1322Impact of system impedance in ablation-index guided lesion formation in an in vitro model

Abstract Funding Acknowledgements Beca de la Sección de Electrofisiología y Arritmias para formación en investigación post-residencia en centros españoles INTRODUCTION Ablation Index and Lesion Size Index are novel markers of ablation lesion quality that incorporate power (W), contact force (CF), and time (T) in a weighted formula to accurately estimate lesion size. While LSI includes system impedance (I) in the formula, this parameter is not considered for AI calculation. PURPOSE The aim of our study was to analyse the impact of I in lesion formation. METHODS Radiofrequency (RF) lesions were created on porcine myocardial slabs by using an open-tip irrigated catheter with real-time monitoring of CF (a TactiCath™ Quartz Contact Force Ablation Catheter for LSI-guided lesions and a ThermoCool® SmartTouch® Catheter for AI-guided lesions). Catheters were mounted in an articulated arm and manually maneuvered over a platform placed within a tank filled with either a low impedance medium (saline solution) or a high impedance medium (running water) with a heating pump to produce non-pulsatile flow directed perpendicularly to the myocardium surface at a rate of 5 l/min and a temperature of 37ºC. For each catheter and medium, ten lesions were performed with a CF of 20 grams and a W of 25, 30, 35 and 40 watts aiming at a LSI of 5 or a AI of 400 (recommended targets for posterior wall pulmonary vein isolation for each index). After RF delivery, the myocardium was cross-sectioned at the level of each lesion and its blanched zone was measured with a dial calliper with a 0.1 mm resolution (image, panel A). Lesion volume was calculated using width and depth, according to a validated formula (image, panel B). RESULTS No difference in application time was noted in the AI-guided lesions depending on the medium (23.8 ± 1.6s, 17.2 ± 1.4s, 13.7 ± 0.8s and 12.2 ± 0.7s for 25W, 30W, 35W and 40W, respectively) while a significant reduction in application time was noted in the LSI-guided lesions performed in a low I medium (93.8 ± 6.6 ohms; 17.9 ± 1.9s, 11.3 ± 3.7s, 9.1 ± 0.9s and 7.3 ± 0.5s for 25W, 30W, 35W and 40W) compared with those performed in a high impedance medium (132.4 ± 6.6 ohms; 27.3 ± 1.4s, 17.9 ± 2.5s, 15.5 ± 1.4 and 13 ± 1.2 for the same programmed W (p < 0.0001 for all comparisons). Both catheters showed differences in lesion size according to the I, with lower lesion volumes in the low I medium and higher lesion volumes in the high I medium. Although globally smaller in size, higher lesion volumes were noted in the AI-guided lesions compared to LSI-guided lesions in a low I medium (image, panel C). On the contrary, a better performance of the LSI-guided lesions was observed in the high I medium (image, panel D). CONCLUSIONS System impedance affected lesion size both in LSI-guided an AI-guided ablation lesions, with smaller lesions seen in a lower I medium. Further studies are needed to assess the clinical relevance of this findings in an in-vivo scenario. Abstract Figure.

Download Full-text

Impact of power and contact force in ablation-index guided radiofrequency lesions in an in vitro model

EP Europace ◽

10.1093/europace/euab116.085 ◽

2021 ◽

Vol 23 (Supplement_3) ◽

Author(s):

C Lozano-Granero ◽

E Franco Diez ◽

R Matia Frances ◽

A Hernandez-Madrid ◽

I Sanchez Perez ◽

...

