BACKGROUND Radiofrequency (RF) has become an accepted energy source for myocardial ablation but may result in discontinuous lesions and nontargeted tissue injury. We examined the feasibility and safety of lesion formation using high-amplitude, bipolar pulsed electric fields delivered from a multielectrode array catheter. OBJECTIVE The purpose of this study was to compare duty-cycled radiofrequency ablation (RFA) to pulsed field ablation (PFA) in terms of acute electrical effects, 2-week lesion formation, and injury to nontargeted tissues. METHODS Intracardiac ablations were performed in 6 pigs using a circular pulmonary vein ablation catheter. The energy source for ablation delivery was randomized to deliver either PFA or RFA to 3 atrial endocardial sites. Bipolar pace capture and electrogram amplitude measurements were recorded at each site. Histopathology and necropsies were performed after 2 weeks. RESULTS The circular pulmonary vein ablation catheter was used to deliver pulsed electric fields to produce cardiac lesions without skeletal muscle stimulation. Evaluating all ablations in each site, electrogram amplitudes were reduced to ,0.5 mV in 67.5% of PFA vs 27.0% of RFA deliveries (P ,.001). Bipolar cardiac capture was lost after 100% vs 92.0% of PFA vs RFA (P 5 .005). At 2 weeks, PFA resulted in consistent transmural and homogeneous replacement fibrosis devoid of lingering myocyte "sequesters." RFA lesions showed a stronger inflammatory response extending to the epicardial fat, arterial injury, and thrombosis. Neither PFA nor RFA lesions showed endocardial thrombus. CONCLUSION Intracardiac PFA can be feasibly delivered from a circular catheter to create fibrotic lesions that have acute electrical effects, without injury to nontargeted tissue.
Background Pulsed field ablation (PFA) has been identified as an alternative to thermal‐based ablation systems for treatment of atrial fibrillation patients. The objective of this Good Laboratory Practice (GLP) study was to characterize the chronic effects and safety of overlapping lesions created by a PFA system at intracardiac locations in a porcine model. Methods A circular catheter with nine gold electrodes was used for overlapping low‐ or high‐dose PFA deliveries in the superior vena cava (SVC), right atrial appendage (RAA), and right superior pulmonary vein (RSPV) in six pigs. Electrical isolation was evaluated acutely and chronic lesions were assessed via necropsy and histopathology after 4‐week survival. Acute and chronic safety data were recorded peri‐ and post‐procedurally. Results No animal experienced ventricular arrhythmia during PFA delivery, and there was no evidence of periprocedural PFA‐related adverse events. Lesions created in all anatomies resulted in electrical isolation postprocedure. Lesions were circumferential, contiguous, and transmural, with all converting into consistent lines of chronic replacement fibrosis, regardless of trabeculated or smooth endocardial surface structure. Ablations were non‐thermally generated with only minimal post‐delivery temperature rises recorded at the electrodes. There was no evidence of extracardiac damage, stenosis, aneurysms, endocardial disruption, or thrombus. Conclusion PFA deliveries to the SVC, RAA, and RSPV resulted in complete circumferential replacement fibrosis at 4‐week postablation with an excellent chronic myocardial and collateral tissue safety profile. This GLP study evaluated the safety and efficacy of a dosage range in preparation for a clinical trial and characterized the non‐thermal nature of PFA.
Background - Pulmonary vein stenosis (PVS) is a highly morbid condition that can result after catheter ablation for pulmonary vein isolation (PVI). We hypothesized that pulsed field ablation (PFA) would reduce PVS risk and collateral injury compared to irrigated radiofrequency ablation (IRF). Methods - IRF and PFA deliveries were randomized in eight dogs with two superior PVs ablated using one technology and two inferior PVs ablated using the other technology. IRF energy (25-30W) or PFA was delivered (16 pulse trains) at each PV in a proximal and in a distal site. Contrast computed tomography (CT) scans were collected at 0, 2, 4, 8, and 12-week (termination) time points to monitor PV cross-sectional area at each PV ablation site. Results - Maximum average change in normalized cross-sectional area at 4-weeks was -46.1 ±45.1% post-IRF compared to -5.5% ±20.5% for PFA (p Ȧ4; 0.001). PFA-treated targets showed significantly fewer vessel restrictions compared with IRF (p Ȧ4; 0.023). Necropsy showed expansive PFA lesions without stenosis in the proximal PV sites, compared to more confined and often incomplete lesions after IRF. At the distal PV sites, only IRF ablations were grossly identified based on focal fibrosis. Mild chronic parenchymal hemorrhage was noted in three left superior pulmonary vein (LSPV) lobes after IRF. Damage to vagus nerves as well as evidence of esophagus dilation occurred at sites associated with IRF. In contrast, no lung, vagal nerve or esophageal injury was observed at PFA sites. Conclusions - PFA significantly reduced risk of PV stenosis compared to IRF post-procedure in a canine model. IRF also caused vagus nerve, esophageal and lung injury while PFA did not.
R ecent reports of asymptomatic cerebral lesions imaged with diffusion weighted MRI (DWI) after catheter ablation of atrial fibrillation have raised concerns about the safety of this procedure. [1][2][3][4][5] It has been speculated that these DWI lesions may be the result of cerebral microembolization, and that they could be a marker for procedure-related clinical stroke risk. 6 In addition, some speculate that the asymptomatic cerebral DWI lesions may, in fact, be associated with subtle abnormalities discernable with neuropsychiatric testing. 7,8 It has been established that thrombus, gas bubbles, and particulate debris (coagulum) can be introduced or produced with left atrial catheterization and catheter ablation in this chamber.9 New data are available on catheter ablation-related subclinical DWI lesions, often seen as punctate hyperintensities, from recent studies. However, the link between the size and characteristics of the emboli, produced with left atrial catheter ablation procedures has not been correlated to clinical stroke or subclinical DWI lesions. Clinical Perspective on p 30Considerable differences have been reported in typical lesion dimensions seen on DWI between various clinical stroke cohorts and patients with asymptomatic cerebral lesions detected on DWI after left atrial catheter ablation. There is a lack of causal data for any of the lesion types. The purpose of this canine study was to elucidate the characteristics of emboli capable of creating the DWI punctate hyperintensities seen in the clinical setting after left atrial catheter ablation procedures. We sought to differentiate the effects of embolizing pure gas microbubbles versus microparticles of smaller and larger size because smaller particles and gas microbubbles might be more likely to occlude flow in terminal cerebral vessels, and produce DWI lesions typical to those seen in asymptomatic patients after atrial fibrillation ablation. MethodsAll animal procedures were approved by and carried out in compliance with a preclinical research protocol by the Institutional Animal Care and Use Committee of the Medtronic Physiological Research Laboratories. General animal husbandry and care was supervised by a veterinary staff in accordance with the guidelines in Background-Asymptomatic cerebral lesions have been observed on diffusion weighted MRI (DWI) scans shortly after catheter ablation of atrial fibrillation, but the pathogenesis of these lesions is incompletely understood. Methods and Results-Twelve dogs underwent selective catheterization of the internal carotid or vertebral arteries. Either a microbubbled mixture of air (1.0-4.0 mL), blood, contrast, and saline (n=5), or heat-dried pulverized blood (particle size <600 μm) mixed with saline and contrast (n=6) was injected. One sham control experiment was performed. MRI scans were performed preinjection, and at 1, 2, and 4 days postinjection. Neurological tests were performed daily. Gross pathology and histopathology were performed on the brains after being euthanized on day 4. Three ...
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