CARNEGIE-MELLON UNIVERSITY IMPROVED PRIMITIVE EXTRACTION FOR SYNTACTIC ANALYSIS OF LONG-TERM AMBULATORY ELECTROCARDIOGRAMS A DISSERTATION SUBMITTED TO THE GRADUATE SCHOOL IN PARTIAL FULFILLMENT OF THE REQUIREMENTS for the degree MASTER OF SCIENCE in ELECTRICAL ENGINEERING

Abstract A system developed for arrhythmia analysis of Holter ECGs employs a syntactic pattern recognition approach. This system consists of two independent stages: 1) primitive extractiondigitized ECG data is reduced to sequence of predefined subpattern shapes or "primitives", and 2) syntactical analysisthe primitive sequence is analyzed in accordance with syntactic principles to detect and classify arrhythmic beats. Further evaluation of this system using data with commonly encountered clinical artifact (muscle noise, baseline variation) resulted in numerous detection and classification errors. Considering each stage separately, the performance deficiencies were identified as errors in the primitive extraction stage. In particular, the extraction algorithm did not accurately detect QRS complexes or accurately determine the onset and offset of those which were detected. This research proposes improvements in the primitive extraction stage. Specifically, the primitive shape set was modified to more accurately represent the structure of the ECG waveform components, especially the QRS complex. In addition, a new primitive extraction algorithm was developed which segments the ECG waveform on the bagis of frequency content. This technique allows the QRS complex to be accurately and consistently delineated with respect to onset and offset despite clinical levels of artifact. Subsequent extraction of "V"-shaped primitives then provides a detailed structural representation of the QRS complex which is easily recognizable as a primitive sequence. ACKNOWLEDGEMENT Acknowledgement I would like to thank my advisor, Dr. S. A. Briller for his guidance and suggestions, and for the opportunity to conduct this research. I would would also like to thank Dr. A.T. Bahill and Dr. D. Cassasent for agreeing to participate as committee members, and for their valuable suggestions and criticisms. I would especially like to thank Dr. G. Cano for carefully reading and critiquing this manuscript and for the many useful suggestions offered throughout the course of this research.