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Radiofrequency Lesions (radiofrequency + lesion)
Selected AbstractsEffects of Corticosteroid Therapy on the Long-Term Outcome of Radiofrequency Lesions in the Swine Caval VeinsPACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 8 2008GUILHERME FENELON M.D. 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, 60°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-RF. 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. [source] Acute and Chronic Effects of Extensive Radiofrequency Lesions in the Canine Caval Veins: Implications for Ablation of Atrial ArrhythmiasPACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 12 2006GUILHERME FENELON M.D. 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°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. [source] Mapping of Atrial Activation Patterns After Inducing Contiguous Radiofrequency Lesions: An Experimental StudyPACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 2 2001FRANCISCO J. CHORRO CHORRO, F.J., et al.: Mapping of Atrial Activation Patterns After Inducing Contiguous Radiofrequency Lesions: An Experimental Study. High resolution mapping techniques are used to analyze the changes in atrial activation patterns produced by contiguous RF induced lesions. In 12 Langendorff-perfused rabbit hearts, left atrial activation maps were obtained before and after RF induction of epicardial lesions following a triple-phase sequential protocol: (phase 1) three separate lesions positioned vertically in the central zone of the left atrial wall; (phase 2) the addition of two lesions located between the central lesion and the upper and lower lesions; and (phase 3) the placement of four additional lesions between those induced in the previous phases. In six additional experiments a pathological analysis of the individual RF lesions was performed. In phase 1 (lesion diameter = 2.8 ± 0.2 mm, gap between lesions = 3 ± 0.8 mm), the activation process bordered the lesions line in two (2.0-ms cycles) and four experiments (1.0-ms cycles). In phase 2, activation bordered the lesions line in eight (2.0-ms cycles, P < 0.01 vs control) and nine experiments (1.0-ms cycles, P < 0.001), and in phase 3 this occurred in all experiments except one (both cycles, P < 0.001 vs control). In the experiments with conduction block, the increment of the interval between activation times proximal and distal to the lesions showed a significant correlation to the length of the lesions (r = 0.68, P < 0.05, 100-ms cycle). In two (17%) experiments, sustained regular tachycardias were induced with reentrant activation patterns around the lesions line. In conclusion, in this acute model, atrial RF lesions with intact tissue gaps of 3 mm between them interrupt conduction occasionally, and conduction block may be frequency dependent. Lesion overlap is required to achieve complete conduction block lines. Tachycardias with reentrant activation patterns around a lesions line may be induced. [source] Preliminary Study of the Efficacy of Radiofrequency Lesions of Stellate Ganglion in Chronic Pain PatientsPAIN MEDICINE, Issue 1 2010Shinobu Yamaguchi MD No abstract is available for this article. [source] Claustral Lesions Delay Amygdaloid Kindling in the RatEPILEPSIA, Issue 9 2000Paul Mohapel Summary: Purpose: Lesions of the claustrum in cats and primates have been shown to disrupt the development and expression of amygdaloid-kindled seizures in cats and primates. Because the structure and connectivity of the claustrum can vary between species, we wanted to examine the effects of claustral lesions on kindling in rats. Methods: One group of rats received bilateral radiofrequency lesions of both anterior and posterior regions of the claustrum before amygdaloid kindling. Another group of rats received bilateral anterior and posterior radiofrequency lesions of the claustrum after amygdaloid kindling. Some rats were tested for transfer of kindling to the contralateral amygdala after claustral lesions. Results: Small lesions that destroyed 13% of the claustrum were capable of delaying, but not blocking, amygdaloid kindling. The delay in kindling was due to an increase in the stimulation trials required to kindle to stage 5 seizures. The lesions had no effect on established kindled seizures or on transfer to the contralateral amygdala. Conclusions: As in other species, the claustrum in the rat appears to play a role in kindling from the amygdala. Because of the restricted size of our claustral lesions, however, we were unable to conclusively assess the full extent of the claustrum's participation in limbic kindling. [source] Acute Effect of Circumferential Pulmonary Vein Isolation on Left Atrial SubstrateJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 7 2009AMEYA R. UDYAVAR M.D. Introduction: The left atrial (LA) substrate plays an important role in the maintenance of atrial fibrillation (AF). However, little is known about the acute effect of circumferential pulmonary vein isolation (CPVI). This study was to investigate the acute change of LA activation, voltage and P wave in surface electrocardiogram (ECG) after CPVI. Methods and Results: Electroanatomic mapping (NavX) was performed in 50 patients with AF (mean age = 54 ± 10 years, 36 males) who underwent only CPVI. The mean peak-to-peak bipolar voltage and total activation time of LA were obtained during sinus rhythm before and immediately after CPVI. The average duration and amplitude of P waves in 12-lead ECG were also analyzed before and after CPVI. Change in the earliest LA breakthrough sites could cause decreased LA total activation time. Downward shift in the breakthrough site was inversely proportional to the proximity of the breakthrough