Microembolism and Catheter Ablation II

Abstract

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 ...

Evaluation and Reduction of Asymptomatic Cerebral Embolism in Ablation of Atrial Fibrillation, But High Prevalence of Chronic Silent Infarction

“…Within 24 hours of ablation, patients also underwent transesophageal echocardiography to rule out LA thrombus. A single transseptal puncture was performed and the MER catheter was inserted into the LA using a steerable sheath (n=35; 10 [Medtronic]). Intravenous unfractionated heparin was administered just before or immediately after transseptal puncture and maintained throughout the ablation procedure to keep the ACT ≥350 seconds.…”

“…Pre-existing lesions were predominantly found in the frontal and parietal lobes, as demonstrated in this sample patient. There were a median of 8 lesions per subject (interquartile range, [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22]. spontaneous; 45% were electrical).…”

“…10 Three categories of embolic materials may be generated during LA ablation: (1) gaseous emboli produced from introduction of air in sheaths or during heating/boiling of blood; (2) particulate emboli ACT indicates activated clotting time; E1, distal electrode on the circular multielectrode radiofrequency (MER) catheter; E10, proximal electrode on the circular MER catheter; INR, international normalized ratio; and RF, radiofrequency.…”

“…In animal studies with the circular MER catheter, it was found that the largest source of gaseous and solid emboli occurred when the distal and proximal electrodes of the catheter were in close proximity or overlapping. 10 This electrode overlap creates a bipolar short circuit resulting in excessive tissue and blood heating. By deactivating either the proximal or distal electrode in the current study, this important potential source of emboli was prevented.…”

“…These gaseous and solid emboli were found to be the cause of cerebral embolic MRI findings in animal models similar to those seen in humans. 10 Thus, the aim of this study was to establish if ACE incidence in patients could be reduced by applying specific procedural techniques identified in the preclinical setting to reduce the embolic load. …”