Search

An improved high-solid-loading slurry impregnation process was developed to introduce HfB2 particles into a low-density C/C preform efficiently, and precursor infiltration and pyrolysis process was used for densification to obtain a C/C-HfB2-SiC composite. The microstructure characterization revealed that HfB2 particles uniformly filled the pores in the C/C preform, and SiC well densified the interstices between HfB2 particles and the small pores in the carbon fiber bundles. After being tested, the C/C-HfB2-SiC composite had a density of 4.07 g/cm3 and a bending strength of 344.8 MPa, and exhibited a non-brittle fracture behavior. After ablation with oxyacetylene flame at 2500 ℃ for 120 s, the mass ablation rate and linear ablation rate of the C/C-HfB2-SiC composite were 0.5 mg/s and 0.415 μm/s, respectively. The good ablation performance is attributed to the hindering effect of the HfO2 scale on oxygen diffusion at high temperature.

Complex ablation for persistent atrial fibrillation (AF) aims to modify the arrhythmogenic substrates to become incapable to perpetuate the arrhythmia. Ablation-associated determinants of atrial tachycardia (AT) rather than AF recurrences are unknown. The aim of the study was to evaluate the association between the type of arrhythmia recurrence and electrophysiological findings during redo procedures. A total number of 384 consecutive patients with persistent AF underwent complex ablation consisting of PV isolation (PVI), biatrial electrogram-guided ablation, and linear ablation with the desired procedural endpoint of AF termination. Electrophysiological findings during redo procedures and its relation to AR type are the subject of this study. Overall, 177 (46%) patients underwent a second procedure. Patients with AT recurrences had significantly more often persistent PVI (47 vs. 25%; P = 0.002). Moreover, a higher number of recovered PVs were associated with AF recurrence (3 PVs recovered, AF = 16.1% vs. AT = 5.2%; P = 0.02; 4 PVs recovered, AF = 18.5% vs. AT = 6.3%; P = 0.01), regardless of the extent of substrate ablation during the first procedure. Durable PV isolation but not the extent of atrial substrate ablation determines the type of arrhythmia recurrence. Thus, the PVs may represent dominant perpetuators (and not only triggers) of persistent AF even in the presence of a significantly modified atrial substrate.

The ablation properties and mechanisms of BN-coated Cf-reinforced SiBCNZr composites under an oxyacetylene combustion torch were investigated. The mass and linear ablation rates of the Cf/SiBCNZr ceramic matrix composites were lower than those of Cf/SiBCN and SiCf/SiBCN composites, reaching 0.0022 mg/s and 0.0136 mm/s, respectively. The ablation resistance of the SiBCN ceramics was enhanced by the addition of Zr, whereas the BN-coated Cf increased the thermal shock resistance of the SiBCNZr ceramics. No macrocracks were found on the ablation surface of the Cf/SiBCNZr specimen. The ablation mechanisms based on different ablation temperatures, phase evolution during ablation, and ablation morphologies in the different ablation regions consisted of oxidation of the carbon fibre and ceramic matrix, emission of various gases, the flow of high-viscosity SiO2, and denudation of Cf under the erosion of the ablation flame.

We report 3 cases (mean age 48.3 ± 11.6 years) of idiopathic ventricular fibrillation (IVF), in which a triggering premature ventricular complex leading to IVF could not be identified. All patients underwent posterior fascicle transection with empirical linear ablation of the mid-Purkinje potentials identified along the left ventricular interventricular inferior septum, and no ventricular fibrillation recurrence was documented in any of the patients. (Level of Difficulty: Advanced.), Graphical abstract

INTRODUCTION The optimal ablation approach for persistent atrial fibrillation (AF) remains unclear. METHODS AND RESULTS Objective was to compare the long-term rates of freedom from AF/AT in patients that underwent STAR mapping guided ablation against outcomes of patients undergoing conventional ablation procedures. Patients undergoing ablation for persistent AF as part of the Stochastic Trajectory Analysis of Ranked signals (STAR) mapping study were included. Outcomes following 'pulmonary vein isolation (PVI) plus STAR mapping guided ablation (STAR mapping cohort) were compared to patients undergoing PVI alone ablation during the same time period and also a propensity-matched cohort undergoing PVI plus the addition of complex fractionated electrogram (CFAE) and/or linear ablation ("conventional ablation"). Rates of procedural AF termination and freedom from AF/AT during follow-up were compared. Sixty-five patients were included in both the STAR cohort and propensity matched conventional ablation cohort. AF termination rates were significantly higher in the STAR cohort (51/65, 78.5%) than conventional ablation cohort (10/65, 15.4%) and PVI alone ablation cohort (13/50, 26.0%; STAR cohort vs. other 2 cohorts both p

Background The ablation therapy for persistent atrial fibrillation (PerAF) is still a challenge due to the high recurrence rate. This study was aimed to investigate the value of extensive linear ablation with contact force sensing techniques for PerAF. Methods A total of 214 patients with PerAF were enrolled in five centers. The patients were randomly assigned to Group I (PVI + LA roof line+ LA anterior wall line) and Group II (PVI + LA roof line), mitral valve isthmus lines were added in both groups if the atrial fibrillation (AF) could not be terminated after all approaches above. Results Acute success rate of AF termination during the ablation procedure in Group I was significantly higher than Group II (P = 0.028). Two-years follow-up showed no significant difference in the sinus rhythm maintenance rate between the two groups (63.4% in group I vs. 57.2% in group II, P = 0.218). More patients in Group I recurred as organized atrial tachycardia (AT) and can be precisely mapped during repeat ablation procedures (15 vs. 2, P = 0.001). The Kaplan–Meier estimates of AF/AT-free survival after repeat ablation procedures were 76.2% in Group I and 47.1% in Group II (P = 0.039). Conclusions Extensive linear ablation with contact force monitoring did not improve the long-term outcomes for PerAF patients. Repeat ablation procedure showed a possible higher chance of sinus rhythm restoration during follow-up.

