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Funding Acknowledgements Type of funding sources: None. Background Left atrial appendage (LAA) electrical isolation (ei) may be achieved via radiofrequency (RF) energy applications at the level of the appendage ostium targeting the sites of earliest activation recorded by a mapping catheter. Notably, RF has long been used in vascular, orthopedic, and aesthetic surgery to promote thermal-induced collagen matrix contraction, fibrosis, and tissue retraction. LAA anatomical changes associated to RF-induced tissue retraction have never been reported. Purpose To quantify the anatomical changes of the LAA ostium following RF-based LAAei. Methods Thirty-four consecutive patients requiring AF ablation with LAAei underwent transesophageal echocardiography (TEE) within 7 days before (baseline TEE) and apx 6 months after (follow-up TEE) ablation. The diameter of LAA orifice and landing zone were measured at 4 different views (0°, 45°, 90°, 135°). Measurements were performed by two independent reviewers blinded to the patient’s identity. Results Among 43 AF patients (67±6yrs, 72.1% males), the LAA morphology was classified as chicken wing in 19 (44.2%) patients, windsock in 12 (27.9%), cactus in 8 (18.6%), and cauliflower in 4 (9.3%). At baseline TEE, the mean maximum and mean minimum ostial diameters were 25±4mm and 22±4mm, respectively. The mean maximum and mean minimum diameters of the landing zone were 26±4mm and 23±3mm, respectively. On average, LAAei was achieved after 17±6 minutes of RF at a power of 45W. Follow-up TEE was performed 294±136 days after LAAei. The median LAA contraction velocity was 0.1 m/s (IQR: 0.02-0.18) and was significantly impaired in all patients. At follow-up TEE, the mean maximum and mean minimum ostial diameters were 19±4mm and 17±3mm, respectively. The mean maximum and mean minimum diameters of the landing zone were 20±4mm and 18±4mm, respectively. The mean relative reduction of the ostium and the landing zone was -24.4% and -22.5%, respectively. Box-Whisker plots of the maximum and minimum ostial diameters before and after LAAei are reported in Fig.1. Conclusion RF led to a >20% reduction of the diameters of the ostium and the landing zone. These changes may have important implications for a successful percutaneous occlusion procedure and justify a staged approach of isolation and occlusion.

Funding Acknowledgements Type of funding sources: None. Background Left atrial appendage (LAA) imaging is critical during percutaneous occlusion procedures. 3D-intracardiac echocardiography (ICE) features direct visualization of LAA from multiple cross-sectional planes at a time. Purpose To report procedural success of 3D-ICE-guided LAA occlusion and the correlation between pre-procedural transesophageal echocardiography (TEE) and intraprocedural 3D-ICE for LAA sizing. Methods Among 274 patients undergoing LAAO, periprocedural ICE guidance was achieved via a commercially available 2D-ICE catheter (220 patients) or a novel 3D-ICE one (54 patients; Fig.1). Primary endpoint was a composite of procedural success and LAA sealing at follow-up TEE. Secondary endpoint was a composite of periprocedural device recapture/resizing plus presence of leaks≥3mm at follow-up TEE. Results 3D-ICE measurements of maximum landing zone correlated highly with preprocedural TEE reference values [Pearson’s: 0.94; p The agreement between 3D-ICE-based device selection and final device size was 96.3% versus 79.1% with 2D-ICE (p=0.005). The incidence of the primary endpoint was 98.1% with 3D-ICE and 97.3% with 2D-ICE (p=0.99). 2D-ICE patients had a trend towards a higher incidence of periprocedural device recapture/redeployment (31.5% vs 44.5%; p=0.09). The secondary endpoint occurred in 31.5% of 3D-ICE patients versus 45.9% of 2D-ICE ones (p=0.065). Conclusions ICE-guided LAAO showed a very high success, with no major adverse events. A very high level of agreement for LAA sizing was found between pre-procedural TEE and periprocedural 3D-ICE. 3D-ICE performed significantly better than 2D-ICE for device size selection and may provide better guidance during device deployment.

This study investigated the use of direct visualization to enhance minimally invasive epicardial procedures. A commercially available miniature camera was placed in a prototype subxiphoid introducer needle and bench top, in vitro and in vivo tests of system performance were made during simulated and actual attempts at pericardial access and cardio-endoscopy. This system had an unshielded field of view of 100° and a resolution of 220 × 224 pixels. When a sleeve used to maintain depth of field was slid past the distal tip of the camera probe, the field of view would decrease by ≈15° per millimetre of sleeve extension, but without loss of image quality. While tests during in vivo subxiphoid access in a porcine model revealed that the pericardial membrane was difficult to localize, the results also showed excellent resolution of the coronary arteries on the epicardial surface. These findings and potential improvements are discussed in detail.

