Burden of AS is higher than previously assumed. Degenerative aetiology is the main cause of AS. Most of the patients are elder with high prevalence of significant co-existing valvular disease. LFLG severe AS is present in an important proportion of patients, showing high grade of left ventricle remodelling.

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Introduction: His-bundle pacing (HBP) and left bundle branch area pacing (LBBAP) are novel techniques that have demonstrated their efficacy in patients needing right ventricular pacing and in candidates for resynchronization therapy. The purpose of this study was to compare acute and short-term outcomes between HBP and LBBAP. Methods: Retrospective review of the success rate and change in QRS duration obtained by HBP and LBBAP in patients requiring anti-bradycardia pacing or cardiac resynchronization, evaluating the complications and pacing parameters at implantation and at 3 months. Results. The study included 90 procedures (46 HBP and 44 LBBAP) in 87 patients. Success was achieved in 77 procedures (85.6%): 37 (80.4%) in the HBP group and 40 (90.9%) in the LBBAP group (P = .23). Paced QRS duration was shorter in the LBBAP patients (109 ± 8 vs. 117 ± 19 ms; P < .05), who had a lower threshold during implantation (0.5 V/0.5 ms vs. 1.5 V/1 ms; P < .001) and at 3 months (0.72 V/0.5 ms vs. 1.75 V/1 ms; P < .001) and an increased sensed R-wave amplitude. The fluoroscopy time was shorter in the LBBAP group (10 vs. 19 minutes; P < .001). The complication rate was similar (6.8% vs. 12.8%; P = .48). Conclusion. In our experience, LBBAP obtains a similar success rate to that of HBP and achieves a shorter paced QRS duration, greater R-wave detection, lower threshold, and shorter fluoroscopy time, with a similar complication rate.

Introduction Drug-induced long QT syndrome (DI-LQTS) is a clinical entity with prevalence and arrhythmic risk not well defined. Purpose To determine the clinical characteristics of patients with DI-LQTS diagnosed in the setting of a tertiary hospital center. Methods Prospective observational study with consecutive inclusion of patients with the diagnosis of DI-LQTS as per standard criteria, in a tertiary hospital, between 2018 and 2022. Results Eighty-five patients were included (age 65±15 years, 59% male). The mean corrected QT interval (QTc) of the entire cohort was 545±56 ms. The drugs responsible for QTc prolongation were: psychotropic drugs 51%, antiarrhythmics 38%, anesthetics 29%, antibiotics 15%, antineoplastics 3%, other 2%. QTc prolongation was due to the combination of ≥2 responsible drugs in 46 (54%) patients, and to the use of a single drug in 39 (46%). Twenty-one patients (25%) presented ventricular arrhythmias at the time of drug-induced QT prolongation: 10 (12%) ventricular fibrillation, 7 (8%) sustained ventricular tachycardia, 3 (3%) non-sustained ventricular tachycardia, 1 (1%) frequent ventricular extrasystole. Patients with ventricular arrhythmias were older (73±12 vs 62±15 years, p&lt;0.05) and exhibited longer QTc prolongation (600±59 vs 528±42 ms, p&lt;0.05). Conclusion The DI-LQTS is a rare clinical entity but may be cause of clinically-relevant ventricular arrhythmias. Older age and greater prolongation of the QTc interval are associated with an increased risk of ventricular arrhythmic events. Funding Acknowledgement Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Health Institute Carlos III, Spain

Background The recognition of advanced IAB is becoming an important clinical landmark due to its association with atrial fibrillation, the so-called Bayes' syndrome. The electrocardiographic (ECG) criteria of interatrial block (IAB) have been established. A P-wave duration ≥120 ms is considered partial IAB and if there is a biphasic P-wave in the inferior leads advanced IAB. The pathophysiology of this ECG finding has been largely discussed. IAB has been explained as the result of the retrograde activation of left atrium due to complete block in the Bachmann bundle (BB). Purpose To assess the ECG changes resulting of blocking BB conduction in an experimental healthy animal model. Additionally, to compare the pattern of activation of the left atrium before and after the block. Methods Six open-chest anesthetized healthy adult swine were studied. A twelve-lead ECG was continuously recorded. The BB was epicardially accessed at the traversus sinus of the pericardium. At that level, monopolar electrosurgical energy (3 animals) and radiofrequency energy (3 animals) (Boston Scientific Blazer™ II XP, 8 mm tip) was applied until extensive tissue disruption was present and permanent P-wave changes observed. An electroanatomical map CARTO® XP (Biosense Webster Inc) of the right and left atrium was performed in two animals before and after energy deployment. Finally, animals were sacrificed, and tissue samples collected for anatomopathological examination. Results After energy application, all animals showed a significant prolongation of P-wave duration from 59±11 msec to 115±13 msec (p<0.001) with appearance of a biphasic P-wave pattern in the inferior leads. The CARTO® maps showed a change in left atrial activation, cranio-caudal at baseline and caudo-cranial at the end of the procedure. (Figure) The histological analysis showed transmural lesions at the level of the BB in all the specimens. ECG/CARTO maps: Baseline and after block Conclusion IAB ECG pattern, accompanied by a marked change in the activation of the left atrium, develops after blocking the conduction at the level of the BB in an experimental healthy animal model. These results confirm the association of IAB and BB conduction block and suggest that IAB represents an independent entity. Acknowledgement/Funding Fundaciό Privada Daniel Bravo Andreu