Background: Left bundle branch pacing (LBBP) and left bundle fascicular pacing (LBFP) are conduction system pacing techniques that preserve physiological ventricular activation. Whether proximal or distal capture yields superior electrical or echocardiographic outcomes is uncertain. Objective: To systematically evaluate and compare LBFP versus left bundle branch trunk pacing (LBTP) in terms of electrical synchrony and echocardiographic characteristics in patients requiring permanent cardiac pacing. Methods: We searched PubMed, Embase, and Cochrane through May 21, 2025, for randomized and observational studies comparing LBFP with LBTP. Outcomes of interest included QRS duration, V6 R-wave peak time (RWPT), left ventricular activation time (LVAT), left ventricular ejection fraction (LVEF), left ventricular end-diastolic diameter (LVEDD), and pacing thresholds. Statistical analysis was performed using a random-effects model, with heterogeneity assessed using I 2 statistics. Risk of bias was evaluated using the ROBINS-I. Results: Six studies involving 2,989 patients (1,241 LBFP; 249 LBTP) were included. LBFP was associated with a significantly shorter V6-RWPT (mean difference: –3.50 ms; 95% CI: –5.74 to –1.26; p=0.002), suggesting improved electrical synchrony. No significant differences were observed in QRS duration, LVAT, LVEF, LVEDD, or pacing thresholds. Both modalities demonstrated high procedural success and low, stable capture thresholds. Conclusion: LBFP achieved faster ventricular activation compared with LBTP, while maintaining comparable mechanical performance and pacing stability. Its broader anatomical accessibility and favorable electrical profile support LBFP as a practical alternative particularly when proximal conduction capture is not feasible. Further randomized trials are warranted to assess long-term outcomes. Keywords: Conduction system pacing; left bundle branch pacing; fascicular pacing; ventricular synchrony; permanent pacemaker; meta-analysis; cardiac resynchronization Glossary of Abbreviations: CSP: Conduction system pacing; HBP: His bundle pacing; LBBAP: Left bundle branch area pacing; LBBP: Left bundle branch pacing (proximal/trunk); LBFP: Left bundle fascicular pacing; LBTP: Left bundle trunk pacing; LVAT: Left ventricular activation time; LVEDD: Left ventricular end-diastolic diameter; RWPT: R-wave peak time (lead V6); ROBINS-I: Risk of Bias in Non-Randomized Studies of Interventions; RoB 2: Cochrane Risk of Bias 2.0 tool; PROSPERO: International Prospective Register of Systematic Reviews; NYHA: New York Heart Association (functional class).

Background: Heart failure with reduced ejection fraction (HFrEF) is a leading cause of morbidity and mortality, with many patients remaining symptomatic despite optimal medical therapy. Cardiac contractility modulation (CCM), which delivers non-excitatory electrical impulses during the refractory period, enhances myocardial contractility without increasing oxygen demand. This therapy targets symptomatic HFrEF patients with narrow QRS complexes who are ineligible for cardiac resynchronization therapy (CRT). Methods: We performed a systematic review and single-arm meta-analysis, following PRISMA guidelines, to evaluate the functional, structural, and quality-of-life effects of CCM in symptomatic HFrEF patients. Primary outcomes were six-minute walk test (6MWT), peak oxygen consumption (Peak VO 2), New York Heart Association (NYHA) functional class, and Minnesota Living with Heart Failure Questionnaire (MLHFQ) scores. Secondary outcomes included left ventricular ejection fraction (LVEF), left ventricular end-systolic volume (LVESV), and left ventricular end-diastolic volume (LVEDV). Results: Fifteen studies encompassing 1,658 patients were included. CCM therapy resulted in a significant improvement in 6MWT distance (mean increase: 44.96 meters, 95% CI: 2.73 to 87.20; p = 0.037) and a reduction in NYHA functional class (mean change: −0.89, 95% CI: −1.18 to −0.60; p < 0.001). Quality of life, as measured by MLHFQ, improved significantly (mean decrease: 11.83 points, 95% CI: −15.65 to −8.02; p < 0.001). Although there was a nominal increase in Peak VO 2 (mean increase: 0.13 mL/kg/min, 95% CI: −0.73 to 0.98; p = 0.770), it was not statistically significant. Structural improvements included a 5.96% increase in LVEF (95% CI: 4.65 to 7.26; p < 0.001), a reduction in LVESV of 24.17 mL (95% CI: −40.12 to −8.22; p = 0.003), and a reduction in LVEDV of 18.44 mL (95% CI: −29.97 to −6.91; p = 0.002). Sensitivity analyses confirmed the robustness of these findings. Conclusion: CCM therapy provides significant improvements in functional capacity, symptom relief, quality of life, and cardiac remodeling in symptomatic HFrEF patients who are ineligible for CRT. These findings support the role of CCM in addressing an important therapeutic gap. Further large-scale randomized trials are needed to validate long-term clinical outcomes.

