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Investigação de ablação a laser no regime de femtossegundo em materiais homogêneos e estruturados; Investigation of the femtosecond laser ablation on homogeneous and structured materials

Nicolodelli, Gustavo
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 31/03/2011 PT
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Embora a ablação a laser venha sendo bastante utilizada em materiais em geral, pouco é entendido sobre o comportamento deste processo perto de uma interface separando dois materiais distintos. Neste contexto, o principal objetivo deste trabalho foi realizar um estudo macroscópico e microscópico dos processos que envolvem a ablação a laser em regime de femtossegundos em materiais homogêneos e estruturados. No caso de materiais estruturados, o estudo focou-se em uma situação de interface, na qual ocorrem mudanças nas propriedades de ablação. Baseado nos resultados, nós pretendemos obter subsídios científicos para entender as aplicações da ablação em regime de pulsos ultracurtos para estruturas estratificadas, tais como de dentes, ossos, interface resina-dente, dente-metal, e outras. Diferentes técnicas experimentais foram idealizadas para determinar a progressão da ablação dentro do material e obter dados extraídos da superfície. Utilizando luz espalhada de uma fonte externa, o processo de ablação foi temporalmente monitorado, permitindo determinar a velocidade de ablação em materiais transparentes, assim como perfis típicos de ablação nestes materiais. Em um segundo experimento, nosso estudo permitiu quantificar a variação da geometria de ablação perto de uma interface separando dois materiais distintos. Nossos dados foram suficientes para prever a ocorrência de uma descontinuidade no perfil da ablação entre dois meios: resina A e resina B...

Estudo sobre o efeito de técnicas preventivas na incidência de lesões esofageanas após ablação do átrio esquerdo para tratamento de fibrilação atrial; Study on the effect of preventive techniques in the incidence of esophageal lesions after left atrial ablation for treatment of atrial fibrillation

Oliveira , Barbara Daniela da Eira
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 20/05/2015 PT
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Introdução: Na última década, desde a descrição inicial da ablação das veias pulmonares, a ablação por cateter da fibrilação atrial (FA) tem evoluído consideravelmente em eficácia e segurança, consolidando-se como opção terapêutica em pacientes selecionados com FA. No entanto, a ablação da FA é um procedimento complexo e não isento de riscos. Ainda que seja uma complicação rara, o desenvolvimento de fístulas átrio-esofágicas (FAE) é a segunda complicação responsável por morte relacionada ao procedimento e responde por 16% dos casos de morte após ablação de FA. Consensos atuais não orientam recomendações definitivas para prevenção de lesões esofágicas, consideradas lesões precursoras de FAE. O objetivo deste trabalho foi comparar a incidência de lesões esofageanas e periesofageanas por ecoendoscopia após ablação de fibrilação atrial, utilizando diferentes estratégias de proteção esofágica durante as aplicações de radiofrequência na parede posterior do átrio esquerdo. Método: No período de outubro/2012 a julho/2014, foram estudados 45 pacientes submetidos à ablação percutânea de FA, portadores de FA paroxística ou persistente há menos de um ano. Todos os pacientes foram submetidos a ablação circunferencial com isolamento elétrico das veias pulmonares...

L-histidine reduces inhibitory avoidance in Carassius auratus submitted to cerebellar ablation

Garção,D.C.; Mattioli,R.
Fonte: Associação Brasileira de Divulgação Científica Publicador: Associação Brasileira de Divulgação Científica
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2009 EN
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The effect of post-training treatment with L-histidine (LH) on the memory consolidation of inhibitory avoidance was investigated in Carassius auratus submitted to cerebellar ablation. The inhibitory avoidance procedure included 3 days: one habituation day, one training day (5 trials, T1-T5) and one test day. On the training day, each fish was placed individually in a white compartment separated from a black compartment by a sliding door. When the fish crossed into the black compartment, a weight was dropped in front of it (aversive stimulus) and the time to cross was recorded. Saline or LH (100 mg/kg) was injected intraperitoneally 10 min after the trials. Data were log10 transformed and analyzed by ANOVA and the Student-Newman-Keuls test (P < 0.05). In T5, all groups [ablation/LH (N = 15; 189.60 ± 32.52), ablation/saline (N = 14; 204.29 ± 28.95), sham/LH (N = 14; 232.36 ± 28.15), and sham/saline (N = 15; 249.07 ± 25.82)] had similar latencies that were significantly higher than T1 latencies [ablation/LH (89.33 ± 20.41), ablation/saline (97.00 ± 25.16), sham/LH (73.86 ± 18.42), and sham/saline (56.71 ± 17.59)], suggesting acquisition of inhibitory avoidance. For the test, there was a significant reduction in latencies of ablation/LH (61.53 ± 17.70) and sham/saline (52.79 ± 25.37) groups compared to the ablation/saline (213.64 ± 29.57) and sham/LH (199.43 ± 24.48) groups...