Catheter ablation of long-standing persistent atrial fibrillation is not yet clearly defined with respect to endpoints, and different ablative strategies are offered to patients. Presented here is an approach aiming at biatrial debulking in the form of extensive linear ablation, specifically targeting areas of low-voltage complex fractionated electrograms, in addition to pulmonary vein isolation. Its main advantage is that it is not dependent on operator/system variability, since the strategy of isolating the pulmonary veins, superior vena cava and left atrial posterior wall together with achievement of bidirectional block during linear ablation provides objective endpoints that can consistently be reproduced.

C/C-SiC-ZrC composites with different ZrC distributions were fabricated using precursor infiltration pyrolysis combined with different drying processes. The microstructural and ablation resistance properties of the composites with different ZrC distributions were investigated. For the C/C-SiC-ZrC composites fabricated using conventional heating-drying, where ZrC particles were largely agglomerated into islands with a dimension range of 10–20 μm, the mass and linear ablation rates under a plasma flame for 60 s were 0.558 mg/s and 16.33 μm/s, respectively. By contrast, for the composites fabricated using freeze-drying, where isolated ZrC particles with a size range of 200–300 nm were uniformly dispersed in the matrix, the mass and linear ablation rates were only 0.078 mg/s and 14.20 μm/s, respectively. This difference in the distribution of ZrC particles led to the difference in ablation resistances, as the uniformly distributed fine ZrC particles were easily oxidized and well dispersed in SiO2 molten glass, which increased the viscosity of the molten glass layer. The high-viscosity SiO2-ZrO2 molten layer covering the surface of the composites effectively prevented the penetration of oxygen and resisted the scour of airflow.

BACKGROUND: Liver cancer is one of the most common malignant tumors with a high incidence and mortality. Hepatitis-liver cirrhosis-liver cancer is known as the trilogy of liver cancer. At present, due to significant development of imaging interventions, they occupy an irreplaceable position in the field of liver cancer treatment, especially ultrasound-guided ablation. Because patients with liver cancer often present with liver cirrhosis, which leads to morphological deformation of the liver, it is difficult to perform a linear ablation of liver cancer in the areas near the phrenic top and within large blood vessels, among others. The present study reports on two cases of liver cancer that have been subjected to curvilinear ablation. After 1 mo, magnetic resonance imaging showed complete ablation, demonstrating that ultrasound-guided curved ablation is feasible and effective in the treatment of liver cancer. CASE SUMMARY: Two patients were treated at the Liver Disease Department of the Xixi Hospital Affiliated to Zhejiang University of Chinese Medicine in 2019. Because the first liver cancer patient’s tumor was located close to the diaphragm, it was difficult to complete a straight needle ablation procedure in one session. In order to achieve accurate and minimally invasive treatment of this tumor, a curved needle ablation procedure was designed. The second patient presented with a hepatic cyst in front of the tumor. In order not to damage the hepatic cyst, a looper needle ablation technique was used. The procedure was successfully completed in both cases. CONCLUSION: Curved ablation is a new technique that can be used to treat tumors situated in a variety of locations, providing new ideas for interventional techniques. Its operation difficulty is higher and further animal experiments are necessary to improve the operation procedure.

Multi-electrode mapping (MEM) is increasingly applied in ablation of complex atrial arrhythmias. This study aimed to evaluate MEM for analysis and treatment of complex macroreentry atrial tachycardia (MAT).Patients with MAT related to scarring, history of heart surgery or atrial linear ablation were studied. Patients were mapped with conventional activation mapping (CAM) or MEM. After characterizing the mechanism of atrial tachycardia (AT), the ablation was performed.The study consisted of 114 eligible patients, 74 in the CAM and 40 in MEM. Compared with CAM, MEM had a shorter procedure duration (156.7 ± 59.1 ms vs. 127.3 ± 59.3 ms, P = 0.003) and mapping duration (62.6 ± 35.7 ms vs. 30.5 ± 15.3 ms, P 0.001) and more mapping points (1364.9 ± 828.7 points vs. 148.3 ± 79.6 points, P 0.001). There were no significant differences between CAM and MEM in acute ablation success rate, complication, postoperative AADs, and ablation duration. The mean disease-free survival time in CAM versus MEM was 20.8 (95% CI: 17.6-24.1) months versus 26.6 (95% CI: 22.7-30.4) months. The median disease-free survival time in the CAM versus MEM was 20.0 (95% CI: 13.9-26.1) months versus 30.0 (95% CI: 26.7-36.3) months. The AT recurrence risk of MEM was 0.522 times that of CAM (HR 95% CI: 0.282-0.968; P = 0.039).MEM is strongly recommended in ablation of complex MAT.

Cavotricuspid isthmus (CTI) linear ablation has been established as the treatment for typical atrial flutter. Recently, ablation index (AI) has emerged as a novel marker for estimating ablation lesions. We investigated the relationship between CTI depth and ablation parameters on the procedural results of typical atrial flutter ablation. A total of 107 patients who underwent CTI ablation were retrospectively enrolled in this study. All patients underwent computed tomography before catheter ablation. From the receiver-operating curve, the best cut-off value of CTI depth was p p 420 and > 386, respectively. Among patients with these cut-off values, the first-pass success rate was 89% in the SC and 50% in the DC (p

Aims To evaluate the clinical outcome in patients undergoing repeat procedures for recurrent persistent atrial fibrillation following an index cryoballoon (CB‐A) pulmonary vein isolation ablation on a mid‐term follow‐up of 12 months. Methods In this propensity score‐matched comparison, 50 patients undergoing left atrial posterior wall isolation (LAPWI) with the CB‐A were matched to 50 patients treated with additional linear ablation using radiofrequency catheter ablation (RFCA). Results Meantime to repeat the procedure was 9.74 ± 4.36 months. At 12 months follow‐up freedom from atrial tachyarrhythmias (ATas) was achieved in 82% of patients in the LAPWI group and in 62% of patients in the linear ablation group (P = .03). Regression analysis demonstrated that relapses during the blanking period and LA dimensions were independent predictors of ATas recurrences following the repeat procedure. Conclusion LAPWI using CB‐A is associated with a significantly higher freedom from atrial arrhythmias when compared with the RFCA mediated left atrial linear lesions on a mid‐term follow‐up of 12 months in patients with persAF undergoing a redo procedure., LAPWI using CB‐A is associated with a significantly higher freedom from atrial arrhythmias when compared with the RFCA mediated left atrial linear lesions on a mid‐term follow‐up of 12 months in patients with persAF undergoing a redo procedure.

