Multimodale Iterative Sinusapproximation (MIS) - Eine dynamische Zeit-Frequenz-Transformation zur kardialen Risikostratifizierung

The topics of this thesis are the development, evaluation, and application of a novel method for short-term analysis of the heart rate variability, in particular for dynamic changes after temporary disturbances, caused for example by premature beats. The main objective is cardiac risk stratification, based on the analysis of spontaneous fluctuations of the heart rate. The method shall be compared with accepted and standardized algorithms in the time- and frequency-domain. The methodological approach represents a time-frequency-transformation which is based on a multimodal approximation of sine half-waves in the time-domain applying an iterative optimizing process. This novel method, referred as the Multimodal Iterative Sine Approximation (MIS), takes the physiological dependency of the heart rate variability on the activities of the autonomic nervous system into account, in order to support clinical interpretations. For the evaluation recordings from healthy persons, from patients after heart transplantation and during dialysis sessions, as wells as recordings from a sleep laboratory and fetal ECGs have been applied. The advantages of the MIS in contrast to standardized methods will be demonstrated. For an application within an implantable device, based on a 16 bit microprocessor, the necessary mathematical simplifications as well as an efficient implementation will be presented.