MRI-detected brain lesions in AF patients without further stroke risk factors undergoing ablation - a retrospective analysis of prospective studies

Abstract Background Atrial fibrillation (AF) without other stroke risk factors is assumed to have a low annual stroke risk comparable to patients without AF. Therefore, current clinical guidelines do not recommend oral anticoagulation for stroke prevention of AF in patients without stroke risk factors. We analyzed brain magnetic resonance imaging (MRI) imaging to estimate the rate of clinically inapparent (“silent”) ischemic brain lesions in these patients. Methods We pooled individual patient-level data from three prospective studies comprising stroke-free patients with symptomatic AF. All study patients underwent brain MRI within 24–48 h before planned left atrial catheter ablation. MRIs were analyzed by a neuroradiologist blinded to clinical data. Results In total, 175 patients (median age 60 (IQR 54–67) years, 32% female, median CHA2DS2-VASc = 1 (IQR 0–2), 33% persistent AF) were included. In AF patients without or with at least one stroke risk factor, at least one silent ischemic brain lesion was observed in 4 (8%) out of 48 and 10 (8%) out of 127 patients, respectively (p > 0.99). Presence of silent ischemic brain lesions was related to age (p = 0.03) but not to AF pattern (p = 0.77). At least one cerebral microbleed was detected in 5 (13%) out of 30 AF patients without stroke risk factors and 25 (25%) out of 108 AF patients with stroke risk factors (p = 0.2). Presence of cerebral microbleeds was related to male sex (p = 0.04) or peripheral artery occlusive disease (p = 0.03). Conclusion In patients with symptomatic AF scheduled for ablation, brain MRI detected silent ischemic brain lesions in approximately one in 12 patients, and microbleeds in one in 5 patients. The prevalence of silent ischemic brain lesions did not differ in AF patients with or without further stroke risk factors

Simulating Hodgkin-Huxley-like Excitation using Comsol Multiphysics

Abstract: Most simulations concerning electrical activation of human muscles are based on the modeling approach of Hodgkin and Huxley. Calculating the response of a muscle or nerve fiber membrane to an applied electrical field, needs to consider two different potential distributions. On the one hand the "macroscopic", extracellular potential distribution in the tissue surrounding the fiber, and on the other hand the "microscopic", intracellular potential distribution inside the fiber. Knowledge of the potential distributions in both domains is necessary for calculating the development and the propagation of action potentials along the fiber. Consequently, the simulation is based on 2 coupled models: a simplified 1D line model of a muscle fiber and a 2D model of the surrounding thigh

Simulation of the electrical field in equine larynx to optimize functional electrical stimulation in denervated musculus cricoarythenoideus dorsalis

Distribution of the electrical field is very important to activate muscle and nerve cells properly. One therapeutic method to treat Recurrent Laryngeal Neuropathy (RLN) in horses can be performed by Functional Electrical Stimulation (FES). Current method to optimize the stimulation effect is to use implanted quadripolar electrodes to the musculus cricoarythenoideus dorsalis (CAD) and testing electrode configuration until best possible optimum is reached. For better understanding and finding of maximum possible activation of CAD a simulation model of the actual entire setting is currently in development. Therefore the geometric model is built from CT-data of a dissected larynx containing the quadripolar electrodes as well as fiducials for later data registration. The geometric model is the basis for a finite difference method containing of voxels with corresponding electrical conductivity of the different types of tissue due to threshold segmentation of the CT-data. Model validation can be done by the measurement of the 3D electrical potential distribution of a larynx positioned in an electrolytic tray. Finally, measured and calculated results have to be compared as well as further investigated. Preliminary results show, that changes of electrode as well as conductivity configuration leads to significant different voltage distributions and can be well presented by equipotential lines superimposed CT-slices – a Matlab graphical user interface visualizes the results in freely selectable slices of the 3D geometry. Voltage distribution along theoretically estimated fiber paths could be calculated as well as visualized. For further calculation of nerve or denervated muscle fiber activation and its optimization, real fiber paths have to be defined and referenced to the potential- and the CT-data

HRV (Heart Rate Variability) as a non-invasive measurement method for performance diagnostics and training control

