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Medical Electronics, IRE Transactions on

Date Dec. 1957

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  • [Front cover]

    Page(s): c1
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  • IRE Professional Group on Medical Electronics

    Page(s): nil1
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  • [Breaker page]

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  • [Table of contents]

    Page(s): 1
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  • History and Present Status of Phonocardiography

    Page(s): 2 - 3
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    Phonocardiography originated in an attempt to time the occurrence of heart sounds in the cardiac cycle in relation to the mechanical activity of the heart, as recorded in the apex beat or in arterial pulsations. The method evolved from an era when the observer manually inserted a signal in a pulse tracing at the time he heard the sounds. Later, this was done by mechanical synchronous record, then by an electric signal produced by a telephone pickup which stimulated a frog muscle to contract, then by direct recording through a capillary electrometer, or string galvanometer, and finally by electron tube amplification. Low-inertia capsule and mirror with photographic recording were also used, as well as other ingenious variations. Present day phonocardiography has developed mainly through improved instrumentation with low-noise level amplifiers and satisfactory filters. Spectral phonocardiography is the most important advance. The value of phonocardiography in clinical work lies in its ability to record for objective analysis the transient sounds and murmurs to which the hearing mechanism of different observers adds or subtracts subjective variants. It has been most useful in timing and explaining heart sounds having abnormal components├é┬┐split sounds, atrial sounds, opening snaps, and gallop rhythms. It is also valuable in the study of certain murmurs, particularly in mitral disease and congenital heart disease. It has contributed to teaching and has been a useful diagnostic aid prior to cardiac surgery. View full abstract»

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  • Physiological Auscultatory Correlations: Heart Sounds and Pressure Pulses

    Page(s): 4 - 5
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    Our knowledge of the cause of sounds arising in the heart has depended on indirect evidence of events of the cardiac cycle in man and direct observations made in other animals. The accessibility of the human heart for study in this era of cardiac surgery now permits the direct observation made in animals to be repeated in man and the indirect correlations to be confirmed. View full abstract»

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  • Discussion of Session I-A

    Page(s): 6 - 7
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  • The Genesis of Musical Murmurs

    Page(s): 11 - 12
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    First Page of the Article
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  • Transients in Heart Sounds and Murmurs

    Page(s): 12 - 14
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    A new approach to the analysis of heart sounds and murmurs has been developed. These acoustic phenomena are considered to be generated by a series of transient sounds which because of the long persistence of the low-frequency components of the sounds, tend ordinarily to fuse into a single sound. The separate events such as valve closures which produce discrete clicks, therefore tend to fuse, and time discrimination of these important events is lost. An apparatus which filters out the low frequencies has been developed. The remaining high-frequency, short duration waves can thereby be displayed as a series of separate events, each representing closure or opening of a valve. Several records obtained with this system are shown, and the potential value of this mode of analysis is discussed. View full abstract»

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  • Discussion of Session I-B

    Page(s): 15 - 16
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  • Absolute vs Acoustic Standardization in Electrostethography and the Need for Studying Cardiac Vibrations As Transients

    Page(s): 17 - 18
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    The marked variations in the audiograms of the individuals and the wide variation in frequency response of different flexible stethoscopes preclude the possibility of any widespread system of standardization. Phonocardiography has well recognized teaching and clinical value but is limited in usefulness as a clinical tool. Electrostethography eliminates the use of auditory recordings and is a direct measure of vibrations and can be easily calibrated in absolute, i.e., cgs units. The patterns produced have a gross resemblance to phonocardiographic patterns but provide measurable frequency and amplitude data. The many factors which affect heart vibrations together with the numerous types of artefacts that can occur suggest the electrostethograms should not be studied according to the techniques developed from electrocardiography but should be done with long records, multifrequency channels, and calibrated amplifiers. This method is further improved by studying the vibrations as transients on a cv scope with locked sweep and provisions for recording of selected single cycles. View full abstract»

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  • Newer Studies of Selective Phonocardiography Including a New Method for the Identification of the Frequency Range of Extra Sounds