Keyword(s):

Contact Force ◽

Lesion Size ◽

Public Institution ◽

Lesion Volume ◽

Lesion Depth ◽

Lower Index ◽

Ablation Index ◽

Radiofrequency Lesions ◽

Size And Morphology

Abstract Funding Acknowledgements Type of funding sources: Public Institution(s). Main funding source(s): Electrophisiology Section of the Spanish Society of Cardiology Introduction. Lesion Size Index (LSI) and Ablation Index (AI) are markers of lesion quality that incorporate power, contact force (CF), and time in a weighted formula to estimate lesion size. Although accurate predicting lesion depth in-vitro, their precision in lesion size estimation has not been well established for certain power and CF settings. Purpose. We conducted an experimental ex-vivo study to analyse the effect of power and CF in size and morphology of ablation lesions in a porcine heart model. Methods. 24 sets of 10 perpendicular epicardial radiofrequency applications were performed with two commercially available catheters (TactiCath, Sensor Enabled; and SmartTouch) on porcine left ventricle submerged in 37ºC saline, combining different power (25, 30, 35, 40, 50 and 60W) and CF (10 and 20g) settings, and aiming at a lower (LSI/AI of 5/400) or higher (LSI/AI of 6/550) index. After each application, lesions were cross-sectioned and measured. Results. 480 lesions were performed. For a given target index and CF, significant differences in lesion volume and depth with different power settings were observed with both catheters. Regarding lesion volume, statistically significant differences were observed with all CF and LSI targets with TactiCath, except for 10 g and LSI 5 (10 g and LSI 5, p = 0.4134; 10 g and LSI 6, p < 0.0001; 20 g and LSI 5, p < 0.0001; 20 g and LSI 6, p < 0.0001). The same occurred for SmartTouch, showing statistically significant differences with all CF and AI targets, except for 20 g and AI 550 (10 g and AI 400, p = 0.0001; 10 g and AI 550, p < 0.0001; 20 g and AI 400, p < 0.0001; 20 g and AI 550, p = 0.001). Similar differences could be found in lesion depth with each catheter. Globally, lesions performed with 50 and 60W were significantly smaller and shallower than those performed with 35 or 40W (figure). Regarding CF, catheters behaved differently: lesions performed with 10g were smaller and shallower than those performed with 20g with Tacticath, while being bigger and deeper with SmartTouch. In a side-by-side comparison, lesions performed with TactiCath were smaller and shallower than those performed with SmartTouch when applying a lower CF of 10g, both when targeting a lower index objective (volume: 41.8 ± 54.3mm3 vs 158.3 ± 33.2mm3, p < 0.0001; depth: 2 ± 1.7mm vs 4.6 ± 0.5mm, p < 0.0001) or a higher index objective (volume: 103.1 ± 56.5mm3 vs 280 ± 54mm3, p < 0.0001; depth: 4 ± 1.1mm vs 5.8 ± 0.5mm, p < 0.0001). However, lesions with TactiCath were bigger and deeper when applying a higher CF of 20g aiming at a lower index objective (volume: 123.8 ± 39.9mm3 vs 89.7 ± 29.4mm3, p < 0.0001; depth: 4 ± 0.8mm3 vs 3.6 ± 0.5mm, p < 0.0001). No statistically significant difference was observed when applying a higher CF of 20g aiming at a higher index objective. Conclusions. Size and morphology of index-guided radiofrequency lesions varied significantly with different power and CF settings, highlighting the importance of achieving a good CF in any ablation procedure. Abstract Figure. Box-plot of lesion volume

Download Full-text

Considerations for Thermal Injury Analysis for RF Ablation Devices

The Open Biomedical Engineering Journal ◽

10.2174/1874120701004010003 ◽

2010 ◽

Vol 4 (1) ◽

pp. 3-12 ◽

Cited By ~ 13

Author(s):

Isaac A. Chang

Keyword(s):