Summary As the mechanisms underlying persistent atrial fibrillation (AF) are still incompletely understood, a ‘gold standard’ strategy for ablation is lacking. The results of catheter ablation, independent of the ablation strategy applied, are disappointing. Hybrid ablation, combining a thoracoscopic epicardial and transvenous endocardial approach, has shown more favourable outcomes. To date, studies comparing both techniques are lacking. Therefore, we conducted a systematic review and meta-analysis of hybrid versus catheter ablation in patients with persistent or longstanding persistent AF. A systematic literature search of studies reporting on catheter and hybrid ablation of persistent or longstanding persistent AF was performed in the PubMed database. All identified articles were screened and checked for eligibility. A meta-analysis was performed on inter-study heterogeneity and pooled correlation between baseline characteristics, primary and secondary outcomes of hybrid and catheter studies. From the 520 articles identified by the search, 34 articles could be included in the analysis. Hybrid ablation resulted in higher freedom of atrial arrhythmias in patients with persistent and longstanding-persistent AF than catheter ablation (70.7% vs 49.9%, P

Aims Mitral isthmus (MI) ablation is challenging. We hoped to close those conduction breakthrough sites (CBS) across the MI by elaborate mapping. Methods and results After the initial linear ablation, elaborately mapping large areas above and below the MI line and inside the coronary sinus (CS) was sequentially performed to identify the CBS. The shortest distance from the CBS to the MI line was measured. The distant CBS (D-CBS) was identified as those CBS >5.0 mm away from the MI line. We prospectively enrolled 177 consecutive patients. Bidirectional conduction blockage across MI was obtained in 50 (28.2%) patients after the initial linear ablation and was achieved in additional 115 (65.0%) patients following elaborate mapping and reinforcement ablation. After initial linear ablation, 272 CBS (2.14 ± 0.99 CBS/person) were identified, and 226 (83.1%) of them were characterized as D-CBS, including 98 sites (36.0%) >10.0 mm and 39 sites (14.3%) >15.0 mm away. Endocardial and epicardial (CS) reinforcement ablation eliminated 119/272 (43.8%) and 58/272 (21.3%) CBS, respectively. Among the 177 eliminated CBS, 138 D-CBS (78.0%, 11.2 ± 5.6 mm) were confirmed in 95 (74.8%) patients. Moreover, CBS along the course of ligament of Marshall was closed by endocardial ablation more frequently than that along the course of great cardiac vein (52.6%% vs. 35.1%, P = 0.004). Eventually, CS ablation was required only in 64 (38.8%) patients. Conclusion Distant CBS, accounted for the majorities of the residual conduction across the MI after initial ablation, could be effectively identified and accurately eliminated by elaborate mapping and ablation around the MI ablation line.

Background: It is established that ethanol infusion in the vein of Marshall (EIVOM) effectively creates a linear ablation lesion in the mitral isthmus (MI). However, data on the long-term success rates of MI ablation remains limited. Methods and Results: Our cohort consisted of 560 patients with non-paroxysmal atrial fibrillation (AF) who underwent an initial MI ablation. Ablations were performed by only radiofrequency (RF) in 384 patients (RF group) or by RF and EIVOM in 176 patients (EIVOM/RF group). Ethanol of 5 mL was used to perform EIVOM in advance of RF. Following EIVOM, RF pulses were delivered to the lateral MI line. Bidirectional MI block was fully achieved in 353 (first 318, re-do 35) patients of the RF group and 171 (first 128, re-do 43) patients of the EIVOM/RF group (p = 0.09 in the first, 0.10 in the re-do ablation cases). In cases with complete MI line block, recurrent AF or atrial tachycardia (AT) was observed in 130 (37%) patients of the RF group and in 64 (37%) patients of the EIVOM/RF group (log-rank p = 0.12 in the first, 0.30 in the re-do ablation cases). Of the total 194 patients, 112 with drug refractory AF or AT proceeded to the subsequent ablation process. Reconnection of MI block line was observed in 39 (49%) patients in the RF group and 25 (58%) patients in the EIVOM/RF group (p = 0.32). Conclusion: EIVOM effectively ensures MI line block; however, the reconnection rate was similar between the two groups.

BACKGROUND The STAR AF II (Substrate and Trigger Ablation for Reduction of Atrial Fibrillation 2) was a multicenter, randomized trial which randomized patients to pulmonary vein isolation (PVI) alone, PVI plus complex fractionated electrograms (CFE), or PVI plus linear ablation (roof line and mitral line). The study failed to show any additional benefit of additional substrate ablation (CFE or lines) in addition to PVI. However, complete block of linear ablations or total elimination of CFE was not achieved in all patients in the adjuvant ablation arms and this could explain why these additive ablation strategies did not improve outcome. We sought to determine whether completeness of adjuvant linear or CFE ablation affected the outcome of these additive ablation strategies when combined with PVI. METHODS AND RESULTS In STAR AF II, 549 patients were randomized 1:4:4 to PVI alone, PVI plus lines, and PVI plus CFE. In this substudy, outcomes of patients with complete linear block and without complete linear block in the PVI + lines group and outcomes for patients with all CFE regions successfully ablated and without all of them ablated in the PVI + CFE are analysed. Of the 243 patients in the PVI plus lines group who received both mitral and roof lines, bidirectional block across both lines was achieved in 179 (74%) but was not achieved in 65 (26%). At 18 months follow-up, AF recurrence occurred in 107 of 179 patients (59.8%) with complete block conduction block across lines and in 40 of 64 patients (62.5%) without complete block (p=0.89) (Figure 1). Even after 2 procedures, AF recurred in 51.9% of patients with complete linear block and 46% of patients without complete block (p=0.09). Of the 207 patients in the PVI plus CFE group who actually underwent CFE ablation, 188 (91%) had elimination of all CFE sites while all CFE were not eliminated in 19 (9%). At 18 months follow-up, AF recurrence occurred in 117 of 188 patients (62.2%) with all the CFE ablated and in 11 of 19 patients (57.9%) without all CFE ablated (p=0.47) (Figure 1). After 2 procedures, AF recurrence occurred in 56.7% of patients with all CFE ablated and 68.0% of patients without all CFE ablated (p=0.29). CONCLUSION PVI combined with both linear and CFE ablation did not result in less AF recurrence compared to PVI alone even after more than one procedure regardless of how well empiric linear or CFE ablation is performed.

