Standard Ablation Research Articles

The Effect of the Asphericity of Myopic Laser Ablation Profiles on the Induction of Wavefront Aberrations

To compare the effects of laser profile asphericity on the induction of wavefront aberrations, susceptibility to decentration, and depth of focus in a polymethylmethacrylate (PMMA) model. Four PMMA lenses received an excimer laser ablation of -6 D with a 6-mm optical zone and different amounts of primary spherical aberration (Z(4)(0)): 0, -0.346, -1.038, and -2.076 microm. The curvature of each lens was measured by using surface profilometry, and wavefront changes were computed from curvature differences. Changes in optical quality were compared by treatment simulation of 13 real myopic eyes. The influence of pupil diameter, ablation decentration, and defocus on retinal image quality was measured by using the optical transfer function-based visual Strehl ratio (VSOTF). Aspheric ablation profiles induced significantly less primary but higher secondary spherical aberration (Z(6)(0)) than did the standard profile; however, Z(4)(0) compensation was incomplete. Simulated treatments with aspheric profiles resulted in significantly better retinal image quality and higher decentration tolerance than did the standard profile. Optical depth of focus was not affected with a 3-mm pupil, whereas with a 6-mm pupil, there was a small but statistically significant decrease in depth of focus. Aspheric laser profiles showed theoretical optical benefits over standard ablation profiles for the treatment of myopia, including terms of decentration tolerance. However, there remained profound induction and thus, undercorrection of Z(4)(0), due to loss of laser ablation efficiency in the lens periphery.

Measurement of intrahepatic pressure during radiofrequency ablation in porcine liver

To identify the most effective procedures to avoid increased intrahepatic pressure during radiofrequency ablation, we evaluated different ablation methods. Laparotomy was performed in 19 pigs. Intrahepatic pressure was monitored using an invasive blood pressure monitor. Radiofrequency ablation was performed as follows: single-step standard ablation; single-step at 30 W; single-step at 70 W; 4-step at 30 W; 8-step at 30 W; 8-step at 70 W; and cooled-tip. The array was fully deployed in single-step methods. In the multi-step methods, the array was gradually deployed in four or eight steps. With the cooled-tip, ablation was performed by increasing output by 10 W/min, starting at 40 W. Intrahepatic pressure was as follows: single-step standard ablation, 154.5 +/- 30.9 mmHg; single-step at 30 W, 34.2 +/- 20.0 mmHg; single-step at 70 W, 46.7 +/- 24.3 mmHg; 4-step at 30 W, 42.3 +/- 17.9 mmHg; 8-step at 30 W, 24.1 +/- 18.2 mmHg; 8-step at 70 W, 47.5 +/- 31.5 mmHg; and cooled-tip, 114.5 +/- 16.6 mmHg. The radiofrequency ablation-induced area was spherical with single-step standard ablation, 4-step at 30 W, and 8-step at 30 W. Conversely, the ablated area was irregular with single-step at 30 W, single-step at 70 W, and 8-step at 70 W. The ablation time was significantly shorter for the multi-step method than for the single-step method. Increased intrahepatic pressure could be controlled using multi-step methods. From the shapes of the ablation area, 30-W 8-step expansions appear to be most suitable for radiofrequency ablation.

Visual performance after LASIK for a Q-optimized and a standard ablation algorithm

We test visual performance after LASIK (laser in situ keratomileusis) for a Q-optimized ablation algorithm and one based on the Munnerlyn formula. The visual functions tested include aberrometry, monocular and binocular contrast sensitivity function (CSF), and a discrimination test under low-illumination conditions. This test is useful to quantify night-vision disturbances. A total of 102 patients took part in the experiments, and visual data were taken before (with best correction) and after LASIK. Results show a deterioration in aberrometry, CSF, binocular summation, and discrimination index for the two algorithms tested, although this deterioration is significantly lower for the Q-optimized algorithm.

