Background: High-frequency low-tidal-volume (HFLTV) ventilation is a safe and cost-effective strategy that improves catheter stability, first-pass pulmonary vein isolation, and freedom from all-atrial arrhythmias during radiofrequency catheter ablation (RFCA) of paroxysmal and persistent atrial fibrillation (AF). However, the incremental value of adding rapid-atrial pacing (RAP) to HFLTV-ventilation has not yet been determined. Objective: To evaluate the effect of HFLTV-ventilation plus RAP during RFCA of paroxysmal AF on procedural and long-term clinical outcomes compared to HFLTV-ventilation alone. Methods: Patients from the REAL-AF prospective multicenter registry, who underwent RFCA of paroxysmal AF using either HFLTV+RAP (500-600 msec) or HFLTV ventilation alone from April 2020 to February 2023 were included. The primary outcome was freedom from all-atrial arrhythmias at 12-month follow-up. Secondary outcomes included procedural characteristics, long-term clinical outcomes, and procedure-related complications. Results: A total of 545 patients were included in the analysis (HFLTV+RAP=327 vs. HFLTV=218). There were no significant differences in baseline characteristics between the groups. No differences were observed in procedural (HFLTV+RAP 74 [57-98] vs. HFLTV 66 [53-85.75] min, p=0.617) and RF (HFLTV+RAP 15.15 [11.22-21.22] vs. HFLTV 13.99 [11.04-17.13] min, p=0.620) times. Both groups showed a similar freedom from all-atrial arrhythmias at 12-month follow-up (HFLTV+RAP 82.68% vs. HFLTV 86.52%, HR=1.43, 95% CI [0.94-2.16], p=0.093). There were no significant differences in freedom from AF-related symptoms (HFLTV+RAP 91.4% vs. HFLTV 93.1%, p=0.476) or AF-related hospitalizations (HFLTV+RAP 98.5% vs. HFLTV 97.2%, p=0.320). Procedure-related complications were low in both groups (HFLTV+RAP 0.6% vs. HFLTV 0%, p=0.247). Conclusion: In patients undergoing RFCA for paroxysmal AF, adding RAP to HFLTV-ventilation was not associated with improved procedural and long-term clinical outcomes.

Background: The anterior and lateral position of the anterolateral papillary muscle (ALPM) has found to be reached with better catheter stability and less mechanical bumping via the transseptal (TS) compared to the retrograde aortic (RA) approach. Aim: To compare the TS and RA approaches on mapping and ablation of ventricular arrhythmias (VAs) arising from ALPMs. Methods: Thirty-two patients with ALPM-VAs undergoing mapping and ablation via the TS approach were included and compared with 31 patients via the RA approach within the same period. Acute success was compared, as well as other outcomes including misinterpreted mapping results due to bumping, radiofrequency (RF) attempts, procedural time and success rate at 12 months’ follow-up. Results: Acute success was achieved in more cases in the TS group (96.4% vs 72.0%, P=0.020). During activation mapping, bump-provoked premature ventricular complexes (PVCs) misinterpreted as clinical PVCs were more common in the RA group (30.0% vs 58.3%, P=0.036), leading to more RF attempts (3.5±2.7 vs 7.2±6.8, P=0.006). Suppression of VAs were finally achieved in the unsuccessful cases by changing to the alternative approach, but the procedural time was significantly less in the TS group (90.0±33.0 vs 113.7±41.1min, P=0.027) with less need to change the approach, although follow-up success rates were similar (75.0% vs 71.0%, P=0.718). Conclusion: A TS rather than RA approach as the initial approach appears to facilitate mapping and ablation of ALPM-VAs, specifically by decreasing the possibility of misleading mapping results caused by bump-provoked PVC, and increase the acute success rate thereby.

The wall of unintended consequences: is the main benefit of posterior LA wall isolation simply more durable pulmonary vein isolation?Paul C. Zei, MD PhD FHRSDepartment of MedicineBrigham and Women’s HospitalHarvard Medical SchoolBoston, MAFunding: NoneConflict of Interest: None

Lamin Cardiomyopathy (LC) is associated with refractory ventricular arrhythmias. Catheter ablation success rate is low due to presence of multiple circuits and intramural substrate. We present a LC case presented with electrical storm. During catheter ablation, arrhythmia was easily inducible but activation mapping, including full epicardial and endocardial mapping, failed to demonstrate the full tachycardia cycle length (70% only) suggesting intramural activation. Critical isthmus was not identified even with successful concealed entrainment on both Endo/epicardial surfaces. This case shows that even combined endocardial and epicardial catheter approach can be ineffective in identifying the full arrhythmogenic substrate in LC.

Introduction: Septal mass reduction is beneficial for hypertrophic obstructive cardiomyopathy (HOCM) patients with severe left ventricular outflow (LVOT) gradient and symptoms, with surgical myectomy or alcohol septal ablation (ASA) currently recommended in selected patients. Radiofrequency (RF) ablation of hypertrophied septum has been published as a novel method to alleviate LVOT obstruction in small populations. This study aims to investigate factors influencing clinical outcomes of radiofrequency septum ablation. Methods and results: In this study, twenty patients with HOCM who underwent endocardial ablation were included. Echocardiography and cardiac MRI (CMR) data was collected and analyzed pre- and (or) post- procedure. Nineteen patients underwent ablation successfully, while ablation was aborted in one patient with prior RBBB due to transient complete atrioventricular block (AVB). After six months of follow-up, NYHA heart functional class improved from III (2 - 3) to II (1 - 2) (p < 0.001), and resting LVOT gradient was significantly reduced (87.6 ± 29.5 mmHg vs. 48.1 ± 29.7, p < 0.001). LVOT gradient reduction was significantly higher in patients with limited basal septal hypertrophy (60.9 ± 8.3 vs. 27.9 ± 7.1, p = 0.01), shorter anterior mitral leaflet (56.1 ± 6.4 vs. 20.4 ± 5.0, p<0.01) and normally positioned papillary muscle (36.9 ± 7.1 vs. 75.0 ± 6.3, p <0.05). Conclusions: Endocardial septal ablation appears to be a safe and effective procedure for alleviating LVOT gradient in patients with HOCM, especially in those with limited basal septal hypertrophy, shorter anterior mitral leaflet and normal positioned papillary muscle.