Ablation Point Research Articles

Additional Lesion Sets in Ablation of Outflow Tract Premature Ventricular Contractions

Recurrence remains a challenge after ablation of outflow tract premature ventricular contractions (OT-PVCs). Although adding additional lesions next to the index effective ablation site is sometimes performed to reinforce the ablation, it remains uncertain whether this approach is effective. To test the hypothesis that additional ablation lesions would reduce the recurrence rate compared with single-point ablation at the index effective site for the ablation of OT-PVCs. This study was a multicenter, prospective, randomized clinical trial. Patients receiving their first catheter ablation for OT-PVCs were enrolled from 18 hospitals in China between October 2021 and February 2023. Scheduled follow-up duration was 3 months after the procedure. After identifying the target point and eliminating the PVC by a single-point ablation, patients were randomized 1:1 into an additional ablation group or a control group. The primary end point of the study was freedom from PVC recurrence (≥80% reduction of PVC burden, which is the number of PVCs in 24 hours/total heartbeats in 24 hours × 100%) from baseline to 3 months postprocedure. Of 308 patients enrolled in the study, 286 (mean [SD] age, 49.2 [14.6] years; 173 female [60.5%]) were randomized to the additional ablation or the control group. The additional ablation group had a mean (SD) of 6.3 (1.1) radiofrequency applications, whereas the control group (single-point ablation group) had a mean (SD) of 1 (0) radiofrequency application. After a median (IQR) follow-up of 3.2 (0) months, the rate of freedom from PVCs was significantly higher in the additional ablation group (139 of 142 [97.9%]) compared with the control group (115 of 139 [82.7%]; P < .001). Patients in the additional ablation group also had a more substantial reduction in PVC burden than the control group (mean [SD] reduction, 23.0% [10.5%] vs 19.0% [10.4%]; P = .002). There were no severe periprocedural complications in either group. This randomized clinical trial showed a benefit of additional ablation in reducing the recurrence of OT-PVCs compared with the single-point ablation strategy, without increased complication risk. Additional ablations surrounding the index effective ablation point should be considered in OT-PVC ablation. Chinese Clinical Trials Registry Identifier: ChiCTR2200055340.

Evaluation of microembolic signals on carotid ultrasound during pulmonary vein isolation with high-power short-duration and cryoballoon ablations: When and where do bubble and solid emboli arise?

The underlying risks of asymptomatic embolization during high-power short-duration (HPSD) ablation for atrial fibrillation remain unclear. We aimed to evaluate microembolic signals (MESs) during HPSD ablation with power settings of 50and 90 W in comparison with those during cryoballoon (CB) ablation using a novel carotid ultrasound-Doppler system that classifies solid and air bubble signals using real-time monitoring. Forty-seven patients underwent HPSD ablation using radiofrequency (RF), and 13 underwent CB ablation. MESs were evaluated using a novel pastable soft ultrasound probe equipped with a carotid ultrasound during pulmonary vein isolation. We compared the detailed MESs and their timing between RF and CB ablations. The number of MESs and solid signals were significantly higher in the RF group than in CB group (209 ± 229 vs. 79 ± 32, p = .047, and 83 ± 89 vs. 28 ± 17, p = .032, respectively). In RF ablation, the number of MESs, solid, and bubble signals per ablation point, or per second, was significantly higher at 90 W than at 50 W ablation. The MESs, solid, and bubble signals were detected more frequently in the bottom and anterior walls of the left pulmonary vein (LPV) ablation. In contrast, many MESs were observed before the first CB application and decreased chronologically as the procedure progressed. Signals were more prevalent during the CB interval rather than during the freezing time. Among the 28 patients, 4 exhibited a high-intensity area on postbrain magnetic resonance imaging (MRI). The MRI-positive group showed a trend of larger signal sizes than did the MRI-negative group. The number of MESs was higher in the HPSD RF group than in the CB group, with this risk being more pronounced in the 90 W ablation group. The primary detection site was the anterior wall of the LPV in RF and the first interval in CB ablation.

The procedural characteristics of radiofrequency ablation points in patients undergoing atrial fibrillation ablation: comparison between standard vs very high-power short-duration

