiles. Results: Four pacing strategies (Even, Positive, Reverse J-Shaped, and U-Shaped) are identified from the clustering process. Boat size, round (Heat vs Finals), rank, gender, and weight class are all found to affect pacing profiles. Conclusion: We use an objective methodology with more granular data to identify four pacing strategies. We identify important associations between these pacing profiles and race factors. Finally, we make the full data set public to further rowing research and to replicate our results.

Serum brain-derived neurotrophic factor (BDNF) and self-paced time-trial performance in older untrained men.

This study examined the effect of 12 weeks of concurrent aerobic and resistance training on brain derived neurotrophic factor (BDNF) levels, neuromuscular performance and cerebral oxygenation on self-paced cycling exercise in previously untrained older men. Eight untrained healthy males aged 53-64 years performed a familiarisation and a pre-training self-paced cycling time trial before 12 weeks of exercise training which combined aerobic and resistance exercise. The self-paced cycling time trial comprised a 30 s maximal effort sprint for every 4.5 min of lower intensity pace for a total of 25 min. Upon completion of 12 weeks of training, a comparison of the pre-training trial analysed for serum BDNF, neuromuscular performance, and cerebral oxygenation was undertaken. Serum BDNF decreased significantly from 10.02 ± 4.63 to 6.96 ± 3.56 ng/ml after 12 weeks of training. There was also attenuated physiological strain for a comparable self-paced cycling performance. Despite positive physiological responses during the time trial pacing strategy was not altered compared with pre training. BDNF decreases following 12 weeks of concurrent training and might reflect neuroplasticity for this type of training stimulus. Exercise training in previously sedentary older men can result in a multitude of physical benefits, which may also confer a neuroprotective effect. However, specific training is required to improve pacing strategies in previously untrained older males. Australian New Zealand Clinical Trials Registry number ACTRN12622001477718.

Estimation of horizontal running power using foot-worn inertial measurement units.

Feedback of power during running is a promising tool for training and determining pacing strategies. However, current power estimation methods show low validity and are not customized for running on different slopes. To address this issue, we developed three machine-learning models to estimate peak horizontal power for level, uphill, and downhill running using gait spatiotemporal parameters, accelerometer, and gyroscope signals extracted from foot-worn IMUs. The prediction was compared to reference horizontal power obtained during running on a treadmill with an embedded force plate. For each model, we trained an elastic net and a neural network and validated it with a dataset of 34 active adults across a range of speeds and slopes. For the uphill and level running, the concentric phase of the gait cycle was considered, and the neural network model led to the lowest error (median ± interquartile range) of 1.7% ± 12.5% and 3.2% ± 13.4%, respectively. The eccentric phase was considered relevant for downhill running, wherein the elastic net model provided the lowest error of 1.8% ± 14.1%. Results showed a similar performance across a range of different speed/slope running conditions. The findings highlighted the potential of using interpretable biomechanical features in machine learning models for the estimating horizontal power. The simplicity of the models makes them suitable for implementation on embedded systems with limited processing and energy storage capacity. The proposed method meets the requirements for applications needing accurate near real-time feedback and complements existing gait analysis algorithms based on foot-worn IMUs.

CORE™ wearable sensor: Comparison against gastrointestinal temperature during cold water ingestion and a 5 km running time-trial

Five km running time-trials (TT) are associated with rapid and significant increases in core body temperature (TC). For such races, real-time feedback from pre-exercise and exercise TC may be helpful in the design of an optimal pacing strategy aimed at limiting the possibility of developing heat-related illnesses. This study compared measurements of TC obtained with a wearable device, the CORE™, to those of a gastrointestinal pill (GI pill), during cold water ingestion and a 5 km running TT. Twelve participants (25 ± 4 yrs) ingested 7.5 mL/kg fat-free mass of 4 °C water over the first 5 min of a 120 min sitting period, after which they completed a 5 km running TT at 30 °C, 50% relative humidity. A TC difference > ± 0.25 °C between sensors was deemed clinically unacceptable. Prior to water ingestion, the CORE-derived TC was 0.49 ± 0.25 °C lower than the GI pill. The CORE was irresponsive to the 0.26 ± 0.22 °C peak decline in TC captured with the GI pill 40 min following water ingestion. Prior to the TT, TC was 0.30 ± 0.25 °C lower with the CORE than the GI pill. During the TT, the CORE underestimated the rate of increase in TC by 0.0125 ± 0.019 °C/min compared with the GI pill, and mean absolute difference in TC between sensors was of 0.47 ± 0.34 °C. In conclusion, the CORE does not capture the cooling effect of cold water ingestion and provides a clinically relevant underestimation of TC during a 5 km running TT in the heat.

