Arrhythmic Risk in Biventricular Pacing Compared With Left Bundle Branch Area Pacing: Results From the I-CLAS Study.

BACKGROUND: Left bundle branch area pacing (LBBAP) may be associated with greater improvement in left ventricular ejection fraction and reduction in death or heart failure hospitalization compared with biventricular pacing (BVP) in patients requiring cardiac resynchronization therapy. We sought to compare the occurrence of sustained ventricular tachycardia (VT) or ventricular fibrillation (VF) and new-onset atrial fibrillation (AF) in patients undergoing BVP and LBBAP. METHODS: The I-CLAS study (International Collaborative LBBAP Study) included patients with left ventricular ejection fraction ≤35% who underwent BVP or LBBAP for cardiac resynchronization therapy between January 2018 and June 2022 at 15 centers. We performed propensity score-matched analysis of LBBAP and BVP in a 1:1 ratio. We assessed the incidence of VT/VF and new-onset AF among patients with no history of AF. Time to sustained VT/VF and time to new-onset AF was analyzed using the Cox proportional hazards survival model. RESULTS: Among 1778 patients undergoing cardiac resynchronization therapy (BVP, 981; LBBAP, 797), there were 1414 propensity score-matched patients (propensity score-matched BVP, 707; propensity score-matched LBBAP, 707). The occurrence of VT/VF was significantly lower with LBBAP compared with BVP (4.2% versus 9.3%; hazard ratio, 0.46 [95% CI, 0.29-0.74]; P<0.001). The incidence of VT storm (>3 episodes in 24 hours) was also significantly lower with LBBAP compared with BVP (0.8% versus 2.5%; P=0.013). Among 299 patients with cardiac resynchronization therapy pacemakers (BVP, 111; LBBAP, 188), VT/VF occurred in 8 patients in the BVP group versus none in the LBBAP group (7.2% versus 0%; P<0.001). In 1194 patients with no history of VT/VF or antiarrhythmic therapy (BVP, 591; LBBAP, 603), the occurrence of VT/VF was significantly lower with LBBAP than with BVP (3.2% versus 7.3%; hazard ratio, 0.46 [95% CI, 0.26-0.81]; P=0.007). Among patients with no history of AF (n=890), the occurrence of new-onset AF >30 s was significantly lower with LBBAP than with BVP (2.8% versus 6.6%; hazard ratio, 0.34 [95% CI, 0.16-0.73]; P=0.008). The incidence of AF lasting >24 hours was also significantly lower with LBBAP than with BVP (0.7% versus 2.9%; P=0.015). CONCLUSIONS: LBBAP was associated with a lower incidence of sustained VT/VF and new-onset AF compared with BVP. This difference remained significant after adjustment for differences in baseline characteristics between patients with BVP and LBBAP. Physiological resynchronization by LBBAP may be associated with lower risk of arrhythmias compared with BVP.

Centennial of the original description of Mobitz type II second-degree atrioventricular block.

The year 2024 marks the centenary of Mobitz's description of type II second-degree atrioventricular block. Its definition remains valid to this day with only minor modification for the diagnosis of infranodal conduction block. Mobitz a century ago indicated that his type II atrioventricular block was associated with Stock-Adams attacks and a prolonged duration of the QRS complex before the eventual description of bundle branch block.

Adjunct posterior wall isolation reduces the recurrence of atrial fibrillation in patients undergoing cryoballoon ablation: A systematic review and meta-analysis.

BACKGROUND: Recurrence rates of atrial fibrillation (AF) remain high even after complete wide area circumferential pulmonary vein isolation (PVI). In recent years adjunct posterior wall isolation (PWI) has been performed in patients with more persistent forms of AF but the benefits remain unclear. AIM: The objective of this meta-analysis was to evaluate the efficacy of adjunct posterior wall isolation in reducing recurrence rates of AF using cryoballoon ablation (CBA). METHODS: We searched PubMed, Google Scholar, Clinicaltrials.gov and Cochrane CENTRAL. We included studies comparing PVI to PVI + PWI in patients with either persistent or paroxysmal AF (PAF) undergoing CBA. After data extraction and quality assessment of the studies, we assessed recurrence rates of atrial tachy-arrhythmias (AF, atrial flutter, and atrial tachycardia) as well as total ablation time and procedural adverse events. Risk ratio (RR), mean difference (MD), and 95% confidence interval (CI) were calculated using Review Manager. RESULTS: Concomitant PWI exhibited a substantial reduction in the risk of AF recurrence (RR: 0.51; 95% CI: 0.42-0.63, p < .00001), as well as all atrial arrhythmias (RR: 0.58; 95% CI: 0.49-0.68, p < .00001). On subgroup analysis, in patients with only PAF, adjunct PWI resulted in significant reduction in recurrence risk of AF (RR: 0.56; 95% CI: 0.41-0.76, p = .0002) as well. There was no significant difference in adverse events between both groups (RR: 0.90; 95% CI: 0.44-1.86; p = .78), whereas total ablation time was significantly increased in PVI + PWI group (MD: 21.75; 95% CI: 11.13-32.37, p < .0001). CONCLUSION: Adjunct PWI when compared to PVI alone decreases recurrence rates of atrial fibrillation after CBA of patients with persistent as well as paroxysmal atrial fibrillation.

