Circuit Impedance Could Be a Crucial Factor Influencing Radiofrequency Ablation Efficacy and Safety: A Myocardial Phantom Study of the Problem and Its Correction

Bhaskaran, Abhishek; Barry, Michael A.; Pouliopoulos, Jim; Nalliah, C.; Qian, Pierre; Chik, W.; Thavapalachandran, Sujitha; Davis, Lloyd M.; McEwan, Alistair; Thomas, Stuart P.; Kovoor, Pramesh; Thiagalingam, Aravinda

doi:10.1111/jce.12893

Cited by 36 publications

(38 citation statements)

References 44 publications

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“…For instance, the endocardial contact force was set up to 300 gr and the endocardial force at 30 gr and endocardial impedance close to ideal 120 Ω. 26 Therefore, we might postulate that the lower impedance, employed in our previous experiments, as well as the difference in tip temperature, could explain the different outcomes.…”

Section: Discussionmentioning

confidence: 93%

One-Stage Versus Sequential Hybrid Radiofrequency Ablation: An In Vitro Evaluation

Matteucci

Maesen

Vernooy

et al. 2020

Innovations�(Phila)

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Objective To compare lesion size and depth between a 1-step, a sequential, and a delayed radio-frequency ablation in a hybrid setup. Methods Left atrium tissues obtained from fresh porcine hearts were mounted into the ABLABOX simulator. Based on the time differences between the index epicardial (epi) and consequent endocardial (endo) ablation, 3 study groups were compared: a 1-stage (SEQ- 0) group (0-minute delay), an SEQ 1 group (60-minute delay), and an SEQ 2 group (240-minute delay). During the experiment, a constant epicardial (300 gr) and endocardial (30 gr) force were applied. Per group, 20 samples were studied, and the resulting lesion size and depth were quantified with morphometric evaluation. Results Overall, no transmural lesion was obtained. Lesions in SEQ 0 had better maximum and minimum diameters ( P < 0.001), a larger total area ( P < 0.001), and volume ( P < 0.001) than SEQ 1 and SEQ 2. There was no statistical difference in morphometric parameters (all, P > 0.05) between the delayed procedures (SEQ 1 and SEQ 2). Conclusions In our in vitro model, different time sequences of combined epi–endo ablation did not result in transmural lesions. However, simultaneous epi–endo ablation produced broader and deeper lesions. Our findings need to be confirmed by further research.

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Section: Discussionmentioning

confidence: 93%

One-Stage Versus Sequential Hybrid Radiofrequency Ablation: An In Vitro Evaluation

Matteucci

Maesen

Vernooy

et al. 2020

Innovations�(Phila)

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“…The details of RFA applications in the baseline state ("high baseline impedance") are shown in Table 2. The number applications applied to putative arrhythmia sites was 10.43 ± 3.14 (11,(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15). There were more applications in patients with scar-related VT compared to patients with idiopathic VPCs (11.92 ± 2.1 [12,[7][8][9][10][11][12][13][14][15] (14,.…”

Section: Ablation Characteristicsmentioning

confidence: 99%

“…Therefore, when ablation is performed in a power-controlled mode, resistance has a direct and negative relationship to current; ablation at lower resistance yields higher current output (and tissue temperature) compared to ablation at a similar power but, higher resistance. 5,8 The relationship of power, current and resistance to lesion dimensions is illustrated in Figure 1.…”

Section: Introductionmentioning

confidence: 99%

Modulating the Baseline Impedance

Shapira‐Daniels

Barkagan

Rottmann

et al. 2019

Circ: Arrhythmia and Electrophysiology

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Background-Radiofrequency ablation (RFA) of intramural ventricular substrate is often limited by insufficient tissue penetration despite high energy settings. As lesion dimensions have a direct and negative relationship to impedance, reducing the baseline impedance may increase the ablation effect on deep ventricular tissue. Methods-This study included 16 patients with ventricular tachycardia (VT) or frequent ventricular premature complexes (VPCs) refractory to ablation with irrigated catheters. Following a failed response to RFA, impedance was modulated by adding or repositioning return patches in attempt to decrease the circuit impedance. Ablation was repeated at similar location and power settings, and the effect on arrhythmia suppression and adverse effects were evaluated. Results-Six patients with idiopathic VPCs originating from the left ventricular summit (n=4) or papillary muscles (n=2), 6 patients with non-infarct related VT and 4 patients with infarct related VT had unsuccessful response to RFA at critical sites (number of applications: 10.4±3.1, power: 42.3±2.9W, duration: 55.3±25.5sec, impedance reduction: 14.6±3.5Ohms, low ionic solution was used in 81.25%). Modulating the return patches resulted in reduced baseline impedance (111.7 ± 8.2 vs. 134.7±6.6 Ohms, p<0.0001), increased current output (0.6±0.02 vs. 0.56±0.02Amp; p<0.0001) and greater impedance drop (16.8±3.0Ohms, p<0.001). Repeat ablation at similar locations had a successful effect in 12 out of 16 (75.0%) patients. During a follow-up duration of 13±5 months, 10 out of 12 (83.3%) patients remained free of arrhythmia recurrence. The frequency of steam-pops was similar between the higher and lower baseline impedance settings (7.1 vs. 8.2%; p=0.74). Conclusions-In patients with deep ventricular substrate, reducing the baseline impedance is a simple, safe and effective technique for increasing the effect of RFA. However, its combination with low-ionic solutions may increase the risk for steam-pops and neurological events.

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“…A prior study evaluating total circuit impedance demonstrated larger lesion size and a larger zone of heating when the total circuit impedance was lower . In that study, the investigators used a phantom model and altered the surface area of the grounding patch electrode in contact with a conductive fluid to alter the electrical impedance of the entire circuit, including tissue and surrounding environmental impedance.…”

Section: Introductionmentioning

confidence: 99%

“…A prior study evaluating total circuit impedance demonstrated larger lesion size and a larger zone of heating when the total circuit impedance was lower. 6 In that study, the investigators used a phantom model and altered the surface area of the grounding patch electrode in contact with a conductive fluid to alter the electrical impedance of the entire circuit, including tissue and surrounding environmental impedance. We hypothesize that isolated alteration of the surrounding environmental impedance with unchanged tissue impedance in the circuit will preferentially shunt RF electrical current to targeted tissue, and thus affect lesion characteristics.…”

Section: Introductionmentioning

confidence: 99%

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

Nguyen¹,

Nguyen²,

Zheng³

et al. 2017

Cardiovasc electrophysiol

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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.

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Circuit Impedance Could Be a Crucial Factor Influencing Radiofrequency Ablation Efficacy and Safety: A Myocardial Phantom Study of the Problem and Its Correction

Cited by 36 publications

References 44 publications

One-Stage Versus Sequential Hybrid Radiofrequency Ablation: An In Vitro Evaluation

One-Stage Versus Sequential Hybrid Radiofrequency Ablation: An In Vitro Evaluation

Modulating the Baseline Impedance

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

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