Objectives To evaluate the feasibility, procedural data, and lesion characteristics of the anterior line (AL) and roofline (RL) ablation by using ablation index (AI)-guided high power (50 W) among patients with recurrent atrial fibrillation (AF) or atrial tachycardia (AT) after pulmonary vein isolation (PVI). Methods Data from 35 consecutive patients with macro-reentrant left atrial tachycardia or substrate at the left atrium anterior wall or roof after previous PVI were collected. Ablation power was set to 50 W, targeting AI 500 for AL and 400 for RL. The first-pass conduction block (FPB) was evaluated. The AL was arbitrarily divided into three (caudal, middle, and cranial) segments to analyze the location of conduction gaps in non-FPB patients. Results A total of 32 AL and 17 RL were deployed and FPB was achieved in 24 (75%) and 14 (82%) of them, respectively. In the non-FPB group, the most frequent gap location along the AL was the middle third. The final block of AL was achieved in 97%, and the block of RL was achieved in 100%. The radiofrequency (RF) ablation time was short (2.9 ± 0.8 min for AL and 46.2 ± 15.6 s for RL). For AL, the female gender was significantly more frequent in FPB than in non-FPB patients (p = .028); patients with non-FPB were associated with significantly longer RF time as compared to patients with FPB (204 ± 47 s vs. 161 ± 41 s; p = .02). No procedural complications occurred. Conclusion AI-guided high-power (50 W) ablation appears to be a feasible, effective, and fast technique for AL and RL ablation.

Background: We aimed to evaluate the effect of Bachmann bundle (BB) impairment on electrical and mechanical function of the left atrium (LA), as well as the long-term clinical impact of such impairment. Design: We measured activation time in the five LA walls in 56 patients with atrial fibrillation. LA reservoir, conduit, and contractile function were also evaluated. Patients were divided into two groups based on ablation strategy: the circumferential pulmonary vein isolation (CPVI) group and CPVI with anterior wall linear ablation (LAWA) group. Patients in the CPVI+LAWA group were divided into two sub-groups based on ECG differences following ablation: the BB impairment group and intact BB group. LA activation time and function were then compared between the ablation strategy groups and the CPVI+LAWA subgroups. Results: Patients in the CPVI+LAWA group exhibited longer activation times in the anterior and lateral walls of the LA, poorer LA synchrony, and reduced LA contractile and reservoir function when compared with those in the CPVI group. In the BB impairment subgroup, we observed a discrepancy between electrical/mechanical remodeling. Among five walls, activation time was longest in this region. BB impairment was also associated with reduced LA function. Conclusion: Significant changes in LA function and conductibility were observed in patients with anterior wall ablation, especially those with iatrogenic BB impairment.

Biatrial macro-reentrant tachycardia (Bi-MAT) is a relatively uncommon arrhythmia. Sometimes, it can be produced by the left atrial (LA) anterior or septal-anterior linear ablation. However, data concerning the proarrhythmic role of this ablation lesions are lacking. Here, we reported a case of a single-loop Bi-MAT developing after the LA anterior ablation line performed in one patient with persistent atrial fibrillation.

Purpose: We aimed to determine whether biatrial enlargement could predict reablation of atrial fibrillation after first ablation. Methods: 519 consecutive patients with drug resistant atrial fibrillation [paroxysmal AF (PAF) 361, non-PAF 158] who underwent catheter ablation in Capital Medical University Xuanwu hospital between 2009 and 2014 were enrolled. Biatrial enlargement (BAE) was diagnosed according to trans-thoracic echocardiography (TTE). Ablation strategies included complete pulmonary vein isolation (PVI) in all patients and additional linear ablation across mitral isthmus, left atrium roof, left atrium bottom and tricuspid isthmus, or electrical cardioversion on the cases that AF could not be terminated by PVI. Anti-arrhythmic drugs or cardioversion were used to control the recurred atrial arrhythmia in patients with recurrence of atrial fibrillation after ablation. Reablation was advised when the drugs were resistant or that patient could not tolerate. Risk factors for reablation were analyzed. Results: After 33.11±21.45months, 170 patients recurred atrial arrhythmia, and reablation were applied in 117 patients. Multivariate Cox regression analysis demonstrated that that biatrial enlargement (BAE, HR 1.755, 95%CI 1.153-2.670, P=0.009) was an independent predictor for reablation and was associated with reablation (Log rank P=0.007). Conclusion: Biatrial enlargement is an independent risk predictor for the reablation in atrial fibrillation patients after first ablation.

To improve the ablation resistance of carbon/carbon composites at the temperature above 2000 K, a ZrB2-SiC-ZrC ultra-high temperature ceramic coating was prepared by combination of supersonic atmosphere plasma spray (SAPS) and reaction melt infiltration. The micro-holes in ZrB2-Si-ZrC coating prepared by SAPS were effectively filled and the compactness and interface compatibility between the coating and C/C composites was improved through the reaction melt infiltration process. The ultra-high temperature ceramic coating exhibited good ablation resistance under oxyacetylene torch ablation above 2000 K. After ablation for 120 s, the mass and linear ablation rates of the ZrB2-SiC-ZrC coated C/C samples were only −0.016 × 10−3 g/s and 1.30 µm/s, respectively. Good ablation resistance of the ultra-high temperature ceramic coating is mainly attributed to the dense coating structure and the improvement of interface compatibility between the coating and C/C composites.

