Medizinische Universität Graz Austria/Österreich - Forschungsportal - Medical University of Graz
Gewählte Publikation:
Arnold, R.
Beat-to-Beat Behavior of Atrial Activation Sequences Under Impaired Conduction Conditions - Macroscopic and Microscopic Aspects
[ Dissertation ] Medical University of Graz; 2013. pp. 113
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- Autor*innen der Med Uni Graz:
- Arnold Robert
- Betreuer*innen:
- Ahammer Helmut
- Hofer Ernst
- Kockskämper Jens
- Altmetrics:
- Abstract:
- Atrial flutter and atrial fibrillation have evolved to one of the leading cardiovascular diseases over the past decades and their prevalence is expected to strongly increase. The cavotricuspid isthmus (CTI), a subregion in the right atrium, is seen as a potential arrhythmogenic substrate and is therefore a preferential target for clinical catheter ablation procedures. Structure of the CTI is complex at a macroscopic and microscopic level and determines the excitation pathways of electrical activation. These structural complexities lead to characteristic distributions of extracellular potentials and under certain circumstances to fractionation of electrograms within the CTI. At elevated heart rates additionally functional heterogeneities arise, resulting in changes of activation patterns. From a clinical point of view the detection of local conduction block preceding arrhythmias is of particular interest. The aim of this work was to characterize the complex macroscopic structures within the CTI, investigate distribution of extracellular signals and activation spread during normal sinus rhythm of the heart, and to explore the changes of local activation patterns at increased heart rates. Therefore, electrophysiological experiments with tissue preparations from rabbits and guinea pigs were carried out. Comprehensive morphological characterization of the CTI yielded representative topologies comparable to human atria which could facilitate the development of rule-based computer models of electrical excitation spread in this region. Morphology was combined with multisite extracellular recordings to electro-anatomical maps of the CTI. The influence of macroscopic and microscopic structures on excitation spread at varying heart rates was studied by applying electrical pacing with dynamic protocols. The results shown in this work suggest that it is possible to predict upcoming conduction block and to identify substrates of increased heterogeneity of conduction by means of adequate pacing techniques before reaching local conduction block and therefore without inducing atrial flutter or fibrillation.