Clinical and biophysical evaluation of variable bipolar configurations during radiofrequency ablation for treatment of ventricular arrhythmias

Self Cite

Introduction Both bipolar and simultaneous radiofrequency ablation (bRFA, simRFA) have been used to treat thick midmyocardial substrate as well as during circular, multipolar ablation between shorter distances. Objectives We sought to evaluate the biophysical parameters of simRFA, sequential unipolar RFA (seqRFA), and bRFA. Methods Bovine myocardium was placed in a circulating saline bath. To simulate thick substrate conditions, two open irrigated ablation catheters were oriented across from each other, with myocardium in between. Thermocouples were placed in the center, ±2 mm, of the myocardium. Unipolar ablations were performed sequentially or simultaneously at 50 W for 60 seconds and compared to bRFA using the same settings. In addition, to simulate multipolar ablation, two open irrigated ablation catheters were oriented on the same side and perpendicular to myocardium at 1, 2, and 4 mm spacing. SimRFA were performed at 15 and 25 W for 60 seconds and compared to bRFA. Results For thicker tissue, simRFA produced similar lesion volume and depth compared to bRFA but with a lesion geometry similar to seqRFA. Unlike seqRFA and simRFA, bRFA had a necrotic core spanning the myocardium. Core depths, volumes, and temperatures were significantly greater for bRFA lesions compared to simRFA or seqRFA (Figure, P < .001). Similar results were consistent for bRFA and simRFA at shorter spacings. Conclusions BRFA has greater core lesion temperatures, corresponding to a denser and larger necrotic core, than either simRFA or seqRFA. This may have implications for considering the optimal strategy for deep midmyocardial substrates or during multipolar ablation.

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Bipolar radiofrequency ablation creates different lesion characteristics compared to simultaneous unipolar ablation

Nguyen

Zheng²,

Zipse³

et al. 2019

Self Cite

“…This study builds upon prior research into varying certain biophysical parameters to facilitate RF ablation . In this case, by altering environmental impedance, which is most pertinent for epicardial ablation, we demonstrate that RF ablation can be augmented.…”

Section: Discussionmentioning

confidence: 84%

Effect of Environmental Impedance Surrounding a Radiofrequency Ablation Catheter Electrode on Lesion Characteristics

Nguyen¹,

Nguyen²,

Zheng³

et al. 2017

Self Cite

Environmental Impedance and Ablation Lesions Introduction The electrical conductivity of the environment surrounding a catheter electrode may affect radiofrequency (RF) current. A higher impedance environment enveloping a catheter tip can be insulating and thus direct RF preferentially into targeted cardiac tissue. We sought to evaluate whether different environmental impedances will affect RF lesions. Methods An ex vivo model using bovine myocardium, load cell, and 4 mm ablation catheter was tested using a circulating bath of normal (0.9%; NS) and half normal (0.45%; HNS) saline. Ablations were performed at 50 W. In addition, using a porcine thigh prep model, warmed heparinized blood was circulated at 350 mL/min. Prior to ablation, circulating bath impedance was altered with NS and HNS. RF was applied at 30 W with a force‐sensing, open irrigated catheter. Results Ex vivo RF with a 4 mm catheter using an HNS bath led to larger lesions, 286.7 ± 64 mm³ versus 198.9 ± 61 mm³ (P < 0.001), compared to an NS bath. In the porcine thigh prep, for RF in the high impedance (HNS) bath, initial and final impedances were higher, and the measured impedance reductions during ablation were larger, compared to RF in the low impedance (NS) bath. In vivo ablation within a higher impedance bath created larger lesion sizes, compared to a lower impedance bath, 222.4 ± 63.4 mm3 versus 135.4 ± 61.7 mm3 (P < 0.001). Conclusions A higher impedance surrounding an RF catheter can facilitate more effective RF and thereby increase lesion size. This may have implications for RF safety and efficacy, especially in the epicardium where pericardial fluid can be altered with infusion of ionic solutions.

“…27 Use of half-normal saline as the irrigant for open-irrigated RF ablation using a standard ablation catheter (ThermoCool SmartTouch or ThermoCool SF, Biosense Webster) was another nonstandard ablation approach employed. Bipolar ablation, as previously described, was performed using an ablation catheter on one side and a second ablation catheter on the opposing side of the myocardium (both 3.5-mm externally irrigated or 8-mm tip, Biosense Webster).…”

Section: Ablation Strategies and Endpointsmentioning

confidence: 99%

“…Other alternative techniques that we did not employ but that have been previously reported include transcoronary ethanol ablation, neuraxial modulation, and simultaneous unipolar ablation [35][36][37]. We used adjunctive techniques with which we had the most experience and which we had previously demonstrated success, although the decision about which adjunctive technique to use in a given case was operator-dependent and patient-specific, and future study comparing techniques with respect to procedural efficacy is warranted 27,28. In the present series, no single nonstandard technique was demonstrated to provide clear superiority in achieving ultimate success.…”

mentioning

confidence: 99%

Repeat ablation of refractory ventricular arrhythmias in patients with nonischemic cardiomyopathy: Impact of midmyocardial substrate and role of adjunctive ablation techniques

Tzou¹,

Rothstein²,

Cowherd³

et al. 2018

Self Cite