A 51-year-old man with long-standing persistent atrial fibrillation underwent a hybrid ablation procedure with right thoracoscopic epicardial ablation. Fluoroscopy was utilized in a novel way to visualize the magnetic tip catheters of the linear ablation surgical device and allow easier coupling of the tips, making this procedure more efficient and reducing the risk of improper positioning of the ablation device.

HfC-SiC coatings have promising applications in the field of ablation protection for carbon-carbon (C/C) composites. In this work, HfC-SiC coatings with different ratios were designed and successfully prepared by low pressure chemical vapor co-deposition using HfCl4-MTS-CH4-H2-Ar system under the guidance of thermodynamic calculations. The phase composition, microstructure, and ablation behavior of HfC-SiC coating with different phase proportions were investigated. The coating with HfC/SiC ratio of 1:1 showed the best ablation resistance after ablation for 90 s, and its mass and linear ablation rates of HfC-SiC coating was only 1.016 ± 0.12 mg/s and 0.998 ± 0.08 µm/s, respectively.

Introduction The optimal ablation approach for persistent atrial fibrillation (AF) remains unclear. Methods and Results Objective was to compare the long‐term rates of freedom from AF/AT in patients that underwent STAR mapping guided ablation against outcomes of patients undergoing conventional ablation procedures. Patients undergoing ablation for persistent AF as part of the Stochastic Trajectory Analysis of Ranked signals (STAR) mapping study were included. Outcomes following 'pulmonary vein isolation (PVI) plus STAR mapping guided ablation (STAR mapping cohort) were compared to patients undergoing PVI alone ablation during the same time period and also a propensity‐matched cohort undergoing PVI plus the addition of complex fractionated electrogram (CFAE) and/or linear ablation (“conventional ablation”). Rates of procedural AF termination and freedom from AF/AT during follow‐up were compared. Sixty‐five patients were included in both the STAR cohort and propensity matched conventional ablation cohort. AF termination rates were significantly higher in the STAR cohort (51/65, 78.5%) than conventional ablation cohort (10/65, 15.4%) and PVI alone ablation cohort (13/50, 26.0%; STAR cohort vs. other 2 cohorts both p

PubMed ID: 29208256 Background: To achieve sinus rhythm, ablation of long-standing persistent atrial fibrillation (LSPAF) usually requires substrate modification in addition to pulmonary vein isolation (PVI). In the present article, we aimed to compare clinical and substrate modification effects of 2 distinct PVI strategies during stepwise ablation in patients with LSPAF: (1) Combined approach: cryoballoon (CB) for PVI and radiofrequency (RF) ablation for substrate modification and (2) RF-only approach: RF ablation for both PVI and substrate modification. Materials and Methods: A total of 34 patients were divided into 2 groups: 19 in the combined group and 15 in the RF group. Left atrial (LA) complex fractionated atrial electrogram (CFAE) maps were acquired before and after PVI and compared between groups. The groups were compared for acute atrial fibrillation termination (AFT) rates and long-term arrhythmia-free survival. Results: A significant reduction on total LA CFAE area was observed with PVI in both groups. In the CB group, when pulmonary veins were excluded, the reduction of LA CFAE area was the most significant on the posterior wall of left atrium and which was greater than in the RF group. Although the ratio of AFT was higher in the CB group (44% versus 33%, respectively), single-procedure arrhythmia-free survival at 1 year was comparable between groups (68% in the CB group versus 66% in the RF group). Times of total procedure, fluoroscopy and post-PVI RF were all shorter in the CB group. Conclusions: CB may cause greater substrate modification on the posterior wall and increase AFT rate during LSPAF ablation. © 2017 Southern Society for Clinical Investigation

To improve the ablation resistance of SiC coating, HfB 2 -SiC coating was prepared on SiC-coated carbon/carbon (C/C) composites by in-situ reaction method. Owing to the penetration of coating powders, there is no clear boundary between SiC coating and HfB 2 -SiC coating. After oxyacetylene ablation for 60 s at heat flux of 2400 kW/m 2 , the mass ablation rate and linear ablation rate of the coated C/C composites were only 0.147 mg/s and 0.267 µm/s, reduced by 21.8% and 60.0%, respectively, compared with SiC coated C/C composites. The good ablation resistance was attributed to the formation of multiple Hf-Si-O glassy layer including SiO 2 , HfO 2 and HfSiO 4 .

C/C-ZrC-SiC composites with different ZrC particle size was fabricated by organic precursor infiltrations and pyrolysis (PIP) combined with additional heat treatment at different temperatures and further PIP of SiC precursor. Effect of ZrC particle size on the ablation resistance of C/C-ZrC-SiC composites was investigated under heat flux of 4.18±0.42MW/m2 containing high scouring. Results showed that small ZrC particle size (0.2μm) caused low viscosity and unfavorable anti-scouring of the formed oxides, leading to unsatisfactory ablation resistance of the composites. Oxides for composites with big ZrC particles (2μm) failed to seal large gaps between ZrC particles, resulting in massive ablation of the composites. Composites with ZrC particle size of around 1μm showed good ablation resistance, with linear ablation rate decreased by 91.3% relative to C/C-ZrC-SiC composites with ZrC particle size of 200nm. The good ablation resistance was mainly ascribed to the formed viscous oxides containing particles, which could resist scouring and meanwhile seal gaps in composites during ablation. Keywords: Carbon/carbon composites, Ablation, Ceramic, Particle size

A bipolar voltage reflects a thick musculature where formation of a transmural lesion may be hard to achieve. The purpose of this study was to explore the association between local bipolar voltage and conduction gap in patients with persistent atrial fibrillation (AF) who underwent atrial roof or septal linear ablation. This prospective observational study included 42 and 36 consecutive patients with persistent AF who underwent roof or septal linear ablations, respectively. After pulmonary vein isolation, left atrial linear ablations were performed, and conduction gap sites were identified and ablated after first-touch radiofrequency application. Conduction gap(s) after the first-touch roof and septal linear ablation were observed in 13 (32%) and 19 patients (53%), respectively. Roof and septal area voltages were higher in patients with conduction gap(s) than in those without (roof, 1.23 ± 0.77 vs 0.73 ± 0.42 mV, p = 0.010; septal, 0.96 ± 0.43 vs 0.54 ± 0.18 mV, p = 0.001). Trisected regional analyses revealed that the voltage was higher at the region with a conduction gap than at the region without. Complete conduction block across the roof and septal lines was not achieved in 3 (7%) and 6 patients (17%), respectively. Patients in whom a linear conduction block could not be achieved demonstrated higher ablation area voltage than those with a successful conduction block (roof, 1.91 ± 0.74 vs 0.81 ± 0.51 mV, p = 0.001; septal, 1.15 ± 0.56 vs 0.69 ± 0.31 mV, p = 0.006). In conclusion, a high regional bipolar voltage predicts failure to achieve conduction block after left atrial roof or septal linear ablation. In addition, the conduction gap was located at the preserved voltage area.