Abstract Introduction Atrial fibrillation ablation has a central role in the treatment of atrial fibrillation. Radiofrequency (RF) ablation is one of the possible energy sources used for the procedure. Recently, the development of new catheters has made it possible to modify the amount of power delivered by moving from a standard ablation to a very high-power short-duration (VHPSD). The objective of the study is to compare the delivery features of the RF points between standard RF vs VHPSD. Methods All the patients underwent RF ablation of paroxysmal atrial fibrillation. The procedure was performed using an electroanatomical mapping system under conscious sedation. All patient received a heparin bolus for ACT&amp;gt;300. The anatomy of the left atrium was reconstructed with a high-density catheter. Radiofrequency (RF) was applied following a wide antral circumferential approach (WACA) obtaining the isolation of the veins. The use of the ablation catheter was at the discretion of the operator and the choice was between a standard open-irrigated catheter with force sensor (Smartouch SF) and an irrigated, temperature-controlled contact-force sensing capable of delivering VHPSD (QDOT MICRO). For every patient, data from each individual RF delivery point were collected and analysed. Results A total of 72 consecutive patients were collected (26 QDOT group vs 46 standard group). Average total number of ablation point for obtaining complete pulmonary vein isolation with WACA was lower in the QDOT group (QDOT group 37,8±11 vs 42,1±18 standard group). As expected, the average duration (QDOT group 3.9±0.1s vs 12.7±2.4s standard group) and the average power delivered was significantly different between the two group (QDOT group 89,8±0.8W vs 33.0±1.4W standard group). Average basal impedence was similar (QDOT group 133.2±11,6 ohm vs 122.4±11,4ohm standard group) while impedence drop was significantly different (QDOT group 12.2±2.4 vs 9.9±2.4s standard group). Conclusion VHPSD ablation allows isolation of the pulmonary veins to be achieved with fewer ablation points and more quickly. It is also associated with a greater impedence drop during delivery. More studies are needed to see if this also corresponds to a lower number of recurrences after ablation.

Incidence and predictors of thermal oesophageal and vagus nerve injuries in Ablation Index-guided high-power-short-duration ablation of atrial fibrillation: a prospective study.

High-power-short-duration (HPSD) ablation is an effective treatment for atrial fibrillation but poses risks of thermal injuries to the oesophagus and vagus nerve. This study aims to investigate incidence and predictors of thermal injuries, employing machine learning. A prospective observational study was conducted at Leipzig Heart Centre, Germany, excluding patients with multiple prior ablations. All patients received Ablation Index-guided HPSD ablation and subsequent oesophagogastroduodenoscopy. A machine learning algorithm categorized ablation points by atrial location and analysed ablation data, including Ablation Index, focusing on the posterior wall. The study is registered in clinicaltrials.gov (NCT05709756). Between February 2021 and August 2023, 238 patients were enrolled, of whom 18 (7.6%; nine oesophagus, eight vagus nerve, one both) developed thermal injuries, including eight oesophageal erythemata, two ulcers, and no fistula. Higher mean force (15.8 ± 3.9 g vs. 13.6 ± 3.9 g, P = 0.022), ablation point quantity (61.50 ± 20.45 vs. 48.16 ± 19.60, P = 0.007), and total and maximum Ablation Index (24 114 ± 8765 vs. 18 894 ± 7863, P = 0.008; 499 ± 95 vs. 473 ± 44, P = 0.04, respectively) at the posterior wall, but not oesophagus location, correlated significantly with thermal injury occurrence. Patients with thermal injuries had significantly lower distances between left atrium and oesophagus (3.0 ± 1.5 mm vs. 4.4 ± 2.1 mm, P = 0.012) and smaller atrial surface areas (24.9 ± 6.5 cm2 vs. 29.5 ± 7.5 cm2, P = 0.032). The low thermal lesion's rate (7.6%) during Ablation Index-guided HPSD ablation for atrial fibrillation is noteworthy. Machine learning based ablation data analysis identified several potential predictors of thermal injuries. The correlation between machine learning output and injury development suggests the potential for a clinical tool to enhance procedural safety.

Difference in radiofrequency ablation profile between during sinus rhythm and atrial fibrillation: Considerations in this era of high‐power short‐duration strategy

AbstractBackgroundThe concept of ablation index (AI) was introduced to evaluate radiofrequency (RF) ablation lesions. It is calculated from power, contact force (CF), and RF duration. However, other factors may also affect the quality of ablation lesions. To examine the difference in RF lesions made during sinus rhythm (SR) and atrial fibrillation (AF).MethodsSixty patients underwent index pulmonary vein isolation during SR (n = 30, SR group) or AF (n = 30, AF group). All ablations were performed with a power of 50 W, a targeted CF of 5–15 g, and AI of 400–450 using Thermocool Smarttouch SF. The CF, AI, RF duration, temperature rise (Δtemp), impedance drop (Δimp), and the CF stability of each ablation point quantified as the standard deviation of the CF (CF‐SD) were compared between the two groups.ResultsA total of 3579 ablation points were analyzed, which included 1618 and 1961 points in the SR and the AF groups, respectively. Power, average CF, RF duration per point, and the resultant AI (389 ± 59 vs. 388 ± 57) were similar for the two rhythms. However, differences were seen in the CF‐SD (3.5 ± 2.2 vs. 3.8 ± 2.1 g, p &lt; .01), Δtemp (3.8 ± 1.3 vs. 4.0 ± 1.3°C, p &lt; .005), and Δimp (10.3 ± 5.8 vs. 9.4 ± 5.4 Ω, p &lt; .005).ConclusionsDespite similar AI, various RF parameters differed according to the underlying atrial rhythm. Ablation delivered during SR demonstrated less CF variability and temperature increase and greater impedance drop than during AF.