Introduction: Focal impulse and rotor modulation (FIRM)-guided ablation targets localized sources that are thought to sustain AF. In previous reports, it has been shown that FIRM is effective in terminating or organizing AF. We sought to evaluate the acute success of FIRM in patients with persistent and LSP AF undergoing ablation in our centers. Methods: This was a multicenter prospective observational study. FIRM was performed alone or before conventional ablation. Rotors were ablated as confirmed by their absence during remapping and acute success was defined as AF termination, organization or slowing 10%. Results: 57 patients were enrolled (mean age 63 ± 10; 7% LSP). Rotors-only ablation was performed in 56% of patients, and preceded conventional ablation in 44%. There were no major periprocedural adverse events. No focal impulses were found, while rotors were present in all patients (3.9 ± 1.2 per patient; 66% in the LA). In the RA, the majority of rotors were in the lateral wall (53%) and in the septum (30%). In the LA, most of the rotors were in proximity of the pulmonary veins (48%), with the second most common locations being around the mitral annulus or in the septum (17% and 13% respectively). Mean procedural time for FIRM only procedures was 226 ± 52 minutes vs a median of 210 (168-240) minutes for FIRM + conventional ablation procedures (p = NS). Overall acute success was achieved in 35% of patients (3% AF termination, 16% AF organization, 16% AF slowing) with a mean RF time to complete FIRM ablation of 30 ± 15 minutes; no difference in acute success was found when comparing persistent to LSP patients (28% vs 50%; p = NS). Conventional ablation following FIRM did not significantly increase the rate of acute success (1 additional patient converted to sinus rhythm during pulmonary vein isolation). Conclusion: Rotors were present in all patients undergoing ablation for non-paroxysmal AF, most commonly the right atrial lateral wall, septum or around the pulmonary veins. Their ablation was not effective in obtaining AF organization/termination during the procedure.

Introduction: We sought to investigate the characteristics and outcomes of patients who underwent RF ablation of PM ventricular arrhythmias (VA) in our center. Results: 26 patients were included, median age was 66 years (16 to 85), 46% female, all with normal LVEF. PM VAs were PVCs in 68% patients, and PVC + VT in 32%. Site of origin was the LV infero-septal PM in 73%, LV antero-lateral PM in 15% and right ventricular RV septal PM in 12%. 46% of patients showed other VAs in addition to the one originating from the PMs; in 33% of these patients, additional VAs were 2 or more. These VAs were mostly PVCs (92%), localized in the LVOT (64% - 56 % in the basal LV and 44% in the aortic cusps) and the septal RVOT (36%). The only additional VT was fascicular. All the PMs and mappable additional VAs were ablated with RF energy through an irrigated catheter and the aid of ICE; a remote magnetic navigation system (RMS) was used in half of the procedures. In one case, PVC suppression required additional epicardial ablation. Major complications occurred in 2 patients (8%): 1 pericardial effusion (the patient underwent ablation of a crista terminalis premature atrial complex in the same procedure) and 1 pseudoaneurysm. Acute success (PM VA suppression/non-inducibility) was achieved in 96% of patients (the patient with pericardial effusion could be anticoagulated further and the procedure was stopped). After a median follow-up period of 8 (4-14) months, long-term success (no PM VT recurrence or PVC burden reduced by 80% off antiarrhythmic drugs) was 92% after a single procedure, 96% after repeat procedures. When considering additional VAs, the only recurrence was a parahisian RVOT PVC. No difference in acute or overall long-term success was observed when comparing RMS-guided vs standard procedures (respectively 92% vs 100 % and 100% vs 92%; P = NS). Conclusion: PM VAs are most commonly PVCs originating from the LV infero-septal PM and are frequently (48%) associated with an additional ventricular focus (LVOT > RVOT >> fascicular VT). RF ablation is safe and effective in eliminating or significantly reduce the burden of PM VAs, as well the extra-PM foci that are commonly encountered in this population. RMS guided ablation is not inferior to standard ablation in this subset of patients.

Background: Pulmonary vein isolation (PVI) offers an estimated cure rate from atrial fibrillation (AF) of 60 to 80% after the first procedure. While some data suggest that lack of inducibility of AF by electrical stimulation after atrial fibrillation ablation may predict improved outcomes, chemical induction of AF during PVI has not been well-studied. In an on-going prospective study, we seek to determine if chemical induction of AF after PVI with subsequent ablation of elicited triggers improves overall success. Herein, we report acute results of attempted re-induction of AF using adenosine and isoproterenol in patients undergoing PVI. Methods: Fourty-three consecutive patients with symptomatic AF presented for PVI. Following initial isolation and while catheters were still in place in the left atrium, 18 to 24 mg of IV adenosine was administered as a single bolus. Subsequently, infusion of isoproterenol was administered at up to 20 mcg/min. After administration of each drug, patients were observed for induction of AF or other atrial arrhythmias, focal firing including frequent monomorphic PAC’s or focal atrial tachycardias or evidence of recovery of conduction from the pulmonary veins. Results: Adenosine administration induced atrial fibrillation in 3 of 43 patients. Notably, no arrhythmias or focal firing were seen with isoproterenol in these three patients. Adenosine did not uncover recovery of conduction from the pulmonary veins in any patient or induce focal firing. Isoproterenol administration induced atrial fibrillation in 3 patients. Focal firing was induced in 18 patients. Recovery of conduction into pulmonary veins was observed after isoproterenol in 6 of 43 patients resulting in application of additional lesions to achieve re-isolation in each case. Conclusions: Our initial data suggests atrial fibrillation may be chemically re-induced with adenosine and isoproterenol administration in a minority of patients undergoing PVI. Focal firing may also be induced with isoproterenol. Isoproterenol but not adenosine uncovered recovery of conduction into the pulmonary veins in several patients. The mechanism by which arrhythmias and AF initiate may differ with adenosine versus isoproterenol.