title: Digital Subtraction Phonocardiography (DSP) applied to the detection and characterization of heart murmurs.
abstract: BACKGROUND
  During the cardiac cycle, the heart normally produces repeatable physiological sounds. However, under pathologic conditions, such as with heart valve stenosis or a ventricular septal defect, blood flow turbulence leads to the production of additional sounds, called murmurs. Murmurs are random in nature, while the underlying heart sounds are not (being deterministic).
  
  
  METHODS
  We show that a new analytical technique, which we call Digital Subtraction Phonocardiography (DSP), can be used to separate the random murmur component of the phonocardiogram from the underlying deterministic heart sounds.
  
  
  METHODS
  We digitally recorded the phonocardiogram from the anterior chest wall in 60 infants and adults using a high-speed USB interface and the program Gold Wave http://www.goldwave.com. The recordings included individuals with cardiac structural disease as well as recordings from normal individuals and from individuals with innocent heart murmurs. Digital Subtraction Analysis of the signal was performed using a custom computer program called Murmurgram. In essence, this program subtracts the recorded sound from two adjacent cardiac cycles to produce a difference signal, herein called a "murmurgram". Other software used included Spectrogram (Version 16), GoldWave (Version 5.55) as well as custom MATLAB code.
  
  
  RESULTS
  Our preliminary data is presented as a series of eight cases. These cases show how advanced signal processing techniques can be used to separate heart sounds from murmurs. Note that these results are preliminary in that normal ranges for obtained test results have not yet been established.
  
  
  CONCLUSIONS
  Cardiac murmurs can be separated from underlying deterministic heart sounds using DSP. DSP has the potential to become a reliable and economical new diagnostic approach to screening for structural heart disease. However, DSP must be further evaluated in a large series of patients with well-characterized pathology to determine its clinical potential.
authors.affiliation: Department of Biomechanics, Science and Research Branch, Islamic Azad University, Tehran, Iran.
authors.forename: Mohammad Ali
authors.initials: MA
authors.lastname: Akbari
authors.forename: Kamran
authors.initials: K
authors.lastname: Hassani
authors.forename: John D
authors.initials: JD
authors.lastname: Doyle
authors.forename: Mahdi
authors.initials: M
authors.lastname: Navidbakhsh
authors.forename: Maryam
authors.initials: M
authors.lastname: Sangargir
authors.forename: Kourosh
authors.initials: K
authors.lastname: Bajelani
authors.forename: Zahra Sadat
authors.initials: ZS
authors.lastname: Ahmadi
mesh_terms: D000293:Adolescent; D000328:Adult; D001024:Aortic Valve Stenosis / Q000175:diagnosis / Q000473:pathology / Q000503:physiopathology; D016022:Case-Control Studies; D002648:Child; D002675:Child, Preschool; D005260:Female; D006337:Heart Murmurs / Q000175:diagnosis* / Q000473:pathology / Q000503:physiopathology*; D006801:Humans; D007223:Infant; D008297:Male; D008944:Mitral Valve Insufficiency / Q000175:diagnosis / Q000473:pathology / Q000503:physiopathology; D010701:Phonocardiography / Q000379:methods*; D013382:Subtraction Technique; D055815:Young Adult