Aims The ESC EORP EHRA Atrial Fibrillation (AF) Ablation Long-Term registry was designed to assess management and outcomes of AF catheter ablation procedures in Europe. To investigate the current ablation approaches and their outcomes for patients with paroxymal AF (PAF) and non-PAF in Europe. Methods and results Data from index ablations were collected in 27 European countries at 104 centres in a prospective fashion. Pre-procedural, procedural, and 1-year follow-up data were captured on a web-based electronic case record form. Data on the ablation procedure were available for 3446 patients. Of these, 2513 patients and 933 patients underwent pulmonary vein isolation (PVI) or PVI plus (PVIplus) additional ablation, respectively. The ablation strategy was limited to PVI in 81% and 56% of patients in the PAF and non-PAF group, respectively (P Conclusion In patients with PAF and non-PAF, the ablation strategies of PVI and PVIplus led to similar arrhythmia-free survival rates after 1 year. A considerable hospital readmission rate was noted.

Arrhythmia after surgical MAZE procedures is often misinterpreted as recurrence of atrial fibrillation. This case demonstrates recurrent mitral annular flutter as a result of incomplete surgical mitral isthmus ablation. Examination of local electro grams provides an instructive diagnostic demonstration of linear ablation breakthrough.

Atypical atrial flutters with clockwise mitral activation usually originate in the left atrium (LA). However, in patients with prior linear ablation for atrial fibrillation (AF), this can be misleading. A 62-year-old female who underwent 3 prior AF ablations, presents for ablation of recurrent

Introduction Pulmonary vein isolation (PVI) and linear ablation with a roof line and bottom line on the left atrial (LA) posterior wall (LAPW) can be achieved with a cryoballoon (CB). This study sought to investigate the long-term durability of these linear lesions. Methods and results Among 290 persistent patients with atrial fibrillation (AF) who had undergone linear ablation with a CB on the roof and bottom line of the LAPW in addition to the PVI, we analyzed those patients who underwent a re-do AF ablation. Arrhythmia recurrence was confirmed in 70 (24%) out of 290 patients, and 47 (16%) patients underwent re-do sessions. At the beginning of the re-do ablation, we examined the reconnection sites of the linear lesions on the LAPW and PVI. Maintenance of the conduction block on the LAPW roof and bottom lines was observed in 35 out of 47 patients (74.5%), and 16 out of 35 patients (45.7%), respectively. The length of the roof line was significantly shorter in patients with preservation of the conduction block on the LAPW roof than in those without (36.2 ± 6.5 mm vs 41.6 ± 4.7 mm, P = .02). Conclusion Durable lesions could be obtained after linear ablation with the CB for the LAPW roof line, especially in those with a relatively short LAPW roof line. However, patients requiring touch-up ablation with radiofrequency were included, and that was associated with a potential financial implication.

To further improve the ablation resistance of SiBCN ceramics, nanosized HfB2 was introduced by mechanical alloying and subsequent reactive hot-pressing techniques to fabricate HfB2-HfC/SiBCN multiphase ceramics. The mass and linear ablation rates of the 30 vol% HfB2-HfC containing SiBCN ceramics under an oxyacetylene flame for 10 s were lower than those of ZrB2-ZrN/SiBCN and SiBCN, reaching to 0.0025 mg/s and 0.0004 mm/s respectively. Even ablated for 60 s, no trace of cracks appeared on the ablation surface. Oxidation of ceramic matrix, denudation of oxides, erosion by the combustion flow and the re-oxidation of the exposed matrix governed the ablation process.

To improve the oxidation protective ability of carbon–bonded carbon fiber (CBCF) composites, double anti-oxidation protection for CBCF composites were prepared, i.e., ceramic coating-coated CBCF composites combined with ceramic-modified carbon fiber in CBCF matrix. The ablation behavior of modified CBCF composites was tested under an oxyacetylene flame at 1600 °C for 300 s and 800 s, respectively. The results indicate that the ZrB2 in matrix and ZrB2-based ceramic coating can play double protection for CBCF composites during ablation process. The linear ablation rate of the sample after ablation for 300 s and 800 s were −1.1×10−4 and 8.38×10−4 cm s−1, respectively. The modified CBCF composites presented excellent oxidation resistance for 300 s. With the increase of the oxidation time for 800 s, the ZrB2-based ceramic coating experienced catastrophic damage. However, the carbon fiber surface only exhibited some circular pits instead of complete oxidation, implying that the ZrB2 on the carbon fiber surface improved the anti-oxidation and ablation resistance of CBCF composites.

Three-dimensional (3D) braided C/ZrC–SiC composites with various SiC/ZrC ratios were fabricated by precursor infiltration and pyrolysis (PIP) process. The effects of SiC/ZrC ratios on the ablation and mechanical properties were investigated systematically. The flexural strength of 3D C/ZrC–SiC grows with the increase of SiC/ZrC ratios. The compact and stiff ZrC-SiC matrix, moreover, the carbon fiber and PyC interphase with the less reaction damage account for the improved flexural strength of C/ZrC–SiC with higher SiC/ZrC ratios. As for the ablation properties, both mass and linear ablation rates drop with the decrease of SiC/ZrC ratios at the beginning. However, the ablation rates start to increase with the further decrease of SiC/ZrC ratio, where the high open porosity deteriorates the ablation properties. Herein, in order to obtain a balance between ablation and mechanical properties, an appropriate SiC/ZrC ratio should be considered.

