Atrial low voltage areas: A comparison between atrial fibrillation and sinus rhythm

[EN] Background: 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 reproduced accurately to identify fibrosis in the ventricles, but these values are not well defined in atrial tissue. Methods: This study is a prospective single-center study. Patients with persistent AF referred for ablation were included. EAM was performed before ablation. We recorded bipolar signals, first in AF and later in sinus rhythm (SR). Two thresholds delimited low-voltage areas (LVA), 0.5 and 0.3 mV. We compared LVA extension between maps in SR and AF in each patient. Results: A total of 23 patients were included in the study. The percentage of points with voltage lower than 0.5 mV and 0.3 mV was significantly higher in maps in AF compared with maps in SR: 38.2% of points < 0.5 mV in AF vs. 22.9% in SR (p < 0.001); 22.3% of points < 0.3 mV in AF vs. 14% in SR (p < 0.001). Areas with reduced voltage were significantly larger in maps in AF (0.5 mV threshold, mean area in AF 41.3 ± 42.5 cm2 vs. 11.7 ± 17.9 cm2 in SR, p < 0.001; 0.3 mV threshold, mean area in AF 15.6 ± 22.1 cm2 vs. 6.2 ± 11.5 cm2 in SR, p < 0.001). Conclusions: 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.Andrés Lahuerta, A.; Roberto, C.; Saiz Rodríguez, FJ.; Cano, Ó.; Martínez-Mateu, L.; Alonso, P.; Saurí, A.... (2022). Atrial low voltage areas: A comparison between atrial fibrillation and sinus rhythm. Cardiology Journal. 29(2):252-262. https://doi.org/10.5603/CJ.a2021.0125S25226229

Assisting Electrophysiological Substrate Quantification in Atrial Fibrillation Ablation

[EN] Catheter ablation (CA) is the most popular treatment of atrial fibrillation (AF) with good results in paroxysmal AF, while its efficiency is significantly reduced in persistent AF. With the equipment used for CA strongly depending on electro-gram (EGM) fractionation quantification, the use of a reliable fractionation estimator is crucial to reduce the high recurrence rates in persistent AF. This work introduces a non-linear EGM fractionation quantification technique, which is based on coarse-grained correlation dimension (CGCD) computed over epochs of 1 second. Recordings were firstly normalized, denoised and lowpass filtered. The final CGCD value was calculated by the median CGCD value of all the epochs that a recording consisted of. Results were evaluated on three groups. Groups 1 and 2 contained 24 high-quality and 119 mid-range EGMs, respectively, manually pre-classified by AF types following Wells' criteria, then classified according to their CGCD values. 20 pseudo-real Type IV EGMs formed group 3 that was also automatically classified by AF type. In Groups 1 and 2, classification accuracy was 100% and 84-85.7%, respectively, using 10-fold cross-validation. The receiver-operating characteristics (ROC) analysis for highly fractionated EGMs, showed 100% specificity and sensitivity in Group 1 and 87.5% specificity and 93.6% sensitivity in Group 2. CGCD was always consistent with the fractionation degree of EGMs. 100% of the EGMs in Group 3 were correctly identified as Type IV AF. High accuracy results indicate that the method can estimate precisely the AF Type and detect the existence of AF Type IV cases. Both things are crucial in assisting improved substrate mapping during CA procedures of persistent AF.Research supported by grants DPI2017-83952-C3 from MINECO/AEI/FEDER UE, SBPLY/17/180501/000411 from JCCLM and AICO/2019/036 from GVA.Vraka, A.; Hornero, F.; Osca, J.; Faes, L.; Alcaraz, R.; Rieta, JJ. (2019). Assisting Electrophysiological Substrate Quantification in Atrial Fibrillation Ablation. IEEE. 1-4. https://doi.org/10.1109/EHB47216.2019.8969928S1

Study on How Catheter Ablation Affects Atrial Structures in Patients with Paroxysmal Atrial Fibrillation: The Case of the Coronary Sinus

[EN] It has been shown that substrate modification due to catheter ablation (CA), the first-line treatment of paroxysmal atrial fibrillation (PAF), provokes alterations in P-wave features of the surface electrocardiogram. The absence of knowledge on whether invasive recordings acquired during CA can track similar modifications, creates nevertheless a significant void in the thorough understanding of CA effect on PAF. By analyzing 5-minute bipolar coronary sinus (CS) recordings from 26 PAF patients in sinus rhythm (SR) undergoing CA, this study aims to shed light on whether CA affects local activation waves (LAWs) features recorded in the CS, which is a widely used reference point to assess AF substrate. Recordings were obtained before and after CA. The analysis consisted of LAWs detection and processing of features such as duration, amplitude, positive and negative area, morphology variability (MV), dispersion and number of deflections and inflections (NODI). These features were defined similarly as with previous studies made with surface P-waves. Statistical analysis contained median calculation and comparison with Mann-Whitney U-test. Although some variations in line with previously reported results on P-wave analysis have been observed, none of them was statistically significant (p>0.05). Duration, amplitude, positive and negative area marked a minor decrease (- 1.4% to - 14.3%). MV and dispersion showed a minor to moderate increase + 64.8%). NODI showed no alteration. CA in PAF does not lead to significant variations on LAWs features of bipolar CS recordings. The alterations reported by previous studies on the P-waves may be the product of substrate modification of other atrial regions or the superposition of less significant alterations occurring at each atrial site.Research supported by grants DPI2017-83952-C3 from MINECO/AEI/FEDER UE, SBPLY/17/180501/000411 from JCCLM and AICO/2019/036 from GVA.Vraka, A.; Bertomeu-González, V.; Osca, J.; Ravelli, F.; Alcaraz, R.; Rieta, JJ. (2020). Study on How Catheter Ablation Affects Atrial Structures in Patients with Paroxysmal Atrial Fibrillation: The Case of the Coronary Sinus. IEEE. 1-4. https://doi.org/10.1109/EHB50910.2020.9280243S1

Conduction System Pacing for Cardiac Resynchronization Therapy

Cardiac resynchronization therapy (CRT) via biventricular pacing (BiVP-CRT) is considered a mainstay treatment for symptomatic heart failure patients with reduced ejection fraction and wide QRS. However, up to one-third of patients receiving BiVP-CRT are considered non-responders to the therapy. Multiple strategies have been proposed to maximize the percentage of CRT responders including two new physiological pacing modalities that have emerged in recent years: His bundle pacing (HBP) and left bundle branch area pacing (LBBAP). Both pacing techniques aim at restoring the normal electrical activation of the ventricles through the native conduction system in opposition to the cell-to-cell activation of conventional right ventricular myocardial pacing. Conduction system pacing (CSP), including both HBP and LBBAP, appears to be a promising pacing modality for delivering CRT and has proven to be safe and feasible in this particular setting. This article will review the current state of the art of CSP-based CRT, its limitations, and future directions