Transapical left ventricular access for difficult to reach interventional targets in the left heart

Interventional targets may be virtually "excluded" due to vascular access problems or complex previous surgical procedures. This study reviews our experience using transapical ventricular puncture to gain direct access to the systemic ventricle. Patient 1 (74 years, 2 previous sternotomies), patient 2 (66 years, 5 previous sternotomies), and patient 5 (69 years, 3 previous sternotomies) with prosthetic valves had paravalvular mitral valve leaks. Patient 3 (6.3 years, 2 previous sternotomies) with an extracardiac Fontan conduit, had a significant residual leak after two previous surgical attempts of patch closure of a severely regurgitant right atrioventricular valve. Patient 4 (10 months) had failure of standard ablation of the posteroseptal region of the mitral valve with persistent life-threatening episodes of ventricular tachycardia. Procedures were performed under general anesthesia. Entry site was percutaneous in three patients and in two (and one conversion) a mini-thoracotomy was used. Sheaths were placed (6 F) using standard Seldinger technique, followed by the procedure as required. Direct surgical closure of the puncture site was done in 4 patients and in patient 3, a percutaneous vascular occlusion device was used. Easy and immediate access was obtained in all patients. The paravalvular leaks were crossed within seconds and completely closed with Amplatzer occluders. In patient 3 the valve was crossed using a Brokenbrough needle and a 12-mm Amplatzer device was placed in the patch leak. Patient 4 was successfully ablated using a 7-F irrigated catheter endo- and epicardially. Complications were in the percutaneous puncture group: in one patient a coronary artery was punctured and in one a hemothorax developed. Direct left ventricular puncture offers a very useful alternative access site in selected patients to reach "inaccessible" targets for certain percutaneous interventions in patients where standard approaches may be impossible or difficult.

Endovenous laser ablation: Does standard above-knee great saphenous vein ablation provide optimum results in patients with both above- and below-knee reflux? A randomized controlled trial

Endovenous laser ablation: Does standard above-knee great saphenous vein ablation provide optimum results in patients with both above- and below-knee reflux? A randomized controlled trial

Endovenous laser ablation: Does standard above-knee great saphenous vein ablation provide optimum results in patients with both above- and below-knee reflux? A randomized controlled trial

Endovenous laser ablation: Does standard above-knee great saphenous vein ablation provide optimum results in patients with both above- and below-knee reflux? A randomized controlled trial

Endovenous laser ablation: Does standard above-knee great saphenous vein ablation provide optimum results in patients with both above- and below-knee reflux? A randomized controlled trial

Endovenous laser ablation: Does standard above-knee great saphenous vein ablation provide optimum results in patients with both above- and below-knee reflux? A randomized controlled trial

An Alternative Approach for Radiofrequency Catheter Ablation for Intra-atrial Reentrant Tachycardia Associated with Open-Heart Surgery

We present case reports of 2 patients with scar-related intra-atrial reentrant tachycardia (IART) associated with previous open-heart surgeries, in which standard ablation strategies failed to eliminate atrial tachycardia (AT). The strategies targeted a narrow conducting channel between the right atrial scars or between the scar and inferior vena cava. In these patients, an alternative approach to transect another narrow conducting pathway between the scar and crista terminalis (CT), which was revealed by a noncontact mapping system, successfully terminated and eliminated the IART. Both the cases were free of recurrent AT at the 24-and 25-month follow up visits, respectively. Transection of the corridor between the CT and the incision scar appears to be an effective technique for eliminating scar-related IART and can be considered as a second-line procedure for radiofrequency catheter ablation to eliminate IART.

An Alternative Approach for Radiofrequency Catheter Ablation for Intra-atrial Reentrant Tachycardia Associated with Open-Heart Surgery

We present case reports of 2 patients with scar‐related intra‐atrial reentrant tachycardia (IART) associated with previous open‐heart surgeries, in which standard ablation strategies failed to eliminate atrial tachycardia (AT). The strategies targeted a narrow conducting channel between the right atrial scars or between the scar and inferior vena cava. In these patients, an alternative approach to transect another narrow conducting pathway between the scar and crista terminalis (CT), which was revealed by a noncontact mapping system, successfully terminated and eliminated the IART. Both the cases were free of recurrent AT at the 24‐and 25‐month follow up visits, respectively. Transection of the corridor between the CT and the incision scar appears to be an effective technique for eliminating scar‐related IART and can be considered as a second‐line procedure for radiofrequency catheter ablation to eliminate IART.

