title: Detection of the third and fourth heart sounds using Hilbert-Huang transform.
abstract: BACKGROUND
  The third and fourth heart sound (S3 and S4) are two abnormal heart sound components which are proved to be indicators of heart failure during diastolic period. The combination of using diastolic heart sounds with the standard ECG as a measurement of ventricular dysfunction may improve the noninvasive diagnosis and early detection of myocardial ischemia.
  
  
  METHODS
  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.
  
  
  RESULTS
  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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Institute of Biomedical Engineering, National Taiwan University, Taipei, Taiwan.
authors.forename: Yi-Li
authors.initials: YL
authors.lastname: Tseng
authors.forename: Pin-Yu
authors.initials: PY
authors.lastname: Ko
authors.forename: Fu-Shan
authors.initials: FS
authors.lastname: Jaw
mesh_terms: D000293:Adolescent; D000465:Algorithms; D002648:Child; D003971:Diastole / Q000502:physiology; D042241:Early Diagnosis; D004562:Electrocardiography / Q000379:methods; D005260:Female; D006333:Heart Failure / Q000175:diagnosis; D006347:Heart Sounds / Q000502:physiology*; D006801:Humans; D008297:Male; D017202:Myocardial Ischemia / Q000175:diagnosis*; D010701:Phonocardiography / Q000379:methods*; D012680:Sensitivity and Specificity; D012815:Signal Processing, Computer-Assisted; D018487:Ventricular Dysfunction, Left / Q000175:diagnosis*; D055815:Young Adult