Electrophysiologic and clinical consequences of linear catheter ablation to transect the anterior left atrium in patients with atrial fibrillation

Sanders, P.; Jais, P.; Hocini, M.; Hsu, L.; Scavee, C.; Sacher, F.; Rotter, M.; Takahashi, Y.; Pasquie, J.L.; Shah, D.; Garrigue, S.; Clementy, J.; Haissaguerre, M.
Fonte: Elsevier Inc. Publicador: Elsevier Inc.
Tipo: Artigo de Revista Científica
Publicado em //2004 EN
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Background While the Maze procedure is effective in maintaining sinus rhythm in patients with AF, it is associated with significant morbidity. This prospective clinical study evaluates the feasibility and consequences of limited LA linear ablation to transect the anterior LA in patients with AF. Methods Twenty-four patients (51.2 ± 7.3 years) with paroxysmal (n = 16) or chronic (n = 8) AF resistant to pulmonary vein (PV) isolation were studied. To transect the anterior LA, linear ablation was performed joining the superior PVs; this line was then connected to the anterior mitral annulus. Pulmonary vein isolation and cavotricuspid isthmus ablation were performed in all cases. Ablation was performed using an irrigated catheter with the endpoint of achieving complete linear block demonstrated by online double potentials, differential pacing techniques, and an activation detour. Results Of 20 patients in AF prior to linear ablation, arrhythmia terminated in 12 (60%), including half the patients with chronic AF, during ablation. Despite repeated ablation, complete linear block was achieved in only 14 of 24 patients (58%). Complete linear conduction block resulted in an activation detour around the mitral annulus and PVs with a delay of 158 ± 30 ms (P = .0001)...

Prevalence of pulmonary vein disconnection after anatomical ablation for atrial fibrillation: consequences of wide atrial encircling of the pulmonary veins

Hocini, M.; Sanders, P.; Jais, P.; Hsu, L.; Weerasooriya, R.; Scavee, C.; Takahashi, Y.; Rotter, M.; Raybaud, F.; MacLe, L.; Clementy, J.; Haissaguerre, M.
Fonte: W B Saunders Co Ltd Publicador: W B Saunders Co Ltd
Tipo: Artigo de Revista Científica
Publicado em //2005 EN
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Aims Anatomical and wide atrial encircling of the pulmonary veins (PVs) has been proposed as a cure of atrial fibrillation (AF). We evaluated the acute achievement of electrical PV isolation using this approach. In addition, the consequences of wide encircling of the PVs with isolation were assessed. Methods and results Twenty patients with paroxysmal AF were studied. Anatomically guided ablation was performed utilizing the CARTO system to deliver coalescent lesions circumferentially around each PV to produce a voltage reduction to ,0.1 mV, with the operator blinded to recordings of circumferential PV mapping. After achieving the anatomical endpoint, the incidence of residual conduction and the amplitude and conduction delay of residual PV potentials were determined. Electrical isolation of the PV was then performed and the residual far-field potentials evaluated. Individual PV ablation was performed in all PVs. Anatomically guided PV ablation was performed for 47.3+11 min, after which 44 (55%) PVs were electrically isolated. In the remaining 45%, despite abolition of the local potential at the ablation site, PV potentials [amplitude 0.2 mV (range 0.09–0.75) and delay of 50.3+12.6 ms] were identified by circumferential mapping. After electrical isolation (12.2+11.7 min ablation)...