Left Bundle Branch Area Pacing and Atrioventricular Node Ablation in a Single-Procedure Approach for Elderly Patients with Symptomatic Atrial Fibrillation.

Implantation of a permanent pacemaker and atrioventricular (AV) node ablation (pace-and-ablate) is an established approach for rate and symptom control in elderly patients with symptomatic atrial fibrillation (AF). Left bundle branch area pacing (LBBAP) is a physiological pacing strategy that might overcome right ventricular pacing-induced dyssynchrony. In this study, the feasibility and safety of performing LBBAP and AV node ablation in a single procedure in the elderly was investigated. Consecutive patients with symptomatic AF referred for pace-and-ablate underwent the treatment in a single procedure. Data on procedure-related complications and lead stability were collected at regular follow-up at one day, ten days and six weeks after the procedure and continued every six months thereafter. 25 patients (mean age 79.2 ± 4.2 years) were included and underwent successful LBBAP. In 22 (88%) patients, AV node ablation and LBBAP were performed in the same procedure. AV node ablation was postponed in two patients due to lead-stability concerns and in one patient on their own request. No complications related to the single-procedure approach were observed with no lead-stability issues at follow-up. LBBAP combined with AV node ablation in a single procedure is feasible and safe in elderly patients with symptomatic AF.

Physiological responses and performance factors for double-poling and diagonal-stride treadmill roller-skiing time-trial exercise.

To compare physiological responses between a self-paced 4-min double-poling (DP) time-trial (TTDP) versus a 4-min diagonal-stride (DS) time-trial (TTDS). The relative importance of peak oxygen uptake ([Formula: see text]O2peak), anaerobic capacity, and gross efficiency (GE) for projection of 4-min TTDP and TTDS roller-skiing performances were also examined. Sixteen highly trained male cross-country skiers performed, in each sub-technique on separate occasions, an 8 × 4-min incremental submaximal protocol, to assess individual metabolic rate (MR) versus power output (PO) relationships, followed by a 10-min passive break and then the TTDP or TTDS, with a randomized order between sub-techniques. In comparison to TTDS, the TTDP resulted in 10 ± 7% lower total MR, 5 ± 4% lower aerobic MR, 30 ± 37% lower anaerobic MR, and 4.7 ± 1.2 percentage points lower GE, which resulted in a 32 ± 4% lower PO (all P < 0.01). The [Formula: see text]O2peak and anaerobic capacity were 4 ± 4% and 30 ± 37% lower, respectively, in DP than DS (both P < 0.01). The PO for the two time-trial (TT) performances were not significantly correlated (R2 = 0.044). Similar parabolic pacing strategies were used during both TTs. Multivariate data analysis projected TT performance using [Formula: see text]O2peak, anaerobic capacity, and GE (TTDP, R2 = 0.974; TTDS, R2 = 0.848). The variable influence on projection values for [Formula: see text]O2peak, anaerobic capacity, and GE were for TTDP, 1.12 ± 0.60, 1.01 ± 0.72, and 0.83 ± 0.38, respectively, and TTDS, 1.22 ± 0.35, 0.93 ± 0.44, and 0.75 ± 0.19, respectively. The results show that a cross-country skier's "metabolic profile" and performance capability are highly sub-technique specific and that 4-min TT performance is differentiated by physiological factors, such as [Formula: see text]O2peak, anaerobic capacity, and GE.

