Elimination of the Negative Component of the Unipolar Atrial Electrogram as an In Vivo Marker of Transmural Lesion Creation

Abstract

E lectrophysiological pulmonary vein isolation (PVI) is the cornerstone of paroxysmal atrial fibrillation (AF) ablation.1 However, the incidence of AF recurrence remains high and mostly because of PV reconnection, 2,3 emphasizing the need for more understanding of PVI durability and associated factors.In this regard, it has been elegantly shown in a swine model that elimination of the negative component of the unipolar atrial electrogram during radiofrequency applications reflects transmural lesions creation, whereas the persistence of such a negative component constantly corresponds to nontransmural lesions. 4 We have subsequently reported, in patients affected by paroxysmal AF episodes, the relevance of the atrial unipolar modification analysis as a local ablative end-point while performing PVI and its positive impact in terms of mid-term SR maintenance rate. However and interestingly, this study also has strongly suggested that the elimination of the negative component of the atrial electrogram, although it did not provide histological evidence because it was conducted in humans, may correspond either to transmural but reversible lesions (likely related to edema or transient cell damage) or to transmural and irreversible lesions (likely corresponding to transmural necrosis). 5The aim of the present study is to determine, at the histological level, whether the elimination of the negative component of the atrial electrogram during radiofrequency energy applications might in some circumstances reflect transmural but potentially reversible lesions or it might correspond to transmural and irreversible (necrotic) lesions in others.© 2015 American Heart Association, Inc. Original ArticleBackground-It has been experimentally shown that elimination of the negative component of the unipolar atrial electrogram (R morphology completion) during radiofrequency applications reflects transmural lesions creation. Subsequently, it has been clinically suggested that such a transmurality can be either irreversible or reversible. The present study is aimed to determine, at the histological level, whether transmural lesions, assessed by R morphology completion, might indeed be reversible in some circumstances or not. Methods and Results-In 6 Mongrel hound dogs, superior and inferior vena cavae were isolated and individual lesions were created in the right atrium using radiofrequency energy (30 W/48°C/17 mL/min as presettings and 10g of force in average) under CARTO guidance. Five types of lesions were created; R+0: termination of ablation at the time of R morphology completion; R+5, R+10, or R+20: extension of ablation for 5, 10, or 20 seconds, respectively, after R morphology achievement; and conventional: radiofrequency applications lasting 30 seconds irrespective of the atrial electrogram modification. All conventional, R+5, R+10, and R+20 lesions were necrotic and transmural, whereas some R+0 lesions were not (comprising a part of necrosis and a part of reversible cell damage). Interestingly, surrounding organ injuries were ob...

Assessment of the transmural unipolar electrogram morphology change radius during contact force-guided pulmonary vein isolation using the VISITAG™ Module and CARTOREPLAY™

“…Furthermore, in view of the second-annotated site "per protocol" RF duration of ~9s, yet with near instantaneous pure R UE morphology change evident, most second-site RF applications were to at least that duration employed by Bortone et al when achieving single-site 100% histologically-confirmed TM lesions of 4.3mm depth. 16 Although it is scientifically invalid to draw firm conclusions from such comparisons (particularly when VISITAG™ Module annotation was not employed during these animal studies), together with the previously reported high procedural efficacy of this present CF and VISITAG™ Module-guided protocol 15 , it is very unlikely that RF application at these LAPW sites resulted in non-TM lesions. 15 All UE morphology data were collected retrospectively, so this report does not prove that modification of RF delivery based on real-time UE morphological assessment during VISITAG™ Module and CF-guided PVI is appropriate.…”

“…Furthermore, while increasing the RF duration to pure R + 5s resulted in histologically TM ablation in 100% without extra-cardiac thermal trauma, lesions terminated at pure R + 10s, +20s and "conventional" 30s total RF, although resulting in 100% pure R UE morphology and histologically proven TM ablation, had 11-17% occurrence of extra-cardiac thermal trauma. 16 Subsequently, the release of CARTOREPLAY™ (Biosense Webster) permitted assessment of UE morphology change following PVI employing this previously derived CF and VISITAG™-guided PVI protocol. These investigations demonstrated significantly shorter time to pure R UE morphology change at left-sided first-annotated LAPW sites (4.9s v 6.7s; p=0.02), associated with significantly greater impedance drop, compared to right-sided sites.…”

“…However, this is an important area for future investigations since without such facility there is no suitable means to standardise and report approaches to RF delivery during future randomised controlled trials, making the task of translating any useful findings into clinical practice, impossible. 16…”

Ablation catheter motion detection during contact force and VISITAG™ Module-guided pulmonary vein isolation

“…Twenty-five patients underwent first-time PVI as described, between November 2016 and May 2017: 13 persistent AF, 12 PAF; 19 male (76%); mean age 57 [SD: 14] years and mean CHA 2 DS 2 -VASc score 1.3 [SD: 1.3]. Complete PVI was achieved in all without spontaneous 11 / dormant recovery of PV conduction, following mean 16.2 [SD: 3.1] minutes of RF, with no procedural complications. The ACCURESP™-triggering cohort comprised 8 of 25 cases (32%); considering age, body mass index and RF duration required for case completion, there were no significant differences between the cohorts with and without ACCURESP™ threshold triggering.…”

“…(2) There was no incorporation of measures of the TM tissue response to RF delivery, yet in vivo animal studies have demonstrated that a change in the unipolar electrogram (UE) morphology from RS to "pure R" may be indicative of histologically-confirmed TM lesions. 10,11 Furthermore, a study conducted in humans has confirmed the utility of RF titration according to real-time assessments of pure R UE morphology change towards a highly effective CF-guided PVI protocol 12 ;…”