In vitro and in vivo cardiac toxicity of flavored electronic nicotine delivery systems.

The usage of flavored electronic nicotine delivery systems (ENDS) is popular, specifically in the teen and young adult age-groups. The possible cardiac toxicity of the flavoring aspect of ENDS is largely unknown. Vaping, a form of electronic nicotine delivery, uses "e-liquid" to generate "e-vapor," an aerosolized mixture of nicotine and/or flavors. We report our investigation into the cardiotoxic effects of flavored e-liquids. E-vapors containing flavoring aldehydes such as vanillin and cinnamaldehyde, as indicated by mass spectrometry, were more toxic in HL-1 cardiomyocytes than fruit-flavored e-vapor. Exposure of human induced pluripotent stem cell-derived cardiomyocytes to cinnamaldehyde or vanillin-flavored e-vapor affected the beating frequency and prolonged the field potential duration of these cells more than fruit-flavored e-vapor. In addition, vanillin aldehyde-flavored e-vapor reduced the human ether-à-go-go-related gene (hERG)-encoded potassium current in transfected human embryonic kidney cells. In mice, inhalation exposure to vanillin aldehyde-flavored e-vapor for 10 wk caused increased sympathetic predominance in heart rate variability measurements. In vivo inducible ventricular tachycardia was significantly longer, and in optical mapping, the magnitude of ventricular action potential duration alternans was significantly larger in the vanillin aldehyde-flavored e-vapor-exposed mice than in controls. We conclude that the widely popular flavored ENDS are not harm free, and they have a potential for cardiac harm. More studies are needed to further assess their cardiac safety profile and long-term health effects.NEW & NOTEWORTHY The use of electronic nicotine delivery systems (ENDS) is not harm free. It is not known whether ENDS negatively affect cardiac electrophysiological function. Our study in cell lines and in mice shows that ENDS can compromise cardiac electrophysiology, leading to action potential instability and inducible ventricular arrhythmias. Further investigations are necessary to assess the long-term cardiac safety profile of ENDS products in humans and to better understand how individual components of ENDS affect cardiac toxicity.

The evolution of cardiac resynchronization therapy and an introduction to conduction system pacing: a conceptual review.

In chronic systolic heart failure and conduction system disease, cardiac resynchronization therapy (CRT) is the only known non-pharmacologic heart failure therapy that improves cardiac function, functional capacity, and survival while decreasing cardiac workload and hospitalization rates. While conventional bi-ventricular pacing has been shown to benefit patients with heart failure and conduction system disease, there are limitations to its therapeutic success, resulting in widely variable clinical response. Limitations of conventional CRT evolve around myocardial scar, fibrosis, and inability to effectively simulate diseased tissue. Studies have shown endocardial stimulation in closer proximity to the specialized conduction system is more effective when compared with epicardial stimulation. Several observational and acute haemodynamic studies have demonstrated improved electrical resynchronization and echocardiographic response with conduction system pacing (CSP). Our objective is to provide a systematic review of the evolution of CRT, and an introduction to CSP as an intriguing, though experimental physiologic alternative to conventional CRT.

Utilization of Permanent His-Bundle Pacing for Management of Proarrhythmia Related to Biventricular Pacing.

Biventricular pacing has occasionally been associated with ventricular proarrhythmia, which at times can be refractory to conventional antiarrhythmic drug therapy and ablative intervention. Recently, permanent His-bundle pacing has emerged as a reasonable alternative to right ventricular and biventricular pacing. In addition, by maintaining the physiologic pattern of ventricular electrical activation, it is less likely to be arrhythmogenic. We report the use of permanent His-bundle pacing to manage ventricular proarrhythmia that developed after initiation of biventricular pacing and was unresponsive to antiarrhythmic and ablative therapy.