Thermal Injury ◽

Tissue Injury ◽

Recursive Algorithm ◽

Geometric Model ◽

Volume Measurement ◽

Lesion Size ◽

Voltage Source ◽

Lesion Volume ◽

The Impact

Background: The estimation of lesion size is an integral part of treatment planning for the clinical applications of radiofrequency ablation. However, to date, studies have not directly evaluated the impact of different computational estimation techniques for predicting lesion size. In this study, we focus on three common methods used for predicting tissue injury: (1) iso-temperature contours, (2) Cumulative equivalent minutes, (3) Arrhenius based thermal injury. Methods: We created a geometric model of a multi-tyne ablation electrode and simulated thermal and tissue injury profiles that result from three calculation methods after 15 minutes exposure to a constant RF voltage source. A hybrid finite element technique was used to calculate temperature and tissue injury. Time-temperature curves were used in the assessment of iso-temperature thresholds and the method of cumulative equivalent minutes. An Arrhenius-based formulation was used to calculate sequential and recursive thermal injury to tissues. Results: The data demonstrate that while iso-temperature and cumulative equivalent minute contours are similar in shape, these two methodologies grossly over-estimate the amount of tissue injury when compared to recursive thermal injury calculations, which have previously been shown to correlate closely with in vitro pathologic lesion volume measurement. In addition, Arrhenius calculations that do not use a recursive algorithm result in a significant underestimation of lesion volume. The data also demonstrate that lesion width and depth are inadequate means of characterizing treatment volume for multi-tine ablation devices. Conclusions: Recursive thermal injury remains the most physiologically relevant means of computationally estimating lesion size for hepatic tumor applications. Iso-thermal and cumulative equivalent minute approaches may produce significant errors in the estimation of lesion size.

Download Full-text

A Dual Role for Nitric Oxide in NMDA-Mediated Toxicity in vivo

Journal of Cerebral Blood Flow & Metabolism ◽

10.1038/jcbfm.1995.115 ◽

1995 ◽

Vol 15 (6) ◽

pp. 904-913 ◽

Cited By ~ 18

Author(s):

Mordecai Y.-T. Globus ◽

Ricardo Prado ◽

J. Sanchez-Ramos ◽

Weizhao Zhao ◽

W. Dalton Dietrich ◽

...

Keyword(s):

Nitric Oxide ◽

Injection Site ◽

Treated Group ◽

Lesion Size ◽

Lesion Volume ◽

Excitotoxic Damage ◽

Peripheral Areas ◽

Oxide Synthase

Nitric oxide has been implicated in N-methyl-d-aspartate (NMDA)-mediated damage in vitro; however, its role in excitotoxic damage in vivo is not clear. In the present study we evaluated the histopathological and hemodynamic consequences of intrastriatal injections of various doses of NMDA and determined the effects of nitric oxide synthase inhibition on these changes. NMDA was injected into the striatum at doses of 50, 150, and 300 nmol with or without Nω-nitro-l-arginine methyl ester (L-NAME; 100 μg, locally). Three days following injections histopathological assessment was performed by morphometric analysis of the lesion area in multiple sections taken from the anterior to the posterior borders of the lesion. In animals injected with 150 and 300 nmol of NMDA (±L-NAME), local CBF (lCBF) was determined 30 min following injections using 14C-iodoantipyrine autoradiography. All NMDA-treated animals showed a well-demarcated lesion extending beyond the injection site. The volume of the lesion correlated significantly with the NMDA dose injected. The effects of L-NAME on lesion size were dependent on the dose of the NMDA. The lesion induced by 50 nmol of NMDA was not affected by L-NAME. With a dose of 150 nmol of NMDA, L-NAME induced a 43% increase in lesion volume. In contrast, a 38% decrease in lesion size was observed in animals treated with 300 nmol of NMDA combined with L-NAME. At a dose of 150 nmol, NMDA induced a significant elevation in lCBF, which was restricted to regions close to the injection site including the center areas of the anterior and middle striatum. The increase in lCBF observed with 150 nmol of NMDA was significantly attenuated in the NMDA + L-NAME-treated group. The lCBF changes induced by 300 nmol of NMDA were not significantly different from those in the 150-nmol group; however, the extent of the regions involved was larger. The increases in lCBF were observed in all striatal regions including the central and peripheral areas. L-NAME did not have a significant effect on the lCBF changes induced by NMDA at a dose of 300 nmol. These data suggest that in vivo the involvement of nitric oxide in NMDA toxicity depends on the NMDA dose and on the participation of hemodynamic mechanisms secondary to NMDA exposure.