Bimodal electric tissue ablation (BETA) - in-vivo evaluation of the effect of applying direct current before and during radiofrequency ablation of porcine liver

Cockburn, J.; Maddern, G.; Wemyss-Holden, S.
Fonte: W B Saunders Co Ltd Publicador: W B Saunders Co Ltd
Tipo: Artigo de Revista Científica
Publicado em //2007 EN
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AIM: To examine the effect of applying increasing amounts of direct current (DC) before and during alternating current radiofrequency ablation of porcine liver. MATERIALS AND METHODS: Using a Radiotherapeutics RF3000 generator, a 9 V AC/DC transformer and a 16 G plain aluminium tube as an electrode, a control group of 24 porcine hepatic radiofrequency ablation zones was compared with 24 zones created using a bimodal electric tissue ablation (BETA) technique in three pigs. All ablations were terminated when tissue impedance rose to greater than 999 Omega or radiofrequency energy input fell below 5 W on three successive measurements taken at 1 min intervals. BETA ablations were performed in two phases: an initial phase of variable duration DC followed by a second phase during which standard radiofrequency ablation was applied simultaneously with DC. During this second phase, radiofrequency power input was regulated by the feedback circuitry of the RF3000 generator according to changes in tissue impedance. The diameters (mm) of each ablation zone were measured by two observers in two planes perpendicular to the plane of needle insertion. The mean short axis diameter of each ablation zone was subjected to statistical analysis. RESULTS: With increased duration of prior application of DC...

The safety and efficacy of radiofrequency and electrolytic ablation created adjacent to large hepatic veins in a porcine model

Metcalfe, M.; Mullin, E.; Texler, M.; Berry, D.; Dennison, A.; Maddern, G.
Fonte: Elsevier Science Ltd Publicador: Elsevier Science Ltd
Tipo: Artigo de Revista Científica
Publicado em //2007 EN
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INTRODUCTION: Immediately adjacent to large hepatic veins, tumour ablation by radiofrequency or electrolysis may be impaired by heat or current sink effects. Ablation may also cause vessel injury and thrombosis. The aim of this study was to evaluate the safety and efficacy of radiofrequency and electrolytic ablative techniques adjacent to large hepatic veins. METHODS: Electrolytic and radiofrequency zones of ablation were created adjacent to hepatic veins in large white pigs. After 72 h the zones of ablation created were examined histologically for (a) the extent of tissue necrosis up to the vessel and (b) the presence of intimal damage and mural thrombus in the veins. RESULTS: An unexpected complication of electrolysis near large veins was cardiac tamponade. This current related phenomenon could easily be avoided. In seven of nine electrolysis zones of ablation necrosis was completely adjacent to the vessel wall, but in only four of seven radiofrequency zones of ablation. All zones of ablation were associated with intimal necrosis, and most with mural thrombosis. CONCLUSIONS: Ablation of hepatic tumours by radiofrequency and electrolysis is unreliable adjacent to hepatic veins. Both techniques are associated with mural thrombus formation...

The future of radiofrequency ablation is looking BETA : short and long term studies of bimodal electric tissue ablation (BETA) in a porcine model.

Dobbins, Christopher
Fonte: Universidade de Adelaide Publicador: Universidade de Adelaide
Tipo: Tese de Doutorado
Publicado em //2008
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Introduction: Radiofrequency ablation (RFA) is a popular method of treating unresectable liver tumours by the use of a high frequency, alternating electrical current that heats and destroys tumour cells. The size of the ablation is limited by localised charring of adjacent tissue that prevents further conduction of the radiofrequency current. In the clinical setting, this results in increased rates of local recurrence in tumours that are greater than 3 cm in diameter as multiple, overlapping ablations need to be performed to treat the one tumour. To overcome this problem, a modified form of RFA called Bimodal Electric Tissue Ablation (BETA) has been created. BETA adds a direct electrical current to the alternating radiofrequency current, thus establishing its bimodal character. When direct currents are used in biological tissues, water is transferred from anode to cathode by a process called electro-osmosis. By attaching the cathode to the radiofrequency electrode, water is attracted to the area thus preventing tissue desiccation and charring. The BETA circuit has been constructed and tested using a porcine model. The aims of the studies are to confirm that larger ablations can be produced with the BETA system and that it is safe to use in an animal model. Three studies have been performed to test these aims in porcine liver. Methods: The first study was designed to compare sizes of the ablation produced between standard RFA and the BETA circuit. This was followed by a long-term study to assess associated changes to liver function and pathological changes within the liver as well as identifying any other treatment related morbidity. The third study assessed the difference in ablation size and safety aspects when the positive electrode of the direct current circuitry was moved from small surface area under the skin to a large surface area on the skin. Results: Ablations with significantly larger diameters are created with the BETA circuit using a multi-tine needle (49.55 mm versus 27.78 mm...