Transcatheter occlusion of the coronary sinus increases radiofrequency ablation lesion size in the left ventricular myocardium: a new approach to improve the efficiency of ventricular tachyarrhythmia substrate destruction

The aim. The results of ventricular tachyarrhythmia catheter ablation in patients with structural heart diseases remains to be improved. Both evolution of the arrhythmia substrate and its deep location are the main reasons for standard endocardial ablation limitations. Theoretically, the reduction of myocardial perfusion rate may improve convective heating of the myocardium during radiofrequency (RF) ablation, expanding the volume of damage. The purpose of this study was to assess the effect of coronary sinus (CS) occlusion in order to reduce myocardial perfusion during RF ablation on the volume of myocardial damage.Methods. The study was performed on 13 pigs. Following vascular access accomplishment, a balloon catheter was inserted into the lumen of the CS. A 3.5-mm open-irrigated RF ablation catheter was inserted into the cavity of the left ventricle. RF applications were applied in an alternate order, with and without CS occlusion (power 30 and 40W, application time 40 and 30 s, respectively). Each ablation point was marked on a three-dimensional electroanatomic map. After euthanasia, myocardial lesions were analyzed.Results. The analysis of 50 RF applications was performed (22 with CS occlusion and 28 without CS occlusion). At the same time, 28 applications (13 with occlusion and 15 without occlusion) were performed at a power of 40W, and 22 applications (9 with occlusion and 13 without occlusion) at a power of 30 watts. There was a trend toward the increase in lesion sizes created during CS occlusion. Significantly larger lesions were detected with 40W applications during CS occlusion when compared with open CS applications: depth 11.6±3.9 vs. 8.8±3.8 mm (p=0.04), diameter 11.7±4.6 vs. 8.5±3.9 mm (p=0.03), volume 504.2±499.5 vs. 183.0±157.5 mm3 (p=0.01). Transmural myocardial lesions were more often encountered during applications with CS occlusion with both power settings, 30 and 40W: 68.2% of transmural lesions versus 39.3%; p=0.046.Conclusion. RF applications with a power of 40W and CS occlusion are characterized by greater depth, diameter, and volume of damage, as well as a greater frequency of transmural necrosis. Temporary transcatheter occlusion of CS can be proposed for ablation of ventricular arrhythmia with extended and deep substrate.

Safety of YAG laser vitreolysis for intraocular tissues: analysis of postoperative complications

PurposeTo evaluate the safety of yttrium–aluminum-garnet (YAG) laser vitreolysis for intraocular tissues.MethodsThirty-six New Zealand rabbits were divided as follows: Group 1000 (n = 12) treated with YAG laser of 1000 mJ (5 mJ × 200 shots), Group 2000 (n = 12) treated with YAG laser of 2000 mJ (5 mJ × 400 shots), Group 3000 (n = 12) treated with YAG laser of 3000 mJ (5 mJ × 600 shots). Either a single eye was chosen as the study eye in study groups while the other was untreated as the control group. Intraocular pressure (IOP), slit-lamp, optical coherence tomography (OCT), transmission electron microscopy (TEM), and inflammatory cytokines of aqueous humor (interleukin-1α (IL-1α), interleukin-1β (IL-1β), interleukin-8 (IL-8), and tumor necrosis factor-α (TNF-α)) were performed to examine the rabbits.ResultsThere were no abnormalities in the study groups of IOP, slit-lamp, and OCT examinations. Group 3000 of TEM showed: neutrophils and mitochondrial swelling on day 1, and fibroblasts and neocollagen on day 14. No abnormalities were observed in Group 1000 and 2000 of TEM. Levels of IL-1α and TNF-α increased at 12 h and decreased to baseline on day 3. Levels of IL-1β increased at 12 h and decreased to baseline on day 7. Levels of IL-8 increased on day 1 and decreased to baseline on day 3.ConclusionYAG laser vitreolysis is safe when the distance is more than 2 mm from ablation point to the lens and the retina, and the total energy is less than 2000 mJ for one treatment procedure.

A novel esophageal retractor with eccentric balloon during atrial fibrillation ablation.

Due to the anatomically adjacent relationship between the left atrium (LA) and esophagus, energy delivery on the posterior wall of LA is limited. The aim of this study was to evaluate the feasibility of a novel esophageal retractor (SAFER) with an inflatable C-curve balloon during atrial fibrillation (AF) ablation. Nine patients underwent AF ablation assisted with the SAFER. After inflation, the esophagus was deviated laterally away from the intended ablation site of the posterior wall under local anesthesia. The extent of mechanical esophageal deviation (MED) was evaluated under fluoroscopy, defined as the shortest distance from the trailing esophageal edge to the closest point of the ablation line. Gastroscopy was performed before and after ablation. The target ablation index used in all LA sites including the posterior wall was 400-450 after effective MED. All adverse events during the periprocedural period were recorded. The mean deviation distance achieved 16.2±9.6mm away from the closest ablation point of the pulmonary vein lesion set. With respect to the individual left and right pulmonary vein lesion sets, the deviation distance was 19.7±11.5 and 12.7±6.8mm, respectively. The extent of deviation was 0 to 5mm, 5.1 to 10mm, or>10mm in 0(0%), 7(38.9%), and 11(61.1%), respectively. Procedural success was achieved in all patients without acute reconnection. There was only one esophageal complication which manifested as esophageal erosion and this patient experienced throat pain possibly related to the SAFER retractor with no clinical sequelae. Esophageal deviation with the novel eccentric balloon is a novel feasible choice during AF ablation, enabling adequate energy delivery to the posterior wall of LA. Additional prospective randomized controlled studies are required for further validation.