Objective Creating transmural linear lesions on the beating heart is an important component of minimally invasive surgical ablation for atrial fibrillation. Animal studies have shown poor efficacy for surface bipolar radiofrequency ablation (RFA). Clinicians have developed strategies including multiple device applications and vena caval occlusion (VCO) to improve ablation efficacy. These techniques were evaluated in an acute porcine model. Methods In the first experiment, an RFA device was used to perform two 40-second epicardial ablations on the right atrium of six pigs. Ablations were performed with and without VCO. Ultrasonic flow probes were used to verify VCO. In the second experiment, an RFA device was used to perform two 40-second epicardial ablations at six locations on the left and right atria of six pigs. All animals were sacrificed. The hearts were removed and stained with 2,3,5-triphenyltetrazolium chloride. Sections were examined using digital photography. Results With VCO, 42 (81%) of 52 sections were transmural; without VCO on the RA, only 12 (24%) of 50 sections were transmural (P < 0.01). In thick (>2 mm) tissue, 10 (59%) of 17 VCO sections were transmural compared with only two (8%) of 24 with normal caval blood flow. Compared with a single ablation, multiple device applications improved transmurality on the LA but not the RA (92% vs 71%, P < 0.05). Conclusions In an acute animal model, VCO improved the efficacy of beating-heart RFA on the RA. Multiple device applications improved the efficacy of RFA on the LA.

SiC coated C/C (SiC-C/C) composites were designed to determine effects of hypervelocity impact on ablation behavior of coated carbon/carbon (C/C) composites. They were impacted at 2 km/s and 3 km/s by steel projectiles driven by solid explosive of pentaerythritol tetranitrate and then ablated by oxyacetylene torch for 100 s at 2500 °C. Results showed that ablation areas, the integrity of ablated boundary and ablation rates of all samples increased with the increase of impact velocity. Mass ablation rates of SiC-C/C composites were lower than those of C/C composites under the same test condition. On the contrary, linear ablation rates of SiC-C/C composites were higher than those of C/C composites after the same impact tests. The difference was attributed to the interfaces between SiC coatings and matrix C/C composite. These results demonstrated that morphology of interfaces between coatings and matrix C/C composite was one major factor for the usage of coated C/C composites and could affect the service time of structures with impact damages in high temperature environments. Keywords: SiC-C/C composite, Hypervelocity impact, Ablation behavior

To protect carbon/carbon (C/C) composites against ablation, a TaB 2 SiC coating was prepared on their surface by pack cementation. Ablation behavior of the coated C/C composites was investigated under oxyacetylene torch. After ablation for 30 s, the linear ablation rate of the TaB 2 SiC coated C/C composites was 4.2 μm/s. Compared with the SiC coated C/C composites and bare C/C composites, the linear ablation rate was reduced by 40% and 51%, respectively. During ablation, a mosaic-structured Ta Si O glassy layer was formed, playing a positive role in preventing oxidizing species from attacking C/C substrate. Oxidation products of TaB 2 , existing as “pinning phases” in the coating, induced the deflection of the crack formed by the attack of oxyacetylene torch, which was beneficial to enhance the stability of TaB 2 SiC coating and improve the ablation resistance.

Background This study aimed to evaluate an approach for an endpoint of non-inducibility using a combined high-dominant frequency (DF) and continuous complex fractionated atrial electrogram (CFAE) ablation following circumferential pulmonary vein isolation (PVI) in a sequential fashion, including linear ablation as compared to PVI alone. Methods and results A total of 84 non-paroxysmal patients with atrial fibrillation (AF) were investigated retrospectively. The AF patients were divided into two groups: patients with PVI following a combined high-DF and continuous CFAE ablation with linear ablation (substrate modification group, n = 59) and those with PVI alone (n = 25). DF sites of ≥8 Hz and then continuous CFAE sites defined by fractionation intervals of ≤50 ms were modified after PVI. The ablation endpoint was non-inducibility. Atrial tachyarrhythmias (ATs) could not be induced in 54 of 59 (92%) patients after a sequential ablation, and in 18 of 25 (64%) with PVI alone. The ATs freedom without antiarrhythmic drugs in the substrate modification group was significantly greater than that in those with PVI alone after 1 procedure during 12 months of follow-up (78.6% vs. 53.8%, log-rank test p = 0.039). Conclusion This sequential approach using a substrate based ablation was associated with a better clinical long-term outcome as compared to PVI alone.

This paper reviews the simulations of catheter ablation in computer models of the atria, from the first attempts to the most recent anatomical models. It describes how postulated substrates of atrial fibrillation can be incorporated into mathematical models, how modelling studies can be designed to test ablation strategies, what their current trade-offs and limitations are, and what clinically relevant lessons can be learnt from these simulations. Drawing a parallel between clinical and modelling studies, six ablation targets are considered: pulmonary vein isolation, linear ablation, ectopic foci, complex fractionated atrial electrogram, rotors and ganglionated plexi. The examples presented for each ablation target illustrate a major advantage of computer models, the ability to identify why a therapy is successful or not in a given atrial fibrillation substrate. The integration of pathophysiological data to create detailed models of arrhythmogenic substrates is expected to solidify the understanding of ablation mechanisms and to provide theoretical arguments supporting substrate-specific ablation strategies.

Porous carbon/carbon composites were infiltrated by Mo–Si–Ti/Al mixed powder to develop a Cf/MoSi2–SiC–C based composites below 1600 °C in this research. Effects of Ti/Al addition on the microstructures and ablation properties of infiltrated samples were investigated and compared together with Si–Mo infiltrated samples. The infiltrated samples are composed of SiC, MoSi2 and ceramic phases containing Ti or Al. Ceramic phases containing Al distribute close to carbon fiber bundles while ceramic phases containing Ti distribute far away from carbon fiber bundles. Samples infiltrated by Mo–Si–Ti showed excellent ablation properties. The linear ablation rate and mass ablation rate after ablated for 300 s under an oxyacetylene torch system are 0.002 mm/s and 0.01 mg/s, respectively. Addition of Al has not improved ablation resistance significantly in this research.

