Atrioventricular Nodal Reentrant Tachycardia Ablation Using Mini-Electrode Recordings

Catheter ablation of the slow pathway in patients with atrioventricular nodal reentrant tachycardia (AVNRT) is mainly performed using anatomical landmarks. We sought to see whether a new ablation catheter equipped with mini-electrodes may facilitate the mapping of slow pathway potentials for AVNRT ablation. We prospectively included patients referred for AVNRT in our center. Mapping and ablation were performed using an irrigated catheter equipped with 3 insulated mini-electrodes on the distal tip. Thirteen consecutive patients were included (85% female, median age 46 years). Slow pathway potentials could be identified in 77% of cases on mini-electrode bipolar tracings, versus 15% on conventional bipolar tracings (p = 0.0009). At the end of the procedure, double potentials on the ablation line were identified in all patients, only on mini-electrode bipolar tracings. Following ablation, an interval separating double potentials in sinus rhythm ≥15% of baseline tachycardia cycle length was associated with non-inducibility in all patients (p < 0.0001). No recurrence occurred during 1 year of follow-up. The use of mini-electrodes may help target slow pathway potentials during AVNRT ablation. Identification of sufficiently split double potentials on the ablation line might represent an electrophysiological endpoint in these patients.

Propagation Vectors Facilitate Differentiation between Conduction Block, Slow Conduction and Wavefront Collision

Background - Differentiation between conduction block, slow conduction, and wavefront collision can be difficult using activation mapping alone, often requiring differential pacing. Therefore, a real-time method for determination of complex patterns of conduction may be desired. We hereby report a novel algorithm for displaying propagation vectors, allowing differentiation between complex patterns of conduction and facilitating real-time detection of block during ablation. Methods - In 10 swine, a chronic transcaval ablation line with an intentional gap or complete block was created, simulating conduction block, slow conduction and wavefront collision. The line was mapped during atrial pacing using Carto 3 and a novel high-resolution array that includes 48 mini-electrodes (surface area-0.9mm 2 , spacing 2.4mm) distributed over 6 splines (Optrell™, Biosense Webster). Propagation vectors were created from unipolar waveforms of adjacent electrodes along and across splines that were acquired at single beats. In order to examine the utility of propagation vectors for detection conduction block during ablation, a cavotricuspid isthmus line (CTI) was created during coronary sinus pacing with the array positioned lateral to the line. Results - Propagation vectors detected the gap in all 6 interrupted ablation line, while activation maps only identified gap in 3/6 lines; in the remainder, activation maps alone could not differentiate between conduction block, slow conduction or wavefront collision. Propagation vectors accurately determined block in all 4 contiguous ablation line, while activation maps suggested conduction block or was indeterminant due to wavefront collision in 2/4 lines. CTI block was detected during ablation by abrupt reversal of propagation vectors from a lateral to a septal direction and acute reconnection was detected by reversal of the propagating vectors back to a lateral direction. Conclusions - Real-time propagation vectors enhance the ability of standard activation maps to differentiate between complex patterns of conduction, including determination of conduction block during ablation.

Novel Clue to Locate Conduction Gaps in the Pulmonary Vein Isolation Ablation Line

Background: Several methods have been reported for locating the conduction gap (CG) in the pulmonary vein isolation (PVI) ablation line. However, the value of the interval between far-field atrial potential (FFP) and pulmonary vein potential (PVP) remains unknown.Methods: Consecutive patients with a CG during observation on the table after PVI were included. The PVP, FFP, and the CG location were evaluated to develop a novel algorithm to identify the CG location in the left superior pulmonary vein. The performance of this novel algorithm was prospectively tested in a validation cohort of consecutive patients undergoing repeat PVI ablation.Results: A total of 116 patients with atrial fibrillation (AF) were recruited, 56 of whom formed the validation cohort. The interval between FFP and PVP of the left superior pulmonary vein was associated with the CG location, and an interval &lt;5 ms predicted the presence of CG in the upper portion of the ostium with a sensitivity of 92.9% and a specificity of 96.9%. In the prospective evaluation, the interval was able to correctly predict the site of CG in 89.6% of cases.Conclusions: The interval between FFP and PVP is a novel and accurate index that can be used to predict the CG location in the left superior pulmonary vein. An far-field atrial potential and pulmonary vein potential (FFP–PVP) interval value of ≥5 ms could be used to exclude a CG in the upper portion of the ostium in the majority of patients undergoing AF ablation.

Incidence and location of residual gaps identified by a high-density grid-style catheter after PVI is confirmed by pacing the ablation lines