Dynamics of local unipolar electrograms during epicardial pulsed field ablation (PFA)

Abstract Funding Acknowledgements Type of funding sources: Public Institution(s). Main funding source(s): Instituto de Salud Carlos III Background The use of irreversible electroporation (IRE) as a method for cardiac ablation in the treatment of cardiac arrhythmias, known as Pulsed Field Ablation (PFA), has rapidly moved from preclinical studies to clinic. The reference indicator of acute lesion formation during cardiac ablation with thermal techniques consists in recording the local electrical activity changes. In the case of PFA, modifications in the electrical activity have been observed in areas that are not permanently damaged (reversible electroporation) but this is still poorly characterized. Of particular interest from a clinical perspective is to determine how and when the electrical activity of the reversible electroporation areas recovers after PFA. Purpose The purpose of this work was to simultaneously characterize the dynamic evolution of local electrograms after PFA in areas exposed to different levels of tissue damage. Methods High-density local unipolar electrograms were acquired at baseline, and continuously and during 60 min after each PFA application. The measurements were performed in different points of the right and left ventricular epicardial surface of 5 swine weighing 57±8 kg using an open-chest approach following the Principles of laboratory animal care" (NIH Publication no. 85-23 revised 1985). Under general anesthesia, a median sternotomy was made to create a surgical window. Unipolar electrograms were recorded using a 128-channel electrode matrix attached to the epicardial surface. For PFA ablation, a standard 8F, 3.5 mm tip monopolar catheter was positioned in the region corresponding to the center of the electrode array and a return electrode patch was attached to the back of the animals (see Fig. 1). At least 3 hours after the last ablation point, animals were euthanized and tissue was processed and stained with Triphenyltetrazolium Chloride (TTC) to assess acute lesion morphology. Results Our results show an immediate change in the morphology of unipolar electrograms: from basal biphasic electrograms to monophasic electrograms displaying a sudden ST-segment elevation (from 0.0±0.3 mV to 5.9±1.7mv; p&amp;lt;0.01), reduction in the R-S amplitude (from 3.4±3.3 mV to 0.3±0.2 mV; p&amp;lt;0.01) and reduction in the maximum derivative of the QRS-complex (from 3051±2473 mV/s to 394±242 mV/s; p&amp;lt;0.01). Interestingly, the extent and dynamics of the observed changes clearly depended on the ablation level (distance from the ablation point) (see Fig 2.). Conclusions Our observations confirmed that the electrical activity of the reversible electroporation area was also acutely modified while the recovery dynamics were different from the irreversible damaged areas. Our preliminary analysis suggests that the different recovery dynamics observed could help in differentiating between reversible and irreversible electroporation areas.

Local impedance tissue characterization to implement pulmonary veins isolation success in AF patients

Abstract Funding Acknowledgements Type of funding sources: None. Background Novel radiofrequency (RF) ablation technology permits local impedance (LI) assessment, enabling increased knowledge of the underlying tissue’s properties. In addition, LI can provide details on catheter tip contact and extent/effectiveness of radiofrequency (RF) delivery. To date, the extent to which left atrial (LA) tissue characterization by LI can guide RF ablation has not yet been explored. Purpose We aimed to assess LI capabilities of predicting RF ablation success in consecutive AF cases with different underlying cardiac tissue characteristics. Methods Two-hundred twelve consecutive patients undergoing de novo AF ablation at 16 European centers were included in the CHARISMA registry. A novel ablation catheter (Stablepoint) with dedicated algorithm (DirectSense) was used to measure LI at the distal electrode. Each ablation point was characterized in terms of RF delivery time, baseline LI and LI drop during ablation according to different atrial substrates: normal-voltage (NV, &amp;gt;0.5mV), intermediate-voltage (IV, 0.1-0.5mV) and low-voltage tissue (LV, &amp;lt;0.1mV). First pass isolation (FPI) was defined as successful PVI at or before completion of the first encircling lesion set regardless of visual gaps. Ablation endpoint was pulmonary vein isolation (PVI) as assessed by entrance and exit block. Data are reported as mean±SD. Results Atrial substrate was analyzed at 11405 (82%) sites with complete high-quality data. Ablation spots were more frequently deployed in NV areas (n=6714, 58.9%) than in areas of IV (n=4065, 35.6%) or LV (n=625, 5.5%). Both baseline LI (163.8±19Ω) and LI drop (23.0±9Ω) were higher in NV areas than in IV areas (baseline LI: 159.4±18Ω, p&amp;lt;0.0001; LI drop: 20.5±9Ω, p&amp;lt;0.0001) and LV areas (baseline LI: 157.8±18Ω, p&amp;lt;0.0001; LI drop: 19.5±9Ω, p&amp;lt;0.0001). RF delivery time was shorter in the NV (9±5s) than both in IV and LV areas (10±4s, p&amp;lt;0.0001 for IV; 10±4s, p&amp;lt;0.0001 for LV, respectively). The LI drop that best predicted successful ablation spots was &amp;gt;20Ω for NV areas (Sensitivity=62.5%, Specificity=91.5%, PPV=99.6%, Area under the receiver-operating characteristic curve (AUC)=0.7896, p&amp;lt;0.0001) and &amp;gt;18Ω for IV and LV areas (Sensitivity=57.7%, Specificity=94.6%, PPV=99.8%, AUC=0.8008, p&amp;lt;0.0001). No complication occurred. The acute procedural success was 100%, with all PVs successfully isolated in all study patients. Conclusion LI drop during ablation significantly differs according to atrial substrates. These findings suggest that a tailored AF ablation strategy taking into account the underling LA substrate may be useful.