Healthcare Utilization and Quality of Life Improvement after Ablation for Paroxysmal AF in Younger and Older Patients.

BACKGROUND: Atrial fibrillation (AF) prevalence increases significantly with age. Little is known about the effect of AF ablation on quality of life and healthcare utilization in the elderly. The objective of this study was to quantify the healthcare utilization and quality of life benefits of catheter ablation for AF, for patients ≥65 years compared to patients <65 years. METHODS: Two multicenter U.S. registry studies enrolled patients with paroxysmal AF. Baseline characteristics and acute outcomes were collected for 736 patients receiving catheter ablation with the Navistar® ThermoCool® SF Catheter (Biosense Webster, Inc., Diamond Bar, CA, USA). Healthcare utilization and quality of life outcomes were collected through 1 year postablation for 508 patients. RESULTS: The rates of acute pulmonary vein isolation were high and similar between patients ≥65 years and <65 years (97.5% vs 95.8%, P = 0.2130). Length of stay for the index procedure was similar between age groups with 82.2% of the older group and 83.2% of the younger group having one-day hospitalization. Disease-specific quality of life instrument scores improved significantly and similarly for older and younger patients at 1 year postablation, compared to baseline. AF-related hospitalizations and emergency department visits were similar or lower in older patients compared to younger patients, as reported at 1 year postablation. CONCLUSION: For older patients undergoing catheter ablation for paroxysmal AF, healthcare utilization parameters were lower or not significantly different than for younger patients, and quality of life outcomes were similarly improved. These findings support the use of catheter ablation as a treatment option in older patients with paroxysmal AF.

Permanent His Bundle Pacing in Intra-Hisian Conduction Block: Mechanistic Insights.

We are reporting a patient with discrete intra-His conduction block and describe a refined technique of permanent His bundle pacing assuring reliable ventricular capture. Meticulous mapping of the site of block with lead placement distal to the site of block and non-selective His bundle pacing with local myocardial capture as an additional safety back up appears to be the technique of choice.

MRI Assessment of Ablation-Induced Scarring in Atrial Fibrillation: Analysis from the DECAAF Study.

BACKGROUND: There is limited knowledge on the extent and location of scarring that results from catheter ablation and its role in suppressing atrial fibrillation (AF). We examined the effect of atrial fibrosis and ablation-induced scarring on catheter ablation outcomes in AF. METHODS: We conducted a prospective multicenter study that enrolled 329 AF patients presenting for catheter ablation. Delayed enhancement magnetic resonance imaging (DE-MRI) of the left atrium was obtained preablation. Scarring was evaluated in 177 patients with a DE-MRI scan obtained 90 days postablation. We evaluated residual fibrosis, defined as preablation atrial fibrosis not covered by ablation scar. The primary outcome was freedom from recurrent atrial arrhythmia. RESULTS: In the analysis cohort of 177 patients, preablation fibrosis was 18.7 ± 8.7% of the atrial wall. Ablation aimed at pulmonary vein (PV) isolation was performed in 163 patients (92.1%). Ablation-induced scar averaged 10.6 ± 4.4% of the atrial wall. Scarring completely encircled all 4 PVs only in 12 patients (7.3%). Residual fibrosis was calculated at 15.8 ± 8.0%. At 325 days follow-up, 35% of patients experienced recurrent arrhythmia. Multivariable Cox proportional hazards models demonstrated that baseline atrial fibrosis (HR and 95% CIs) (1.09 [1.06-1.12], P < 0.001) and residual fibrosis (1.09 [1.05-1.13], P < 0.001) were associated with atrial arrhythmia recurrence, while PV encirclement and overall scar were not. CONCLUSIONS: Catheter ablation of AF targeting PVs rarely achieves permanent encircling scar in the intended areas. Overall atrial fibrosis present at baseline and residual fibrosis uncovered by ablation scar are associated with recurrent arrhythmia.

Acute safety of an open-irrigated ablation catheter with 56-hole porous tip for radiofrequency ablation of paroxysmal atrial fibrillation: analysis from 2 observational registry studies.

