Panagiotis Mililis

Background: Premature ventricular contractions (PVCs) are common arrhythmias associated with symptoms such as fatigue and, in severe cases, PVC-induced cardiomyopathy. Catheter ablation (CA) is a primary treatment for symptomatic PVCs, particularly when pharmacological therapies fail or are undesired. While improvements in: quality-of-life following ablation are documented, its impact on functional capacity remains underexplored. Objectives: This study evaluated the impact of CA on functional capacity and cardiac stress markers in patients with symptomatic PVCs using cardiopulmonary exercise testing (CPET) and NT-proBNP levels. Methods: A total of 30 patients underwent successful PVC ablation and completed baseline and follow-up CPET evaluations under the Bruce protocol. PVC burden, left ventricular ejection fraction (LVEF), NT-proBNP levels, and CPET parameters, including VO₂ max, METS, ventilatory efficiency, and anaerobic threshold (AT), were analyzed pre- and post-ablation. Results: PVC burden significantly decreased post-ablation (23,509.3 ± 10,700.47 to 1759 ± 1659.15, p < 0.001). CPET revealed improved functional capacity, with VO₂ max increasing from 24.97 ± 4.16 mL/kg/min to 26.02 ± 4.34 mL/kg/min (p = 0.0096) and METS from 7.16 ± 1.17 to 7.48 ± 1.24 (p = 0.0103). NT-proBNP significantly decreased (240.93 ± 156.54 pg/mL to 138.47 ± 152.91 pg/mL, p = 0.0065). LVEF and ventilatory efficiency metrics (VE/VO₂ and VE/VCO₂) remained stable. Conclusions: Catheter ablation improves functional capacity, reduces cardiac stress, and minimizes medication dependency in patients with symptomatic PVCs. These findings support the utility of ablation in enhancing aerobic capacity and overall exercise performance.

Background: The advent of subcutaneous implantable cardioverter defibrillators (S-ICDs) marked a significant milestone in the course of cardiac rhythm devices, particularly for patients who are deemed at high risk for ventricular arrhythmias and sudden cardiac death. This extracardiac approach makes the S-ICD an especially valuable option for young patients, those with difficult venous access, or those at high risk of infection. Although the S-ICD does not provide pacing for bradycardia or heart failure, it has shown efficacy in treating ventricular arrhythmias while minimizing complications associated with transvenous systems. Methods: The purpose of this multicenter retrospective analysis was to assess the real-world efficacy and safety of the S-ICD in a heterogeneous population. Results: The GASP registry consisted of 114 patients, 68% male, aged 41 ± 15 years, with a mean LVEF of 50%. In the follow-up of 35 months, inappropriate shocks occurred in 7% while appropriate shocks occurred in 6.2%. The most common reasons for inappropriate shocks were myopotentials and atrial tachyarrhythmias. Thirty-day complication-free rates were 97.3%, with the majority of patients requiring device extraction due to infection. Over the longer term, four patients required re-intervention due to local discomfort, while one device was extracted for infection. In a multivariate analysis, complications were not significantly higher in the sicker population, such as those with diabetes, kidney disease requiring dialysis, or heart failure. Conclusions: These findings support the growing role of the S-ICD as an alternative to the TV-ICD, especially in patients without pacing indications.

Objectives: The study sought to evaluate the impact of the stricter Strauss criteria for left bundle branch block (St-LBBB) on cardiac resynchronization therapy (CRT) response, hospitalizations, ventricular arrhythmia (VA) events and mortality. Background: Although left bundle branch block (LBBB) is a strong predictor of response to CRT, a significant number of patients remain non-responders. Methods: This is a retrospective analysis of prospectively collected data on heart failure (HF) patients with LBBB admitted for CRT implantation. Patients were divided in two groups according to the fulfillment or not of St-LBBB criteria. Results: 82 patients with ischemic (ICM) and non-ischemic (NICM) HF [46 (56%) with St-LBBB and 36 (44%) with non-St-LBBB] were included. CRT response was more likely to occur in patients with St-LBBB (p<0.01), with the group of NICM exhibiting the greatest benefit (p<0.01). St-LBBB CRT responders displayed significantly lower rates of HF hospitalization (p<0.0001) compared to non-St-LBBB group. This was mostly evident in patients with NICM (p<0.0001) according to Kaplan-Meier time curves. CRT responders displayed significantly fewer VA events (p<0.001) and lower mortality rates (p<0.0001) than non-responders. Kaplan-Meier estimates demonstrated a significantly lower incidence of VAs in NICM patients with St-LBBB (p:0.049) in comparison to ICM patients with St-LBBB (p:0.25). Lower mortality rates were observed in CRT responders than non-responders (p<0.0001) with the group of NICM with St-LBBB criteria exhibiting the greatest benefit (p:0.0238). Conclusions: Patients with NICM and St-LBBB present the greatest benefit with respect to CRT response, HF hospitalizations, VA events, and mortality. St-LBBB criteria may improve patient selection for CRT.

