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Publico-13173d.pdf: 1426873 bytes, checksum: 6ecb51e6ca1ef726a7f46752c7c14e0f (MD5) === Os efeitos tardios da radiofrequencia (RF) parecem estar relacionados à extensão da lesão. Avaliamos os efeitos da indução da termotolerância nas lesões por RF e a ocorrência de apoptose agudamente na periferia das lesões na parede livre do ventrículo de ratos. Métodos: Dois grupos foram avaliados: grupo tratado (GT,n=22) submetido a choque térmico por (420C ± 0,5°C por 10 min.) e (GC, n=22) e grupo controle (GC) (37,5-38ºC por 10 min.). Após 48 horas, os ratos foram submetidos aplicação RF (12 Watts; 10 segundos) na parede livre do VE. Após 2 horas, 10 ratos de cada grupo foram sacrificados as lesões mensuradas macroscopicamente e histologicamente e após 4 semanas realizou-se ECO em ambos os grupos (N=24) e os corações retirados e analisados macroscópica e histologicamente. Outros 30 ratos, não submetidos a choque térmico, 2 horas após a ablação foram sacrificados e os corações preparados para avaliação de apoptose pela técnica de TUNEL (TdT-mediated dUTP Nick End-Labeling), imunohistoquímica (IHQ) com anticorpo próapoptótico anti-BAD, Anti-Caspase 3 (n=18) e Western Blotting (WB) anti-BAD (n=12). Não houve diferença entre os grupos agudos nas dimensões das lesões nos eixos transversal (GC 11,1 ± 0,9 mm vs. GT 11,1 ± 1,4mm, p=NS), longitudinal (GC 9,0 ± 0,6 mm vs. GT 9,5 ± 1,0mm, p=NS), profundidade (GC 1,4 ± 0,4mm vs. GT 1,4 ± 0,2 mm, p=NS) e área (GC 17± 1mm2 vs. GT 19±1mm2, p=NS) e na histologia, caracterizada por fibrose bem demarcada. Quanto aos grupos crônicos, os achados nos eixos transversal (GC 11 ± 0,9mm vs. GT 11 ± 1,4mm, p=NS), longitudinal (GC 9,3 ± 0,6mm vs. GT 9,5 ± 1,0mm, p=NS), profundidade (GC 1,4 ± 0,4mm vs. GT 1,4 ± 0,2mm, p=NS) e área (GC 17 ± 1mm2 vs. GT 19 ± 1mm2, p=NS) não diferiram entre os grupos, tampouco as análises do diâmetro sistólico ventricular esquerdo (DSVE) (GC 6,4 ± 0.4mm vs. GT 6,3± 0,3mm p=NS), diâmetro diastólico ventricular esquerdo (DDVE) (GC 4,9 ± 0,4mm vs. GT 4,6 ± 0,4mm p=NS) e a fração de ejeção (FE) (0.66 ± 0.04% vs. 0.67 ± 0.02% p=NS). Nos animais submetidos ao TUNEL houve marcação sugerindo apoptose. No entanto, as análises de IHQ, Western Blotting (BAD) foram negativas. Conclusão: A indução da termotolerância não reduz o tamanho e o remodelamento da lesão por RF no miocárdio de ratos e a ablação por RF não induz apoptose no miocárdio ventricular de ratos. === The delayed effects of radiofrequency (RF) seem to be related to the extent of the lesion. We evaluated the effects of thermotolerance on the dimensions and remodeling of RF lesions in the rat myocardium and whether RF promotes apoptosis in the region surrounding acute ablation lesions in a rat model. Methods: Two groups were evaluated: treated (TG, n=22), subjected to thermal shock (a bath at 42oC for 10 min.), and control (CG, n=22, bath at a 37ºC for 10 min.). After 48 hours, an RF lesion (customized catheter, tip 4.5 mm in diameter; 12 Watts; 10 seconds) was performed on the free wall of the left ventricle (LV). The rats were sacrificed 2 hours (n=10 per group) and 4 weeks (n=12 per group) after RF for macroscopic and histological analysis of the lesions and echocardiogram was obtained at 4 weeks to assess ventricular remodeling. Additional animals (n=30) were killed after 2 hours for apoptosis evaluation using histological (H.E. - hematoxylin and eosin, TdT-mediated dUTP Nick End-Labeling [TUNEL] assay), immunohistochemical (anti-BAD and anticaspase 3 antibodies) analysis (n = 18) and anti-BAD Western Blotting analysis. Results: There was no difference between groups regarding the size of acute (CG 27± 2 mm2 vs. TG 27±3 mm2) and chronic lesions (CG 17 ± 1 mm2 vs. TG 19 ± 1 mm2). Histology revealed coagulative necrosis in the acute lesions and welldemarcated fibrosis, with no difference between groups. The echocardiogram revealed dilation of the cavities and moderate systolic dysfunction. The diameters of the left atrium and of the left ventricle (LV) (diastolic, TG 9.8±0.9 mm vs. CG 9.6±1.1 mm, p=NS), the ejection fraction and the fractional shortening of the transverse area of the LV (TG 45±3% vs. CG 39±3%. p=NS) did not differ between groups. TUNEL assay revealed positive luminescent reaction cells suggesting apoptosis, however IHQ, Western Blotting and histology were negative. Conclusion: Thermotolerance does not reduce the size and remodeling of RF lesion in the rat myocardium and RF ablation does not promote apoptosis in the periphery of the myocardial lesion. === TEDE === BV UNIFESP: Teses e dissertações
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