The relevance of pacing strategies in managing symptoms of post-COVID-19 syndrome

BackgroundPost-COVID-19 syndrome (PCS) shares many features with myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS). PCS represents a major health issue worldwide because it severely impacts patients’ work activities and their quality of life. In the absence of treatment for both conditions and given the beneficial effect of pacing strategies in ME/CFS, we conducted this study to assess the effectiveness of pacing in PCS patients.MethodsWe retrospectively included patients meeting the World Health Organization definition of PCS who attended the Internal Medicine Department of Angers University Hospital, France between June 2020 and June 2022, and were followed up until December 2022. Pacing strategies were systematically proposed for all patients. Their medical records were reviewed and data related to baseline and follow-up assessments were collected. This included epidemiological characteristics, COVID-19 symptoms and associated conditions, fatigue features, perceived health status, employment activity, and the degree of pacing adherence assessed by the engagement in pacing subscale (EPS). Recovery was defined as the ability to return to work, and improvement was regarded as the reduction of the number and severity of symptoms.ResultsA total of 86 patients were included and followed-up for a median time of 10 [6–13] months. Recovery and improvement rates were 33.7% and 23.3%, respectively. The EPS score was the only variable significantly associated with recovery on multivariate analysis (OR 40.43 [95% CI 6.22–262.6], p < 0.001). Patients who better adhered to pacing (high EPS scores) experienced significantly higher recovery and improvement rates (60–33.3% respectively) than those with low (5.5–5.5% respectively), or moderate (4.3–17.4% respectively) scores.ConclusionOur findings demonstrated that pacing is effective in the management of patients with PCS, and that high levels of adherence to pacing are associated with better outcomes.

Can we predict long-duration running power output? A matter of selecting the appropriate predicting trials and empirical model.

When facing a long-distance race, athletes and practitioners could develop an efficient pacing strategy and training paces if an accurate performance estimate of the target distance is achieved. Therefore, this study aims to determine the validity of different empirical models (i.e. critical power [CP], Power law and Peronnet) to predict long-duration power output (i.e. 60min) when using two or three time trial configurations. In a 5-week training period, fifteen highly trained athletes performed nine-time trials (i.e. 1, 2, 3, 4, 5, 10, 20, 30, and 60min) in a randomized order. Their power-duration curves were defined through the work-time (CPwork), power-1/time (CP1/time), two-parameter hyperbolic (CP2hyp), three-parameter hyperbolic (CP3hyp) CP models using different two- and three-time trial configurations. The undisclosed proprietary CP models of the Stryd (CPstryd) and Golden Cheetah training software (CPcheetah)were also computed as well as the non-asymptotic Power law and Peronnet models. These were extrapolated to the 60-min power output and compared to the actual performance. The shortest valid configuration (95% confidence interval < 12 W) for CPwork and CP1/time was 3-30min (Bias: 8.3 [4.9 to 11.7] W), for CPstryd was 10-30min (Bias: 4.2 [-1.0 to 9.4] W), for CP2hyp, CP3hyp and CPcheetah was 3-5-30min (Bias < 5.7 W), for Power law was 1-3-10min (-1.0 [-11.9 to 9.9] W), and for Peronnet was 4-20min (-3.0 [-10.2 to 4.3] W). All the empirical models provided valid estimates when the two or three predicting trial configurations selected attended each model fitting needs.

Comparison of novel ventricular pacing strategies using an electro-mechanical simulation platform.

Focus of pacemaker therapy is shifting from right ventricular (RV) apex pacing (RVAP) and biventricular pacing (BiVP) to conduction system pacing. Direct comparison between the different pacing modalities and their consequences to cardiac pump function is difficult, due to the practical implications and confounding variables. Computational modelling and simulation provide the opportunity to compare electrical, mechanical, and haemodynamic consequences in the same virtual heart. Using the same single cardiac geometry, electrical activation maps following the different pacing strategies were calculated using an Eikonal model on a three-dimensional geometry, which were then used as input for a lumped mechanical and haemodynamic model (CircAdapt). We then compared simulated strain, regional myocardial work, and haemodynamic function for each pacing strategy. Selective His-bundle pacing (HBP) best replicated physiological electrical activation and led to the most homogeneous mechanical behaviour. Selective left bundle branch (LBB) pacing led to good left ventricular (LV) function but significantly increased RV load. RV activation times were reduced in non-selective LBB pacing (nsLBBP), reducing RV load but increasing heterogeneity in LV contraction. LV septal pacing led to a slower LV and more heterogeneous LV activation than nsLBBP, while RV activation was similar. BiVP led to a synchronous LV-RV, but resulted in a heterogeneous contraction. RVAP led to the slowest and most heterogeneous contraction. Haemodynamic differences were small compared to differences in local wall behaviour. Using a computational modelling framework, we investigated the mechanical and haemodynamic outcome of the prevailing pacing strategies in hearts with normal electrical and mechanical function. For this class of patients, nsLBBP was the best compromise between LV and RV function if HBP is not possible.

