Linking Activation Patterns with Substrate Based Electrogram Characteristics to Develop Individualized Ablation Strategies for Atrial Fibrillation

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Atrial fibrillation is the most common cardiac arrhythmia in industrialized societies and poses immense burdens on public healthcare systems. Underlying mechanisms and best treatment strategies are intensively discussed in current research. Several concepts are considered for patients in a progressed state, mainly the ablation of tissue showing fractionated electrograms and the ablation of rotational excitation patterns. Both concepts, however, are under debate and a theory is still lacking which links both phenomena. Studies have shown strongly varying success rates for the ablation of fractionated electrograms, which is often explained by the missing standardized quantitative description of the targeted signals. Consequently, physicians in all centers develop rather subjective treatment strategies, which are difficult to compare. Rotor ablation is a rather novel concept, and basic questions have not been answered yet. Among those is the stability of rotors and the amount of tissue, which is to be ablated. Both temporal and spatial stability of rotors are intensively discussed, raising the question whether rotors anchor at certain anatomical regions or meander through the atria.Major goal of the proposed project is to link existing strategies of catheter ablation. Special focus is laid on the atrial substrate, which is expected to show proarrhythmogenic properties due to electrical and structural remodeling and fibrosis. Areas which are critical to the tachycardia can be identified by specialized pacing protocols, in combination with novel signal processing techniques. Computer algorithms will be developed, which can identify the cardiac excitation pattern both on the local scale and when measured using panoramic basket type mapping catheters. The statistical analysis of depolarization patterns observed during fibrillation (e.g. rotors, wave-front collisions, ... ) is expected to indicate, whether or not pathological tissue is prone to harboring rotors. Additional measurements with LGE-magnetic resonance imaging will be conducted in a subgroup of patients to obtain extended information about the atrial substrate (e.g. fibrosis) and its impact on excitation dynamics and electrograms morphology. Determination of characteristics of proarrhythmogenic substrate would allow for prospective detection and ablation of areas, which did not currently show rotors, but generally have the potential to maintain the fibrillatory process. By dominantly using equipment which is already available in electrophysiological laboratories, we will ensure that the obtained results can be applied in everyday's clinical work, without increasing the patient burden by additionally required X-ray or MRI diagnostics. The outcome of this project will help to understand the underlying mechanisms of atrial fibrillation and improve success rates of ablations in the long term.