Outcomes of long-standing persistent atrial fibrillation ablation: A systematic review

Brooks, A.; Stiles, M.; Laborderie, J.; Lau, D.; Kuklik, P.; Shipp, N.; Hsu, L.; Sanders, P.
Fonte: Elsevier Inc. Publicador: Elsevier Inc.
Tipo: Artigo de Revista Científica
Publicado em //2010 EN
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BACKGROUND: Ablation of long-standing persistent atrial fibrillation (AF) is highly variable, with differing techniques and outcomes. OBJECTIVE: The purpose of this study was to undertake a systematic review of the literature with regard to the impact of ablation technique on the outcomes of long-standing persistent AF ablation. METHODS: A systematic search of the contemporary English scientific literature (from January 1, 1990 to June 1, 2009) in the PubMed database identified 32 studies on persistent/long-standing persistent or long-standing persistent AF ablation (including four randomized controlled trials). Data on single-procedure, drug-free success, multiple procedure success, and pharmaceutically assisted success at longest follow-up were collated. RESULTS: Four studies performed pulmonary vein isolation alone (21%-22% success). Four studies performed pulmonary vein antrum ablation with isolation (PVAI; n = 2; 38%-40% success) or without confirmed isolation (PVA; n = 2; 37%-56% success). Ten studies performed linear ablation in addition to PVA (n = 5; 11%-74% success) or PVAI (n = 5; 38%-57% success). Three studies performed posterior wall box isolation (n = 3; 44%-50% success). Five studies performed complex fractionated atrial electrogram ablation (n = 5; 24%-63% success). Six studies performed complex fractionated atrial electrogram ablation as an adjunct to PVA (n = 2; 50%-51% success)...

Bimodal electric tissue ablation (BETA) - Effect of reversing the polarity of the direct current on the size of ablation

Tiong, L.; Finnie, J.; Field, J.; Maddern, G.
Fonte: Academic Press Inc Elsevier Science Publicador: Academic Press Inc Elsevier Science
Tipo: Artigo de Revista Científica
Publicado em //2012 EN
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BACKGROUND: Bimodal electric tissue ablation (BETA) is a new technique that uses the direct current in electrolysis to improve the efficacy of radio frequency (RF) ablation. It was hypothesized that attaching the cathode of the electrolytic circuit to the RF electrode will increase the tissue hydration, therefore delaying tissue desiccation during ablation. Consequently, the ablation process can continue for a longer period of time and produce larger ablations. This hypothesis was tested by reversing the polarity of the electrolytic circuit, which theoretically would cause tissue desiccation and therefore produce smaller ablations. This new setup is called reversed polarity bimodal electric ablation (RP-BEA). MATERIALS AND METHODS: Three types of ablations standard radiofrequency ablation (RFA), BETA, and RP-BEA) were tested in a pig liver model. In BETA and RP-BEA, 9 V of direct current were provided for 10 min, after which the rf generator were switched on and both electrical circuits allowed to run concurrently. In all three setups, ablations were continued until "roll-off." The size of ablation was measured and compared with each other. RESULTS: The duration of ablation was significantly shorted in RP-BEA compared with standard RFA and BETA (48 s verus 148 s and 84 s...

Substrate and trigger ablation for reduction of atrial fibrillation trial - Part II (STAR AF II): design and rationale

Verma, A.; Sanders, P.; MacLe, L.; Deisenhofer, I.; Morillo, C.; Chen, J.; Jiang, C.Y.; Ernst, S.; Mantovan, R.
Fonte: Mosby Inc Publicador: Mosby Inc
Tipo: Artigo de Revista Científica
Publicado em //2012 EN
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BACKGROUND: The optimal ablation approach for patients with persistent atrial fibrillation (AF) remains unknown. In particular, it is unclear if pulmonary vein (PV) antral isolation (PVI) is sufficient as a lone strategy for persistent AF. Furthermore, if additional substrate ablation is to be added, the ideal approach to substrate ablation is yet to be determined. OBJECTIVE: The aim of this study is to determine the optimal strategy of catheter ablation of persistent AF by comparing the efficacy of 3 strategies: PVI vs PVI plus complex fractionated electrogram (CFE) ablation (PVI + CFE) vs PVI plus linear ablation (PVI + Lines). STUDY DESIGN: The STAR AF II study (ClinicalTrials.gov NCT01203748) is a prospective, multicenter, randomized trial with a blinded assessment of outcomes. A total of 549 patients will be randomized in a 1:4:4 fashion to one of the investigation arms: PVI, PVI + CFE, and PVI + Lines, respectively. Patients undergoing a first-time ablation procedure for symptomatic, persistent AF that is refractory to at least 1 antiarrhythmic medication will be included. Persistent AF will be defined as a sustained episode lasting >7 days and <3 years. Patients with a left atrial parasternal size ≥60 mm will be excluded. The primary end point is freedom from documented AF >30 seconds at 18 months after 1 or 2 ablation procedures with or without antiarrhythmic medications. CONCLUSIONS: The STAR AF II study is a randomized trial designed to evaluate the optimal approach for catheter ablation of persistent AF.; Atul Verma...