Download Full-text

Seasonal Variation in Host Susceptibility to Fusarium Canker in Young Almond Trees

Plant Disease ◽

10.1094/pdis-06-19-1292-re ◽

2020 ◽

Vol 104 (3) ◽

pp. 772-779

Author(s):

Abigail J. Stack ◽

Meera Madra ◽

Thomas R. Gordon ◽

Richard M. Bostock

Keyword(s):

Cold Storage ◽

Fusarium Species ◽

Lesion Size ◽

Host Susceptibility ◽

Seasonal Effect ◽

Canker Disease ◽

Almond Trees ◽

Bare Root ◽

The Impact

Loss of water that reduces the relative water content (RWC) of bark can occur during processing, cold storage, and planting of bare-root stone fruit trees. In California nurseries and newly planted orchards, this stress can predispose young almond trees (Prunus dulcis) to a canker disease caused primarily by Fusarium species. While reduced bark RWC contributes to disease development, anecdotal observations suggest a seasonal effect on host physiology may also influence disease severity. We evaluated the effect of season and the impact of drying and reduced RWC on susceptibility of almond branch segments excised from orchard trees (cv. Nonpareil) to Fusarium acuminatum, Fusarium avenaceum, Fusarium brachygibbosum, and Fusarium californicum sp. nov. With lesion size as the criterion, excised inoculated branch segments were most susceptible in spring, of intermediate susceptibility during winter dormancy, and least susceptible during summer and fall. Consistent with an earlier study, branches with RWC between 80 and 85% yielded lesions that were significantly larger than lesions from branches with bark that was above or below that range. However, the effect of reduced bark moisture on lesion size was only apparent in the spring. These results affirm the importance of avoiding conditions that diminish moisture status in bare-root almond trees in Fusarium canker disease management, especially during transport and planting operations in the spring, a period of high physiological vulnerability. California nurseries apply fungicides to bare-root trees prior to cold storage to reduce “mold” growth. Of eight fungicides currently registered for use on almond trees, fludioxonil (Scholar), fluopyram/trifloxystrobin (Luna Sensation), and fluxapyroxad/pyraclostrobin (Merivon) were most inhibitory to in vitro mycelial growth of F. acuminatum, F. avenaceum, and F. brachygibbosum. However, our almond branch disease assay did not demonstrate preventive or curative fungicide action against infections by F. acuminatum or F. avenaceum.

Download Full-text

Inhibition of Nitric Oxide Synthesis Increases Focal Ischemic Infarction in Rat

Journal of Cerebral Blood Flow & Metabolism ◽

10.1038/jcbfm.1992.102 ◽

1992 ◽

Vol 12 (5) ◽

pp. 717-726 ◽

Cited By ~ 207

Author(s):

Seiji Yamamoto ◽

Eugene V. Golanov ◽

Scott B. Berger ◽

Donald J. Reis

Keyword(s):

Nitric Oxide ◽

Reactive Hyperemia ◽

Competitive Inhibitor ◽

Lesion Size ◽

Lesion Volume ◽

Lesion Formation ◽

Spontaneously Hypertensive ◽

Ischemic Infarction ◽

Platelet Disaggregation

We investigated whether inhibition of nitric oxide (NO) biosynthesis with N-ω-nitro-l-arginine (NNA), a competitive inhibitor of NO synthase (NOS), would modify the volume of the focal ischemic infarction produced by occlusion of the middle cerebral artery (MCA) in spontaneously hypertensive rats. NNA was infused for 1 h (2.4 mg/kg/h) immediately following occlusion of the MCA. NNA increased lesion volume 24 h later by 32% over controls (150.8 ± 16.6 to 199.2 ± 17.4 mm3; p < 0.001, n = 6). This effect was antagonized by co-infusion of l- but not d-arginine. The antihypertensive rilmenidine (0.75 mg/kg) reduced the lesion by 27% (p < 0.05, n = 4). Changes in lesion size were confined to the penumbra. NNA increased arterial pressure (AP) (118 ± 8.9 to 149 ± 16.0 mm Hg; p < 0.01, n = 3) but did not change regional CBF. However, elevation of AP did not change the lesion volume or distribution. We conclude that inhibition of the constitutive form of NOS in vivo increases the volume of focal ischemic infarction as a consequence of reduced NO biosynthesis. The absence of NO availability may extend lesion formation by inhibition of reactive hyperemia, platelet disaggregation, and/or release of neuroprotective neuromodulators in the penumbra, which may counteract and override any of its neurotoxic actions.

