Optimizing Outcomes in Bipolar Ablation for Refractory Septal VT: The Role of Intracardiac Echocardiography

Optimizing Outcomes in Bipolar Ablation for Refractory Septal VT: The Role of Intracardiac Echocardiography | Authorea try { document.documentElement.classList.add('js'); } catch (e) { } var _gaq = _gaq || []; _gaq.push(['_setAccount', 'G-8VDV14Y67G']); _gaq.push(['_trackPageview']); (function() { var ga = document.createElement('script'); ga.type = 'text/javascript'; ga.async = true; ga.src = ('https:' == document.location.protocol ? 'https://ssl' : 'http://www') + '.google-analytics.com/ga.js'; var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(ga, s); })(); Skip to main content Preprints Collections Wiley Open Research IET Open Research Ecological Society of Japan All Collections About About Authorea FAQs Contact Us Quick Search anywhere Search for preprint articles, keywords, etc. Search Search ADVANCED SEARCH SCROLL This is a preprint and has not been peer reviewed. Data may be preliminary. 18 February 2025 V1 Latest version Share on Optimizing Outcomes in Bipolar Ablation for Refractory Septal VT: The Role of Intracardiac Echocardiography Authors : iremar MACEDO NETO 0000-0002-4299-1143 [email protected] , Muhieddine Chokr 0000-0001-6697-7074 , Jose Carvalho Neto , Eduardo Barreto Gadelha , Ezequiel Thé , and Afonso Albuquerque Authors Info & Affiliations https://doi.org/10.22541/au.173988569.93105228/v1 226 views 204 downloads Contents Abstract Information & Authors Metrics & Citations View Options References Figures Tables Media Share Abstract We report a case of septal ventricular tachycardia with previous failed ablation attempts that was successfully treated using a bipolar ablation strategy, with the significant contribution of intracardiac echocardiography (ICE). ICE was utilized to enhance procedural safety by preventing steam pops and late ventricular septal defects (VSD) and to optimize outcomes by ensuring homogeneous ablation of the septal tissue, visually confirming a transmural lesion. Introduction Intramural septal ventricular tachycardia (VT) is a challenging arrhythmia, with high recurrence rates despite technological advances in mapping and ablation techniques. Tools such as ICE, which is not routinely used in these cases, may provide significant assistance. We report a case in which bipolar ablation was performed with the essential aid of ICE to guide lesion targeting and confirm homogeneous ablation of the interventricular septum. Case report A 73 year-old male, with mild coronary artery disease (past history of angioplasty of left circunflex artery), normal biventricular dimensions and function has presented with highly frequent episodes of sustained ventricular tachycardia (SVT), mostly slow VT, with heart rate of 104-120. He also had frequent PVC´s (22-25% ectopies on 24h holter). He also had cardiac MRI showing less than 1% fibrosis at infero-septal, medio-basal region of the LV. The patient was submitted to 2 previous failed ablation attempts. Then, a bipolar ablation (BA) was proposed. Because there is no proper cable to perform the BA set, we produced a custom cable (Figure 1B). We did a connection between the ablation catheter connector, the referential patch connector (to connect the ground catheter into the “ground” port of the RF generator) and one signal cable to see the electrograms recorded from the ground catheter. During the patient´s last echocardiogram (ECHO), his LV function has declined from normal to 34% and his interventricular septum (IVS) lengthen 11mm width. He had a recent scintigraphy without signs of ischemia. At the start of the procedure, the patient presented ventricular tachycardia (VT) as shown in Figure 1, with a cycle length of 588 ms and no hemodynamic instability. The HV interval during VT was measured at 57 ms. The patient’s baseline electrocardiogram (ECG) in sinus rhythm demonstrated a first-degree left bundle branch block (LBBB). LV voltage mapping was performed using CARTO system (Biosense Webster). Upon advancing the catheter to the basal septum, fragmented pre-systolic potentials, likely far-field signals, were recorded on the Pentaray catheter, with a 34 ms pre-QRS interval (Figure 1C). Bipolar voltage mapping of the LV revealed extensive fibrotic areas in the periaortic and septal regions (Figure 1D), while the bipolar voltage map of the right ventricle (RV) was normal. The procedural setup was as follows: a SmartTouch SF catheter (Biosense Webster) was utilized as the active ablation catheter at the LV septal side, connected to the ablation port of the RF generator. An 8 mm ablation catheter (Abbott) served as the ground catheter, connected to the referential patch port of the RF generator. The ground catheter was positioned on the right ventricular (RV) side of the IVS, aligned in parallel to the septum. The LV septal side was chosen for the active catheter placement due to the presence of the best-recorded potentials in this chamber, despite the activation map indicating a broad area of early activation, consistent with an intramural focus. Catheter positioning was guided by fluoroscopy, 3D electroanatomic mapping, and ICE (Figures 2A, 2B, 2C, and 2D). RF ablation was performed with power initially set at 20 W, gradually increased in 5 W increments up to 40 W, with a temperature limit of 43°C. The target was an impedance drop of 10–20 ohms. Ablation was conducted with an average power of 38.75 W, a mean duration