INTRODUCTION: This report presents safety data on the use of a new open-irrigation radiofrequency ablation (RFA) catheter with a 56-hole porous tip in 742 patients enrolled in 2 US prospective, multicenter observational registry studies representing real-world use of the catheter. METHODS: This analysis is comprised of patients who underwent RFA of drug-refractory recurrent symptomatic paroxysmal atrial fibrillation (AF). Acute adverse events (AEs) were collected and categorized by seriousness, timing, and relatedness, with 7 days of follow-up data in one study and at least 120 days of data from a 1-year follow-up in the other. Acute serious adverse events (SAEs) that were identified as potentially related to the device and/or procedure were adjudicated by an independent safety committee. RESULTS: A total of 30 patients (4.0%) in the combined studies experienced an acute SAE related to the device and/or procedure, which was similar in the subset of patients age 65 and over (4.2%). These SAEs included 1.2% cardiac tamponade/perforation, 0.7% pericarditis, 0.5% pulmonary events, and 0.8% vascular access complications. No myocardial infarction, stroke, transient ischemic attack, or atrioesophageal fistulas within 7 days postprocedure were reported. In the study with extended follow-up, 1 pulmonary vein stenosis and 1 esophageal injury were seen beyond 7 days postprocedure (0.2% each). There were no device or procedure related deaths. CONCLUSION: Results from 2 large observational studies demonstrated that a new porous tip RFA catheter was safe for the treatment of drug refractory, recurrent, symptomatic paroxysmal AF, including treatment of older patients (≥65 years).

The effect of hyperkalaemia on cardiac rhythm devices.

In patients with pacemakers, hyperkalaemia causes three important abnormalities that usually become manifest when the K level exceeds 7 mEq/L: (i) widening of the paced QRS complex from delayed intraventricular conduction velocity, (ii) Increased atrial and ventricular pacing thresholds that may cause failure to capture. In this respect, the atria are more susceptible to loss of capture than the ventricles, and (iii) Increased latency (usually with ventricular pacing) manifested by a greater delay of the interval from the pacemaker stimulus to the onset of depolarization. First-degree ventricular pacemaker exit block may progress to second-degree Wenckebach (type I) exit block characterized by gradual prolongation of the interval from the pacemaker stimulus to the onset of the paced QRS complex ultimately resulting in an ineffectual stimulus. The disturbance may then progress to 2 : 1, 3 : 1 pacemaker exit block, etc., and eventually to complete exit block with total lack of capture. Ventricular undersensing is uncommonly observed because of frequent antibradycardia pacing. During managed ventricular pacing, hyperkalaemia-induced marked first-degree atrioventricular block may induce a pacemaker syndrome. With implantable cardioverter-defibrillators (ICDs) oversensing of the paced or spontaneous T-wave may occur. The latter may cause inappropriate shocks. A raised impedance from the right ventricular coil to the superior vena cava coil may become an important sign of hyperkalaemia in the asymptomatic or the minimally symptomatic ICD patient.

Comparative safety of periablation anticoagulation strategies for atrial fibrillation: data from a large multicenter study.

BACKGROUND: There are a variety of periprocedural anticoagulation strategies for atrial fibrillation (AF) ablation, including the use of dabigatran. It is unclear which strategy is superior. OBJECTIVE: To compare the safety and efficacy of anticoagulation with uninterrupted warfarin, dabigatran, and warfarin with heparin bridging in patients undergoing ablation of AF at four experienced centers. METHODS AND RESULTS: In this retrospective analysis, 882 patients (mean age: 61 ± 11 years) underwent ablation of AF using uninterrupted warfarin (n = 276), dabigatran (n = 374), or warfarin with heparin bridging (n = 232) for periprocedural anticoagulation. The rate of total complications was 23/276 (8.3%) in the uninterrupted warfarin group, 30/374 (8.0%) in the dabigatran group, and 29/232 (12.5%) in the bridged group (P = 0.15). Major complications were more frequent in the uninterrupted warfarin group 12/276 (4.3%) compared with 3/374 (0.8%) in dabigatran and 6/232 (2.6%) in the bridged group (P = 0.01). The most common major complication was the need for transfusion or occurrence of major bleeding. Minor complications did not differ among the three groups. On multivariate analysis, female gender (odds ratio [OR] 1.93, confidence interval [CI] 1.16-3.19, P = 0.011), bridging heparin (OR 2.13, CI 1.100-3.941, P = 0.016), use of triple antithrombotic therapy (OR 1.77, CI 1.05-2.98, P = 0.033), and prior myocardial infarction (OR 2.40, CI 1.01-5.67, P = 0.046) independently predicted total complications. CONCLUSIONS: When comparing the use of uninterrupted warfarin, dabigatran, and warfarin with heparin bridging in patients undergoing catheter ablation of AF, dabigatran was not associated with increased risk, major complications were more common in the uninterrupted warfarin group, and after adjustment, warfarin with bridging increased total complications.

