Estimation of dyssynchrony for the support of the cardiac resynchronization therapy procedures

Ultra-High Frequency Electrocardiography (UHF-ECG) is an innovative imaging technique introduced by Jurak et al. It provides a time-frequency representation of the QRS complexes through UHF-QRS maps. Its peculiarity is that it uses high frequencies of up to 2 kHz. UHF-ECG is useful to measure the electrical cardiac dyssynchrony that describes the sequence of activation and contraction of atria and ventricles relating each other. The measure of electrical dyssynchrony is given by the difference between the first and last ventricular activation. UHF-ECG gives support on the optimization of Cardiac Resynchronisation Therapy (CRT) that, through cardiac pacing, has the ability to improve the electrical function of the heart. The aim of this thesis is to evaluate the actual usefulness of UHF-ECG in assessing cardiac dyssynchrony using UHF-QRS maps, which provide a time-frequency representation of QRS complexes, to optimize CRT as cardiac electrical dyssynchrony varies by varying the energy thresholds on the UHF-QRS maps. In this study, data collected by the research team of the Czech Technical University in Prague from nineteen patients, with CRT system implanted for at least six months, were analyzed. The patients' sinus rhythm was characterized by a QRS duration≥120 ms and New York Heart Association (NYHA) class II and III HF. ECG signals were recorded using ninety-six electrodes through the ProCardio-8 system with 1 kHz as sampling frequency. Seven different pacing configurations were used including monocameral and bicameral stimulations. Signals were analyzed for precordial leads, forty-eight anterior and forty-eight posterior leads, and ninety-six total leads. The signal pre-processing and processing was performed in the MATLAB environment while the statistical analysis was conducted through Microsoft Excel. All electrical dyssynchrony values were computed for all nineteen subjects, for the four electrode setups, for the seven pacing configurations and for the threshold range between 0,4 and 0,99. Also the mean value and the standard deviations of these values were computed and it has been observed that the mean values in the precordial leads are the lowest in pacing configurations number 5, 6 and 7. So, it is better to use biventricular pacing to reduce cardiac electrical dyssynchrony than single-chamber pacing. In addition to that, it has been detected that increasing the energy threshold of the UHF-QRS maps the electrical cardiac dyssynchrony value decreases. Subsequently, the Area Under the Curve (AUC) values, in percentages, were computed showing that the best electrode setup is almost always that of the precordial leads. For what concern the best threshold to use, there are not significant results so other studies are needed to assess it. This study confirmed that electrical cardiac dyssynchrony is a clinical parameter with high discriminating power in CRT optimisation but as the use of UHF-ECG for the study of cardiac dyssynchrony is an under-explored field, it would be useful to develop further analyses from both a computational and practical point of view.