of 2 minutes per application, and an average contact force of 7.5 g. Initial impedance values ranged from 103 to 159 ohms. During energy delivery, ICE was carefully monitored for signs of steam pop, however, no such signs were observed. Instead, progressive echogenicity of the IVS was noted. By the end of the RF applications, the IVS appeared uniformly hyperechogenic from the basal to the mid-septal regions, consistent with successful ablation (Figure 3). During RF energy delivery, the QRS complex progressively widened to a duration of 198 ms, displaying a complete LBBB morphology. Concurrently, the HV interval increased to 123 ms, although no atrioventricular block (AVB) was observed. Following ablation, ventricular arrhythmia was rendered noninducible. Total procedure time was 240 minutes. Despite the absence of AVB, a permanent pacemaker (PPM) was indicated due to the prolonged HV interval. After 4 months of follow up there is no VT recurrence. A recent ECHO showed a preserved LV ejection fraction (68%), and 24-hour Holter monitoring demonstrated a reduction in PVC burden to 4%, with no episodes of non-sustained ventricular tachycardia (NSVT). Figure 1. a) ECG demonstrating septal VT. B) Custom bipolar ablation cable setup. c) Electrogram showing a pre-systolic potential recorded 34ms prior to QRS complex. D) LV voltage map highlighting extensive septal and periaortic scarring. Discussion Ventricular tachycardia (VT) remains a challenging arrhythmia to manage, with recurrence rates ranging between 30% and 70%, depending on the underlying etiology (ischemic or non-ischemic) [1,6]. Intramural/septal VTs represent a unique subset of patients with higher recurrence rates post ablation. This is due to the deeply located myocardial substrate, which reduces the efficacy of conventional RF energy delivery and often necessitates alternative ablation strategies [2]. As reported by Halbfass et al., the non-inducibility rate following catheter ablation is lower in patients with septal substrates [2]. Additionally, unipolar RF ablation is typically limited to a penetration depth of approximately 5–6 mm [4]. Conversely, Koruth et al. demonstrated that BA could achieve tissue penetration of up to 25 mm within the IVS, providing a promising alternative for this arrhythmogenic substrate [6]. In recent years there has been growing interest in new ablation strategies, notably bipolar ablation (BA). We report on a typical case of septal VT in which the patient had multiple VT episodes, without hemodinamic compromisse, but very symptomatic despite the use of high doses of antiarrhythmic drugs. This patient has failed two unipolar ablation procedures before. Therefore, a BA was planned. Figure 2. a) LAO flouroscopic view of the catheters at either side of the IVS. b) RL 3D mapping view of the ablation and the ground catheters with many ablation spots at the IVS. c) Cranial 3D mapping view showing the close relationship between the ablation and the ground catheter. d) ICE view showing the ablation catheter in close contact with the LV septum. Figure 3 - ICE image showing IVS refringency after bipolar ablation completeness. Given the risk of conduction system damage, we prioritized its preservation without compromising the achievement of non-inducibility. This approach was guided by reports highlighting long-term reductions in ejection fraction (EF) and the need to upgrade from conventional PPM to cardiac resynchronization therapy [3]. At the end of the procedure, no AVB was observed. However, the HV interval increased from 57 ms to 123 ms, and the QRS complex widened from 130 ms to 198 ms, demonstrating a complete LBBB. Because of this, a PPM was implanted. The primary contribution of this case lies in the use of ICE as a guiding tool during BA of the IVS. ICE proved valuable for 2 reasons: to monitor for signs of an imminent steam pop and to confirm the efficacy of the ablation. The progressive refringence of the IVS observed on ICE provided visual confirmation of effective energy delivery. As shown in Figure 3, the septum became uniformly hyperechogenic, appearing homogeneously white from its basal to mid-septal portions. This visual endpoint may serve as an additional marker of ablation efficacy, particularly in cases involving deep myocardial substrates. In one of the largest series of septal VT cases, Della Bella et al. [4] reported the use of irrigated catheters with an average power of 33 W, 13mm distance between the tips of the ablation catheters, an ablation area of 4.1 cm², and settings targeting an impedance drop of 20–40 ohms with application duration of 60–90 seconds (no ICE used). They reported no occurrences of steam pops or AVB. Complications included one case of cardiac tamponade, with no deaths or IVS communications. At the conclusion of their ablation procedures, VT non-inducibility was achieved in all but one patient. However, during a median follow-up of 25 months, they observed a recurrence rate of 33%. Considering these findings, the incorporation of ICE could provide an additional layer of procedural guidance and safety. Specifically, ICE could be used to confirm ablation efficacy by monitoring for homogenous refringence of the IVS target region. This visual endpoint, along with VT non-inducibility, may serve as a potential marker of long-term ablation success, possibly contributing to lower recurrence rates in this patient population. With ICE in this case, we could closely follow the aspect