Second generation endometrial ablation techniques for heavy menstrual bleeding: network meta-analysis

Daniels, J.; Middleton, L.; Champaneria, R.; Khan, K.; Cooper, K.; Mol, B.; Bhattacharya, S.
Fonte: BMJ Group Publicador: BMJ Group
Tipo: Artigo de Revista Científica
Publicado em //2012 EN
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Objective To determine the relative effectiveness of second generation ablation techniques in the treatment of heavy menstrual bleeding. Design Network meta-analysis on the primary outcome measures of amenorrhoea, heavy bleeding, and patients’ dissatisfaction with treatment. Data sources Nineteen randomised controlled trials (involving 3287 women) were identified through electronic searches of the Cochrane Library, Medline, Embase and PsycINFO databases from inception to April 2011. The reference lists of known relevant articles were searched for further articles. Two reviewers independently selected articles without language restrictions. Eligibility criteria for selecting studies Randomised controlled trials involving second generation endometrial destruction techniques for women with heavy menstrual bleeding unresponsive to medical treatment. Results Of the three most commonly used techniques, network meta-analysis showed that bipolar radiofrequency and microwave ablation resulted in higher rates of amenorrhoea than thermal balloon ablation at around 12 months (odds ratio 2.51, 95% confidence interval 1.53 to 4.12, P<0.001; and 1.66, 1.01 to 2.71, P=0.05, respectively), but there was no evidence of a convincing difference between the three techniques in the number of women dissatisfied with treatment or still experiencing heavy bleeding. Compared with bipolar radio frequency and microwave devices...

A minimal or maximal ablation strategy to achieve pulmonary vein isolation for paroxysmal atrial fibrillation: a prospective multi-centre randomized controlled trial (the Minimax study)

McLellan, A.J.A.; Ling, L.H.; Azzopardi, S.; Lee, G.A.; Lee, G.; Kumar, S.; Wong, M.C.G.; Walters, T.E.; Lee, J.M.; Looi, K.L.; Halloran, K.; Stiles, M.K.; Lever, N.A.; Fynn, S.P.; Heck, P.M.; Sanders, P.; Morton, J.B.; Kalman, J.M.; Kistler, P.M.
Fonte: Published on behalf of the European Society of Cardiology Publicador: Published on behalf of the European Society of Cardiology
Tipo: Artigo de Revista Científica
Publicado em //2015 EN
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AIMS: Pulmonary vein isolation (PVI) is the cornerstone of catheter ablation of atrial fibrillation (AF). The intervenous ridge (IVR) may be incorporated into ablation strategies to achieve PVI; however, randomized trials are lacking. We performed a randomized multi-centre international study to compare the outcomes of (i) circumferential antral PVI (CPVI) alone (minimal) vs. (ii) CPVI with IVR ablation to achieve individual PVI (maximal). METHODS AND RESULTS: Two hundred and thirty-four patients with paroxysmal AF underwent CPVI and were randomized to a minimal or maximal ablation strategy. The primary outcome of recurrent atrial arrhythmia was assessed with 7-day Holter monitoring at 6 and 12 months. PVI was achieved in all patients. Radiofrequency ablation time was longer in the maximal group (46.6 ± 14.6 vs. 41.5 ± 13.1 min; P < 0.01), with no significant differences in procedural or fluoroscopy times. At mean follow-up of 17 ± 8 months, there was no difference in freedom from AF after a single procedure between a minimal (70%) and maximal ablation strategy (62%; P = 0.25). In the minimal group, ablation was required on the IVR to achieve electrical isolation in 44%, and was associated with a significant reduction in freedom from AF (57%) compared with the minimal group without IVR ablation (80%; P < 0.01). CONCLUSION: There was no statistically significant difference in freedom from AF between a minimal and maximal ablation strategy. Despite attempts to achieve PVI with antral ablation...