Radiofrequency Thermal Ablation of Hepatic Metastases of Adrenocortical Cancer – A Case Report and Review of the Literature

Radiofrequency thermal ablation (RFA) has shown promise as a technique for treating solid tumors. This method has been suggested as an alternative to surgery in patients with adrenocortical carcinoma (ACC). We reviewed the literature, and report the case of a patient with stage 4 ACC who received intraoperative and percutaneous RFA of two liver metastasis according to a standard ablation protocol. Post-interventional imaging in our patient demonstrated that after both interventions, a stellar-like structure of vital tumor tissue had remained within the coagulation necrosis. This was the starting point of a fast and progressive tumor recurrence. We suspect heat-sink effects of blood vessels in the highly vascularized metastasis to cause the tumor recurrence. In literature, there are only a few reports of RFA in ACC patients. In addition, there is no large randomized trial investigating the efficacy of RFA against surgery in those patients. Presently, RFA in ACC should be restricted to patients in whom surgery is contraindicated. It is necessary that strongly vascularized ACC metastases deserve a modified ablation protocol due to perfusion related cooling effects and to increase the efficacy of RFA.

Qualidade visual após retratamento de LASIK personalizado versus convencional

To evaluate visual quality after wavefront-guided LASIK versus standard LASIK in retreatment of primary LASIK for myopia and myopic astigmatism. A prospective study was performed with paired eye control of 74 eyes with LASIK retreatment. Each patient underwent retreatment using custom ablation (Zyoptix, Bausch & Lomb) in 1 eye and standard ablation LASIK (PlanoScan, Bausch & Lomb) in the contralateral eye. A complete ophthalmologic examination was performed, including evaluation of glare test and contrast sensitivity test, with a follow-up of 6 months. Zyoptix eyes showed better results of glare test and contrast sensitivity test than the contralateral eyes. Wavefront-guided LASIK produces better visual quality than standard LASIK in the retreatment of refractive errors after primary LASIK.

Effect of the zone-division LASIK for ultrahigh myopia

目的 评价对角膜相对较薄的超高度近视,应用分区切削模式进行LASIK治疗的临床效果.方法对95例(185眼)超高度近视,因选择6.0mm直径的切削区,剩余角膜厚度小于250μm,而进行LASIK分区切削治疗,分区切削分为2～3区,切削光区4.7～6.0 mm.随访时间6～20月,观察手术前后的屈光状态、裸眼视力、矫正视力、角膜地形图及并发症的发生情况.结果 术后1月视力达到最好并趋于稳定,所有患者的裸眼视力均较术前提高,术后3月183眼(98.92%)裸眼视力超过或等于术前最佳矫正视力.屈光回退47眼(25.41%),术后眩光51眼(27.57%),分析手术后角膜地形图,切削过度区光滑,无偏心切削.与标准手术相比可节省角膜厚度20%～25%,视力、屈光度变化与分区多少及近视度数有关.少数患者出现的眩光、夜视力下降等并发症,1个月后减轻或消失,角膜地形图均为正常负性形态.结论 LASIK分区切削模式是对角膜相对较薄的超高度近视进行激光治疗有效安全的方法.可节省角膜组织,具有安全可靠,稳定性、可预测性强的临床效果。

Image integration in 3D catheter mapping systems: proof of the pudding

Pulmonary vein (PV) isolation can be performed at different levels in the ostium. Initially, segmental isolation, targeting individual strands of atrial myocardial tissue in PV ostia, was performed using the combination of a circular mapping catheter and a standard ablation catheter.1 In most centres, clinical success rates were moderate. Soon, however, it was recognized that wider encircling improved success and reduced complications.2 Additional ablation lines and substrate modification may further increase success, but may also create a substrate for left atrial flutters.3–5 The creation of a long continuous ablation line around a PV antrum using a single ablation electrode is technically challenging. Kistler et al. described a prospective randomized study to investigate the contribution of image integration to catheter ablation of atrial fibrillation.6 The value of Cartomerge® was investigated on the basis of an incomplete Carto map. It is highly remarkable that even then, image integration did not affect the quality of the procedure. The study suggests that an anatomically correct geometry does not facilitate the creation of continuous transmural lesions. Such geometry definitively helps to outline the desired course of the ablation lines, but apparently it does not improve the continuity of that line. Use it if you like it, but don't expect any miracles. The ablation procedure … *Corresponding author. Tel: +31 30 2506184, Fax: +31 30 2505471, Email: fredwittkampf{at}mac.com

2042 Reduction in pulmonary vein size after atrial fibrillation ablation in the absence of pulmonary vein stenosis

Methods Twelve consecutive patients with a mean age of 60 years old undergoing PVI by a single operator underwent cardiac MRI pre and post ablation. PVI was performed using standard ablation techniques and MRI scans were conducted on a 1.5 Telsa system with a protocol optimized for pulmonary venography using a 3D CE MRA sequence. All analysis was performed using a ViewForm workstation. All four pulmonary vein diameters were measured pre and post procedure.

