Analysis of the Heart Sounds and Murmurs of Fetuses and Preterm Infants

Cardiac auscultation is one of the oldest examination methods. Despite the development of modern imaging techniques the stethoscope is still considered a symbol of the doctor’s profession. At the beginning of the 21th century auscultation has found its main role in primary and in home health care when decisions have to be made about any further, more extensive examinations or special care. However, it seems that the real potential of heart sound analysis is still not exploited, especially in the field of fetal-neonatal examinations. The aim of this thesis work has been twofold. First, recent studies showed that the fetal heart sound signal contains much more information than currently utilized in routine cardiotocographic examinations. Although a multitude of tools have been developed in the recent decades for the analysis of phonocardiographic (PCG) signals, their adaptation to fetal PCG is not straightforward because of differences in the cardiac anatomy, physiology and in the properties of the recorded signal (for instance bandwidth). Another major issue is the high level of noise. In this dissertation I present results on improved fetal heart rate calculation based on a method in the time-frequency domain. Furthermore, I describe a heart sound model which can be applied for parameter estimation of the first heart sound. The most important result outlined is the investigation of fetal heart murmurs, which could be a tool contributing to the widespread screening for congenital heart diseases prenatally. A second aim of this work has been the application of phonocardiography to preterm infants with patent ductus arteriosus (PDA). I investigated the possibility of monitoring the state of the PDA through parameters of the heart sound signal. For this reason I introduced a method for sensitive detection of the murmur produced by turbulent blood flow through the ductus arteriosus and extracted parameters of the murmur which showed a relationship with important medical parameters. Another approach was the examination of the separation of the aortic and pulmonary components of the second heart sound (splitting). I applied a heuristic decomposition method and verified this procedure on an adapted heart sound model for preterm neonates. Based on this analysis I found that there is an increased splitting around the time of the closure of the PDA in the case of preterm infants receiving medication for closure. DOI:10.15774/PPKE.ITK.2012.001 DOI:10.15774/PPKE.ITK.2012.001