Endometriumablation und Endometriumresektion mit dem bipolaren Versapoint(R)-System. Eine retrospektive Studie; Endometrial ablation and endometrial resection with the bipolar Versapoint(R)-system. A retrospective study

Schmidt, Frauke Ruth
Fonte: Universidade de Tubinga Publicador: Universidade de Tubinga
Tipo: Dissertação
DE_DE
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Zyklusanomalien sind ein häufiges Beschwerdebild bei Patientinnen in der Perimenopause. Zur Behandlung stehen verschiedene Modalitäten zur Verfügung, wie z.B. die Durchführung einer fraktionierten Abrasio, die Hormontherapie, die Endometriumablation oder die Hysterektomie. Bei Therapieversagen der Hormontherapie stellt die Endometriumablation eine Alternativmethode zur Hysterektomie dar. Sie führt aufgrund der Resektion des Endometriums zur Amenorrhoe oder Eumenorrhoe. Die medikamentöse Vorbehandlung ist ein wichtiges Kriterium für den Erfolg der Endometriumablation. Durch die Vorbehandlung erzielt man ein flacheres Endometrium und erleichtert somit die Resektion der Schleimhaut. In dieser Studie wurden Patientinnen, bei denen eine Endometriumablation im Zeitraum zwischen 01/02 und 12/04 durchgeführt wurde, mit Hilfe eines Fragebogens befragt. Bei allen Patientinnen wurde die Endometriumablation mit dem bipolaren Versapoint®-System durchgeführt. Bei 29% der Patientinnen trat nach der Endometriumablation eine Amenorrhoe auf. 75% der Patientinnen berichteten von einer Eumenorrhoe postoperativ. Im Vergleich der Patientinnen, die mit Orgametril vorbehandelt wurden, zu den Patientinnen ohne Vorbehandlung, zeigt sich ein geringer Vorteil in der Orgametrilvorbehandlung. Mit Orgametrilvorbehandlung hatten 36% der Patientinnen eine Amenorrhoe postoperativ...

Anatomisch geführte zirkumferentielle Pulmonalablation kombiniert mit potentialorientierter ostialer Komplettierung der Pulmonalvenenisolation - eine neue Strategie zur Katheterablation von persistierendem Vorhofflimmern.; Anatomic guided circumferential pulmonary vein ablation in combination with potential-guided ostial completion of the pulmonary vein isolation - a new approach of catheter-based ablation of persistent atrial fibrillation

Schneider, Klaus Martin
Fonte: Universidade de Tubinga Publicador: Universidade de Tubinga
Tipo: Dissertação
DE_DE
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Die Ablation von persistierendem Vorhofflimmern stellt noch immer eine große Herausforderung an die interventionelle Elektrophysiologie dar. Der von uns untersuchte Ansatz kombiniert eine anatomisch geführte zirkumferentielle Ablation um das Antrum aller Pulmonalvenen mit einer ostialen Ablation von verbleibenden Leitungsfasern aus den Pulmonalvenen. Methoden: 43 konsekutive Patienten mit symptomatischem persistierendem Vorhofflimmern (>7 Tage; Rezidive nach elektrischer Kardioversion) wurden eingeschlossen. Es wurde jeweils eine 3D-CT-Rekonstruktion des linken Vorhofs mit einer elektroanatomischen Map fusioniert. Anschließend erfolgte eine anatomisch geführte zirkumferentielle Radiofrequenz-Ablation um das Antrum aller 4 Pulmonalvenen sowie die Anlage einer Dachlinie. Als nächstes wurden verbleibende Pulmonalvenen-Leitungsfasern Lasso-geführt segmental abladiert. Endpunkt war die vollständige elektrische Isolation aller Pulmonalvenen. Außer Beta-Blockergabe erfolgte während des Follow-ups keine antiarrhythmische Medikation. Die Erfolgsrate wurde nach 12 Monaten durch 7-Tage-Langzeit-EKG und einem standardisierten Fragebogen bestimmt. Ergebnisse: Bei 61% aller Patienten konnte durchgehender Sinusrhythmus im 7-Tage-EKG dokumentiert werden...

