Detection of the third and fourth heart sounds using Hilbert-Huang transform

In this paper, an adaptive method based on time-frequency analysis is proposed to detect the presence of S3 and S4. Heart sound signals during diastolic periods were analyzed with Hilbert-Huang Transform (HHT). A discrete plot of maximal instantaneous frequency and its amplitude was generated and clustered. S3 and S4 were recognized by the clustered points, and performance of the method was further enhanced by period definition and iteration tracking.Using the proposed method, S3 and S4 could be detected adaptively in a same method. 90.3% of heart sound cycles with S3 were detected using our method, 9.6% were missed, and 9.6% were false positive. 94% of S4 were detected using our method, 5.5% were missed, and 16% were false positive.The proposed method is adaptive for detecting low-amplitude and low-frequency S3 and S4 simultaneously compared with previous detection methods, which would be practical in primary care.Auscultation has long been important for the diagnosis of heart diseases. Heart sounds heard by a stethoscope can be seen as mechanical instructions that indicate the operation of the cardiac system. The third and fourth heart sounds, which are two abnormal components of heart sounds during diastolic periods, have been found to have relationships with myocardial dysfunction [1-5]. The third and fourth heart sounds have been discovered over a century [6]. The third heart sound (S3) occurs in the rapid filling period of early diastole. It is often present in systolic dysfunction [7]. Abnormal S3 is considered to be caused by altered physical properties of ventricle or increased in the rate and volume of blood flow in the rapid filling phase during ventricle diastole [5]. Sometimes it occurs in children. However, the auscultation of S3 in adults, especially elders older than 40 years old, is abnormal and is connected with heart failure. The fourth heart sound (S4) occurs in late diastolic periods right before the first heart sound. The presence of S4 is due