Quantitative late gadolinium enhancement cardiac magnetic resonance analysis of the relationship between ablation parameter and left atrial tissue lesion following pulmonary vein isolation.

The impact of ablation parameters on acute tissue lesion formation after pulmonary vein isolation (PVI) has not been sufficiently evaluated in patients with atrial fibrillation. Radiofrequency ablation lesion can be visualized by late gadolinium enhancement cardiac magnetic resonance (LGE-CMR). We sought to quantitatively analyze the relationship between ablation parameter and tissue lesion following PVI at different segments of pulmonary vein (PV) using LGE-CMR. Twenty-one patients with atrial fibrillation who underwent PVI procedure were retrospectively enrolled. All patients underwent LGE-CMR examination within 3 days after radiofrequency ablation. Ablation parameters during PVI were documented, including lesion size index (LSI), force-time integral (FTI), power, contact force, temperature, and time of duration. The ablation point was projected onto 3-dimensional (3D) left atrial shell constructed base on LGE-CMR and corresponding image intensity ratio (IIR) was calculated on the same shell. A tissue lesion point was defined when the LGE-CMR IIR was > 1.2. In total, 1,759 ablation points were analyzed. The ablation parameters and IIRs for each PV segment were significantly different (P < 0.0001). IIRs corresponding to ablation points at posterior of PV tended to be higher than those at non-posterior of PV when similar ablation parameters were applied during ablation. LSI was a better predictor of tissue lesion existence following PVI than FTI, contact force, power, temperature, and duration time at non-posterior wall of PV. The IIR showed positive correlation with LSI at non-posterior wall of PV (non-posterior of right PV, r = 0.13, P = 0.001, non-posterior of left PV, r = 0.26, P < 0.0001). When similar ablation parameters were applied during PVI, the posterior wall of PV had more severe tissue lesion than non-posterior wall of PV. Therefore, it was reasonable to decrease ablation energy at posterior wall of PV. Moreover, LSI was a better index to reflect tissue lesion quality following PVI at non-posterior of PV.

Predictors of Lesions Contiguity and Transmurality in Canine Ventricular Models After Catheter Ablation.

BackgroundInterlesion gaps and transmurality of lesions after catheter ablation can precipitate suboptimal efficacy in preventing arrhythmias.AimsWe aim to assess predictors of acute transmural lesion formation and the interlesion distance threshold for creating a continuous, chronic scar after ventricular ablation.Materials and MethodsAblation procedures were performed on 7 canines followed by late gadolinium enhancement MRI (LGE-MRI). Transmurality of lesions was assessed by 2 independent operators. Ablation parameters such as duration (s), power (W), temperature (C), contact force (CF) (g), were collected for each ablation point. After 7-12 weeks, LGE-MRI was performed, followed by euthanasia, and heart excision. Some lesions were created in pair. Lesion pairs were spaced 7-21 mm apart as measured by Electroanatomic mapping (EAM), with different operating parameters (power 35 or 50W, duration of energy delivery 10, 20 or 30s and contact force of 10g or above). We performed a logistic regression analysis to determine predictors of transmural lesion formation.ResultsEighty-one radiofrequency ablation were performed in total [33 in the Left ventricle (LV) and 48 in the Right ventricle (RV)]. Higher CF was a significant predictor of transmural lesion formation (β = 0.15, OR = 1.16, 95% CI [1.03 – 1.3], p = 0.01), and lesions delivered in the RV were more frequently transmural than lesions delivered in the LV (β = −2.43, OR = 0.09, 95%CI [0.02 – 0.34], p < 0.001). For the paired analysis, thirty-eight lesions were created contiguously: fourteen connected lesions and twenty-four unconnected lesions. EAM distance was significantly larger in unconnected lesions than connected lesions (16.17 ± 0.92 mm vs. 11.51 ± 0.68 mm, respectively, p < 0.05). We concluded that an interlesion distance of less than 10 mm is required to prevent gap formation. Average volumes in unconnected lesions (n = 24) at the acute and chronic stages were 0.55 ± 0.11 cm3 and 0.20 ± 0.02 cm3, respectively. On average, lesion volumes were 64% (p < 0.05) smaller at the chronic stage compared to the acute stage. Among connected lesions (n = 14), we observed a volume of 1.19 ± 0.8 cm3 and 0.39 ± 0.15 cm3 at the acute and chronic stages, respectively. These connected lesions reduced in volume by 67% on average.ConclusionTo create contiguous scars on the ventricular endocardial surface, paired lesions should be spaced less than ten millimeters apart. Higher contact force should be used in ventricular ablation to create transmural lesions.