site to the radiofrequency lesions. A shortening of P-wave duration and decrease in voltage after CPVI were observed after CPVI. Patients with recurrent AF had less voltage reduction in the atrial wall 1 cm from the circumferential PV lesions compared with those without recurrent AF (60.1 ± 11.7% vs 74.1 ± 6.6%, P = 0.002). Reduction of voltage ,64.4% in this area after CPVI is related with recurrent AF. Conclusion: CPVI could result in acute change of LA substrate, involving LA activation and voltage. Less reduction of voltage in the atrial wall adjacent to the circumferential PV lesions after CPVI may be associated to the recurrence of AF. [source] Human Pathologic Validation of Left Ventricular Linear Lesion Formation Guided by Noncontact MappingJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 1 2002BRADLEY P. KNIGHT M.D. Linear Lesions Guided by Noncontact Mapping. This case report describes the histopathologic findings associated with two left ventricular, linear radiofrequency lesions in a patient who underwent cardiac transplantation shortly after an ablation procedure for ventricular tachycardia. The lesions were created with conventional ablation equipment guided by a noncontact mapping system. The findings provide pathologic validation that continuous, linear lesions are feasible using a noncontact mapping system for guidance. [source] Mechanism of Atrial Flutter Occurring Late After Orthotopic Heart Transplantation with Atrio-atrial AnastomosisPACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 5 2005JOSEPH E. MARINE Objective: We sought to better define the electrophysiologic mechanism of atrial flutter in patients after heart transplantation. Background: Atrial flutter is a recognized problem in the postcardiac transplant population. The electrophysiologic basis of atrial flutter in this patient population is not completely understood. Methods: Six patients with cardiac allografts and symptoms related to recurrent atrial flutter underwent diagnostic electrophysiologic study with electroanatomic mapping and radiofrequency catheter ablation. Comparison was made with a control nontransplant population of 11 patients with typical counterclockwise right atrial flutter. Results: In each case, mapping showed typical counterclockwise activation of the donor-derived portion of the right atrium, with concealed entrainment shown upon pacing in the cavotricuspid isthmus (CTI). The anastomotic suture line of the atrio-atrial anastomosis formed the posterior barrier of the reentrant circuit. Ablation of the electrically active, donor-derived portion of the CTI was sufficient to terminate atrial flutter and render it noninducible. Comparison with the control population showed that the electrically active portion of the CTI was significantly shorter in patients with transplant-associated flutter and that ablation was accomplished with the same or fewer radiofrequency lesions. Conclusions: Atrial flutter in cardiac transplant recipients is a form of typical counterclockwise, isthmus-dependent flutter in which the atrio-atrial anastomotic suture line forms the posterior barrier of the reentrant circuit. Ablation in the donor-derived portion of the CTI is sufficient to create bidirectional conduction block and eliminate this arrhythmia. Ablation or surgical division of the donor CTI at the time of transplantation could prevent this arrhythmia. [source] The Effect of Ablation Electrode Length and Catheter Tip to Endocardial Orientation on Radiofrequency Lesion Size in the Canine Right AtriumPACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 1 2002RODRIGO C. CHAN CHAN, R.C., et al.: The Effect of Ablation Electrode Length and Catheter Tip to Endocardial Orientation on Radiofrequency Lesion Size in the Canine Right Atrium. Although the determinants of radiofrequency lesion size have been characterized in vitro and in ventricular tissue in situ, the effects of catheter tip length and endocardial surface orientation on lesion generation in atrial tissue have not been studied. Therefore, the dimensions of radiofrequency lesions produced with 4-, 6-, 8-, 10-, and 12-mm distal electrode lengths were characterized in 26 closed-chested dogs. The impact of parallel versus perpendicular catheter tip/endocardial surface orientation, established by biplane fluoroscopy and/or intracardiac echocardiography, on lesion dimensions was also assessed. Radiofrequency voltage was titrated to maintain a steady catheter tip temperature of 75°C for 60 seconds. With a perpendicular catheter tip/tissue orientation, the lesion area increased from 29 ± 7 mm2 with a 4-mm tip to 42 ± 12 mm2 with the 10-mm tip, but decreased to 29 ± 8 mm2 with ablation via a 12-mm tip. With a parallel distal tip/endocardial surface orientation, lesion areas were significantly greater: 54 ± 22 mm2 with a 4-mm tip, 96 ± 28 mm2 with a 10- mm tip and 68 ± 24 mm2 with a 12-mm tip (all P < 0.001 vs perpendicular orientation). Lesion lengths and apparent volumes were larger with parallel, compared to perpendicular tip/tissue orientations, although lesion depth was independent of catheter tip length with both catheter tip/tissue orientations. Electrode edge effects were not observed with any tip length. Direct visualization using intracardiac ultrasound guidance was subjectively helpful in insuring an appropriate catheter tip/tissue interface needed to maximize lesion size. Although atrial lesion size is critically dependent on catheter tip length, it is more influenced by the catheter orientation to the endocardial surface. This information may also be helpful in designing electrode arrays for the creation of continuous linear lesions for the elimination of complex atrial tachyarrhythmias. [source] | ||||||||||