Radiofrequenzablation von primären und sekundären Lungentumoren; Radiofrequency ablation of primary and secondary lung tumours

Bömches, Andrea Alexandra
Fonte: Universidade de Tubinga Publicador: Universidade de Tubinga
Tipo: Dissertação
DE_DE
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Die seit Jahren stetig zunehmende Inzidenz von primären und sekundären Lungentumoren mit nur eingeschränkten Therapieoptionen bei nicht operablen Patienten war Anlass zu vorliegender Studie. So behandelten wir in einem Zeitraum von 30 Monaten bei 10 Patienten mit chirurgisch-resezierbaren Lungentumoren insgesamt 12 pulmonale Läsionen mit Radiofrequenzablation. Da die gegenwärtige Studienlage die lokale Effektivität der pulmonalen RFA hauptsächlich anhand bildmorphologischer Kriterien evaluiert, haben wir 3 Tage im Anschluss an die CT-gesteuerte perkutane Ablation eine Thorakotomie mit onkologischer Lungenresektion durchgeführt, gefolgt von umfangreichen histologischen, immunhistochemischen sowie feingeweblichen Analysen der Ablationszone. So konnte gezeigt werden, dass abladierte Tumorzellen auf ultrastruktureller Ebene im Gegensatz zu den nicht mit RFA behandelten Tumorzellen sog. “apoptotic bodies” aufweisen, die den Zelltod indizieren. Ferner lässt sich die Ablationszone in 4 weitere konzentrische Zonen (I-IV) mit jeweils unterschiedlicher Zellzusammensetzung subklassifizieren. TUNEL- Untersuchungen am Gewebe haben für die Tumorzellen der beiden inneren Zonen I und II eine Fragmentierung der DNA und damit eine komplett erfolgte Ablation nachgewiesen...

Kann das Substrat ventrikulärer Tachykardien im Sinusrhythmus identifiziert werden? Die nicht-ischämische Kardiomyopathie als Herausforderung für eine Katheterablation; Can the substrate of ventricular tachycardia be identified during sinus rhythm? – Non-ischemic dilated cardiomyopathy as a challenge for catheter ablation

Girrbach, Felix Frederic
Fonte: Universidade de Tubinga Publicador: Universidade de Tubinga
Tipo: Dissertação
DE_DE
Relevância na Pesquisa
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Hintergrund: Die substratorientierte Ablation ventrikulärer Tachykardien (VT) bei Patienten nach Myokardinfarkt kann durch endokardiale Elektrogrammcharakteristika im Sinusrhythmus geleitet werden. Die Bedeutung von fraktionierten Elektrogrammen für eine Identifizierung von Arealen mit Ursprung klinischer VTs bei nicht-ischämischen Kardiomyopathie (NICM) wurde in der vorliegenden Studie untersucht. Methoden: 11 Patienten (8 männlich, 3 weiblich, mittlere LVEF 31 ± 11 %) wurden im Zeitraum vom Februar 2005 bis März 2008 einer elektrophysiologischen Untersuchung (EPU) unterzogen. Es wurde eine substratorientierte Ablation durchgeführt mit dem Ziel lokal verzögerte, fraktionierte Potentiale mit einer bipolaren Spannungamplitude von < 1,5 mV in bis zu 1 cm Umkreis um die beste VT-Pace-Map-Position zu abladieren. Der linke Ventrikel wurde in 17 Segmente eingeteilt und Segmente im Bereich des besten VT-Pace-Maps als arrhythmogenes Areal definiert. Als Kontrollareale wurden Areale mit räumlichem Abstand zum arrhythmogenem Areal definiert. Die bei der elektrophysiologischen Untersuchung des linken Ventrikels im Sinusrhythmus und/ oder während ventrikulärem Pacing aquirierten Elektrogramme wurden durch die Parameter bipolare Amplitude...

Validierung der potentialorientierten Substratablation ventrikulärer Tachykardien bei Postinfarktpatienten mittels Positronenemissionstomographie; Validation of the potential orientated substrat ablation technique with positron emission tomography