Re‐treatment after LASIK for correction of myopia and myopic astigmatism

Abstract Purpose To evaluate the results of LASIK re‐treatment for under‐correction or regression after primary LASIK procedures for myopia and myopic astigmatism. Methods Of 360 consecutive LASIK‐treated eyes, for myopia and/or myopic astigmatism, 32 eyes of 34 patients were retreated and followed at 3, 6 and 12 months post retreatment. Re‐treatment was performed by lifting the original flap after cutting the epithelium around the flap edge with a fine needle. Standard ablation was performed based on the patient’s residual refraction. Results 9.4% of eyes patients required retreatment. Prior to re‐treatment the mean manifest spherical equivalent (SE) was –0.99 D ± 1.48 D (range from ‐ 0.75 to ‐2.63). The mean sphere was ‐ 0.79 D ± 1.20 D (range from –2.50 to ‐0.50) and the mean cylinder was –0.90 D ± 1.14 D (from –2.75 to 1.25). At 1 year follow up 56% of the eyes were within ± 0.50 D SE and 78% were within ± 1.00 D SE. 78% percent of the eyes examined at one year post re‐treatment managed unaided vision of 6/9 or better. Peripheral epithelial ingrowth not requiring treatment, developed in two eyes. Second re‐treatment for regression was performed in one eye. Conclusion LASIK re‐treatment for residual myopia, by lifting the original flap is an effective option. Refractive results are fairly predictable and refraction stabilizes by 3 months after re‐treatment. Lifting the corneal flap after cutting the epithelium on the flap edges, is easy to perform and has a very low incidence of epithelial ingrowth.

Re-treatment after laser in situ keratomileusis for correction of myopia and myopic astigmatism

Aim:To evaluate the results of laser in situ keratomileusis (LASIK) re-treatment for under correction or regression after primary LASIK procedures for myopia and myopic astigmatism.Methods:A prospective evaluation of 360 consecutive...

Intracardiac ECHO Integration with Three Dimensional Mapping: Role in AF Ablation.

Background: Catheter ablation of atrial fibrillation (AF) is typically guided by 3D mapping. This involves point-by-point reconstruction of the 3D virtual anatomy and may be time consuming and require substantial fluoroscopy exposure. Intracardiac echocardiography (ICE) affords real time imaging of the cardiac structures during mapping and ablation. Methods: Between February and May 2007, 15 patients (100% men, 10 with paroxysmal AF) presenting for AF ablation were offered mapping using a novel system integrating 3D mapping and ICE. A modified ICE probe with a location sensor tracked by the mapping system was positioned in the right atrium (RA). This allowed acquisition of ECG gated images of the left atrium (LA). Endocardial contours were traced on each image and were used to generate a registered 3D map. Results: 3D maps took a mean of 51+/-25 minutes to create, PRIOR to entering the LA and without fluoroscopy. Pulmonary veins and the esophagus were rendered in 3D. A complete map was built from a mean of 46+/-19 contours. Upon instrumentation of the left atrium, the maps were easily distorted if points collected by the mapping catheter were combined with the original map, due to deformation of the left atrial geometry by the relatively stiff ablation catheter. Pulmonary vein antrum isolation was guided by a circular mapping catheter. Since this catheter could not be visualized on the CARTO map, fluoroscopy was used to track its position and the contact between the ablation catheter and the circular mapping catheter. No substantial reduction in fluoroscopy time was thus realized, as expected. At 10+/-1 months of followup, 73% of the patients were in sinus rhythm after the initial three month blanking period. No patient suffered any complications related to the procedure or in follow-up. Conclusions: A mapping system combining ICE and 3D electroanatomical mapping can feasibly reconstruct a 3D shell of the LA and the pulmonary veins without the need to enter the left heart. The map created is sensitive to distortion during point-by-point mapping with the standard ablation catheter.

