Navegando por Palavras-chave "radiofrequency ablation"
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- ItemSomente MetadadadosAcute and chronic effects of extensive radiofrequency lesions in the canine caval veins: Implications for ablation of atrial arrhythmias(Blackwell Publishing, 2006-12-01) Fenelon, Guilherme; Franco, Marcello; Arfelli, Elerson; Okada, Mieko; De Araujo, Sergio; De Paola, Angelo A. V.; Universidade Federal de São Paulo (UNIFESP)Background: Although radiofrequency (RF) ablation within the caval veins has been increasingly used to treat a variety of atrial tachyarrhythmias, the consequences of RF ablation in the caval veins are unknown. We explored the acute and chronic angiographic and pathological effects of extensive RF ablation in the caval veins.Methods: Under fluoroscopy guidance, conventional (4 mm tip, 60 degrees C, 60 seconds) RF applications (n = 6-7) were delivered in each vena cava (from +/-2 cm into the vein to the veno-atrial junction) of 15 dogs (10 +/- 3 kg). Animals were killed 1 hour and 5 weeks after ablation for histological analysis. Angiography was performed before ablation (acute dogs only) and at sacrifice to assess the degree of vascular stenosis.Results: in acute dogs (n = 5), luminal narrowing was noted in 10/10 (100%) targeted veins (mild in two; moderate in three and severe in five, including two total occlusions). in the six chronic animals that completed the protocol (four died during follow-up), stenosis was also observed in 12/12 (100%) ablated veins (mild in six; moderate in four and severe in two). of these, one superior vena cava was suboccluded with development of extensive collateral circulation. Histologically, acute lesions displayed typical transmural coagulative necrosis, whereas chronic lesions revealed intimal proliferation, necrotic muscle replaced with collagen, endovascular contraction, and disruption and thickening of the internal elastic lamina.Conclusion: in this model, extensive RF ablation in the caval veins may result in significant vascular stenosis. These findings may have implications for catheter ablation of arrhythmias originating within the caval veins.
- ItemSomente MetadadadosAnalysis by MRI of Residual Tumor After Radiofrequency Ablation for Early Stage Breast Cancer(Amer Roentgen Ray Soc, 2012-03-01) Vilar, Vanessa Sales [UNIFESP]; Goldman, Suzan Menasce [UNIFESP]; Ricci, Marcos Desiderio; Pincerato, Katia; Oliveira, Helio; Abud, Thiago Giansante [UNIFESP]; Ajzen, Sergio [UNIFESP]; Baracat, Edmund Chada; Szejnfeld, Jacob [UNIFESP]; Universidade Federal de São Paulo (UNIFESP); Universidade de São Paulo (USP)OBJECTIVE. the objective of our study was to evaluate the effectiveness of MRI in the detection of possible residual lesions after radiofrequency ablation (RFA) in the treatment of breast cancer.SUBJECTS and METHODS. We prospectively evaluated 14 patients who had undergone ultrasound-guided core biopsies diagnostic of invasive ductal carcinoma (IDC; range of diameters, 1.0-3.0 cm) and then ultrasound-guided percutaneous RFA with sentinel node biopsy as the primary treatment. Breast MRI was performed 1 week before RFA to evaluate tumor extension and again 3 weeks after RFA to verify the presence of possible residual lesions. Conventional surgical resection of the tumors was performed 1 week after RFA. the MRI findings were compared with histopathologic analyses to confirm the presence or absence of residual tumor.RESULTS. There was no residual enhancement in seven lesions on the postablation breast MRI scans. These findings were confirmed by negative histopathologic findings in the surgical specimens. the MRI scans of five patients showed small areas of irregular enhancement that corresponded to residual lesions. in the two remaining patients, we observed enhancement of almost the entire lesion, indicating that RFA had failed.CONCLUSION. Breast MRI is effective in detecting residual lesions after RFA in patients with IDC.
- ItemSomente MetadadadosAngiographic and electrophysiological substrates for ventricular tachycardia mapping through the coronary veins(British Med Journal Publ Group, 1998-01-01) De Paola, Angelo Amato Vincenzo [UNIFESP]; Melo, Wesley Duilio Severino de [UNIFESP]; Tavora, Maria Zildany Pinheiro [UNIFESP]; Martinez, E. E. [UNIFESP]; Universidade Federal de São Paulo (UNIFESP)Objective-To study the value of epicardial mapping through the coronary venous system in patients with sustained ventricular tachycardia.Design-20 consecutive patients with sustained ventricular tachycardia who were candidates for radiofrequency ablation.Setting-Electrophysiological laboratory.Interventions-Coronary venous angiography was performed with a catheter, which provided coronary sinus occlusion during injection of contrast media. Multipolar microelectrode catheters were then manoeuvred into the tributaries of coronary sinus, using an over-wire system or an on-wire system. An endocardial ablation catheter was positioned in the left ventricle. Conventional programmed ventricular stimulation was performed for sustained ventricular tachycardia induction. Endocardial radiofrequency ablation was performed using impedance or temperature monitoring.Results-Coronary veins were catheterised in all patients; 20 had induction of sustained ventricular tachycardia, 14 were stable. Presystolic epicardial electrograms were recorded in six patients and concealed entrainment in two, helping as a landmark for endocardial ablation. After simultaneous epicardial and endocardial mapping, successful endocardial radiofrequency ablation was achieved in nine of 14 patients with stable ventricular tachycardia (64%).Conclusions-Epicardial mapping through the coronary veins in patients with ventricular tachycardia is feasible, safe, and can be a useful landmark for endocardial catheter mapping and ablation.
