Influence of environmental conditions in bovine bone ablation by ultrafast laser

Ultrafast lasers are promising tools for surgical applications requiring precise tissue cutting. Shallow ablation depth and slow rate as well as collateral damage are common barriers limiting the use of laser in clinical applications. Localized cooling with water and/or air jet is known to reduce collateral thermal damage. We studied the influence of environmental conditions including air, compressed air flow, still water and water jet on ablation depth, ablation rate and surface morphology on bovine bone samples with an 800 nm femtosecond laser. At 15 J/cm², no thermal effect was observed by electron microscopy and Raman spectroscopy. The experimental results indicate that environmental conditions play a significant role in laser ablation. The deepest cavity and highest ablation rate were achieved under the compressed air flow condition, which is attributed to debris removal during the ablation process. The shallowest ablation depth and lowest ablation rates were associated with water flushing. For surface morphology, smooth surface and the absence of microcracks were observed under air flow conditions, while rougher surfaces and minor microcracks were observed under other conditions. These results suggest that ultrafast ablation of bone can be more efficient and with better surface qualities if assisted with blowing air jet.      

Safety and feasibility of atrial fibrillation ablation using Amigo® system versus manual approach: A pilot study

Background

The Amigo^® Remote Catheter System is a relatively new robotic system for catheter navigation. This study compared feasibility and safety using Amigo (RCM) versus manual catheter manipulation (MCM) to treat paroxysmal atrial fibrillation (PAF). Contact force (CF) and force-time integral (FTI) values obtained during pulmonary vein isolation (PVI) ablation were compared.

What Next After Failed Septal Ventricular Tachycardia Ablation?

Ablation of ventricular tachycardia (VT) by conventional radiofrequency ablation can be impossible if the ventricular wall at the targeted ablation site is very thick, as for example the ventricular septum. We present a case of a patient with incessant, non-sustained slow VT originating from the septal part of the lower outflow tracts. Radiofrequency catheter ablation from both ventricles as well as from the anterior cardiac vein were not successful. Both high power radiofrequency ablation and bipolar radiofrequency ablation neither were successfull. Finally, ethanol ablation of the first septal perforator successfully terminated arrhythmia. We discuss the possibilities to overcome failed conventional radiofrequency VT ablation of a septal focus.     

Comparison between surgical and catheter based ablation in atrial fibrillation,should surgical based ablation be implemented as first line? - A meta-analysis of studies

IntroductionAblation remains a modality of choice in select patients with Atrial fibrillation (AF). Which is done via a surgical or catheter-based approach.ObjectiveThis meta-analysis aimed to compare the efficacy of Surgical and Catheter ablation in the management of AF.MethodsElectronic search on PubMed (MEDLINE), EBSCO, EuropePMC, Clinicaltrials.gov, and Google Scholar was done. Studies comparing the use of surgical or catheter ablation in patients with AF were included. The Primary outcome of interest was Arrhythmia free patients at 12 months post-ablation.ResultsEight studies (744 patients) reported a statistically significant difference in Arrhythmia recurrence rate between surgical and catheter-based ablation. The pooled hazard ratio was chosen to compare the risk of AF recurrence between these groups with pooled Hazard ratio comparing surgical to catheter approach of 0.40 [0.35,0.45], p < 0.001 favoring surgical approach; low heterogeneity I² 22%, p = 0.25. Meta-analyses were also performed on procedural time, length of stay and major adverse events.ConclusionThe increased rate of adverse effects and length of hospitalization impedes the implementation of surgical ablation as primary ablation method of AF in general. However, the result of our meta-analysis shows the promising result of surgical ablation compared to catheter-based ablation.     

Comparison between cryoballoon double stop and single stop in patients with paroxysmal atrial fibrillation

BackgroundCurrently, cryoballoon (CB) thawing after single stop is generally performed. Previous research had reported that long thawing time using a single stop affects pulmonary veins tissue injury. However, it is uncertain whether CB thawing after single stop affects clinical outcomes.ObjectiveThis study aimed to clarify clinical significance of CB thawing in patients with paroxysmal atrial fibrillation.MethodsTwo hundred ten patients with paroxysmal atrial fibrillation who underwent CB from January 2018 to October 2019 were analyzed. We compared the clinical outcomes of patients whose CB applications were completely stopped with only the double stop technique (DS group, n = 99) and patients with single stop (SS group, n = 111). In DS group, we performed double stop technique for all CB application regardless of phrenic nerve injury or the temperature of esophagus.ResultsThe atrial arrhythmia free-survival rate at 2 years after CB was significantly lower for the DS group than the SS group (76.8% vs 87.4%; p = 0.045). Complications occurred in 2 patients from the DS group and no complications were observed in patients from the SS group (p = 0.13). Mean procedural time was shorter in the DS group than in the SS group (53.1 vs 58.1 min; p = 0.046)ConclusionDS group had higher recurrence rate than SS group. There was no significant difference regarding safety between both the groups. We found that the thawing process after single stop is very important for CB application.     