Cardiac Resynchronization Therapy: current guidelines and recent advances beyond drug treatment.

Cardiac resynchronization therapy (CRT) is the therapy of choice for patients with symptomatic systolic heart failure (HF) and left bundle branch block (LBBB), despite optimal medical therapy (OMT). The recently published 2021 European Society of Cardiology (ESC) Guidelines on cardiac pacing and cardiac resynchronization therapy highlight the importance of CRT on top of OMT in HF patients with left ventricular ejection fraction (LVEF) ≤ 35%, sinus rhythm and typical LBBB with QRS duration ≥150ms. In the presence of medically intractable or recurrent after catheter ablation atrial fibrillation (AF), AV nodal ablation as an adjuvant therapy becomes more relevant in patients qualifying for the implantation of a biventricular system. Furthermore, CRT may be considered in cases when increased pacing of the right ventricle is not desirable. However, alternative pacing sites and strategies are currently available, if the CRT is not feasible and effective in patients. However, strategies targeting "multi-sides" or using "multi-leads" have shown superiority over classic CRT. On the other hand, conduction system pacing seems to be a promising technique. Although early results are positive, consistency during the long term is pending. The indication for additional defibrillation therapy (ICD) may occasionally be unnecessary and has to be considered individually. Due to the great development and success of heart failure drug therapy, its positive effect on LV function can lead to enormous improvement. Physicians must await these effects and findings, which hopefully could lead to a relevant LV improvement resulting in a definitive decision against an ICD.

Pathophysiology and treatment of adults with arrhythmias in the emergency department, part 2: Ventricular and bradyarrhythmias.

In an effort to expedite the publication of articles, AJHP is posting manuscripts online as soon as possible after acceptance. Accepted manuscripts have been peer-reviewed and copyedited, but are posted online before technical formatting and author proofing. These manuscripts are not the final version of record and will be replaced with the final article (formatted per AJHP style and proofed by the authors) at a later time. This is the second article in a 2-part series reviewing the pathophysiology and treatment considerations for arrhythmia. Part 1 of the series discussed aspects related to treating atrial arrhythmias. Here in part 2, the pathophysiology of ventricular arrhythmias and bradyarrhythmias and current evidence on treatment approaches are reviewed. Ventricular arrhythmias can arise suddenly and are a common cause of sudden cardiac death. Several antiarrhythmics may be effective in management of ventricular arrhythmias, but there is robust evidence to support the use of only a few of these agents, and that evidence was largely derived from trials involving patients with out-of-hospital cardiac arrest. Bradyarrhythmias range from asymptomatic mild prolongation of nodal conduction to severe conduction delays and impending cardiac arrest. Vasopressors, chronotropes, and pacing strategies require careful attention and titration to minimize adverse effects and patient harm. Ventricular arrhythmias and bradyarrhythmias can be consequential and require acute intervention. As experts in pharmacotherapy, acute care pharmacists can participate in providing high-level intervention by aiding in diagnostic workup and medication selection.

Pacing of Human Locomotion on Land and in Water: 1500 m Swimming vs. 5000 m Running

The study of pace strategy in different environments could help to understand its dependence on athletes’ energetic limits or on sport-specific factors. The aim of this study was to analyse the pacing strategy of finalists during seven swimming and running world events held in 2021–2022. The speed of 32 swimmers every 50 m in 1500 m freestyle competitions, and the speed of 55 runners every 100 m in 5000 m track competitions, were analysed. Differences between swimming and running were statistically significant for Total Time (p = 0.00, ES = 1.9), Average Time of splits (p = 0.00, ES = 2.0), Median Time of splits (p = 0.00, ES = 2.0), and Maximal length of split sequences (p = 0.00, ES = 1.3), and non-significantly different for number of Sequences of splits (p = 0.12, ES = 0.5), Percentage of total splits faster than the median speed (p = 0.08, ES = 0.2), Percentage of splits faster than the median speed in the first half (p = 0.16, ES = 0.4) and Percentage of splits faster than the median speed in the second half (p = 0.21, ES = 0.3). In conclusion, despite similar metabolic requirements of 1500 m swimming and 5000 m running, the influence of specific environment and sport type on the pacing strategy of world level competitions seems to be supported.