of the IVS as we apply BA. This observation could make sure that the RF lesions were transmural. One of the concerns about BA approach is the risk of septum perforation resulting in ventricular septal defect (VSD) late in the follow up [5]. In a recent case series, three cases of VSD were reported following BA. However, ICE was not used in two of these cases. Notably, one of the cases involved a patient with sarcoidosis, a condition known to cause significant damage to the IVS due to prior inflammatory compromise. In this case, a steam pop occurred during the procedure [5]. The second case involved a patient who underwent nine ablation procedures, four of which were BA targeting multiple sites, including the superior RV septal scar, distal anterior interventricular vein, posterior RVOT, left coronary cusp, aortomitral continuity, epicardium and the cusps of the pulmonic valve. Despite these extensive attempts, no steam pops were reported during the BA’s. In the third case, ICE was utilized during the procedure, revealing extensive basal and septal scarring in both ventricles, extending to the aortic subvalvular region. The power was titrated up to 70 W for 3 minutes. Three steam pops were reported. In all cases, VSD was diagnosed late in the follow up (6 to 30 months) [5]. Initially, the VSD’s were relatively small but progressively enlarged over time. This underscores the importance of procedural strategies to minimize the risk of septal damage, including careful power titration and continuous ICE monitoring to detect early signs of tissue compromise. ICE imaging, demonstrating marked refringence of the IVS, may serve as a potential marker for an increased risk of developing VSD. As such, the surveillance for this complication should be actively pursued during follow-up, as early diagnosis and treatment are critical to improving patient outcomes [5]. This report highlights the use of ICE during BA, demonstrating its pivotal role in procedural safety (by avoiding steam pops), efficacy (through the visualization of hyperrefringence as a marker of effective ablation), and as a tool to guide the active search for VSD during follow-up. Further studies with long-term follow-up are needed to validate this strategy and to better understand its impact on outcomes in patients undergoing BA. References: 1- Zeppenfeld K, Tfelt-Hansen J. ESC guidelines for the management of patients with ventricular arrhythmias and the prevention of sudden cardiac death. European Heart Journal 2022; 43: 3997-4126. 2- Halbfass P, Ludwig D, Sonne K, Nentwich K, Ene E, Berkovitz A, Foldyna B, Barth S, Müller J, Lehmkuhl L, Lüsebrink U, Waechter C, Deneke T. Acute and Long-term outcomes of VT radiofrequency catheter ablation in patients with versus without an intramural septal substrate. Indian Pacing and Electrophysiology J 2022; 22: 2-9. 3- Muser D, Santangeli P, Castro SA, Liang JJ, Enriquez A, Liuba I, Magnani S, Garcia FC, Arkles J, Supple G, Lin D, Schaller RD, Kumareswaran R, Zado E, Tschabrunn C, Dixit S, Frankel DS, Callans DJ, Marchlinski FE. Collateral Injury of the conduction system during catheter ablation of septal substrate in non-ischemic cardiomyopathy. Journal of Cardiovascular Electrophysiology 2020; 31: 1726-1739. 4- Della Bella P, Peretto G, Paglino G, Bisceglia C, Radinovic A, Sala S, Baratto F, Limite LR, Cireddu M, Marzi A, D´angelo G, Vergara P, Gulletta S, Mazzone P, Frontera A. Heart Rhythm 2020; 17: 2111-2118. 5- Maher TR, Raza AS, Tapias C, Garcia F, Reynolds MR, Chaudry M., Saenz LC, Valderrábano M, D´Ávila A Ventricular septal defect as a complication of bipolar radiofrequency ablation for ventricular tachycardia. Heart Rhythm 2024; 21: 950-955. 6- Sauer WH, Steckman DA, Zipse MM, Tzou WS, Aleong RG High-power bipolar ablation for incessant ventricular tachycardia utilizing a deep midmyocardial septal circuit. Heart Rhythm case reports 2015; 1 (6): 397-400. 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Keywords basic: activation mapping of arrhythmias basic: ventricular tachycardia/fibrillation clinical: cardiac mapping – 3-dimensional systems clinical: cardiac mapping – intracardiac echo clinical: catheter ablation – ventricular tachycardia Authors Affiliations iremar MACEDO NETO 0000-0002-4299-1143 [email protected] Hospital Esperanca View all articles by this author Muhieddine Chokr 0000-0001-6697-7074 Universidade de Sao Paulo Instituto do Coracao View all articles by this author Jose Carvalho Neto Hospital Esperanca View all articles by this author Eduardo Barreto Gadelha Hospital Esperanca View all articles by this author Ezequiel Thé Hospital Esperanca View all articles by this author Afonso Albuquerque Hospital Esperanca View all articles by this author Metrics & Citations Metrics Article Usage 226 views 204 downloads .FvxKWukQNSOunydq8rnd { width: 100px; } Citations Download citation iremar MACEDO NETO, Muhieddine Chokr, Jose Carvalho Neto, et al. Optimizing Outcomes in Bipolar Ablation for Refractory Septal VT: The Role of Intracardiac Echocardiography. Authorea . 18 February 2025. DOI: https://doi.org/10.22541/au.173988569.93105228/v1 If you have the appropriate software installed, you can download article citation data to the citation manager of your choice. Simply select your manager software from the list below and click Download. For more information or tips please see 'Downloading to a citation manager' in the Help menu . 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