Introduction: High-power short-duration (HPSD) ablation has emerged as a promising alternative to conventional power delivery (CPD) for pulmonary vein isolation (PVI) among patients with atrial fibrillation (AF). However, its efficacy, procedural efficiency, and safety profile remain uncertain. Methods: PubMed, Embase, Cochrane Library and ClinicalTrials.Gov databases were systematically searched for randomized controlled trials (RCTs) comparing HPSD with CPD ablation for PVI in patients with AF. Random-effects models were used to pool hazard ratios (HR) and risk ratios (RR) with 95% confidence intervals (CI). R version 4.4.2 was used for statistical analysis. Results: Seven RCTs with 1,006 patients (514 HPSD, 489 CPD) were included. No significant differences were found in freedom from arrhythmia during the follow-up period (HR 0.77; 95% CI 0.41–1.45; p=0.424). AF recurrence did not differ (RR 0.94; 95% CI 0.65–1.36; p=0.733) between groups. HPSD had a significantly shorter procedural (MD -22.61 min; 95% CI -33.18, -12.04; p<0.001) and RF ablation times (MD -15.70 min; 95% CI -20.86, -10.55; p<0.001). No differences were observed in fluoroscopy time and first-pass isolation for right and left pulmonary veins. There was no difference in esophageal lesion rates, pericardial, or neurological complications, but there was a higher incidence of steam pops in HPSD (RR 3.42; 95% CI 1.45–8.09; p=0.005). Conclusion: In patients with AF undergoing PVI, HPSD did not increase freedom from arrhythmia as compared with CPD ablation, however it was associated with shorter procedure and RF ablation times with a similar safety profile.

INTRODUCTION: Malignant ventricular arrhythmias (MVA) are often the main cause of sudden cardiac death (SCD), especially in patients with pre-existing coronary artery disease (CAD). The identification of factors associated with SCD in this clinical setting is important and might help physicians in identifying this high risk group of patients. We evaluated the association between 12-lead ECG ventricular repolarization parameters and the induction of MVA on the electrophysiological study (EPS). METHODS AND RESULTS: 177 patients [mean age 65±10.1yo, 83.6% male, mean LV ejection fraction (LVEF) 37.5±13.6%] were analyzed. For each 10ms increment in the QT interval, an increase of 7% in MVA inducibility was observed. The QT cut-off point of 452 ms had and accuracy of 0.611 for predicting MVA (p=0.011). Male gender (OR=4.18, p=0.012), LVEF < 35% (OR=2.32, p=0.013), amiodarone use (OR=2.01, p=0.038) and prolonged QT (OR=1.07, p=0.023) were independent factors associated with MVA. QT > 452ms in patients with ventricular dysfunction was associated with significant increased risk of MVA (OR=5.44, p=0.0004). In patients with LVEF ≥ 35%, QT dispersion (QTd) was significantly higher in those with inducible MVA. QTd > 20ms had an accuracy of 0.638 in predicting MVA, with 81.3% negative predictive value (95% CI 63-92.1%). CONCLUSION: QT interval was an independent factor associated with MVA in patients with CAD. The combination of ventricular dysfunction and prolonged QT interval was associated with a 5-fold increase of MVA induction. Male gender, amiodarone use and decreased LVEF were also associated with increased risk of inducibility of MVA on the EPS.