Mechanical and hemodynamic effects of left bundle branch area versus biventricular pacing in virtual heart failure patients with left bundle branch block

Abstract Funding Acknowledgements Type of funding sources: Public grant(s) – National budget only. Main funding source(s): The Dutch Research Council (NWO) Background Left bundle branch area pacing (LBBAP) has been introduced as an alternative, more physiological pacing strategy to biventricular pacing (BiVP). LBBAP can result in selective LBB pacing (sLBBP), non-selective LBB pacing (nsLBBP), or LV septal pacing (LVSP). Direct comparison between the different pacing strategies is challenging due to the practical implications of performing multiple pacing procedures within the same patients, as well as the large heterogeneity of underlying disease in patients. Computational models can be used to perform controlled in silico experiments and to compare all possible pacing modalities under the same conditions. Aim To investigate the effects of LBBAP strategies versus BiVP on cardiac mechanics and hemodynamics in a set of well-defined virtual heart failure patients. Methods An electrophysiological model was used to calculate biventricular electrical activation maps during LBBB and the different pacing strategies. The resulting regional activation times were imposed to the well-validated CircAdapt model of the human four-chamber heart and circulation. A set of virtual patients at different stages of heart failure are then defined within the CircAdapt framework, which is achieved by decreasing the contractility of the LV myocardium, such that LVEF≤35%. The CircAdapt model is then used to compute regional ventricular strain patterns and myocardial work as well as global ventricular pump function during LBBB, BiVP and the different LBBAP modalities. Results Selective LBBP is best at restoring mechanical homogeneity in LV contraction as evidenced by simulated wall strains waveforms (Fig 1, Left). NsLBBP increases septal dyssynchrony and introduces small pre-stretch in the LVfw (1.3±0.3%). This effect is more pronounced in LVSP (2.4±1.4%). In BiVP, pre-stretch occurs only in a single LV free wall (LVfw) segment, but all septal segments display a distinct oscillatory pattern. Work load homogeneity (Fig 1, Center) was best restored in sLBBP (4.9±1.1 kPa). NsLBBP lead to reduced homogeneity (4.9±1.8 kPa). LVSP reduced this further (4.8±2.6kPa), while BiVP performed similarly (4.6±2.6kPa) to LVSP. All modalities vastly improved on the baseline LBBB (4.06±5.6 kPa). Hemodynamically (Fig 1, Right), sLBBP showed greatest improvement in LV function (LVESV:-8.1%; LVEF:+6.8%; MLAP:-16.4%; LVdp/dtmax:+12.8%), followed by nsLBBP (LVESV:-7.2%; LVEF:+6.0%; MLAP:-14.5%; LVdp/dtmax:+12.5%), LVSP (LVESV:-5.6%; LVEF:+4.6%; MLAP:-11.7%; LVdp/dtmax:+12.358%) and finally BiVP (LVESV: -4.6%; LVEF:+3.8%; MLAP:-9.3%; LVdp/dtmax:+9.8%) Conclusion We were able to simulate LBBB and subsequent pacing strategies in virtual heart failure patients. This approach allowed direct comparison of mechanical and hemodynamic effects of BiVP and LBBAP modalities without confounding variables. Our results indicate that all LBBAP modalities perform at least similar to bi-ventricular pacing regardless of mechanical viability.