Association of atrial tissue fibrosis identified by delayed enhancement MRI and atrial fibrillation catheter ablation: the DECAAF study.

IMPORTANCE: Left atrial fibrosis is prominent in patients with atrial fibrillation (AF). Extensive atrial tissue fibrosis identified by delayed enhancement magnetic resonance imaging (MRI) has been associated with poor outcomes of AF catheter ablation. OBJECTIVE: To characterize the feasibility of atrial tissue fibrosis estimation by delayed enhancement MRI and its association with subsequent AF ablation outcome. DESIGN, SETTING, AND PARTICIPANTS: Multicenter, prospective, observational cohort study of patients diagnosed with paroxysmal and persistent AF (undergoing their first catheter ablation) conducted between August 2010 and August 2011 at 15 centers in the United States, Europe, and Australia. Delayed enhancement MRI images were obtained up to 30 days before ablation. MAIN OUTCOMES AND MEASURES: Fibrosis quantification was performed at a core laboratory blinded to the participating center, ablation approach, and procedure outcome. Fibrosis blinded to the treating physicians was categorized as stage 1 (<10% of the atrial wall), 2 (≥10%-<20%), 3 (≥20%-<30%), and 4 (≥30%). Patients were followed up for recurrent arrhythmia per current guidelines using electrocardiography or ambulatory monitor recording and results were analyzed at a core laboratory. Cumulative incidence of recurrence was estimated by stage at days 325 and 475 after a 90-day blanking period (standard time allowed for arrhythmias related to ablation-induced inflammation to subside) and the risk of recurrence was estimated (adjusting for 10 demographic and clinical covariates). RESULTS: Atrial tissue fibrosis estimation by delayed enhancement MRI was successfully quantified in 272 of 329 enrolled patients (57 patients [17%] were excluded due to poor MRI quality). There were 260 patients who were followed up after the blanking period (mean [SD] age of 59.1 [10.7] years, 31.5% female, 64.6% with paroxysmal AF). For recurrent arrhythmia, the unadjusted overall hazard ratio per 1% increase in left atrial fibrosis was 1.06 (95% CI, 1.03-1.08; P < .001). Estimated unadjusted cumulative incidence of recurrent arrhythmia by day 325 for stage 1 fibrosis was 15.3% (95% CI, 7.6%-29.6%); stage 2, 32.6% (95% CI, 24.3%-42.9%); stage 3, 45.9% (95% CI, 35.5%-57.5%); and stage 4, 51.1% (95% CI, 32.8%-72.2%) and by day 475 was 15.3% (95% CI, 7.6%-29.6%), 35.8% (95% CI, 26.2%-47.6%), 45.9% (95% CI, 35.6%-57.5%), and 69.4% (95% CI, 48.6%-87.7%), respectively. Similar results were obtained after covariate adjustment. The addition of fibrosis to a recurrence prediction model that includes traditional clinical covariates resulted in an improved predictive accuracy with the C statistic increasing from 0.65 to 0.69 (risk difference of 0.05; 95% CI, 0.01-0.09). CONCLUSIONS AND RELEVANCE: Among patients with AF undergoing catheter ablation, atrial tissue fibrosis estimated by delayed enhancement MRI was independently associated with likelihood of recurrent arrhythmia. The clinical implications of this association warrant further investigation.

Cryoballoon cardioneuroablation: New electrophysiological insights.