Download Full-text

Characterization of the impact of catheter-tissue contact force in lesion formation during cavo-tricuspid isthmus ablation in an experimental swine model

EP Europace ◽

10.1093/europace/eut351 ◽

2013 ◽

Vol 16 (11) ◽

pp. 1679-1683 ◽

Cited By ~ 11

Author(s):

R. Matia Frances ◽

A. Hernandez Madrid ◽

A. Delgado ◽

L. Carrizo ◽

C. Pindado ◽

...

Keyword(s):

Contact Force ◽

Swine Model ◽

Lesion Formation ◽

The Impact

Download Full-text

The impacts of contact force, power and application time on ablation effect indicated by serial measurements of impedance drop in both conventional and high-power short-duration ablation settings of atrial fibrillation

Journal of Interventional Cardiac Electrophysiology ◽

10.1007/s10840-021-00990-4 ◽

2021 ◽

Author(s):

Li-Bin Shi ◽

Yu-Chuan Wang ◽

Song-Yun Chu ◽

Alessandro De Bortoli ◽

Peter Schuster ◽

...

Keyword(s):

Atrial Fibrillation ◽

Short Duration ◽

Contact Force ◽

High Power ◽

Power Output ◽

Application Time ◽

Ablation Time ◽

Ablation Index ◽

Power Setting ◽

Power Outputs

Abstracts Background This study aimed to clarify the interrelationship and additive effects of contact force (CF), power and application time in both conventional and high-power short-duration (HPSD) settings. Methods Among 38 patients with paroxysmal atrial fibrillation who underwent first-time pulmonary vein isolation, 787 ablation points were collected at the beginning of the procedure at separate sites. Energy was applied for 60 s under power outputs of 25, 30 or 35 W (conventional group), or 10 s when using 50 W (HPSD group). An impedance drop (ID) of 10 Ω was regarded as a marker of adequate lesion formation. Results ID ≥ 10 Ω could not be achieved with CF < 5 g under any power setting. With CF ≥ 5 g, ID could be enhanced by increasing power output or prolonging ablation time. ID for 30 and 35 W was greater than for 25 W (p < 0.05). Ablation with 35 W resulted in greater ID than with 30 W only when CF of 10–20 g was applied for 20–40 s (p < 0.05). Under the same power output, ID increased with CF level at different time points. The higher the CF, the shorter the time needed to reach ID of 10 Ω and maximal ID. ID correlated well with ablation index under each power, except for lower ID values at 25 W. ID with 50 W for 10 s was equivalent to that with 25 W for 40 s, but lower than that with 30 W for 40 s or 35 W for 30 s. Conclusions CF of at least 5 g is required for adequate ablation effect. With CF ≥ 5g, CF, power output, and ablation time can compensate for each other. Time to reach maximal ablation effect can be shortened by increasing CF or power. The effect of HPSD ablation with 50 W for 10 s is equivalent to conventional ablation with 25 W for 40 s and 30–35 W for 20–30 s in terms of ID.

Download Full-text

P1428The outcome of atrial fibrillation ablation in patients undergoing radiofrequency ablation, guided by novel indices incorporating force, time and power

EP Europace ◽

10.1093/europace/euaa162.353 ◽

2020 ◽

Vol 22 (Supplement_1) ◽

Author(s):

T Rattanakosit ◽

K Franke ◽

H Marshall ◽

T Agbaedeng ◽

P Sanders ◽

...

