Arrhythmogenicity of fibro-fatty infiltrations

The onset of cardiac arrhythmias depends on electrophysiological and structural properties of cardiac tissue. One of the most important changes leading to arrhythmias is characterised by the presence of a large number of non-excitable cells in the heart, of which the most well-known example is fibrosis. Recently, adipose tissue was put forward as another similar factor contributing to cardiac arrhythmias. Adipocytes infiltrate into cardiac tissue and produce in-excitable obstacles that interfere with myocardial conduction. However, adipose infiltrates have a different spatial texture than fibrosis. Over the course of time, adipose tissue also remodels into fibrotic tissue. In this paper we investigate the arrhythmogenic mechanisms resulting from the presence of adipose tissue in the heart using computer modelling. We use the TP06 model for human ventricular cells and study how the size and percentage of adipose infiltrates affects basic properties of wave propagation and the onset of arrhythmias under high frequency pacing in a 2D model for cardiac tissue. We show that although presence of adipose infiltrates can result in the onset of cardiac arrhythmias, its impact is less than that of fibrosis. We quantify this process and discuss how the remodelling of adipose infiltrates affects arrhythmia onset

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The Use of Cardiac Magnetic Resonance Imaging in the Diagnostic Workup and Treatment of Atrial Fibrillation

Atrial fibrillation (AF) is the most common cardiac arrhythmia and imposes a huge clinical and economic burden. AF is correlated with an increased morbidity and mortality, mainly due to stroke and heart failure. Cardiovascular imaging modalities, including echocardiography, computed tomography (CT), and cardiovascular magnetic resonance (CMR), play a central role in the workup and treatment of AF. One of the major advantages of CMR is the high contrast to noise ratio combined with good spatial and temporal resolution, without any radiation burden. This allows a detailed assessment of the structure and function of the left atrium (LA). Of particular interest is the ability to visualize the extent of LA wall injury. We provide a focused review of the value of CMR in identifying the underlying pathophysiological mechanisms of AF, its role in stroke prevention and in the guidance of radiofrequency catheter ablation. CMR is a promising technique that could add valuable information for therapeutic decision making in specific subpopulations with AF

Heart rate: an important confounder in the assessment of left atrial volume

Purpose: Left atrial (LA) volume is an important prognostic risk factor in atrial fibrillation (AF) management. Magnetic resonance imaging (MRI) is considered the gold standard to assess cardiac volumes. LA volume is routinely corrected for body surface. However, the influence of heart rate (HR) on LA volume is less well understood. This study investigates the influence of a relatively small change in HR on LA volumes. Methods: MRI was performed on 13 sheep (weight-matched): 6 sheep during sinus rhythm with a mean HR of 76+9 beats per minute (bpm) (SR76+9), and on 7 sheep during right atrial pacing at 90 bpm (AOO90). Short axis cine images, with an interslice gap of 3-4mm, were acquired of the LA. LA volume (total, body and appendage) at maximal (LAmax), minimal (LAmin) and precontraction (LApre) volume was calculated by the summation of disks method (ml). LA function was calculated by following formula: LA expansion index (LAexp): (LAmax–LAmin)/LAmin 100, LA passive emptying fraction (LApas): (LAmax–LApre)/LAmax 100, LA conduit fraction (LAcon): (LVstroke volume-total LA empyting vol)/ LVstroke volume 100, LA active emptying fraction (LAact): (LApre-LAmin)/LApre 100. Results: AOO90 resulted in significant lower LA volumes compared with SR76+9 bpm. There was no significant change in the ratio of LA body to total volume and the ratio of LAA to total volume (SR76+9: 73.4+2.4% vs 26.6+2.4%, AOO 90: 73.3+2.4% vs 26.6+2.4%). Increase in HR altered most of the volume derived function parameters. Conclusion: An increase in HR leads to a decrease of LA volume. This decrease is proportional for both the body of the LA and the LAA. Furthermore, an increase in HR augments LA expansion index and the active emptying fraction. There is a decrease of the conduit fraction. The effect of HR should be considered as an important confounder in the assessment of LA volume and volume derived parameters.status: publishe

Review of periodical articles (2015)

Copyright © Cambridge University Press 2016. One of the key concepts of Max Weber's writings on cities was that in north-western Europe, the landed nobility and urban elites were clearly distinguished. For Weber, this was indeed a main reason to locate the occidental city in the north rather than in the Mediterranean. Christof Rolker tackles this question in his 'Heraldische Orgien und Sozialer Aufstieg. Oder: Wo ist eigentlich oben in der spätmittelalterlichen Stadt?', Zeitschrift für Historische Forschung, 52 (2015), 191-224. The in-depth analysis of one of the largest and at the same time most widespread armorials in the late medieval Holy Empire, namely that of Konrad Grünenberg (d. 1494), demonstrates that in Konstanz (where Grünenberg lived) guilds (and not the nobility) first insisted on patrilineal descent as a proof of status. Traditionally, Grünenberg is seen as a paradigmatic social climber, as he left his guild to join the society of the local nobility (called 'Zur Katz'). Yet his sumptuous armorial, containing over 2,000 coat of arms mainly from the south-west of the Empire, does not mention any single member of this noble society. Instead, it praises the tournament societies of which Grünenberg was not a member, and highlights chivalric events in which he never participated. This, Rolker argues, indicates that armorials were not only about status already gained or to be gained, but also a manual for contemporaries to discuss the social order in a more abstract way. In his 'Wappenbuch', Grünenberg constantly explains why he could not join the noble societies he praised, while at the same time he ignored the 'Zur Katz' association of which he was a member. Therefore, Rolker concludes that it was not only members (or would-be members) of the respective social groups who knew and reproduced social codes. So the boundary between noble and urban elites was more blurred than Weber claimed - though Rolker is of course not the first to criticize Weber on this. Clearly, Grünenberg's armorial was part and parcel of a wider discussion of origins and kinship, namely patrilineal kinship that took place in several social milieux, rather than simply a book which displayed inherited status.license: Copyright © Cambridge University Press 2016 status: publishe

Low-Dose and Slow-Infusion Thrombolysis for Prosthetic Valve Thrombosis After a Transcatheter Valve in the Mitral Position

publisher: Elsevier articletitle: Low-Dose and Slow-Infusion Thrombolysis for Prosthetic Valve Thrombosis After a Transcatheter Valve in the Mitral Position journaltitle: JACC: Cardiovascular Interventions articlelink: http://dx.doi.org/10.1016/j.jcin.2017.01.033 content_type: article copyright: © 2017 by the American College of Cardiology Foundation. Published by Elsevier.status: publishe