Cardiac arrhythmias such as atrial fibrillation occur frequently in industrialized countries. Radiofrequency ablation (RFA) is a standard treatment if drug therapy fails. This minimally invasive surgery aims at stabilizing the heart rhythm on a permanent basis. However, the procedure commonly needs to be repeated because of the high recurrence rate of arrhythmias. Non-transmural lesions as well as gaps within linear lesions are among the main problems during the RFA. The assessment of lesion formation is not adequate in state of the art procedures. Therefore, the aim of this study is to investigate the short-term reversibility of lesions using human electrograms recorded by a high-density mapping system during an electrophysiological study (EPS). A predefined measurement protocol was executed during the EPS in order to create three ablation points in the left atrium. Subsequently, after preprocessing the recorded signals, electrogram (EGM) paths were formed along the endocardial surface of the atrium. By analyzing changes of peak to peak amplitudes of unipolar EGMs before and after ablation, it was possible to distinguish lesion area and healthy myocardium. The peak to peak amplitudes of the EGMs decreased by 40-61% after 30 seconds of ablation. Furthermore, we analyzed the morphological changes of EGMs surrounding the lesion. High-density mapping data showed that not only the tissue, which had direct contact with the catheter tip during the RFA, but also the surrounding tissue was affected. This was demonstrated by low peak to peak amplitudes in large areas with a width of 14 mm around the center of the ablation lesion. After right pulmonary vein isolation, high-density mapping was repeated on the previous lesions. The outer region of RFA-treated tissue appears to recover as opposed to the central core of the ablation point. This observation suggests that the meaningfulness of an immediate remap after ablation during an EPS may lead the physician to false conclusions.
Student Theses (1)
O. Huhn. Comparison of Electrogram Features in High-Density Mapping and Mapping with an Ablation Catheter. Institute of Biomedical Engineering, Karlsruhe Institute of Technology (KIT). Bachelorarbeit. 2018
Cardiac arrhythmias such as atrial fibrillation and atrial flutter occur more frequently in industrialized countries. If the drug therapy does not work, radiofrequency ablation (RFA) in the atria is a common treatment. This minimally invasive operation allows a lasting improvement in the heart rhythm disorder. However, this procedure often has to be repeated because of the high recurrence rate. A significant proportion, 46%, still needs to take anti- arrhythmic drugs. This thesis relates with the evaluation of electrograms (EGMs) which were recorded with a high-density mapping catheter and an ablation catheter. Furthermore, both methods should be tested for their respective advantages and compared with each other. For this purpose, two clinical data sets were evaluated, which were recorded in the Städtisches Klinikum Karlsruhe in interventions performed on humans during an electrophysiological study. A predefined measurement protocol was performed during RFA in the left atrium (LA). A newly defined procedure, the stable holding of the ablation catheter during the ablation and subsequent measurement process, was introduced and proved to be particularly practicable. Three ablation points in the LA were placed near the left pulmonary veins, where later a pulmonary vein isolation was performed to cure the heart arrhythmia. First, the data from each catheter were recorded and then evaluated using self-developed software. Afterwards, the signals were filtered and classified into individual EGMs using the Non-linear Energy Operator. Subsequently, EGM paths were formed along the endocardium. By precisely locating the recorded EGMs, it was possible to assess the ablation areas before and after ablation. With high-density maps, the in vivo data were also analyzed in three-dimensional space. As a result the peak to peak amplitudes of the EGMs decrease by about 40-61% after every 30 seconds of ablation. This procedure forms the basis for studies on how the duration of ablation affects the morphological change of the measured EGMs. With the Orion data high-density voltage maps were generated. High-density mapping showed that not only the tissue, which had direct contact with the catheter tip during the RFA had changed, but also the surrounding tissue was affected. This was demonstrated by low peak-to-peak amplitudes, which existed in large areas, widths up to 14 mm, around the ablation lesions. After the right pulmonary vein isolation, high-density mapping was repeated and the influence of the time factor on the ablation lesions was examined. RFA-treated tissue appears to recover, except at the ablation point itself. In summary, both types of catheters are useful, but a closer examination of the scar can be achieved with the Orion high-density mapping catheter.