Background: Cardioneuroablation (CNA) targeting ganglionated plexi has shown promise in treating vasovagal syncope. Only radiofrequency ablation has been used to achieve this goal thus far. Objective: The purpose of this study was to investigate the utility of cryoballoon ablation (CBA) of the pulmonary veins (PVs) as a potential simplified approach to CNA. Methods: We report our observations of autonomic modulation in a series of 17 patients undergoing CBA for atrial fibrillation and our early experience using CBA of the PVs in 3 patients with malignant vagal syncope. In 17 patients undergoing CBA of AF, sinus cycle length was recorded intraprocedurally after ablation of individual PVs. Results: The most pronounced shortening of the sinus cycle length was observed after isolation of the right upper PV, which was ablated last. Reduced sinus node recovery time and atrioventricular (AV) nodal effective refractory period were observed after CBA. Resting heart rate was elevated by 6-7 bpm after CBA and persisted during 12-month follow-up. CBA of the PVs was performed in 3 patients with recurrent vagal syncope mediated by sinus arrest (n = 2) and AV block (n = 1). In all patients, isolation of the right upper PV resulted in marked shortening of sinus cycle length. During follow-up of 178 ± 43 days (134-219 days), CNA resulted in abolition of pauses, bradycardia-related symptoms, and syncope in all patients. Conclusion: CBA of the PVs (particularly the right upper PV) may be a predictable anatomic CNA approach in patients with refractory vagal syncope due to sinus arrest and/or AV block and may warrant systematic investigation as a tool to perform CNA.

Sex-Specific Outcomes of LBBAP Versus Biventricular Pacing: Results From I-CLAS.

BACKGROUND: Cardiac resynchronization therapy (CRT) using biventricular pacing (BVP) has been associated with greater clinical improvement in women than men. Recently, left bundle branch area pacing (LBBAP) has been shown to be an alternative form of CRT. OBJECTIVES: The purpose of this study was to investigate sex-specific outcomes for death and heart failure events in a large, international, multicenter, cohort of patients undergoing CRT with BVP or LBBAP. METHODS: In this international study of 1,778 patients (575 female and 1203 male), sex-specific survival analysis was performed to compare the effect of LBBAP-CRT relative to BVP-CRT on the combined endpoint of death or heart failure hospitalization (HFH), and secondary endpoints of HFH only, and death alone. RESULTS: Female patients were more likely to have nonischemic cardiomyopathy and left bundle branch block (LBBB) and less likely to have hypertension, diabetes, or coronary artery disease than were male patients. Overall, female patients had a better result with LBBAP compared with BVP than did male patients, with a significant 36% reduction in death or HFH (HR: 0.64; 95% CI: 0.43 to 0.97; P = 0.03) and a significant 60% reduction in HFH alone (HR: 0.4; 95% CI: 0.24 to 0.69, P < 0.01). Women had a greater reduction in death or HFH among those with nonischemic cardiomyopathy (HR: 0.45 95% CI: 0.26 to 0.79; P < 0.01) and LBBB (HR: 0.49; 95% CI: 0.27 to 0.87; P < 0.01). Sex-specific echocardiographic outcomes were better in women than in men. CONCLUSIONS: Women obtained significantly greater reductions in the combined endpoint of death or HFH (primarily driven by reduction in HFH) with LBBAP compared with BVP among patients requiring CRT than did men.

Transvenous extraction of conduction system pacing leads: An international multicenter (TECSPAM) study.

BACKGROUND: Conduction system pacing (CSP) by His bundle pacing or left bundle branch area pacing (LBBAP) is incorporated into Heart Rhythm Society guidelines for the management of bradycardia and cardiac resynchronization therapy. Despite increasing adoption with both lumenless leads and stylet-driven leads, concerns regarding the feasibility and safety of the extraction of CSP leads remain. OBJECTIVE: The aim of the study was to report on the safety, feasibility, and clinical outcomes of the extraction of CSP leads. METHODS: Patients undergoing the extraction of CSP leads from 10 international centers were enrolled in this retrospective study. Data regarding indications, lead location, lead type, extraction tools, procedural success, complications, and reimplantation in the conduction system were collected. RESULTS: Overall, 341 patients (age 69 ± 15 years; female 34%; cardiomyopathy 46%; lead dwell time 22 ± 26 months) underwent the extraction of 224 His bundle pacing and 117 LBBAP leads (lumenless leads 321; stylet-driven leads 20). Complete procedural success was achieved in 338 (99%), while clinical success was 100% with retained distal fragments in 3 patients (1%). Among patients with a lead dwell time of >6 months (6-193 months; n = 226), manual extraction was successful in 198 (87%), mechanical tools in 22 (10%), and laser in 6 (3%). Femoral tools were necessary in 3 patients. Minor complications occurred in 7 patients (2.1%). CSP reimplantation was successful in 233 of 244 patients attempted (95%). CONCLUSION: The overall success rates of the extraction of CSP leads were very high (although the LBBAP lead dwell time was <3 years), with a low need for extraction tools and minimal complication. Reimplantation in the conduction system is feasible and safe.

