Robert Arnold

Medical University of Graz

Sepsis has emerged as a global health burden associated with multiple organ dysfunction and 20% mortality rate in patients. Numerous clinical studies over the past two decades have correlated the disease severity and mortality in septic patients with impaired heart rate variability (HRV), as a consequence of impaired chronotropic response of sinoat...

The aim of this study was to describe the morphology of the cavotricuspid isthmus (CTI) in detail and introduce a comprehensive scheme to describe the topology of this region based on functional considerations. This may lead to a better understanding of isthmus-dependent flutter and fibrillation and to improved intervention strategies. We used imag...

Background Identification of targets for ablation of post-infarction ventricular tachycardias (VTs) remains challenging, often requiring arrhythmia induction to delineate the reentrant circuit. This carries a risk for the patient and may not be feasible. Substrate mapping has emerged as a safer strategy to uncover arrhythmogenic regions. However, V...

As progressive organ shortage in cardiac transplantation demands extension of donor criteria, effort is needed to optimize graft survival. Reactive oxygen and nitrogen species, generated during organ procurement, transplantation, and reperfusion, contribute to acute and late graft dysfunction. The combined application of diverse substances acting v...

Beat to beat variability of cardiac tissue or isolated cells is frequently investigated by determining time intervals from electrode measurements in order to compute scale dependent or scale independent parameters. In this study, we utilize high-speed video camera recordings to investigate the variability of intervals as well as mechanical contract...

Hyperthermia during radiofrequency ablation causes reversible and irreversible changes of the electrophysiological properties of cardiac tissue. However, the mechanisms are incompletely understood. We studied changes of conduction velocity (CV) in rat myocardium under hyperthermic conditions from macroscopic to microscopic scale by using simultaneo...

Heart rate (HR) constantly changes on a beat-to-beat basis due to autonomic influences on the pacemaker process of the sinoatrial node. These changes can be quantified as heart rate variability (HRV). In principle, HRV is caused by complex nonlinear interactions between sinoatrial node cells and the autonomic nervous system. However, a certain degr...

Radiofrequency ablation (RFA) is a standard clinical procedure for treating many cardiac arrhythmias. In order to increase the success rate of this treatment, the evaluation of lesion development with the help of intracar-diac electrogram (EGM) criteria has to be improved further. We are investigating in-vitro the electrophysiological characteristi...

Computer simulation turns out to be beneficial when clinical data lack spatio-temporal resolution or parameters cannot be measured at all. To derive trustworthy results, these in-silico models have to thoroughly parameterized and validated. In this work we present data from a simplified in-vitro setup for characterizing ventricular electromechanics...

The cavotricuspid isthmus (CTI) in the right atrium is the origin of the most common type of atrial flutter (AFL) and therefore focus for arrhythmia research in anatomy and clinical electrophysiology. The impact of complexities and discontinuities of macro- and microstructure on the intercaval conduction in the subregions Crista Terminalis, Pectina...

Computational modeling of ventricular electromechanics is considered to be among the most promising approaches to gain novel insight into cardiac function in health and disease. Such models allow to integrate the wealth of available experimental data into a mechanistic framework which allows to study complex cause-effect relationships across severa...

Extracardiac factors of heart rate variability have commonly been investigated using linear and nonlinear methods for a long time. Recently, intracardiac mechanisms on an electrophysiological basis have been found to be also important. This work is focused on the evaluation of complex measures of temporal signals gained with microelectrode measurem...

Intracellular measurement of action potential duration (APD) restitution is challenging in beating heart tissue preparations because of the risk of loosing impalement of glass microelectrodes during pacing. Therefore short-time pacing protocols are beneficial. In this work we show results from two short lasting pacing protocols applied on a guinea...

E-Learning tools of computer simulation and computer animation in biophysics were used to support medical students in lectures and their self-learning phase. Within an electronic survey of seven questions students (N=106) rated both types of new media tools, the use in lectures and for selflearning as well as the fraction of new media in teaching a...

Micro-obstacles like microvessels, intercellular clefts and fibrotic layers in cardiac tissue influence the propagation of an excitation wavefront and therefore may lead to arrhythmias. Detection and classification of these structures is challeng-ing because of the small dimensions of the fibrotic inlays and their different spatial characteristics....

Two signal processing algorithms for the on-line analysis of local propagation of activation during electrophysiological in-vitro experiments with heart preparations are presented. The first algorithm computes local velocity and direction of the propagating activation wave. Along with the values, their uncertainties due to noise are given. The seco...

The inferior right atrial isthmus consisting of the terminal crest, the network of pectinate muscles, and the vestibule shows very complex anatomical structure. It is seen as potential substrate for atrial flutter. In this work we present results from an electro-anatomical characterization of this region based on Cardiac Near Field recordings taken...

Macro- as well as micro-conduction of the cardiac impulse propagation in Pectinate muscles from Rabbit hearts is studied by means of experiments and by means of computer simulation. Two simultaneous recordings of the cardiac near field E allow an estimation of global conduction times (macro) as well as the analysis of the microscopic local activati...

The aging heart is characterized by increasingly complex microstructure and discontinuous conduction of the cardiac impulse. To examine in electrophysiological experiments how microstructure affects the activation sequence, specific high-density electrode arrays (50°μm spacing) and high resolution recording systems (100 kHz sampling rate) are requi...

Local conduction block may lead to wave breaks which are considered as organizing centers of cardiac arrhythmias. Sustained arrhythmias are associated with fast activation rates which in turn trigger adaptation mechanisms that tend to increase the complexity of activation sequences. Experimentally, rapid pacing protocols can be applied to drive the...