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On the issue of "automated" internet sounds:

May 9, 2007
Chest Online
3300 Dundee Road
Northbrook IL 60062-2348 USA

To the Editor:

Re: Mastering Cardiac Murmurs: The Power of Repetition. Michael J.
Barrett, Carolyn S Lacey, Amy E Sekara, Erica A. Linden, Edward J. Gracely
Chest 2004;126;470-475

Congratulations to the authors for this piece of work, which in some

format will be valuable information in future structuring of the teaching of cardiac auscultation, now known to be ineffectual for undergraduate medical students. This work has led to legal downloading of heart sound files from websites to ipods at a reasonable price, making comparison of heart sounds available for medical students and residents at the bedside. While repetition has been shown to be important in the heart sound learning process, unfortunately the heart sounds that have been used in the publication and which are being downloaded are automated (manufactured). Automated heart sounds have been available for at least twenty years, and are not considered to be satisfactory characterizations of human heart sounds by most teachers of cardiac auscultation. Automated reproductions of the heart sounds themselves are quite good, as they are caused by only short bursts of acoustic energy and of much the same frequency. There is as well the ability to insert and remove the sound in the recording for better learning. None the less the sounds do not sound quite the same as human sounds.

The automation of heart murmurs is another matter. Murmurs have length and are composed of mixed frequencies which may change during the course of the murmur, making the possibility of mimicking the murmur through automation very difficult if not impossible. Accordingly Dr. Barrett has shown that the repeated auscultation of automated heart sounds leads to better learning of automated heart sounds. It is highly likely that the same result would have been reached if human heart sound recordings had been used. However it is unfortunate that now students are downloading automated heart sounds which may have very limited , if any, learning value.

This author is the leading author in a publication mentioned and referenced in Dr. Barrett's publication (1) in which a group of family physicians were studied before and after using a cardiac auscultation CD Rom (2), with all sounds files being recordings of human heart sounds and murmurs. This is stated only to draw attention to the fact that recordings of human heart sounds are available.

As a long time teacher of cardiac auscultation, one can not help but speculate as to how the information regarding repetition will be used in the teaching of medical students. Cardiac auscultation is a difficult skill to acquire, and medical students have a host of other facts as well as skills to absorb before graduating. Of 970 new patients referred to the cardiology out patient clinics of the I.W.K. Children's Health Center, Halifax, Nova Scotia, Canada, in the year 2003, in 64.2 % the diagnosis was innocent heart murmur. The situation is compounded by different sets of norms for children and adults. Perhaps the teaching of heart sounds should be limited to normal heart sounds, and then referral for further study if the findings do not fit the normal. Even with this restriction of required knowledge, difficulty is foreseen, having in mind that five percent of people have amusia.(3) and others may have difficulty interpreting rhythm of heart sounds. Possibly computer assessment of heart sounds will be the ultimate answer in this regard, and research is now well along the way in making this possible. (4).

At any event, Dr. Barrett's work is an important milestone in the future of the teaching of cardiac auscultation.

Yours truly,

Douglas L. Roy M.D .FRCP(C), FAHA. Retired Professor of Pediatrics, Dalhousie Medical School and retired head of the Department of Cardiology of the I.W.K. Children's Health Center, Halifax, N.S. Canada.

References:

1. Roy D, Sargent J, Gray J, Hoyt B, Allen M, Fleming M. Helping family physicians improve their cardiac auscultatory skills with an inter-active CD Rom. J Contin Educ Health Prof. 2002; 22:152-159
2. EarsOn, by Cor Sonics Inc.
http://www.earson.com
3. Stewart L, Walsh V. Congenital amusia. All the songs sound the same. Curr Biol 2002;12:R420-1
4. Kudriavtsev V, Polyshchuk V, Roy D. Heart energy signature spectrogram for cardiovascular diagnosis. BioMedical Engineering OnLine. 2007, 6:16 (4May2007)

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Below please see examples of automated heart sounds available on the internet
(CardioSource) vs. Real Heart Sounds from Our collection

 

Automated HS02 Mitral Regurgitation Murmur frequency exaggerated by a factor
of 2 (should be 80 -230 Hz range). Also S1 and S2 are single frequency
(should have at least 2 separate frequencies corresponding to valve closures).
S3 not present (can be present in MR);  no intensity variation from one heart
beat to another which is due to breathing cycle of a real human.
Spectral Map of Automated Mitral Regurgitation, frequency 270 -470 Hz, peak frequency =325 Hz. Obtained by applying bandpass filter to "white noise"
Not the real murmur. See real Mitral Regurgitation.

 


Real Mitral Regurgitation(2 heart beats)              S1     Sys.Murm      S2           Diast.M

                S1                                          S2           S3?            Diastolic   Murmur                       Automated HS06 Mitral Stenosis Diastolic Murmur. S2 is soft. Not accentuated.
S3 unrealistically strong and single frequency (85Hz). S2 is also single frequency - 85Hz and S1 is single frequency 95Hz.
 
Spectral Map of Automated Mitral Stenosis, frequency 60 -130 Hz, peak frequency =87 Hz. Obtained by applying bandpass filter to "white noise"
Not the real murmur.  Real murmur frequency 45-93 Hz range, peak 79 Hz.

 

                   S1    SystolicMurm       S2                      Diastolic Murmur    
Real Mitral Stenosis. Systolic murmur is present. S2 is accentuated.
 



 

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