Left bundle brunch pacing versus conventional right ventricular pacing in patients with bradycardia and conduction system disorders: a systematic review and meta-analysis

Abstract Funding Acknowledgements Type of funding sources: None. Background Right Ventricular Pacing (RVP) is well established as the widely accepted pacing method. However, its effects in ventricular function can be detrimental, causing electrical and mechanical dysynchrony and potential LVEF impairment. Left Bundle Branch Pacing (LBBP) is a new pacing strategy that appears to have better results preserving left ventricular function, by directly engaging the intrinsic conduction pathway of the heart. Purpose The aim of this systematic review and meta-analysis is to compare the safety and efficacy of the two pacing methods (LBBP and RVP) in patients suffering from bradyarrhythmia and conduction system disorders. Methods Medline, Embase and Pubmed databases were searched for studies comparing LBBP with RVP. Outcomes were QRSd (QRS duration), ventricular mechanical synchrony, LVEF changes, and Heart Failure Hospitalizations (HFH) to assess the efficacy, lead properties and complications to assess the safety. Two independent reviewers identified studies, extracted data, and assessed the risk of bias using the Cochrane Risk of Bias 2 tool for randomized clinical trials and the Newcastle-Ottawa-Scale for observational studies. Pairwise meta-analysis was conducted using random and fixed effects models. Risk Ratios (RRs) and weighted and standard mean difference (WMD, SMD) with 95% confidence intervals (CIs) were used to report dichotomous and continuous variables respectively. Heterogeneity was assessed with the I² statistic. Results 1318 articles were identified, and finally 25 trials with 4250 patients (2127 LBBP and 2123 RVP) were included in the analysis. Pooled analyses verified that QRSd is shorter in LBBP group both at implantation (WMD:-32.32, CI 95%:-35.18 to -29.45; I²=88%; P&amp;lt;.001) and at Follow Up (WMD: -32.20, CI 95%: -40.70 to -23.71; I²=92%; P&amp;lt;.001) and LBBP succeeded better interventricular mechanical synchrony (SMD:-2.04, CI 95%:-2.32 to -1.76; I²=21%; P&amp;lt;.001) than RVP. Intraventricular mechanical synchrony was also significantly better in LBBP vs RVP independently of the way of measurement in each study (SMD:-1.77, CI 95%:-2.45 to -1.09; I²=90%; P&amp;lt;.001) and in the subgroup analysis of the studies that implemented the same way of measurement (P&amp;lt;.001; I²=26%). LVEF alteration was not significant in the LBBP compared to native (P=.68; I²=52%), while in the RVP group showed a significant reduction (P&amp;lt;.001; I²=51%). LBBP showed, significantly better results in HFH (P&amp;lt;.001; I²=0%) and achieved similar pacing thresholds (P=.86) and higher R wave amplitudes (P&amp;lt;.05) than RVP while lead related complications had no difference between the two groups (LBBP=1.90% vs RVP=1.72%; P=0.71). Conclusions To our knowledge this is the first meta-analysis that assess the safety and efficacy of LBBP in such an important number of patients. LBBP preserves ventricular electrical and mechanical synchrony, shows a reduction in HFH compared to RVP and has excellent pacing parameters, without compromising safety.

Stylet-driven vs. non-stylet-driven lead implantation for left bundle branch area pacing

Abstract Funding Acknowledgements Type of funding sources: None. Background Left bundle branch area pacing (LBBAP) is a novel pacing strategy, which overcomes limitations of right ventricular pacing. Conventional stylet-driven and non-stylet-driven leads have been used as a conduction system pacing lead. Procedural outcome data comparing both lead types are, however, scarce. Purpose To compare procedural outcomes during CSP device implantation with respect to the use of stylet-driven vs. non-stylet-driven leads. Methods We prospectively assessed 170 consecutive LBBAP lead implantation attempts at our center from 09/2021 to 11/2022. All implanters had previous experience with His-bundle pacing lead implantation using the non-stylet-driven lead and 91% of all systems were implanted by two high-volume device implanters. Successful conduction system pacing was established according to standard criteria (LBBAP: R-wave peak time in V6, V1-V6-interpeak interval, programmed stimulation or visibility of a left bundle potential) and pacing thresholds (&amp;lt;2V/0.5ms). The used leads in this analysis were the non-stylet-driven 3830 SelectSure lead (Medtronic, US) and the stylet-driven Solia (Biotronik, Germany), Ingevity+ (Boston Scientific, US) and Tendril STS (Abbott, US) lead. Patient selection and implantation strategy was at the operator’s discretion. Results Clinical baseline characteristics, echocardiography/ECG data and indications did not differ between patients, who received a stylet-driven or non-stylet-driven lead (table showing percentages and median values/interquartile ranges). Patients underwent implantation of a non-stylet driven 3830 SelectSure lead in 20% of cases and a stylet-driven lead in 80% of cases (Solia 76%, Ingevity+ 3%, Tendril STS 1%). Electrical outcome data did not differ between lead types. However, procedural success rate was significantly higher using stylet-driven leads (p=0.025) and a trend towards shorter overall intervention duration was observed as well (p=0.1). Conclusion Stylet-driven leads offer higher LBBAP lead implantation success rates while shortening implant duration.