- ItemSomente MetadadadosCombined therapy with steroids and antioxidants prevents ultrastructural damage surrounding chronic radiofrequency lesions(Blackwell Futura Publishing, Inc, 2004-01-01) Fenelon, G.; Franco, M.; Mora, O.; Katchburian, E.; Paola, AAV de; Universidade Federal de São Paulo (UNIFESP)We evaluated the effects of combined therapy with anti-inflammatory and antioxidant drugs on the healing of radiofrequency (RF) lesions (70degreesC, 60 s) produced in the right atrium and each ventricle of 21 adult dogs. Three groups were studied: acute (n = 7, sacrificed 1 hour after RF); control (n = 7, sacrificed 54 +/- 29 days after RF); and dogs (n = 7, sacrificed 32 +/- 5 days after RF) receiving combined therapy with allopurinol (400 mg po 24 and 2 hours before RF); verapamil (200 mug/kg IV 15 min before and after RF); hydrocortisone (10 mg/kg IV after RF) and prednisone (20 mg po for 29 days). Atrial (n = 37) and ventricular (n = 70) lesion dimensions were determined and 21 right ventricular apex lesions (1 per dog) were selected for light and electron microscopy analysis. Histological and ultrastructural (US) characteristics in three zones extending from the visible lesion border, A (0-3 mm); B (3-6 mm); and C (6-9 mm), were assessed. in chronic groups, atrial and ventricular lesion dimensions were similar, but delayed scar formation was noted in treated animals. Acutely and at follow-up, significant US abnormalities occurred in zones A and B and chronic lesions exhibited type I collagen proliferation. in Zone A, the extent of US injury and collagen proliferation was significantly less in treated dogs. Further, Zone B was normal in 5/7 (71%) treated dogs and in 0/7 (0%) controls. Zone C was essentially normal in all groups. Combined therapy with steroids, verapamil, and allopurinol is effective in limiting US damage surrounding chronic RF lesions.
- ItemSomente MetadadadosEffects of corticosteroid therapy on the long-term outcome of radiofrequency lesions in the swine caval veins(Blackwell Publishing, 2008-08-01) Fenelon, Guilherme [UNIFESP]; Nascimento, Thais [UNIFESP]; De Araujo, Sergio [UNIFESP]; Okada, Mieko [UNIFESP]; Franco, Marcello [UNIFESP]; De Paola, Angelo A. V. [UNIFESP]; Universidade Federal de São Paulo (UNIFESP)Background: We explored the angiographic and pathological effects of corticosteroids on the long-term outcome of radiofrequency (RF) ablation lesions in the swine caval veins.Methods: Under fluoroscopy guidance, a single linear RF lesion (4-mm tip, 600 degrees C, 180 seconds) was created in each vena cava (from +/- 2 cm into the vein to the venoatrial junction) of 20 anesthetized minipigs (35 +/- 2 kg). Three groups were studied: acute (n = 4), killed 1 hour after RF; control (n = 8), sacrificed 83 +/- 1 days after RF; and pigs (n = 8) receiving hydrocortisone (400 mg i.v. after RF) and prednisone (25 mg po for 30 days), killed 83 +/- 1 days post-BE Angiography was performed before, immediately after ablation, and at follow-up. Then, animals were sacrificed for histological analysis.Results: Mild (< 40 %) or moderate (41-70 %) acute luminal narrowing occurred in 19/20 (95 %) inferior veins and in 13/20 (65%) superior veins. Severe (> 70%) stenosis and occlusions were not noted. At follow-up, in both chronic groups, mean vessel diameters returned to baseline and progression of luminal narrowing did not occur in any vein. of note, superior and inferior vena cava angiographic diameter for control and treated pigs did not differ. the same was observed for the cross-sectional luminal area. Acute lesions displayed transmural coagulative necrosis whereas chronic lesions revealed marked fibrosis. Histological findings were similar in controls and treated pigs.Conclusion: in this model, mild and moderate stenosis, occurring immediately after ablation, seems to resolve over time. Corticosteroids do not affect the long-term outcome of such RF lesions in the caval veins.