A novel local impedance algorithm to guide effective pulmonary vein isolation in AF patients: preliminary experience among different voltages of atrial substrate

Abstract Funding Acknowledgements Type of funding sources: None. Background Recently, a novel technology able to measure local tissue impedance (LI) and contact force (CF) aimed at validating ablation endpoints has become available for clinical use. Purpose This analysis explores the relationship between LI parameters, substrate characteristics and AF type during ablation in AF patients. Methods A novel ablation catheter with dedicated algorithm was used to measure LI at the distal electrode. Each ablation point was characterized in terms of RF delivery time, baseline LI and LI drop during ablation according to different voltages (above or below 0.5 mV) of the atrial substrate. Ablation endpoint was PVI as assessed by entrance and exit block with local capture. Data are reported as mean±SD. Results A total of 2032 RFC deliveries from 34 consecutive patients were analyzed (71% paroxysmal AF, 29% persistent AF). All PVs were successfully isolated with an overall procedure time of 128±33min (fluoroscopy time=15.6±9min, RF delivery time=9.6±4s, CF=11.1±7g). The baseline LI was 155±17Ω prior to ablation and 136±14Ω after ablation (p&amp;lt;0.0001, absolute LI drop of 21.0±8Ω) with a LI drop rate equal to 2.8±2Ω/s. Ablation spots were more frequently deployed in high-voltage areas (&amp;gt;0.5mv, n=1240, 61%). Baseline LI and LI drops were both higher when underlying atrial voltages were &amp;gt;0.5mV than when &amp;lt;0.5mV (156±18Ω vs 153.6±16Ω for starting LI, p=0.0032; 22.2±8Ω vs 19.1±8Ω for LI drop, p&amp;lt;0.0001, respectively). No differences were found in terms of both CF and LI after ablation between &amp;gt;0.5mV and &amp;lt;0.5mV (11.0±7g vs 11.2±7g for CF, p=0.3435; 136.4±13Ω vs 135.3±15Ω for ablated tissue LI, p=0.1521, respectively). Low-voltage areas were more frequently detected at ablated spots in persistent AF cases (n=288, 51.9%) than in paroxysmal AF cases (n=504, 35.1%, p&amp;lt;0.0001), however, no differences were found in terms of both baseline LI and LI drop between persistent and paroxysmal AF cases (156.3±17Ω vs 154.6±17Ω for starting LI, p=0.135; 20.7±8Ω vs 21.1±9Ω for LI drop, p=0.1722, respectively). Conclusions LI measurements well distinguished contact with high-voltage areas from low-voltage areas and were able to detect significant differences in LI drop during ablation according to the voltage level.

Feeding Vessel Ablation: A Novel Subsegmental Devascularization Technique for the Treatment of Hepatocellular Carcinoma Located at the Liver Marginal Angle.

This pilot clinical study evaluated primarily the efficacy of feeding vessel ablation (FVA) in the treatment of hepatocellular carcinoma (HCC) located at the liver marginal angle (LMA). Nine patients with nine unresectable HCC lesions were prospectively included in this study. The target tumors (mean: 3.0 cm, interquartile range: 2.4-3.6 cm) were located at the LMA (segment 2/3/6) and adjacent to the gastrointestinal tract. Artificial ascites was attempted and failed. Multimode ultrasound technologies, including 2-D and real-time 3-D contrast-enhanced ultrasound, were used to identify the morphology and structure of the feeding vessels for the target tumors. During the treatment, a unipolar cool-tip electrode was used to ablate the feeding vessels, and the target ablation point was set in subsegmental or more distal vessels to induce a downstream ischemia region. Therapeutic outcomes were assessed after FVA, including the rates of technical success, tumor response, local tumor progression (LTP), overall survival (OS) and major complications. Cumulative LTP and OS were estimated with the Kaplan-Meier method. The technical success rate determined immediately after radiofrequency ablation was 7 of 9 (77.8%). Complete response (CR) was achieved in 7 of 7 tumors (100%) at the 1-mo evaluation. During a median follow-up period of 15.6 mo (range: 4.3-53.3 mo), CR remained in 6 of 7 tumors (85.7%), with LTP observed in 1 of 7 tumors (14.3%) 4.7 mo after treatment. The cumulative 1-, 3- and 5-y LTP-free rates were all 83.3%, and the cumulative 1-, 3- and 5-y OS rates were 42.9%, 28.6% and 0%, respectively. No major complications occurred. We concluded that FVA can induce subsegmental devascularization and has the potential to serve as an effective and safe alternative technique for local control of unresectable HCC located at the LMA when artificial ascites fails.