Continuous monitoring of atrial fibrillation in heart failure.

In patients with atrial fibrillation (AF) undergoing cardiac resynchronization therapy (CRT) for heart failure, continuous monitoring of the percentage of biventricular BiV% pacing has shown that the greatest improvement and reduction in mortality occur with a BiV pacing greater than 98%. Continuous monitoring of BiV pacing has improved the CRT management of patients with AF. Continuous monitoring has generated important new questions about anticoagulant therapy, which require randomized trials. Anticoagulant therapy should probably be considered in patients who have a high risk of thromboembolism according to standard scoring systems.

Cardiac Conduction System Pacing: A Comprehensive Update.

The field of cardiac pacing has changed rapidly in the last several years. Since the initial description of His bundle pacing targeting the conduction system, recent advances in pacing the left bundle branch and its fascicles have evolved. The field and investigators' knowledge of conduction system pacing including relevant anatomy and physiology has advanced significantly. The aim of this review is to provide a comprehensive update on recent advances in conduction system pacing.

Comparison of Left Bundle Branch Area Pacing and Biventricular Pacing in Candidates for Resynchronization Therapy.

BACKGROUND: Cardiac resynchronization therapy (CRT) with biventricular pacing (BVP) is a well established therapy in patients with reduced left ventricular ejection fraction (LVEF), heart failure, and wide QRS or expected frequent ventricular pacing. Left bundle branch area pacing (LBBAP) has recently been shown to be a safe alternative to BVP. OBJECTIVES: The aim of this study was to compare the clinical outcomes between BVP and LBBAP among patients undergoing CRT. METHODS: This observational study included patients with LVEF ≤35% who underwent BVP or LBBAP for the first time for Class I or II indications for CRT from January 2018 to June 2022 at 15 international centers. The primary outcome was the composite endpoint of time to death or heart failure hospitalization (HFH). Secondary outcomes included endpoints of death, HFH, and echocardiographic changes. RESULTS: A total of 1,778 patients met inclusion criteria: 981 BVP, 797 LBBAP. The mean age was 69 ± 12 years, 32% were female, 48% had coronary artery disease, and mean LVEF was 27% ± 6%. Paced QRS duration in LBBAP was significantly narrower than baseline (128 ± 19 ms vs 161 ± 28 ms; P < 0.001) and significantly narrower compared to BVP (144 ± 23 ms; P < 0.001). Following CRT, LVEF improved from 27% ± 6% to 41% ± 13% (P < 0.001) with LBBAP compared with an increase from 27% ± 7% to 37% ± 12% (P < 0.001) with BVP, with significantly greater change from baseline with LBBAP (13% ± 12% vs 10% ± 12%; P < 0.001). On multivariable regression analysis, the primary outcome was significantly reduced with LBBAP compared with BVP (20.8% vs 28%; HR: 1.495; 95% CI: 1.213-1.842; P < 0.001). CONCLUSIONS: LBBAP improved clinical outcomes compared with BVP in patients with CRT indications and may be a reasonable alternative to BVP.

Conventional and biventricular pacing in patients with first-degree atrioventricular block.

Recent reports suggest that first-degree atrioventricular block is not benign. However, there is no evidence that shortening of the PR interval can improve outcome except for symptomatic patients with a very long PR interval ≥0.3 s. Because these patients require continual forced pacing, biventricular pacing should be used according to accepted guidelines for third-degree AV block. Functional atrial undersensing may occur in patients with conventional dual-chamber pacing and first-degree AV block because the sinus P-wave tends to be displaced into the post-ventricular atrial refractory period (PVARP) an arrangement that may cause a pacemaker syndrome. Prevention requires programming a shorter AV and PVARP that is feasible because retrograde conduction is rare in first-degree AV block patients. A relatively new pacing mode to minimize right ventricular stimulation has been designed by eliminating the traditional AV interval but with dual-chamber backup. This pacing mode permits the establishment of very long AV intervals that may cause pacemaker syndrome. About 50% of patients undergoing cardiac resynchronization therapy (CRT) have a PR interval ≥200 ms. The CRT patients with first-degree AV block are prone to develop electrical desynchronization more easily than those with a normal PR interval. The duration of desynchronization after exceeding the upper rate on exercise is also more pronounced. AV junctional ablation is rarely necessary in patients with first-degree AV block but should be considered for symptomatic functional atrial undersensing or when the disturbances caused by first-degree AV block during CRT cannot be managed by programming.