Silent Cerebral Events after Atrial Fibrillation Ablation - Overview and Current Data

Abstract

Silent cerebral lesions (SCL) have been identified on brain magnetic resonance imaging (MRI) in apparently asymptomatic patients after cardiovascular procedures. After atrial fibrillation (AF) ablation incidences range from 1 to over 40% depending upon different factors. MRI definition should include diffusion weighted imaging (DWI) to detect hyperintensities (bright spots) due to acute brain ischemia correlated with a hypointensity in the apparent diffusion coefficient mapping (ADC-map) to rule out artifacts. The genesis of SCL appears to be multifactorial and appears to be a result of embolic events either from gaseous or solid particles. The MRI pattern appears to be comparable not hinting towards a specific mechanism. One may distinguish two different MRI definition: one, more sensitive, for silent ischemic events (SCE) not proven to be related to cell death (DWI positive but FLAIR negative); and one for SCL that are due to edema caused by cell death which will lead to glial cell scar formation (DWI positive and FLAIR positive). For ease of data interpretation, future studies should ensure both definitions, and that DWI and FLAIR data is acquired using identical slice thickness and orientation. Risk factors associated with increased SCL-incidences involve patient-specific, technology-associated and procedural determinants. When using a high-sensitive MRI definition differences in SCE-rates in between technologies appear to be less prominent. Further studies on the effects of different periprocedural anticoagulation regimen, different steps of the ablation procedure and new technologies are needed. For now, SCL incidence may determine the thrombogenic potential of an ablation technology and further studies to reduce or avoid SCL generation are desirable. It appears reasonable, that any SCE should be avoided.

Figure 1.. FLAIR (A), DWI (B) and ADC-map (C) of a patient with a single SCE (red circle) only documented on DWI (B) and ADC-map (C) but not identified on FLAIR (A) imaging indicating higher sensitivity of a novel MRI definition of SCE.

Figure 2.. MRI pre (a), 1 day post (b) and at 4 weeks follow-up (c) of a patient undergoing irrigated RF PVI: DWI indicates a hyperinsense lesion (red circle) in the cerebellum corresponding to a hypoattenuation on ADC-map. During follow-up MRI lesion is not detected any more on DWI.

Figure 3.. SCE (silent cerebral ischemic event) rates related to ablation technology in a collection of patients including multiple variations of periprocedural anticoagulation and ablation technological aspects (no significant differences in between groups).