Funding Acknowledgements Type of funding sources: None. Background The continual pursuit of more durable pulmonary vein isolation (PVI) has led ablationists to evaluate many different techniques for confirming isolation. One such technique involves using the ablation catheter to pace along the ablation lines, ensuring loss of pace capture. Initial observations from a small cohort of patients suggested that a high-density, grid style mapping catheter (HD Grid) enabling simultaneous recording of adjacent bipolar EGMs in two directions (HD Wave) may identify residual gaps that are missed when using the technique of pacing the ablation line in isolation. The true incidence of these residual gaps as identified in a large patient population has not been previously reported. Purpose To quantify in a large cohort of AF ablation patients, the presence of residual gaps identified by HD Grid which are missed by a technique of pacing along the ablation lines with the ablation catheter. Methods Self-reported data was prospectively collected in AF radiofrequency ablation procedures in which PVI was first confirmed by pacing along the ablation line followed by assessment using the HD Grid. Procedural characteristics and acute outcomes, including the incidence and location of gaps post-ablation, were analyzed. Results Data was collected in 111 AF ablation procedures performed in 18 centers across the United States and Europe. Paroxysmal (PAF), persistent (PersAF), and longstanding persistent AF (LsPersAF) accounted for 60.4%, 33.3%, and 6.3% of cases, respectively. Overall, 64.0% of ablations were de novo procedures. Following ablation, PVI was confirmed in all cases by pacing the ablation line with an average output of 9.1 ± 2.6mA and pulse width of 2.1 ± 0.5ms. Adenosine was administered in 3.6% of cases, isoproterenol in 3.6%, and a combination in 0.9%. PVI was then reassessed with HD Grid using a variety of techniques including exit block (91.0%), voltage mapping (82.0%), loss of pace capture along the ablation lines (47.7%), and entrance block (27.0%); note: total exceeds 100% as more than one technique may be used in a single case. A second dose of adenosine was administered in 2.7% of cases; isoproterenol in 2.7%. The HD Wave configuration was used in 96.4% of cases. HD Grid identified a total of 130 gaps in 65 (58.6%) patients, which were missed by pacing the ablation line (Figure 1). Conclusions In over half of the patients evaluated, the HD Grid identified residual PVI gaps that were missed when isolation was confirmed by using the ablation catheter to pace the ablation lines. These results suggest that the pacing technique, used in isolation, is not sufficient for complete gap detection. One limitation of this analysis was the use of a workflow which consistently assessed PVI with the HD Grid following confirmation of isolation by pacing the ablation lines. Despite this limitation, the rate at which residual gaps were identified is noteworthy and likely warrants additional study. Abstract Figure.

Ablation of mitral annular flutter ablation utilizing a left atrial anterior line versus a lateral mitral isthmus line: a systematic review and meta-analysis

Purpose Mitral annular flutter (MAF) is a common arrhythmia after atrial fibrillation ablation. We sought to compare the efficacy and safety of catheter ablation utilizing either a left atrial anterior wall (LAAW) line or a lateral mitral isthmus (LMI) line. Methods We performed a systematic review for all studies that compared LAAW versus LMI lines. Risk ratio (RR) and mean difference (MD) 95% confidence intervals were measured for dichotomous and continuous variables, respectively. Results Four studies with a total of 594 patients were included, one of which was a randomized control trial. In the LMI ablation group, 40% of patients required CS ablation. There were no significant differences in bidirectional block (RR 1.26; 95% CI, 0.94–1.69) or ablation time (MD −1.5; 95% CI, −6.11–3.11), but LAAW ablation was associated with longer ablation line length (MD 11.42; 95% CI, 10.69–12.14) and longer LAA activation delay (MD 67.68; 95% CI, 33.47–101.89.14) when compared to LMI. There was no significant difference in pericardial effusions (RR 0.36; 95% CI, 0.39–20.75) between groups and more patients were maintained sinus rhythm (RR 1.19; 95% CI, 1.03–1.37, p = 0.02) who underwent LAAW compared to LMI. Conclusion Ablation of mitral annular flutter with a LAAW line compared to a LMI line showed no difference in rates of acute bidirectional block, ablation time, or pericardial effusion. However, LAAW ablation required a longer ablation line length, resulted in greater LAA activation delayed and was associated with more sinus rhythm maintenance, with the added advantage of avoiding ablation in the CS.

A Circular Multielectrode Pulsed-Field Ablation Catheter "Lasso PFA": Lesion Characteristics, Durability and Effect on Neighboring Structures

Background - Pulsed field ablation (PFA) is a nonthermal energy with potential safety advantages over radiofrequency ablation (RFA). This study investigated a novel PFA system- a circular multielectrode catheter ("PFA lasso") and a multichannel generator designed to work with Carto 3® mapping system. Methods - A 7.5F bidirectional circular catheter with 10 electrodes and variable expansion was designed for PFA (biphasic, 1800 Volts). This study included a total of 16 swine utilized to investigate the following 3 experimental aims: Aim 1 examined the feasibility to create a right atrial ablation line of block from the superior vena cava (SVC) to the inferior vena cava (IVC). Aim 2 examined the effect of PFA on lesion maturation including durability after a 30-day survival period. Aim 3 examined the effect of high intensity PFA (10 applications) on esophageal and phrenic nerve tissue in comparison to normal intensity RFA (1-2 applications). Histopathological analysis of all cardiac, esophageal and phrenic nerve tissue was performed. Results - Acute line of block was achieved in 12/12 swine (100%) and required a total PFA time of 14 sec (IQR:9-24.5) per line. Ablation line durability after 28&3 days was maintained in 11/12 (91.7%) swine. PFA resulted in transmural lesions in 179/183 (97.8%) sections and a median lesion width of 14.2mm. High intensity PFA (9 [IQR:8-14] application) had no effect on the esophagus while standard intensity RFA (1.5 [IQR:1-2] applications) resulted in deep esophageal tissue injury involving the muscularis propria and adventitia layers. High intensity PFA (16 [IQR:10-28] applications) has no effect on phrenic nerve function and structure while standard dose RFA (1.5 [IQR:1-2] applications) resulted in acute phrenic nerve paralysis. Conclusions - In this preclinical model, a multielectrode circular catheter and multichannel generator produced durable atrial lesions with lower vulnerability to esophageal or phrenic nerve damage.