Clinical Outcomes of low-voltage area-guided left atrial linear ablation for non-paroxysmal atrial fibrillation patients

Background The therapeutic effect of low-voltage area (LVA)-guided left atrial (LA) linear ablation for non-paroxysmal atrial fibrillation (non-PAF) is uncertain. We aimed to investigate the efficacy of LA linear ablation based on the preexisting LVA and its effects on LA reverse remodeling in non-PAF patients. Methods We retrospectively evaluated 145 consecutive patients who underwent radiofrequency catheter ablation for drug-refractory non-PAF. CARTO-guided bipolar voltage mapping was performed in atrial fibrillation (AF). LVA was defined as sites with voltage ≤ 0.5 mV. If circumferential pulmonary vein isolation couldn’t convert AF into sinus rhythm, additional LA linear ablation was performed preferentially at sites within LVA. Results After a mean follow-up duration of 48 ± 33 months, 29 of 145 patients had drugs-refractory AF/LA tachycardia recurrence. Low LA emptying fraction, large LA size and high extent of LVA were associated with AF recurrence. There were 136 patients undergoing LA linear ablation. The rate of linear block at the mitral isthmus was significantly higher via LVA-guided than non-LVA-guided linear ablation. Patients undergoing LVA-guided linear ablation had larger LA size and higher extent of LVA, but the long-term AF/LA tachycardia-free survival rate was higher than the non-LVA-guided group. The LA reverse remodeling effects by resuming sinus rhythm were noted even in patients with a diseased left atrium undergoing extensive LA linear ablation. Conclusions LVA-guided linear ablation through targeting the arrhythmogenic LVA and reducing LA mass provides a better clinical outcome than non-LVA guided linear ablation, and outweighs the harmful effects of iatrogenic scaring in non-PAF patients.

703 Koch’s triangle voltage mapping for cryoablation of slow pathway in children: preliminary data of a novel high density technique

Aims Different authors have described three-dimensional (3D) voltage mapping of the Koch’s triangle (KT) in order to find low-voltage bridges (LVBs) as targets for a successful transcatheter ablation (TCA) of the slow pathway (SP) in children. Recently, the advisor high density (HD) Grid™ mapping catheter was introduced as new multipolar catheter for HD mapping. The aim of the study was to describe our preliminary experience with the use of HD Grid™ catheter in LVB and electrophysiologically guided cryoablation of SP in children. Methods and results Twenty-one children (mean age 13 ± 3 years) with atrioventricular nodal re-entrant tachycardia (AVNRT) underwent cryoablation of SP guided by voltage HD mapping of the KT using HD Grid™ catheter. In order to better highlight the differences with conventional mapping, point collection was performed in each patient with this new multipolar catheter and with a quadripolar catheter. The conventional mapping collected 871 ± 262 points and used 211 ± 80 points in 887 ± 275 s, whereas HD mapping collected 7468 ± 2947 points, using 604 ± 165 points in 513 ± 181 s (P < 0.001). Moreover, the LVB area mapped with HD Grid™ was about one-half smaller and clearly delineated. Cryoablation acute success rate was 100%. Overall median fluoroscopy exposure was 0.08 (0.01–5.42) µGy/m2, with a median fluoroscopy time of 0.1 (0.0–0.6) min. During the follow-up (4.8 ± 3.7 months), there were no recurrences. No complications occurred. Conclusions Our preliminary experience shows that HD mapping is faster and offers higher spatial resolution and definition. Procedural time can be reduced maintaining the TCA safe, with reduced fluoroscopy use, and successful.

94 Combined use of voltage mapping and speckle tracking echocardiography for the early diagnosis of ARVC/D: a case report

A 38 years-old man was admitted to our hospital after ventricular tachycardia with left-bundle-branch block and inferior axis morphology. After undergoing different examinations the criteria for the diagnosis of arrhythmogenic right ventricular cardiomyopathy (ARVC) were met. An electrophysiological study was then performed together with endocardial bipolar and unipolar voltage map. Unipolar and bipolar voltage mapping of the right ventricle showed low voltage areas and corresponding fragmented potentials from the tricuspid annulus to the inferior apex. On the right ventricular outer tract (RVOT), the bipolar voltage mapping was normal while the unipolar mapping showed low-voltage areas in the antero-septal outer tract. An off-line map was used to perform speckle tracking analysis on intracardiac echocardiography (ICE) clips of right ventricle and standard echocardiography. A reduction of the strain analysis was stored in correspondence of the fragmented electrograms area, in particular, speckle tracking analysis on ICE views showed a reduction of the RV LS in the segments below tricuspid valve, in the three different myocardial layers. The endocardial longitudinal strain was reduced from sub-tricuspidalic segments to the RV apex in accordance with the fragmentated potentials stored during voltage mapping. On the contrary, at anterior RVOT wall, the unipolar voltage mapping showed fragmented potentials and the STE analysis revealed a reduced epicardial LS. This case report lays emphasis on the importance of the integration of ICE-derived right ventricular strain and voltage mapping in the improvement of the sensibility of an early diagnosis of the ARVC.