Pulsed Laser Deposition of CsPbBr3 Films: Impact of the Composition of the Target and Mass Distribution in the Plasma Plume.

All-inorganic cesium lead bromine (CsPbBr3) perovskites have gained a tremendous potential in optoelectronics due to interesting photophysical properties and much better stability than the hybrid counterparts. Although pulsed laser deposition (PLD) is a promising alternative to solvent-based and/or thermal deposition approaches due to its versatility in depositing multi-elemental materials, deep understanding of the implications of both target composition and PLD mechanisms on the properties of CsPbBr3 films is still missing. In this paper, we deal with thermally assisted preparation of mechano-chemically synthesized CsPbBr3 ablation targets to grow CsPbBr3 films by PLD at the fluence 2 J/cm2. We study both Cs rich- and stoichiometric PbBr2-CsBr mixture-based ablation targets and point out compositional deviations of the associated films resulting from the mass distribution of the PLD-generated plasma plume. Contrary to the conventional meaning that PLD guarantees congruent elemental transfer from the target to the substrate, our study demonstrates cation off-stoichiometry of PLD-grown CsPbBr3 films depending on composition and thermal treatment of the ablation target. The implications of the observed enrichment in the heavier element (Pb) and deficiency in the lighter element (Br) of the PLD-grown films are discussed in terms of optical response and with the perspective of providing operative guidelines and future PLD-deposition strategies of inorganic perovskites.

Investigation of the blast pressure following laser ablation at a solid–fluid interface using shock waves dynamics in air and in water

Simple and universal relations between the laser pulse energy of the third harmonic of a Nd:YAG laser source (5 ns) and the pressure at the ablation point are investigated for the ablation of a solid target in air and in water. Shockwaves propagation are reconstructed using time-resolved shadowgraph imaging. The propagation in air is well-described by Taylor–von Neumann–Sedov’s theory for over-pressure at the shock front larger than ten times the atmospheric pressure, but the energy distribution appears to be anisotropic and mostly directed in the normal direction to the target’s surface. We compare the pressure at the shock front deduced from its velocity using Rankine–Hugoniot’s relation with the pressure deduced from Taylor’s model only related to the laser pulse energy. Rankine–Hugoniot’s relation appears more appropriate to evaluate the early pressure in the plasma plume. The shockwaves velocity in water is hyper-sonic during 50 ns and then reaches the sound velocity. Pressure values at the shock front are compared using two different approaches accounting for different state’s equations, namely the Rice and Walsh’s equation and Tait’s equation. In both cases, the ablation pressure is found out to reach several GPa and increases as the square root of the laser intensity.

Surface flashover patterns of GIS basin insulator under impulse voltage

Basin insulator is an important component of SF6 gas insulated switchgear (GIS), and its fault is also one of the major causes of GIS equipment failure. Due to the large capacity of high voltage power system, the faulty basin insulators are generally burned severely by the high energy arc, so the fault diagnosis is very difficult. In this paper, the surface flashover pictures of several full-scaled GIS basin insulators under impulse voltage are collected, and the morphology features of flashover traces initiating from different positions are summarized. As a result, the surface flashover patterns are divided into three types: 1) surface of shielding electrode initiated flashover, 2) triple junction initiated flashover and 3) surface of insulator initiated flashover. The inception and development process of flashover are also summarized. Besides, the diagnosis method of discharge inception position is proposed. Firstly, check the ablation points at high voltage terminal. If there is a ablation point on the surface of shielding electrode, the flashover initiates from there. If there is only ablation point at the triple junction, the inception position depends on the flashover trace morphology: when the flashover trace disperses in a single direction towards grounding electrode or high voltage electrode, the flashover initiates from the opposite triple junction; when the flashover trace disperses towards both electrodes, the flashover initiates from the insulator surface. The dispersion direction could be directly distinguished from the black carbonized dendritic traces, or from the “white dendritic traces” with the auxiliary methods. The conclusions could help the substation maintenance staff do the root cause analysis of the surface flashover, and assist the researchers in the structural optimization design of basin insulator.

Dynamic, Adaptive Inline Process Monitoring for Laser Material Processing by Means of Low Coherence Interferometry

Surface laser structuring of electrical steel sheets can be used to manipulate their magnetic properties, such as energy losses and contribute to a more efficient use. This requires a technology such as low coherence interferometry, which makes it possible to be coupled directly into the existing beam path of the process laser and enables the possibility for an 100% inspection during the process. It opens the possibility of measuring directly in the machine, without removing the workpiece, as well as during the machining process. One of the biggest challenges in integrating an LCI measurement system into an existing machine is the need to use a different wavelength than the one for which the optical components were designed. This results in an offset between the measurement and processing spot. By integrating an additional scanning system exclusively for the measuring beam and developing a compensation model for the non-linear spot offset, this can be adaptively corrected by up to 98.9% so that the ablation point can be measured. The simulation model can also be easily applied to other systems with different components and at the same time allows further options for in-line quality assurance.