The first human experience of a contact force sensing catheter for epicardial ablation of ventricular tachycardia

Contact force (CF) is one of the major determinants for sufficient lesion formation. CF-guided procedures are associated with enhanced lesion formation and procedural success. We report our initial experience in epicardial ventricular tachycardia (VT) ablation with a force-sensing catheter using a new approach with an angioplasty balloon. Two patients with arrhythmogenic right ventricular cardiomyopathy who underwent prior unsuccessful endocardial ablation were treated with epicardial VT ablation. CF data were used to titrate force, power and ablation time.     

射频及微波消融治疗与单纯化疗治疗中晚期非小细胞肺癌生活质量的对比研究

目的：探讨射频及微波消融治疗与单纯化疗对中晚期非小细胞肺癌患者生活质量（QOL）的影响。方法：从选择2009年8月1日至2011年7月31日在我科治疗的120例中晚期非小细胞肺癌患者,将其分为三组,A组：射频消融组;B组：经皮穿刺微波消融治疗治疗组;C组：单纯化疗。在治疗前、后及治疗结束后1个月,应用欧洲癌症研究与治疗组织（european organization for rese-arch treat-ment of cancer,EORTC）生活质量核心问卷（QLQ-C30）对患者的生存质量进行评估。结果：治疗后1个月,A、B两组所有功能指标评分和治疗前比较均无统计学差异（P〉0.05）,症状指标仅呼吸困难评分较治疗前明显升高（P〈0.05）,C组患者体力功能、情绪功能较治疗前明显下降（P〈0.05）,认知功能、总体状况、角色功能及社会功能和治疗前比较无显着性差异（P〉0.05）,疲乏、恶心呕吐、呼吸困难、食欲丧失、腹泻临床症状较治疗前明显增加（P〈0.05）,其余症状指标评分较治疗前无显着性差异（P〉0.05）。治疗后3个月,三组所有功能指标评分与治疗前比较均无显着性差异（P〉0.05）,C组患者恶心呕吐、呼吸困难、食欲丧失的评分仍较治疗前显著增加（P〈0.05）,A、B组呼吸困难评分仍较治疗前明显升高（P〈0.05）。结论：与单纯化疗相比,射频消融、经皮穿刺微波消融治疗中晚期非小细胞肺癌均对患者的生存质量影响较小。     

A review of antenna designs for percutaneous microwave ablation

Microwave (MW) antenna is a key element in microwave ablation (MWA) treatments as the means that energy is delivered in a focused manner to the tumor and its surrounding area. The energy delivered results in a rise in temperature to a lethal level, resulting in cell death in the ablation zone. The delivery of energy and hence the success of MWA is closely dependent on the structure of the antennas. Therefore, three design criteria, such as expected ablation zone pattern, efficiency of energy delivery, and minimization of the diameter of the antennas have been the focus along the evolution of the MW antenna. To further improve the performance of MWA in the treatment of various tumors through inventing novel antennas, this article reviews the state-of-the-art and summarizes the development of MW antenna designs regarding the three design criteria.     

Catheter microwave ablation therapy for cardiac arrhythmias

This article describes three microwave catheter antennas for percutaneous cardiac ablation. A particular design feature of these antennas is that there is no reflected microwave current from the antenna flowing up the transmission line. Thus, it minimizes heating of the coaxial cable. The power reflection coefficients are very low (4% or less) in phantom equivalent materials. These antennas can also serve as bipolar electrodes for sensing endocardiac electrograms. Our studies in dogs, during both cardiopulmonary bypass and closed‐chest operations via the femoral vein, have shown microwave energy greater than 200 joules (J) delivered to the heart through a split‐tip dipole catheter antenna can produce irreversible block of the heart rhythms. This energy was achieved either by increasing the delivered power from 20 to 40 watts or by increasing the treatment duration from 7 to 11 s (210 to 330 J per application). It produced an endocardium temperature of about 65 ºC. We found that the percutaneous, transcatheter microwave system is capable of inducing AV blocks consistently in dogs using the flexible, curved tip, split‐tip catheter antenna. In addition, our studies have shown that the width and height of SAR distributions for cap‐choke and split‐tip catheter antennas are similar for the same antenna length. The cap‐slot design had a much longer SAR distribution compared to the others. Moreover, a longer (4 mm) split‐tip antenna can also induce larger lesions. These results suggest that it could be possible to ablate a ventricular tachycardia focus using the 4 mm split‐tip as well as the cap‐slot microwave catheter antennas. Bioelectromagnetics 20:120–132, 1999. © 1999 Wiley‐Liss, Inc.     