616 Endocardial lead placement guided by high resolution voltage mapping in a patient with recurrent failure of transvenous pacing system

Methods and results A 58 years-old man was admitted to our intensive care unit for syncope due to inconstant capture of epicardial ventricular lead. His cardiovascular history began 20 years before when he underwent single chamber pacemaker implantation with insertion of a passive fixation ventricular lead for symptomatic complete atrio ventricular block (AVB). Electrical parameters were good at implantation. However, during follow-up a gradual and progressive increase of pacing threshold occurred, with no changes in impedance values, finally leading to complete loss of ventricular capture. Hence, 2 years later, the lead was extracted and a new transvenous ventricular lead was placed in septal position. All electrical parameters were optimal at the end of the procedure. However, in the following months threshold values gradually increased as previously observed. The referring clinicians decided to surgically extract both the device and transvenous lead and to implant an epicardial ventricular lead connected to an abdominal generator. The pacemaker worked properly for about 17 years until he was transferred to our institution with evidence of inconstant lead capture at maximum pacing outputs. A temporary transvenous pacemaker was immediately inserted. Clinical examination, laboratory exams, and echocardiography were normal. Cardiac magnetic resonance (MRI) was not feasible due to the epicardial lead. Thus, in order to obtain cardiac substrate characterization, we decided to perform high density multielectrode voltage mapping of the right ventricular endocardium with HD Grid multielectrode mapping catheter (HD Grid mapping catheter sensor enabled, Abbott Technologies, Minneapolis, MN). Electroanatomic voltage map allows distinction of areas of healthy myocardium (>1.5 mV) from scar tissue (<0.5 mV). Unexpectedly, voltage mapping highlighted no scar zones, showing a globally normal endomyocardial surface. Therefore, a new endocavitary pacemaker was inserted in right prepectoral region and an active fixation right ventricular lead was placed on mid-ventricular septum. A backup pacing lead was placed in a more apical position in an area of endocardial healthy myocardium. Post-procedural sensing, impedance and capture threshold were optimal (0.3 V × 0.4 ms for mid-septal lead and 0.3 × 0.4 ms for the other one). At 1 month follow-up mid-septal lead’s threshold was slightly increased (1.0 V × 0.4 ms) and further increase was observed at 3-month outpatient visit (1.75 V × 0.4 ms). Capture threshold of the other lead and other parameters were stable. The patient received remote monitoring for home surveillance of the implanted system. Home monitoring shows a trend toward a progressive increase of pacing threshold of the mid-septal lead and stable value of the other electrode. Conclusions The present report suggests an innovative use of high-density mapping with HD Grid catheter to characterize endocardial right ventricular myocardium in a patient with contraindication to cardiac MRI and recurrent failure of previous implanted pacing systems for unknown reason and to guide effective lead placement in areas of normal endocardial voltage. Combined use of telemedicine and high-resolution mapping technique allowed us to avoid unnecessary high risk reintervention for novel epicardial lead placement.

Pulsed Field Ablation of Superior Vena Cava: Feasibility and Safety of Pulsed Field Ablation

Background: Studies have shown that pulsed field ablation (PFA) has excellent effectiveness and safety in pulmonary vein isolation (PVI). However, there are few reports about the application of PFA, especially the alternating current (AC) biphase PFA, in superior vena cava (SVC) isolation, and its effectiveness and safety are still unclear.Objective: To investigate the efficacy and safety of the AC biphase PFA for SVC isolation, and to provide evidence for the clinical use of PFA for SVC.Methods: Eight pigs and two dogs were included in the study. PFA was delivered to these pigs and dogs. Pacing threshold and electrogram data were recorded before and after PFA. Voltage mapping of SCV was obtained before, after, and 3 weeks after PFA. At the end, all animals were euthanatized for gross pathology analysis.Results: For eight pigs, the median pacing threshold was 1.5 (1.4, 2.75) mA before PFA, while > 6.0 mA after PFA for all animals. The average electrogram amplitude reduction was 61.33 ± 24.90% for ablations with the initial amplitude≥0.5 mv. For two dogs, pacing threshold change and electrogram amplitude reduction were also observed. No phrenic palsy or sinus node injury was observed during PFA in any animal. Furthermore, voltage mapping showed that the voltage amplitude was significantly decreased in all animals and this could be kept for more than 3 weeks. Moreover, transmural tissue damage with reserved vessel and nerve were shown, no SVC stenosis was found at 3 weeks after PFA.Conclusion: PFA can effectively isolate SVC. Transmural tissue damage of SVC can be achieved without phrenic palsy, sinus node injury nor SVC stenosis.