Keyword(s):

Atrial Fibrillation ◽

Radiofrequency Ablation ◽

Contact Force ◽

Lesion Size ◽

Fluoroscopy Time ◽

Procedure Time ◽

Time Integral ◽

Ablation Index ◽

Force Time ◽

Af Recurrence

Abstract Background Ablation index (AI) and Lesion Size Index (LSI) are novel parameters that incorporates contact force, time, and power in a weighted formula. Recent studies have shown that such indices predict lesion size and durability of pulmonary vein isolation (PVI). However, the outcomes of ablation guided by indices of force-time-power, such as PV reconnections and atrial fibrillation recurrence, have not been well characterised. Objectives To determine the association between indices of force-time-power and acute PV reconnections, procedure and fluoroscopy time and AF recurrence in patients undergoing radiofrequency PVI. Methods PUBMED and EMBASE were searched using the terms "catheter ablation" AND "Ablation index" OR "Contact force" OR "Force time integral" OR "lesion size" from inception through 22 May 2019. Studies reporting the procedure time, ablation time, fluoroscopy time, and incidence of AI acute and late reconnection and AF recurrence were included. Result Six studies were included in this study with 530 patients, which n = 416 were paroxysmal AF and 114 non-paroxysmal AF. All procedural characteristics (procedure, radiofrequency, and fluoroscopy times) were similar between AI guided and non-AI guided ablation (p > 0.05). Two studies comparing mean PV reconnections in AI guided vs. AI Blinded. Two studies compared minimum AI in reconnected vs. non-reconnected PV segments. Acute PV segment reconnection was associated with a lower minimum AI vs. non-reconnection. In 3 studies reporting AI guided vs. AI blinded ablations, AI was associated with an increased freedom from AF after average follow-up of 12 months. Conclusions Radiofrequency ablation guided by AI/LSI was associated with lower acute PV reconnection rates and improved AF freedom after PVI. There was no difference in fluoroscopy, ablation or procedure time with the use of these novel parameters. Abstract Figure.

Download Full-text

Modeling traumatic brain injury combined with hemorrhagic shock in rats: Neurological assessment and PET imaging with 18F-fluorodeoxyglucaric acid

10.1101/2021.06.01.446662 ◽

2021 ◽

Author(s):

Hibah O Awwad ◽

Andria Hedrick ◽

Alex Mdzinarishvili ◽

Hailey Houson ◽

Kelly Standifer ◽

...

Keyword(s):

Traumatic Brain Injury ◽

Brain Injury ◽

Hemorrhagic Shock ◽

Tissue Injury ◽

Brain Lesion ◽

Lesion Size ◽

Neurological Deficits ◽

Lesion Volume ◽

Sprague Dawley ◽

The Impact

Traumatic brain injury (TBI)is a major cause of death and disability worldwide. Hemorrhagic shock (HS) aggravates tissue injury and complicates TBI recovery. We studied the combined insult of mild TBI and HS and investigated the impact of varying loss of blood volume on neurologic deficit and brain lesion volume. A novel positron emission tomography (PET) technique was employed to monitor tissue injury. Male Sprague Dawley rats received mTBI by controlled cortical impact (CCI) followed by withdrawal of 0%, 30-40%, 45%, or 50% of blood (mTBI, mTBI+HS≤40%, mTBI+HS45%, and mTBI+HS50%, respectively). Neurological deficit (mNSS= 5.6, 7.6, and 12.3) and mortality (2/12, 2/6, and 7/12) were higher in mTBI+HS≤40%, mTBI+HS45%, and mTBI+HS50%, than in mTBI alone rats (no death; mNSS=3.3). Histologic lesion size increased 3.5-fold in mTBI+HS50% compared to mTBI alone and the infarct-avid PET agent 18F-fluorodeoxyglucaric acid (FGA) proportionately detected tissue necrosis in mTBI+HS50% rats. Based on these results, we conclude that HS aggravates mTBI-induced neurological deficits, tissue injury and mortality. PET using 18F-FGA as an imaging marker can detect the extent of injury in a non-invasive manner.

Download Full-text