- ItemSomente MetadadadosEpicardial radiofrequency ablation of ventricular myocardium: Factors affecting lesion formation and damage to adjacent structures(Springer, 2006-01-01) Fenelon, G.; Pereira, K. P.; Paola, AAV de; Universidade Federal de São Paulo (UNIFESP)We evaluated the factors affecting epicardial radiofrequency (RF) lesion formation in normal ventricular myocardium. in 16 dogs, a minithoracotomy was made and a sheath was placed in the pericardial space. Standard ablation lesions (4-mm tip catheter; 70 degrees C/60 seconds) were created in each ventricle under fluoroscopy guidance (n = 7) or hand-held with direct visualization of the catheter to assure optimal electrode-tissue contact (n = 6). in the latter, thermally-shielded (TS) electrodes (50% tip surface along its 4 mm length) were used in 3/6 dogs. Catheter tip (4 mm) irrigation (13 mL/minutes; 40 degrees C/60 seconds) was employed with conventional techniques in 3 additional dogs. Results: With optimal electrode-tissue contact (11 lesions), power (3.4 +/- 2.3 W vs. 16 +/- 13 W; p < 0.001) and pacing thresholds (0.2 +/- 0.0 mA vs. 3.6 +/- 5.7 mA; p = 0.004) were lower than standard RF (25 lesions). However, lesion dimensions were similar and transmural lesions did not occur (depth 2.8 +/- 1.1 mm vs. 3.0 +/- 1.5 mm). Catheter irrigation allowed high power outputs (43 +/- 6.1 W; p < 0.001) generating transmural lesions, 5/9 (55%), depth 6.4 +/- 2.1 mm. At constant power (2 W), catheter-tip temperature (52 +/- 5.2 degrees C vs. 57 +/- 6.6 degrees C; p = NS) and lesion (10 in each group) dimensions were similar for conventional and TS electrodes, but damage to parietal pericardium and lungs occurred with conventional electrodes only (70% vs. 0% p = 0.02). Conclusion: Standard epicardial RF ablation does not produce deep lesions and exhibits a significant energy loss probably due to poor electrode-tissue contact. Catheter irrigation allows delivery of high power outputs to the epicardium consistently creating deeper lesions than standard ablation. TS electrodes may reduce damage to neighboring structures during epicardial RF ablation.
- ItemSomente MetadadadosIncreased NHE3 abundance and transport activity in renal proximal tubule of rats with heart failure(Amer Physiological Soc, 2012-01-01) Inoue, Bruna H.; Santos, Leonardo dos; Pessoa, Thaissa D.; Antonio, Ednei L. [UNIFESP]; Pacheco, Bruna P. M.; Savignano, Fernanda A.; Carraro-Lacroix, Luciene R.; Tucci, Paulo J. F. [UNIFESP]; Malnic, Gerhard; Girardi, Adriana C. C.; Universidade de São Paulo (USP); Univ Fed Espirito Santo; Universidade Federal de São Paulo (UNIFESP)Inoue BH, dos Santos L, Pessoa TD, Antonio EL, Pacheco BPM, Savignano FA, Carraro-Lacroix LR, Tucci PJF, Malnic G, Girardi ACC. Increased NHE3 abundance and transport activity in renal proximal tubule of rats with heart failure. Am J Physiol Regul Integr Comp Physiol 302: R166-R174, 2012. First published October 26, 2011; doi:10.1152/ajpregu.00127.2011.-Heart failure (HF) is associated with a reduced effective circulating volume that drives sodium and water retention and extracellular volume expansion. We therefore hypothesized that Na(+)/H(+) exchanger isoform 3 (NHE3), the major apical transcellular pathway for sodium reabsorption in the proximal tubule, is upregulated in an experimental model of HF. HF was induced in male rats by left ventricle radiofrequency ablation. Sham-operated rats (sham) were used as controls. At 6 wk after surgery, HF rats exhibited cardiac dysfunction with a dramatic increase in left ventricular end-diastolic pressure. By means of stationary in vivo microperfusion and pH-dependent sodium uptake, we demonstrated that NHE3 transport activity was significantly higher in the proximal tubule of HF compared with sham rats. Increased NHE3 activity was paralleled by increased renal cortical NHE3 expression at both protein and mRNA levels. in addition, the baseline PKA-dependent NHE3 phosphorylation at serine 552 was reduced in renal cortical membranes of rats with HF. Collectively, these results suggest that NHE3 is upregulated in the proximal tubule of HF rats by transcriptional, translational, and posttranslational mechanisms. Enhanced NHE3-mediated sodium reabsorption in the proximal tubule may contribute to extracellular volume expansion and edema, the hallmark feature of HF. Moreover, our study emphasizes the importance of undertaking a cardiorenal approach to contain progression of cardiac disease.