Schwegler, Alexandra
Fonte: Universidade de Tubinga Publicador: Universidade de Tubinga
Tipo: Dissertação
DE_DE
Relevância na Pesquisa
36.90948%
Viele Patienten mit Zustand nach Myokardinfarkt entwickeln ventrikuläre Tachykardien (VT). Bei Patienten, welche trotz Antiarrhythmikagabe an rezidivierenden Schocks durch den Defibrillator leiden, kann im Rahmen einer elektrophysiologischen Untersuchung (EPU) das arrythmogene Gewebe durch Radiofrequenzenergie zerstört werden (Ablation). Bei der so genannten substratorientierten Ablation werden Ablationslinien im Sinusrhythmus anhand von Elektrogrammkriterien für Narben und Narbenrandgebiete gezogen. Ein wichtiges Kriterium ist hierbei die Höhe der bipolaren Elektrogrammamplitude. Ablationspunkte werde meist nur in Elektrogrammamplitudenbereichen unter 1,5mV gesetzt. Dieser Grenzwert wurde anhand geringer Fallzahlen definiert. Es wurde auch nicht geprüft, bis zu welchem Elektrogrammamplitudenbereich Myokardgewebe Vitalität aufweist. Die Etablierung eines verbindlichen Grenzwertes ist wichtig um bei der Ablation kein vitales Myokard zu zerstören, denn dies könnte die ventrikuläre Funktion zusätzlich schwächen. Methoden: Wir führten eine EPU bei 7 VT-Patienten mit Zustand nach Myokardinfarkt durch und erstellten elektroanatomische Landkarten der linken Ventrikel mit Darstellung der bipolaren Elektrogrammamplituden auf der Ventrikeloberfläche. Als Referenzmethode zur Definition myokardialer Vitalität wählten wir eine Stoffwechseluntersuchung mittels Positronenemissionstomographie (PET) mit radioaktiv markierter Fluordesoxyglukose (18F-FDG). Es wurde ein Bild der linksventrikulären 18F-FDG-Aufnahme rekonstruiert. Beide Ventikelbilder wurde in gleicher Weise segmental aufgeteilt und korrespondierende Segmente beider Untersuchungen miteinander verglichen. So konnten die bipolare Elektrogrammamplituden mit der 18F-FDG Aufnahme in 424 Segmenten (42–84 Segmente pro Patient) korreliert werden. Ergebnisse: Die Korrelation zwischen bipolarer Elektrogrammamplitude und 18F-FDG-Aufnahme ist signifikant (p<0...

The stepwise ablation approach for chronic atrial fibrillation--evidence for a cumulative effect

O'Neill, M.; Jais, P.; Takahashi, Y.; Jonsson, A.; Sacher, F.; Hocini, M.; Sanders, P.; Rostock, T.; Rotter, M.; Pernat, A.; Clementy, J.; Haissaguerre, M.
Fonte: Kluwer Academic Publ Publicador: Kluwer Academic Publ
Tipo: Artigo de Revista Científica
Publicado em //2006 EN
Relevância na Pesquisa
36.880586%
Treatment options for atrial fibrillation (AF) have evolved from simple, fluoroscopy-guided pulmonary vein isolation for those patients with paroxysmal AF to complex, multi-modality procedures targeting not only anatomic structures but also electrophysiologic phenomena including complex fractionated electrograms, sites of dominant frequency and local non-venous drivers in patients with persistent and permanent AF. The stepwise ablation approach is a novel technique whereby structures contributing to initiation and maintenance of AF are sequentially targeted by radiofrequency ablation. Broadly divided into pulmonary veins, left atrial (LA) roof, left atrium (incorporating all anatomic regions of the chamber), mitral isthmus and non-LA structures, each region is targeted in sequence and the impact of ablation upon the global fibrillatory process assessed by measurement of AF cycle length (AFCL) at a site remote from the ablation target. In addition to pulmonary vein electrical disconnection and demonstrable complete conduction block across the roof and mitral isthmus lines (when performed), ablation is performed at those sites displaying continuous electrical and complex fractionated activity, with the endpoint of local organization...

Highly Efficient Thermal Ablation of Silicon and Ablation in Other Materials

Yu, Joe X.Z.
Fonte: Quens University Publicador: Quens University
Tipo: Tese de Doutorado
EN; EN
Relevância na Pesquisa
36.921077%
Laser micromachining has become increasing prominent in various industries given its speed, lack of tool wear, and ability to create features on the order of micrometres. Inherent stochastic variations from thermal ablation along with detrimental heat effects, however, limit the feasibility of achieving high precision. The high number of control parameters that make laser micromachining versatile also hinders optimization due to high exploration time. The introduction of high intensity nonlinear ablation leads to more precise cuts but at a much higher, often restrictive, cost. The work here shows that by combining an imaging technique frequently used in ophthalmology called optical coherence tomography (OCT) with a machining platform, in situ observation of ablation can be made. This combination, known as in-line coherent imaging (ICI), allows information to be gathered about the dynamics of the ablation process. Experimental results show that quality cutting of silicon can be achieved with thermal ablation and at a wavelength of 1070 nm. This result is surprising as silicon absorbs this wavelength very weakly at room temperature. It is shown here that a nonlinear thermal dependence in absorption allows a cascaded absorption effect to enable machining. With the aid of ICI...