Comparative study on purity evaluation of singlewall carbon nanotubes

Here we present a comparative study on Raman spectroscopy and optical absorption spectroscopy (OAS) as two main techniques being used for the purity evaluation of singlewall carbon nanotubes (SWCNT). The raw material was produced by the standard laser ablation technique using cobalt and nickel as catalysts (40 wt.% SWCNT). The presence of impurities influences the measurement of the properties of the carbon nanotubes. Therefore, the systematic purification study and its comparative estimation using the above mentioned characterization tools are presented. In order to reduce the catalyst particles content the diluted aqua regia was applied. In order to eliminate the amorphous carbon and fullerenes (unwanted forms of carbon) the high temperature annealing was used. The measurements were performed in suspension (dimethylformamide (DMF)) and on thin film deposited on potassium bromide crystal. This gave additional information about the effect of the sample preparation technique sensitivity on the purity of SWCNT evaluation.

Standardization and validation of an automated algorithm to identify fractionation as a guide for atrial fibrillation ablation

Atrial fibrillation catheter ablation is frequently guided by identification of fractionated electrograms, which are thought to be critical for maintenance of the arrhythmia. Objective automated means for identifying fractionation independent of physician interpretation have not been standardized or validated. The purpose of this study was to standardize and validate an automated algorithm to rapidly identify fractionated electrograms for high-density atrial fibrillation fractionation mapping. Left and right atrial fractionation maps were generated by EnSite NavX 6.0 software, using standardized ablation catheters in eight patients with atrial fibrillation. Two blinded electrophysiologists interpreted all electrograms as either fractionated or not fractionated. A stepwise approach was used to optimize automated settings to accurately identify fractionation. High-density fractionation maps were generated with a 20-pole mapping catheter in eight other patients. Two blinded electrophysiologists interpreted all electrograms as near field or far field. The algorithm was refined to optimize settings to exclude far-field signals and retain near-field signals. The sampling segment length was adjusted to optimize recording time to ensure reproducibility. Using 1,514 points, the automated software achieved sensitivity of 0.75 and specificity of 0.80 for identification of fractionated electrograms. Using 725 points collected via multipole catheters with optimal automated settings, 94% of near-field fractionated electrograms were accurately identified. A 6-second sampling length was needed for reproducible fractionation measurements. Standardized settings of EnSite NavX 6.0 software with 6-second data collection per point can rapidly and accurately generate high-density fractionation maps independent of physician electrogram interpretation. This may allow for an automated, standardized approach to atrial fibrillation fractionated ablation.

Patient Satisfaction and Visual Symptoms After Wavefront-guided and Wavefrontoptimized LASIK With the WaveLight Platform

To investigate patient satisfaction and visual symptoms after wavefront-guided LASIK. A prospective, randomized, double-masked, controlled study comprised 200 eyes of 100 young patients who underwent LASIK for myopia and astigmatism. Patients were randomly divided into two different treatment groups: standard ablation using wavefront-optimized profiles (wavefront-optimized group) and aberration customized aspheric treatment ablation (customized group) using the WaveLight ALLEGRETTO platform. Patients were asked to complete questionnaires regarding reasons for surgery, satisfaction, and visual symptoms. Patients were followed for 6 months. The most frequent motivating factor for surgery was to improve uncorrected visual acuity (UCVA) in the wavefront-optimized and customized groups (both 100%), followed by freedom from spectacles (86.9% vs 96.3%). At 6 months postoperatively, over 95% of patients in both groups reported their UCVA was as good as anticipated and they were satisfied with the surgery and would recommend the operation to a friend or family member. Satisfaction was not correlated with age, attempted refractive error, residual refractive error, postoperative UCVA, or root-mean-square higher order aberration. The rate of postoperative overall visual symptoms was reduced and the mean analog scores of the symptoms in both groups did not change significantly postoperatively (P > .05). The rate of visual symptoms such as glare (8.7% vs 7.4%), halo (0% vs 7.4%), and night driving difficulty (8.7% vs 3.7%) decreased after LASIK at 6 months postoperatively in the wavefront-optimized and customized groups, respectively. Patient satisfaction was achieved in young myopic patients who underwent wavefront-guided and standard ("wavefront-optimized") LASIK. The rate of visual symptoms such as glare, halo, and night driving difficulty decreased postoperatively after both treatment protocols.