Acute procedural outcomes of left bundle branch area pacing compared to His-bundle pacing

Abstract Funding Acknowledgements Type of funding sources: None. Background Conduction system pacing (CSP), encompassing left bundle branch area pacing (LBBAP) and His-bundle pacing (HBP), is a novel pacing strategy, which overcomes limitations of conventional right ventricular pacing. Feasibility and early safety of both strategies have been established previously. While HBP is mentioned as an alternative pacing strategy in the latest European and American pacing guidelines, implantation recommendations regarding LBBAP are scarce. Notably, HBP was described to be associated with a significantly higher procedural failure rate compared to LBBAP, making it potentially more contestable. Purpose To compare procedural outcomes after HBP and LBBAP lead implantation. Methods We prospectively assessed 303 consecutive CSP lead implantation attempts at our center from 08/2018 to 11/2022. 81% of all implantations were performed by two high-volume device implanters. Successful conduction system pacing was established according to standard criteria (HBP: QRS morphology, R-wave peak time in V6, programmed stimulation, visibility of a His potential; LBBAP: R-wave peak time in V6, V1-V6-interpeak interval, programmed stimulation or visibility of a left bundle potential) and pacing thresholds (HBP: &amp;lt;4.0V/1.0ms; LBBAP: &amp;lt;2V/0.5ms). Patient selection and the implantation strategy used was at the operator’s discretion. Results Patients with a HBP attempt were younger and had a narrower QRS complex but did not differ with respect to left or right ventricular function and dimension (table showing percentages and median values/interquartile ranges). LBBAP systems were more often implanted in lieu of CRT, whereas HBP systems were more commonly used in case of AV block without heart failure (table). Acute procedural success rate, overall procedure duration and fluoroscopy time were significantly better during LBBAP implantations (all p&amp;lt;0.001). Success rates, sensing values and capture thresholds (@1ms for HBP and @0.5ms for LBBAP) were superior in LBBAP systems, while achieved paced QRS duration was slightly shorter in HBP systems (table, figure 1). Conclusion Success rates and acute procedural outcomes favor implantation of LBBAP compared to HBP systems.