- ItemSomente MetadadadosLeft Ventricle Radio-frequency Ablation in the Rat: A New Model of Heart Failure due to Myocardial Infarction Homogeneous in Size and Low in Mortality(Churchill Livingstone Inc Medical Publishers, 2009-08-01) Antonio, Ednei L. [UNIFESP]; Dos Santos, Alexandra A. [UNIFESP]; Araujo, Sergio R. R. [UNIFESP]; Bocalini, Danilo S. [UNIFESP]; Dos Santos, Leonardo [UNIFESP]; Fenelon, Guilherme [UNIFESP]; Franco, Marcelo F. [UNIFESP]; Tucci, Paulo. J. F. [UNIFESP]; Universidade Federal de São Paulo (UNIFESP)Background: the purpose of the Current study was to create a model of myocardial infarction (MI) that is homogeneous in size with a low immediate (24 hours) mortality.Methods and Results: Male and female rats (n = 256) underwent left ventricle (LV) ablation (Ab) by a radiofrequency current (1000 kHz; 12 watts for 12 seconds) to promote a MI. A transmural MI occurred in all rats. Post-Ab complex arrhythmias were frequent (atrioventricular block, ventricular tachycardia, and fibrillation), which rapidly and spontaneously reverted to sinus rhythm. Among 66 male rats, immediate mortality occurred in 7.5%. Small NIT size dispersion was characterized by smaller variability following Ab (x +/- SD: 45 +/- 8%) when compared with coronary occlusion (Oc; 40 +/- 19%). the histopathologic evaluations identified lesions similar to those which occurred following Oc, with scarring complete at 4 weeks. the hemodynamic and Doppler echocardiograms showed comparable increases in LV dimension, end-diastolic pressure, and pulmonary water content I and 4 weeks post-MI. Papillary muscle mechanics 6 weeks post-MI had matched inotropic and lusitropic dysfunction.Conclusions: LV Ab gave rise to a MI within a narrow size limit and with a low immediate mortality. LV Ab resulted in histopathologic evolution. ventricular dilation, and dysfunction, impairment in myocardial mechanics, and congestive outcome that reproduced a MI from Oc. (J Cardiac Fail 2009;15;540-548)
- ItemSomente MetadadadosNonsurgical transthoracic epicardial ablation for the treatment of a resistant posteroseptal accessory pathway(Blackwell Futura Publishing, Inc, 2004-02-01) Paola, AAV de; Leite, L. R.; Mesas, C. E.; Universidade Federal de São Paulo (UNIFESP)A case of Wolff-Parkinson-White syndrome successfully treated by transcutaneous epicardial radiofrequency ablation is described in a patient with a posteroseptal accessory pathway who had failed prior attempts of conventional endocardial and coronary venous system approaches. Simultaneous endocardial and pericardial space mapping was performed and only ablation from the pericardial space was successful, suggesting an epicardial course of the accessory pathway.
- ItemSomente MetadadadosSteroids prevent late extension of radiofrequency lesions in the thigh muscle of infant rats: implications for pediatric ablation(Kluwer Academic Publ, 2003-08-01) Fenelon, G.; Fernandes, R.; Franco, M.; Paola, AAV de; Universidade Federal de São Paulo (UNIFESP)Introduction: Marked late enlargement of radiofrequency (RF) lesions may occur in immature myocardium, suggesting that late proarrhythmic effects may occur in infants and small children undergoing RF ablation. Because late lesion extension may be involved in this phenomenon, we evaluated the impact of corticosteroids on the healing of RF lesions created in the thigh muscle of 29 infant Wistar rats (30 days; 55 g).Methods: Lesion dimensions and histological characteristics were assessed acutely (n = 11), and at 30 days in controls (n = 11, 183 g) and rats (n = 7, 173 g) receiving hydrocortisone after ablation and betametasone for 29 days. Acute (n = 16) and chronic (30 days; n = 5) lesions were also evaluated in adult Wistar rats (300 g).Results: Acutely, lesions in adults and infants were well demarcated from the surrounding tissue. in adults, chronic lesions did not increase in size and were well demarcated histologically. Controls and treated infant rats did not differ with respect to the gross appearance of chronic lesions. Late lesions doubled in size (20 mm in diameter) and were poorly demarcated from the surrounding tissue, exhibiting multiple collagen strands extending from the lesion into normal muscular tissue. in the treatment group, healing was markedly delayed and the extent of collagen proliferation was significantly less than controls.Conclusion: RF lesions created in the thigh muscle of infant rats reveal late enlargement and invasion of normal muscle by intense collagen proliferation. Steroids seem to limit late extension of RF lesions. These findings may have implications for RF ablation procedures in pediatric populations.