Parametric study of radiofrequency ablation in the clinical practice with the use of two-compartment numerical models

The objective of the current work was to simulate radiofrequency ablation (RFA) with theoretical and realistic computational models, which correspond to single-compartment models and clinical scenarios. A 3D model in a cubic region of 12 cm edge was studied representing either a homogeneous model or real clinical scenarios in three human tissues, i.e., liver, lung and kidney. An active electrode was placed at the center of the model. Various tumor sizes (1–3 cm) and source voltages (10–30 V) were investigated for the second case of a two-compartment model. In the case of a 3-cm tumor in diameter, the electrical and thermal problems (at steady state) were solved to calculate the temperature distribution within the tumor and tissue. Lesion volume was quantified using the Arrhenius equation and the isothermals of 50 and 60 °C. The physical properties of all materials were constant during the simulations, i.e., no changes with temperature were considered. It was found that tumor conductivity was low to achieve significant damage in the tumor; in all clinical scenarios, saline-enhanced RFA was necessary and led to a more efficient tumor destruction. It was also shown that highly perfused tissues, such as liver and kidney, block the energy deposition within them, in contrast to lung, and, thus, require a further saline enhancement. Finally, the effect of perfusion on lesion size was studied, and it was concluded that tumor perfusion was more significant than surrounding tissue perfusion.     

The symbiosis of contact force catheter use for hybrid ablation for atrial fibrillation

Objective

Reconduction across an ablation line is a common reason for arrhythmia recurrence over time. The hybrid procedure combines epicardial ablation of the pulmonary vein (PV) and creation of a box lesion with endocardial touch-ups for any electrical gaps. A high contact force (CF) between the ablation tip and cardiac tissue may increase the risk of thrombus formation, catheter tip charring, steam pop formation, and even cardiac perforation. CF monitoring is a significant new parameter for titration of the CF for creating an adequate lesion.

Methods

Thirty-eight consecutive patients underwent epicardial ablation using bipolar radiofrequency devices. After checking electrical bidirectional block of the ablation lines, an endocardial CF catheter was used for further ablation (if needed) to complete the isolation of PVs, box lesion, cavotricuspid isthmus (CTI), and complex fractionated atrial electrograms (CFAE).

Results

Endocardial touch-up was needed for 2 PVs (1.3 %) and 10 (26.3 %) box lesions. It was also used for the CTI line in 7 (18.4 %) patients, atrial tachycardia in 3 (7.9 %) patients, and additional CFAE ablation in 17 (44.7 %) patients. All 5 patients with arrhythmia recurrence had a mean CF < 10 g (p = 0.03). Procedure duration was significantly shorter in the CF group (223 ± 57 vs. 256 ± 60 min, p = 0.03) compared with control group.

Conclusion

Use of CF catheters is safe, feasible, and complementary to a hybrid procedure setup for atrial fibrillation ablation. Its real-time monitoring may predict future arrhythmia recurrence, and decrease procedure time.     

Epicardial Ablation For Ventricular Tachycardia

Epicardial ablation has lately become a necessary tool to approach some ventricular tachycardias in different types of cardiomyopathy. Its diffusion is now limited to a few high volume centers not because of the difficulty of the pericardial puncture but since it requires high competence not only in the VT ablation field but also in knowing and recognizing the possible complications each of which require a careful treatment.This article will review the state of the art of epicardial ablation with special attention to the procedural aspects and to the possible selection criteria of the patients.     

Successful Ablation of an Epicardial Accessory Pathway via the Subxiphoid Approach in a Child

Data is scarce regarding epicardial ablation in children. I herewith present a case of successful epicardial ablation in a child with previous unsuccessful attempts at endocardial ablation. This report could be used to guide further such attempts.     

Pulmonary vein reconnection following cryo-ablation: Mind the “Gap” in the carinae and the left atrial appendage ridge

Pulmonary vein (PV) isolation (PVI) remains cornerstone to ablation of atrial fibrillation (AF). For effective and durable PVI and thus fewer AF recurrences, lesion gaps in transmurality and contiguity responsible for PV reconnection (PVR) could only be addressed when one is cognizant of the potential location and sites where these lesion characteristics may be more prevalent and responsible for PVR. In the case of RF ablation, newer technologies incorporating contact force, time and power with automated monitoring of lesion formation, paying attention to difficult areas (carinae, left superior PV-LAA ridge, right inferior PV) and measuring inter-lesion distance may provide the tools to reduce PVR. On the other hand, the improved thermodynamic characteristics of the latest generation of cryoballloons and operator dexterity to achieve better PV occlusion, may be crucial determinants towards the direction of reduced PVR. Whether newer visualization tools, more vigilant testing during the index ablation procedure in these particular regions, prolonging or adding cryothermic applications, waiting longer to test for entrance and exit block, and/or use of provocative drug testing (isoproterenol/adenosine challenge) might help prevent future PVRs awaits further studies.