Objective: To assess feasibility and reliability of cardiac magnetic resonance (CMR) imaging in visualizing left atrial (LA) structural changes that patients with paroxysmal atrial fibrillation (PAF) undergo acutely and long-term post ablation. Two different ablation methods i.e pulsed filed ablation (PFA) and cryoablation were studied. Background: Pulmonary vein (PV) isolation has become the cornerstone technique for catheter ablation in patients with drug-refractory atrial fibrillation (AF). At present, almost all ablation technologies are mediated by a thermal effect. Recently, pulsed field ablation (PFA) has been introduced as a new energy source. PFA is a non-thermal ablative modality in which high voltage ultra-short pulses are applied to target tissue, while preserving the extracellular matrix architecture, nerves, and microvascular structures. Few data exist showing different structural LA changes between the two methods using Three-Dimensional (3D) Late Gadolinium Enhancement (LGE) Imaging. Methods: CMR imaging was performed pre-ablation, acutely (<24 h), and 3 months post-ablation in 10 patients with paroxysmal atrial fibrillation (AF) undergoing pulmonary vein (PV) isolation with PFA (n = 5) or cryoablation (n = 5). 3D LGE and T2-weighted images were analysed. We obtained two data sets of 3D whole heart LGE imaging with high resolution, 20minutes post gadolinium injection. Patients underwent two acquisitions: the conventional respiratory navigated, electrocardiographically-gated 3D fast gradient echo (1.3slice thickness, 256x256 matrix acquisition) and the image-navigated isotropic high resolution 3D LGE with Dixon water-fat separation. 3D LGE data were analysed using a dedicated (ADAS LA) software in order to produce a 3D-LA model visualization of LGE areas. Results: In the acute stage, LGE volume was 50% larger after PFA vs. cryoablation (P < 0.001), and oedema on T2 imaging was significantly smaller (visual estimation) on PFA cases. LGE rings surrounding PV ostia were more homogeneous after PFA, with no sign of microvascular damage or intramural hemorrhage as compared to cryoablation cases. In the chronic stage, the majority of acute LGE had disappeared after PFA, whereas most LGE persisted after cryo-ablation. The two 3D LGE sequences used for analysis showed complete agreement in the visualization of atrial scar with superior image quality of the novel sequence. The mean acquisition time for 3D LGE imaging was 11±4minutes for the conventional fast gradient echo sequence, and 5±2minutes for the novel 3D self-image navigated LGE sequence. Conclusions: CMR imaging may help in visualization and understanding of LA structural remodeling post different ablation techniques.

Objectives: To assess feasibility and reliability of Cardiac magnetic resonance (CMR)-derived pixel signal intensity (PSI) maps obtained by Three Dimensional (3D)- Late Gadolinium Enhancement (LGE) images for detecting potential targets for VT substrate ablation procedures. Background: Parametric imaging with color-coded PSI maps obtained from pre-ablation 3D LGE -CMR imaging can be used for identification and characterization of arrhythmic abnormal substrate. Recent publications have shown that PSI maps permit visualization of border zone areas inside the scar. Specifically, corridors of viable tissue within the scar connecting healthy myocardium define VT corridors that may be the electrical equivalent of the abnormal conducting channels on the electroanatomical mapping (EAM). Methods: 8 patients with scar-dependent monomorphic VTs who underwent 3D-LGE CMR imaging prior to substrate ablation were included in the study. The studies were performed at 1.5T scanner. We obtained two data sets of 3D whole heart LGE imaging with high resolution. Patients underwent two acquisitions: the conventional respiratory navigated, electrocardiographically-gated 3D fast gradient echo (1.3slice thickness, 256x256 matrix acquisition) and the image-navigated isotropic high resolution 3D GE with Dixon water-fat separation. 3D LGE-CMR images were processed with ADAS-VT software to produce a 3-dimensional model of the heart with 10 layers from the endocardium to epicardium and PSI maps color-coded from the LGE data projected to each of the shells (Figure 1). In the LGE-CMR PSI maps, VT corridors were obtained automatically by the ADAS VT software. Subsequently, data were given to the electrophysiologists and merged with the CARTO3 system EAM data obtained for the ablation (Figure2). CMR information was used to facilitate the identification of target ablation sites in the areas identified by CMR as abnormal substrate and radiofrequency was applied in the presence of both a pathological electrogram (EGM) and a VT corridor as identified by CMR. Results: There was a 95% agreement between the abnormal conducting channels as detected by abnormal electrograms in the EAM and the VT corridors identified by 3D LGE CMR imaging. In two occasions, there was one VT corridor that did not correlate with abnormal electrograms and was not ablated. The two 3D LGE sequences used for ADAS-VT corridors analysis showed complete agreement in the number and location of VT corridors. Mean acquisition time for 3D LGE imaging was 11±4minutes for the conventional fast gradient echo sequence, and 5±2minutes for the novel 3D self-image navigated LGE sequence. The image quality of 3D LGE was superior with the Dixon fat-water separation. Overall CMR-aided VT ablation reduced the procedural and fluoroscopy time by 40%. Conclusions: CMR-aided VT ablation is feasible, reliable and significantly reduces the procedural time.