The aim of this study was to determine whether non-invasive heart rate variability (HRV) recordings can be used to monitor training exercises and to estimate athletic performance. Thus far, condition and performance have been evaluated with lactate test procedures and spirometry. Several tests were conducted to determine the relationship of data from lactate test samplings, spirometry and HRV recordings. Four groups of professional athletes in different disciplines such as ball sports (n=15), martial arts (n=17), endurance sports (n=8) and hobby athletes (n=6) underwent a standardized treadmill or bicycle ergometer step test while increasing load rates, e.g. 2 km/h or 20-50 Watt every 3.5 minutes, synchronized with standardized series of lactate test sampling, spirometry and ECG recording. An inclusion criterion for all athlete groups was a minimum training frequency of an hour, five days a week focusing on continuous performance improvement. Evidence shows that offline analysis of ECG data allows conclusions on actual individual athletic performance without the need for complex instrumentation and laboratory environment. The total power parameter of the HRV reaches a plateau phase in all tested subjects and this plateau phase reaches zero near the 2 mmol threshold of lactate concentration in all subjects recorded on a bicycle ergometer. Nine out of ten subjects measured on the bicycle ergometer had negatively correlating data of lactate concentration and total power of HRV (α < 0.05). Lactate measurements using treadmills require resting periods for blood sampling. As the HRV increases instantly in these resting periods, the use of bicycle ergometers, where no testing breaks are needed, is recommended for further research

Screening for atrial fibrillation: a report of the AF-screen international collaboration.

Approximately 10% of ischemic strokes are associated with atrial fibrillation (AF) first diagnosed at the time of stroke. Detecting asymptomatic AF would provide an opportunity to prevent these strokes by instituting appropriate anticoagulation. The AF-SCREEN international collaboration was formed in September 2015 to promote discussion and research about AF screening as a strategy to reduce stroke and death and to provide advocacy for implementation of country-specific AF screening programs. During 2016, 60 expert members of AF-SCREEN, including physicians, nurses, allied health professionals, health economists, and patient advocates, were invited to prepare sections of a draft document. In August 2016, 51 members met in Rome to discuss the draft document and consider the key points arising from it using a Delphi process. These key points emphasize that screen-detected AF found at a single timepoint or by intermittent ECG recordings over 2 weeks is not a benign condition and, with additional stroke factors, carries sufficient risk of stroke to justify consideration of anticoagulation. With regard to the methods of mass screening, handheld ECG devices have the advantage of providing a verifiable ECG trace that guidelines require for AF diagnosis and would therefore be preferred as screening tools. Certain patient groups, such as those with recent embolic stroke of uncertain source (ESUS), require more intensive monitoring for AF. Settings for screening include various venues in both the community and the clinic, but they must be linked to a pathway for appropriate diagnosis and management for screening to be effective. It is recognized that health resources vary widely between countries and health systems, so the setting for AF screening should be both country- and health system-specific. Based on current knowledge, this white paper provides a strong case for AF screening now while recognizing that large randomized outcomes studies would be helpful to strengthen the evidence bas

Screening for Atrial Fibrillation

International audienceApproximately 10% of ischemic strokes are associated with atrial fibrillation (AF) first diagnosed at the time of stroke. Detecting asymptomatic AF would provide an opportunity to prevent these strokes by instituting appropriate anticoagulation. The AF-SCREEN international collaboration was formed in September 2015 to promote discussion and research about AF screening as a strategy to reduce stroke and death and to provide advocacy for implementation of country-specific AF screening programs. During 2016, 60 expert members of AF-SCREEN, including physicians, nurses, allied health professionals, health economists, and patient advocates, were invited to prepare sections of a draft document. In August 2016, 51 members met in Rome to discuss the draft document and consider the key points arising from it using a Delphi process. These key points emphasize that screen-detected AF found at a single timepoint or by intermittent ECG recordings over 2 weeks is not a benign condition and, with additional stroke factors, carries sufficient risk of stroke to justify consideration of anticoagulation. With regard to the methods of mass screening, handheld ECG devices have the advantage of providing a verifiable ECG trace that guidelines require for AF diagnosis and would therefore be preferred as screening tools. Certain patient groups, such as those with recent embolic stroke of uncertain source (ESUS), require more intensive monitoring for AF. Settings for screening include various venues in both the community and the clinic, but they must be linked to a pathway for appropriate diagnosis and management for screening to be effective. It is recognized that health resources vary widely between countries and health systems, so the setting for AF screening should be both country- and health system-specific. Based on current knowledge, this white paper provides a strong case for AF screening now while recognizing that large randomized outcomes studies would be helpful to strengthen the evidence base