Epicardial versus endocardial pacing in cardiac resynchronization therapy

Abstract Funding Acknowledgements Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Norwegian Research Council. Background/Introduction The timing of left ventricular pressure rise (Td) relative to QRS-onset is associated with dispersion of regional work distribution and prolongs with dyssynchrony and dyssynergistic contractions. Td is short in normal conduction and shortening of Td can be achieved with effective biventricular pacing (BIVP). The effect of endocardial compared to epicardial pacing on Td is unknown and could be important for the interpretation of Td when different pacing strategies are utilized for CRT. Purpose We wanted to analyze the measurement from QRS-onset to onset of LV pressure rise identified as the peak double derivative of LV pressure rise (Onset of Synergy, OoS) and to the peak pressure rise (Td), and test the effects of cardiac resynchronization therapy with endocardial vs epicardial pacing electrodes in a large animal model of LBBB. Methods 5 mongrel dogs were included in the study and handled according to ethics committee approved protocol/GLP. Pacing electrodes were placed epicardial on the left ventricular (LVepi) and right ventricular (RVepi) free wall, and endocardial electrodes were positioned at the right ventricular septum (RVsept) and in the LV endocardial free wall (LVendo). The atrial electrode was placed on the left atrial appendage. Pressure was measured with a Micro-tip pressure sensor (Millar Inc.) in the LV and sampled at 1000Hz. LBBB was created with a retrograde placed 7F standard ablation catheter and confirmed by surface ECG and four endocardial electrodes. Td was measured from 10 consecutive beats. Mixed models were utilized for the repeated measurements. Results Td was measured to 115±2ms at baseline in LBBB. Td decreased by 5ms from RVepi (114±3ms) to RVendo (109±3ms) regardless of LV electrode position. We then compared the effects of using LV endocardial and epicardial pacing in CRT and found that Td was 6ms higher (p&amp;lt;0.01) in LVepi (115±3ms) vs LVendo (109±3ms) regardless of RV electrode position. The interaction between RV RV and LV revealed that RVepi/LVendo (105±3ms) was significant shorter than RVendo/LVendo (110±3ms, p0.01) and RVepi/LVepi (115±3ms, p&amp;lt;0.01). OoS with RVepi/LVendo was 71±2ms, and a significant relationship between OoS and Td were found (R=0.62, p&amp;lt;0.01) to indicate that the myocardial contraction is affected by pacing already at 71ms after QRS-onset early during the pre-ejection period. Conclusion(s) In this study we demonstrate how endocardial and epicardial pacing applied with CRT may affect contraction patterns of the heart differently. The different effects from pacing can be measured as early as 71ms after QRS-onset. Shortening of Td occurs to a larger extent with pacing from the endocardial LV and epicardial RV, while pacing at two endocardial sites did not result in synergistic effects on Td. This may indicate that there might be an interaction between endocardial pacing sites when applied in combination.

Role of RA-LV pacing in patients with symptomatic left bundle branch block with CRT - a single centre experience

Abstract Funding Acknowledgements Type of funding sources: None. Introduction Cardiac Resynchronisation Therapy(CRT) is considered as the cornerstone of treatment for patients with heart failure and left ventricular conduction delay ( left bundle branch block) who remain symptomatic despite optimal medical therapy. However, it has been well documented that the responder and success rates of this therapy are highly variable. Contemporary response rates from clinical trials as well as real world data demonstrate non-response rates of between 30–50%. Suboptimal AV delay timing is the most prevalent modifiable factor on follow up for improving response rates. AV Fusion pacing describes the delivery of CRT pacing with a programming strategy to preserve intrinsic atrioventricular (AV) conduction and ventricular activation via the right bundle branch. This concept is utilised in the RA- LV pacing strategies, which have been described in literature. However, RA-LV only pacing raises certain practical , moral and ethical concerns as it has never been a part of contemporary guidelines nor a part of large randomised control trial. Purpose The purpose of this study was to study the clinical as well as hemodynamic effects of RA-LV pacing in patients with a conventional CRT device with a programmed subthreshold RV lead. Methods All patients with a convention CRT indication ( CRT-P as well as CRT-D), with acceptable intrinsic AV conduction, non pacing dependent and normal Right Ventricular function were enrolled into the study. A total of 60 consecutive patients between 2016-2021 were enlisted from after the implant and followed up in the Device clinic of the institution. The baseline as well as follow-up LV function, Battery life and QRS duration was recorded and analysed. Results Total of 60 patients were enlisted of which 30 were males and 30 females. There were 16 patients were with Ischemic Cardiomyopathy in this group. The average follow-up period was 3 year from implant. The mean baseline Left Ventricular Ejection Fraction was 29% while the mean follow-up Left Ventricular Ejection Fraction was 46.5%. The mean QRS duration at implant was 155msec and the mean follow-up QRS was 123 msec. The subset analysis of ischemic vs the nonischaemic cardiomyopathy groups revealed that both groups had a similar response rates to improvement of clinical as well as Echocardiographic parameters including LVEF. The mean follow up LVEF in the ischemic and nonischaemic groups were 44.5 &amp; 46.5% respectively. This finding suggests that the advantage of AV fusion pacing is not significantly impacted with underlying aetiology of the Cardiomyopathy. Conclusion RA-LV with RV subthreshold CRT is a reasonable strategy for achieving traditional response rates of CRT in patients with a good intrinsic AV conduction. This modality overcomes a large number of procedural as well as ethical roadblocks in the use of fusion pacing for CRT therapy optimisation.