B-PO05-133 ROLE OF ELECTROGRAMS RECORDED FROM THE MINI ELECTRODES IN CATHETER ABLATION OF ATRIOVENTRICULAR NODAL REENTRANT TACHYCARDIA

Analysis of electrograms recorded from mini electrodes (MEs) (IntellaTip MiFi, Boston Scientific) has not been reported. We evaluated the additional value of MEs during ablation of atrioventricular nodal reentrant tachycardia (AVNRT). Consecutive patients with AVNRT who underwent slow pathway ablation using a MiFi catheter were included. A combined electroanatomic approach was used to identify the target site. During ablation, operators were blind to ME electrograms, and ME electrograms immediately before initiation of the first radiofrequency (RF) application were evaluated retrospectively. A total of 62 patients (47 ± 17 years, 46.8% male) with typical (n=58) and atypical (n=4) AVNRT were included. Slow pathway ablation or modification was achieved in all patients. Thirty-two patients (51.6%) showed accelerated junctional rhythm (JR) during the first RF application. Immediately before the first RF, atrial signals at the MEs were observed in 37 patients (59.7%). There was a significant association between presence of atrial signals in MEs and the occurrence of JR (OR 5.36, P=0.002). The positive and negative predictive values of the atrial signals in MEs for the JR induction during the first RF were 67.6% (25/37) and 72.0% (18/25), respectively. Amplitudes of atrial signals of the MEs were not different between patients with and without an inducible JR (0.20 ± 0.13 mV versus 0.14 ± 0.11 mV, P=0.18). Signals recorded from the MEs could be helpful in targeting the ablation point during slow pathway ablation. Ablation should be discouraged in regions with optimal bipolar electrograms not followed by adequate ME electrograms.

The pitfalls of unipolar voltage mapping of the right ventricle

Abstract Funding Acknowledgements Type of funding sources: Other. Main funding source(s): The department of cardiology from Leiden University Medical Center receives unrestricted grants from Edwards Lifesciences, Biotronik, Medtronik, Boston Scientific and BioSense Webster. MS was supported by the Research Fellowship of the European Society of Cardiology 2017/2018. Background The current golden standard to accurately delineate scar potentially related to ventricular tachycardia relies on electroanatomical voltage mapping. Endocardial unipolar voltage (UV) mapping is increasingly used to detect intramural or subepicardial non-ischemic scars. 3D mapping systems determine and display the largest peak-to-peak amplitude of the electrogram within the window-of interest usually set from the QRS onset, but cannot not identify far-field electrograms or artifacts. Purpose To evaluate the influence of manual adjustment of the window-of-interest on the amplitude of endocardial and epicardial right ventricular (RV) unipolar electrograms. Methods Patients who underwent ablation of a RV scar-related VT with combined endo- and epicardial RV mapping were included. Endo- and epicardial points were reviewed with special interest towards the unipolar signal. In case a far-field, ST-segment elevation/depression or artifact was present, the window-of-interest was adjusted and the corresponding unipolar amplitude was collected. Results Thirty-three patients were included (age 50 ± 14years and 79% male). The underlying aetiology was definite arrhythmogenic right ventricular cardiomyopathy (ARVC; n = 17), athlete’s right ventricular outflow tract scar in (n = 9), cardiac sarcoidosis in (n = 3), scar of unknown origin (n = 2), borderline ARVC (n = 1) or myocarditis (n = 1). In total, 4225 endocardial points and 1960 epicardial points were re-analyzed. In 2987 (71%) endocardial points and 689 (65%) epicardial points the window-of-interest needed to be adjusted. Reason for this adjustment was ‘inclusion of far-field’ in 1380 (33%) endocardial- and 700 (36%) epicardial points; ‘inclusion of ST-segment elevation/depression’ in 1246 (29%) endocardial- and 316 (16%) epicardial points; RV-pacing artefact in 266 (6%) endocardial- and 116 (6%) epicardial points; and miscellaneous (e.g. unstable baseline or ablation point with artifact) in 95 (2%) endocardial- and 139 (7%) epicardial points (Figure). The median difference between the ‘automatically generated’ UV and the ‘adjusted’ UV was 0.81mV (IQR: 0.40-1.39) for the endocardial points and 0.54mV (IQR: 0.27-0.98) for the epicardial points. In 320 (8%) endocardial points the UV was changed from &amp;gt;5.5mV to &amp;lt;5.5mV, in 412 (10%) points from &amp;gt;4.4 to &amp;lt;4.4mV and in 396 (9%) points from &amp;gt;3.8mV to &amp;lt;3.8mV. Conclusion In the majority of endocardial and epicardial points the window-of-interest for unipolar voltage mapping needs to be adjusted to exclude far-field signal or ST-segment elevation/depression contributing to the automatically determined amplitude. Unadjusted unipolar voltage mapping underestimates low UV regions. RV-pacing generates a large unipolar far-field signal, which can obscure the local unipolar near-field signal. Accordingly, RV UV mapping during RV pacing should be used with caution. Abstract Figure. The pitfalls of UV mapping of the RV