Introduction: Conduction system pacing (CSP) has emerged as an ideal physiologic pacing strategy for patients with permanent pacing indications. We sought to evaluate the safety and feasibility of CSP in a consecutive series of unselected patients with congenital heart disease (CHD). Methods: Consecutive patients with CHD in which CSP was attempted were included. Safety and feasibility, implant tools and electrical parameters at implant and at follow-up were evaluated. Results: A total of 20 patients were included (10 with a previous device). Ten patients had complex forms of CHD, 9 moderate defects and 1 a simple defect. His bundle pacing (HBP) or left bundle branch area pacing (LBBAP) were achieved in all patients (10 HBP, 5 LBBP and 5 left ventricular septal pacing). Procedure times and fluoroscopy times were prolongued (126±82 min and 27±30 min, respectively). CSP lead implant times widely varied ranging from 4 to 115 minutes, (mean 31±28 min) and the use of multiple delivery sheaths was frequent (50%). The QRS width was reduced from 144±32 ms at baseline to 116±16 ms with CSP. Implant electrical parameters included: CSP pacing threshold 0.85±0.61V; R wave amplitude 9.8±9.2mV and pacing impedance 735±253 Ohms, and remained stable at a median follow-up of 478 days (IQR 225-567). Systemic ventricle systolic function and NYHA class (1.50±0.51 vs 1.10±0.31; p=0.008) significantly improved at follow-up. Lead revision was required in one patient at day-4. Conclusions: Permanent CSP is safe and feasible in patients with CHD although implant technique is complex.

Introduction:Stand-alone substrate ablation without baseline ventricular tachycardia (VT) induction and activation mapping has become a standard VT ablation strategy. We sought to evaluate the influence of baseline VT inducibility and activation mapping on ablation outcomes in patients with structural heart disease (SHD) undergoing VT ablation. Methods:This is a single center, observational and retrospective study including consecutive patients with SHD and documented VT undergoing ablation. Baseline VT induction was attempted before ablation in all patients and VT activation mapping performed when possible. Ablation was guided by activation mapping for mappable VTs plus substrate ablation for all patients. Ablation outcomes and complications were evaluated. Results: 160 patients were included (203 VT ablation procedures) and were classified in 3 groups according to baseline VT inducibility: group 1 (non inducible, n=18), group 2 (1 VT morphology induced, n=53), and group 3 (>1VT morphology induced, n=89). VT activation mapping was possible in 35%. After a median follow-up of 38.5 months, baseline inducibility of >1VT morphology was associated with a significant incidence of VT recurrence (42% for group 3 vs. 15.1% for group 2 and 5.6% for group 1, Log-rank p<0.0001) and activation mapping with a lower rate of VT recurrence (24% vs. 36.3%, Log-rank p=0.035). Independent predictors of VT recurrences and mortality were baseline inducibility of >1VT morphology (HR 12.05 IC 95% 1.60-90.79, p=0.016) and LVEF<30% (HR 2.43 IC 95% 1.45-4.07, p=0.001), respectively. Complications occurred in 11.2% (5.6% hemodynamic decompensation). Conclusions:Baseline VT inducibility and activation mapping may add significant prognostic information during VT ablation procedur

Aims Atrial fibrosis can promote atrial fibrillation (AF). Electroanatomic mapping (EAM) can provide information regarding local voltage abnormalities that may be used as a surrogate marker for fibrosis. Specific voltage cut-off values have been reproducibly shown to accurately identify fibrosis in the ventricles but they are not well defined in atrial tissue. Methods Unicenter prospective study. Consecutive patients with persistent AF referred for ablation were included. EAM was performed with Carto3 mapping system (Biosense Webster, Inc.). We recorded bipolar signals, first in AF and later in sinus rhythm (SR) after electrical cardioversion. Two thresholds delimited low-voltage areas (LVA): 0.5 and 0.3mV. We compared LVA extension between maps in SR and AF in each patient. Results 23 patients were included. Percentage of points with voltage lower than 0.5mV and 0.3 mV was significantly higher in maps in AF compared to maps in SR: 38.2% of points <0.5mV in AF vs. 22.9% of points <0.5mV in SR (p<0.001); 22.3% of points <0.3mV in AF vs. 14% of points <0.3mV in SR (p<0.001). Areas with reduced voltage were significantly bigger in maps in AF (0.5mV threshold, mean area in AF 41.3cm2 ± 42.5cm2 vs 11.7cm2 ±17.9cm2 in SR, p <0.001; 0.3mV threshold, mean area in AF 15.6cm2 ±22.1cm2 vs 6.2cm2 ±11.5cm2 in SR, p <0.001). Conclusion Using the same voltage thresholds, LVA extension in AF is greater than in SR in patients with persistent AF. These findings provide arguments for defining a different atrial fibrosis threshold based on EAM rhythm.