Histological findings induced by different energy sources in experimental atrial ablation in sheep (original) (raw)
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Dose Response Curves for Microwave Ablation in the Cardioplegia-Arrested Porcine Heart
The Heart Surgery Forum, 2005
Introduction: Microwave ablation has been used clinically for the surgical treatment of atrial fibrillation, particularly during valve procedures. However, dose-response curves have not been established for this surgical environment. The purpose of this study was to examine dosimetry curves for the Flex 4 and Flex 10 microwave devices in an acute cardioplegia-arrested porcine model. Methods: Twelve domestic pigs (40-45 kg) were acutely subjected to Flex 4 (n = 6) and Flex 10 (n = 6) ablations. On a cardioplegically arrested heart maintained at 10-15 o C, six endocardial atrial and seven epicardial ventricular lesions were created in each animal. Ablations were performed for 15 s, 30 s, 45 s, 60 s, 90 s, 120 s, and 150 s (65 W, 2.45 GHz). The tissue was stained with 2,3,5-triphenyl-tetrazolium chloride and lesions were sectioned at 5 mm intervals. Lesion depth and width were determined from digital photomicrographs of each lesion (resolution ± .03 mm). Results: Average atrial thickness was 2.88 ± .4 mm (range 1.0 to 8.0 mm). 94% of ablated atrial sections created by the FLEX 4 (n = 16) and the FLEX 10 (n = 16) were transmural at 45 seconds. 100% of atrial sections were transmural at 90 seconds with the FLEX 10 (n = 14) and at 60 seconds with the Flex 4 device (n = 15). Lesion width and depth increased with duration of application. Conclusion: Both devices were capable of producing transmural lesions on the cardioplegically arrested heart at 65 W. These curves will allow surgeons to ensure transmural ablation by tailoring energy delivery to the specific atrial geometry.
Innovations (Philadelphia, Pa.), 2009
OBJECTIVE: To perform a minimally invasive procedure for atrial fibrillation without cardiopulmonary bypass, it is necessary to create transmural lesions on the beating heart. Although bipolar radiofrequency clamps can isolate the pulmonary veins, they have difficulty in performing any other left atrial lesions, particularly those of the traditional Cox-Maze procedure. This study examined the performance of an internally cooled, bipolar radiofrequency device designed for such an application. METHODS: Eleven domestic pigs underwent median sternotomy. Five animals had eight atrial lesions created with the radiofrequency device at times of 20, 30, 40, and 50 seconds. In six other pigs, the device was compared with another technology that has been used clinically for epicardial, beating heart ablation, the Guidant Flex 4 microwave device. The tissue was stained with 2,3,5-triphenyl-tetrazoluim chloride, and the lesions were sectioned at 5-mm intervals. Lesion width, depth, and transmura...
Europace, 2002
Background Radiofrequency ablation is currently used in the treatment of various cardiac arrhythmias. However, this technique is limited by impedance rise, leading to coagulum formation and desiccation of tissue. We developed a new generator, providing very high frequency (27 MHz) current, which is in the intermediate range between radiofrequency and microwave energy. The aim of this study was to evaluate the results for catheter ablation of the atrioventricular junction and characteristics of the lesions obtained at ventricular sites.
Experimental observation of vitro pigs' hearts with bipolar radiofrequency ablation
International journal of clinical and experimental medicine, 2013
Bipolar ablation is an innovative direction of catheter ablation technology. The aim of this study was to investigate the damaged area of bipolar radiofrequency ablation in vitro pigs' hearts under different conditions and to evaluate the effectiveness and safety. The bipolar radiofrequency ablation was performed in vitro pigs' hearts with a 4 mm bipolar electrode under different conditions at various combinations of the parameters (Distance: from 12 mm to 17 mm; Power: 30 w or 40 w; Time: from 20 s to 90 s; Temperature: 45°C or 60°C; Saline Perfusion: 0 ml/h, 1000 ml/h or 1500 ml/h). We measured the length, width, depth, connection rate and blasting rate of the connective ablation lesion and then evaluated the effectiveness and safety of connective ablation lesion. Numerical analysis showed that there was a positive correlation between the time, temperature and the length, depth, connection rate, blasting rate. There was a negative correlation between the power, perfusion a...
Innovations Technology and Techniques in Cardiothoracic and Vascular Surgery, 2006
Background: Microwave energy is commonly used on the beating heart to create lesions for the surgical treatment of atrial fibrillation. However, lesion transmurality is likely to depend on several factors including tissue thickness and blood flow. This study was designed to determine the effect of cavitary blood flow on transmurality of acute atrial lesions with the FLEX 10 (Guidant Corporation, Santa Clara, Calif ) microwave device.
Endocardial Laser Ablation for the Treatment of Atrial Fibrillation in an Acute Sheep Model
Journal of Cardiac Surgery, 2008
Background: The purpose of this study was to test the feasibility, effectiveness, and safety of the use of a new laser energy catheter for linear endocardial ablation in an acute sheep model. Methods: Bipolar pacing electrodes were positioned on the left atrial appendage (LAA) and the pulmonary veins (PVs). Laser ablation within the left atrium was performed around the LAA and PVs in six sheep. The temperature in the esophagus was measured continuously during ablation. The animals were weaned from cardiopulmonary bypass (CPB) and were sacrificed two hours after ablation. The heart, lungs, and esophagus were retrieved for histological examination. Results: Aortic cross clamp time was 26.2 ± 6.1 minutes and CPB time was 81 ± 29 minutes. Electrical isolation of the LAA and PVs was confirmed in all sheep. On histological analysis, there was an extensive transmural alteration of the left atrial tissue including vascular lesions, myocardial degeneration, and necrosis, and epi-and endocardial necrosis. In six out of six cases, extensive lesions of the esophagus (muscular layer) were also found. Significant changes in esophageal temperature were observed, reaching up to 70 • C. The epithelial layer of the esophagus was not affected by the laser energy, but mild focal degeneration of the subepithelial connective tissue was observed in all sheep. There were no injuries to the circumflex coronary artery. Conclusions: Laser is an effective tool in endocardial ablation, resulting in electrical isolation and transmurality. Future studies should more completely assess the safety of laser ablation, especially with regards to the nearby esophagus, as well as examine the results of epicardial application.
Journal of interventional cardiac electrophysiology : an international journal of arrhythmias and pacing, 1999
Radiofrequency catheter ablation of atrial flutter, atrial fibrillation or ventricular tachycardia may be favoured by large lesions. We compared lesions created in unipolar mode using 10-mm/8 F electrodes with those of 4-mm/7 F catheters. Ablations were first performed in porcine hearts in vitro (70 degrees C, 60 s, tangential catheter tip-tissue orientation). Anaesthetized pigs were thereafter ablated with 10- or 4-mm catheters in the right atrial free wall (RAFW), inferior vena cava-tricuspid valve (IVC-TV) isthmus and left ventricle (LV). In vitro, lesion length doubled and lesion volume tripled using the 10-mm catheter. Average power supply was 69 (SD12) (10-mm tip) versus 26 (SD7) W (4-mm tip). In vivo, lesion length increased by 50% and lesion volume fivefold. Charring at the lesion surface or sudden impedance rises were not observed in vivo. Histologically, coagulation necrosis and minor haemorrhages were found. One RAFW lesion (10-mm) showed a dissection approaching the epic...