WSi2-HfB2-SiC outer coatings were prepared by in-situ sintering reaction methods. The effect of WSi2 content on the oxidation resistance of HfB2-SiC coating was investigated. The results show that the WSi2-HfB2-SiC coating with 25 wt.% WSi2 (W2) has the best oxidation resistance and can protect C/C substrate for 100 h at 1973 K in air environment. After ablation for 90 s, the linear ablation rate and mass ablation rate of W2 are −3.89 × 10−7 m/s and 6.78 × 10-5 g/s, respectively, showing excellent ablation resistance. The good oxidation and ablation resistance of W2 is attributed to the formation of flowing multiphase glass with inlay.

A self-designed oxygen-kerosene ablation system was employed to research the ablation properties of silicone rubber-based insulation material under different oxygen-rich conditions, that is, 0%, 5.00%, 7.71%, 17.01%, and 18.50%. The morphology of posttest specimens was analyzed via a scanning electron microscope (SEM), and the ablation rates were calculated. Experimental results showed that when the particle concentration was a fixed value, the mass and the linear ablation rates increased first and then decreased with the rise of oxygen content; the maximum values were 0.572 g/s and 0.933 mm/s, respectively. Under high oxygen-rich conditions, the formation of silicone rubber restricted the further increase of the ablation rates, filling more gaps of the reaction layer with liquid silicone rubber. Meanwhile, the thickness of the liquid glass layer attached to the surface was increased, which acted as a buffer against the impacts and erosion of particles and retarded the consumption and recession of materials. Excess oxygen spread to the edge of the ablation pit and reacted. Finally, these led to the increase in diameter of the ablation pit and the decrease of two types of ablation rates.

C/C-ZrC-SiC composites were fabricated by carbothermal reaction of hydrothermal co-deposited oxides and resulted in homogeneous microstructure. The fracture behavior passed from pseudo-plastic to brittle fracture with the increase in ZrC/SiC molar ratios. The composites with a molar ratio of ZrC/SiC≈2:1 presented outstanding ablation resistance with a mass ablation rate of 0.06 mg cm−2 s−1 and a linear ablation rate of 0.13 μm s−1. The optimal ZrC/SiC molar ratio provided a suitable balance of viscosity and flowability of the oxides scale, which not only possessed enough solid ZrO2 to endure the scouring but also had moderate liquid-phase to seal the defects and limited the oxidation.

AimsConducting gaps in lesion sets are a major reason for failure of ablation procedures. Voltage mapping and pace-capture have been proposed for intra-procedural identification of gaps. We aimed to compare gap size measured acutely and chronically post-ablation to macroscopic gap size in a porcine model.Methods and resultsIntercaval linear ablation was performed in eight Göttingen minipigs with a deliberate gap of ∼5 mm left in the ablation line. Gap size was measured by interpolating ablation contact force values between ablation tags and thresholding at a low force cut-off of 5 g. Bipolar voltage mapping and pace-capture mapping along the length of the line were performed immediately, and at 2 months, post-ablation. Animals were euthanized and gap sizes were measured macroscopically. Voltage thresholds to define scar were determined by receiver operating characteristic analysis as P = 0.003, Tukey's multiple comparisons test). Chronically, voltage mapping and pace-capture mapping overestimated macroscopic gap size by 11.9 ± 3.7 and 9.8 ± 3.5 mm, respectively.ConclusionBipolar voltage and pace-capture mapping overestimate the size of chronic gap formation in linear ablation lesions. The most accurate estimation of chronic gap size was achieved by analysis of catheter-myocardium contact force during ablation.

Patients with persistent atrial fibrillation (AF) may additionally suffer from a concealed sinus node disease. We sought to determine the incidence, indications and predictors of acute pacemaker [PM] implantation within 1 week after the ablation of persistent AF. We performed a retrospective analysis of patients, who had had an ablation of persistent AF at our center. Between 01/2011 and 08/2016, 1234 patients (mean age 65 ± 10 years, 66.7% male) without prior PM implantation underwent an ablation of persistent AF. Pulmonary vein isolation (PVI) was performed in 1158 (93.8%), the additional ablation of complex fractionated atrial electrograms (CFAE) in 1109 (89.9%) and linear ablation in 524 (42.5%) patients. Temporary cardiac pacing was necessary in 27 (2.2%) patients. The temporary PM was removed in 15 patients (1.2%) because sinus node recovered after a median of 1.0 (minimum 0.1−maximum 2.0) day. The remaining 12 (1.0%) patients required the implantation of a permanent PM. Another 13 (1.1%) patients required permanent PM implantation without prior temporary pacing. In a multivariable regression model, age [OR 1.07 (1.02–1.12), p = 0.006], sinus pauses prior to ablation [OR 7.97 (2.36–26.88), p = 0.001] and atria with low voltage [OR 2.83 (1.31–6.11), p = 0.008] were identified as significant predictors for acute cardiac pacing. Acute cardiac pacing within 1 week after the ablation of persistent AF was necessary in 40 (3.2%) patients. Age, sinus pauses in history prior to ablation and the existence of low-voltage areas in the atria were identified as relevant risk factors.

Carbon fiber reinforced carbon matrix containing ZrC (C/C–ZrC) composites were prepared by hydrothermal deposition combined with carbothermal reduction. The submicron ZrC particles (100–300 nm) were dispersed in the matrix. The stress-strain curves of the composites presented a typical pseudo-plastic fracture behavior. The mass and linear ablation rates of the composites were 3.7 × 10−3 g/s and 4.2 × 10−3 mm/s, respectively. The formation of ZrO2 glass layer reduced erosion of the composites in the ablation center. The continuous C–ZrC–ZrO2 skeleton layer generated from the oxidation of ZrC can protect the composites from erosion at the ablation brim region. The obtained C/C–ZrC composites present a promising potential as ablation resistance materials.