    Page(s): 19 - 21
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    Problems dealing with the registration of either apical or basal diastolic murmurs of poor magnitude are discussed. Current methods of phonocardiography are reviewed. Eight normal subjects and thirty abnormal cases were studied by means of a variable band-pass filter with additional amplification. The various frequencies of the cardiac murmurs were analyzed. A band between 60 and 110 vibrations per second was found adequate for magnifying and recording murmurs caused by mitral stenosis. A band between 150 and 200 was found adequate for magnifying and recording murmurs caused by aortic defects or mitral insufficiency. A routine method of study of cardiac murmurs, called ``selective phonocardiography'' is outlined. It is based on the use of the two above bands, in addition to ``stethoscopic'' phonocardiograms. Incorporation of filters in the case of the phonocardiograph is recommended. A new method of study of the frequency of extra sounds is described. Preliminary observations are reported. A new technique of intracardiac(ic) phonocardiography during routine catheterization is described. Preliminary studies in animals are reported. View full abstract»

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  • Discussion of Session II-A

    Page(s): 22 - 25
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  • Part I--Phonocatheters: Their Design and Application

    Page(s): 25 - 30
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    A miniature cylindrical barium titanate tubular element has been designed as an acoustic pickup and placed at the distal end of a specially designed catheter. The catheter is, in fact, an extension of the general design technique used to evolve underwater sound transducers used in antisubmarine warfare. Catheters have been designed in both single and double-lumen types, with provisions in the latter case for the usual practice of heart catheterization simultaneously with the phono work. Details of the response of the catheters and performance of the experimental system used are given. Sound spectrograms which plot time as the abscissa, frequency as the ordinate, and amplitude as the density have been made, as well as conventional photographic recording galvanometer records. Preliminary experimentation was carried out in dogs where both left and right catheterizations are cited. View full abstract»

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  • Part II--Intracardiac Phonocardiography

    Page(s): 31 - 34
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    Using specially designed catheters and amplifying equipment, studies of intracardiac sounds have been carried out in man at the time of cardiac catheterization. The catheters, either single- or double-lumen, are passed into the lesser circulation under fluoroscopic guidance. The first and second heart sounds are heard in the heart and in the great vessels leading to and from the heart. The first sound is loudest in the ventricle and the second sound is loudest in the pulmonary artery. In some cases a third heart sound has been detected. In all cases with atrial contractions, a fourth sound is detected and is loudest in the atrium. With atrial fibrillation no fourth sound is heard. Even when no murmurs are heard on the chest or in the heart, there is routinely a midsystolic murmur in the pulmonary artery. In the presence of disease, abnormal murmurs are heard inside the heart. In certain types of congenital heart disease the localization of the murmur is of help in the diagnosis. Records are shown to illustrate that this technique is capable of localizing heart sounds and murmurs to an extent not heretofore obtainable. View full abstract»

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  • High-Sensitivity Capacitance Pickup for Heart Sounds and Murmurs

    Page(s): 35 - 40
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    Exploration of heart murmur frequencies requires a pickup and associated electronics having great sensitivity and a wide range. Such a system, employing a capacitance principle, has been applied to reproduction of sounds from the precordium. The pickup is of the direct contact type, is relatively insensitive to extraneous noise, and is capable of recording murmurs of extremely low intensity. View full abstract»

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  • Evaluation of the Spectral Phonocardiographic Analysis

    Page(s): 41 - 43
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    Heart sounds can be divided into three classes: short duration pulses (first and second heart sounds); broadband long duration noise (murmur); and long duration sounds having distinct harmonic pattern (musical murmurs). The characteristics of the analysis of these classes are illustrated, and the timing, duration, and filtering artifacts are discussed. A comparison between phase and amplitude filtering is given. Application of this research instrument to clinical size and cost is considered. View full abstract»

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  • Instrumentation Problems in a High-Frequency Heart Sound Analyzer

    Page(s): 44 - 47
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    It is accepted generally in medical practice that the low-frequency vibrations (up to 600 cps) of heart sounds and murmurs contain virtually all the available information. Newer concepts have been proposed that these signals actually consist of irregularly occurring transients which comprise the important information regarding heart action. These transients can be analyzed by recording the frequencies above 1000 cps. The level of these signals is subaudible and in some cases is below the noise level of the usual electronic amplifier. A preliminary model of such a heart sound analyzer which has been built and tested reveals the existence of vibrations in the range mentioned with amplitudes less than 1 per cent of those in the lower frequency ranges. Instrumentation aspects of this are discussed. Limitations imposed by lack of suitable microphones are mentioned and specifications for such a microphone are suggested. Available variable cutoff frequency filters have the inherent capability of introducing artifactual signals not present in the original heart sound. A specially designed filter, free of such artifact, is described. View full abstract»

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  • Discussion of Session II-B

    Page(s): 48
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  • Evening Panel Discussion

    Page(s): 49 - 53
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  • [Front cover]

    Page(s): c2
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Aims & Scope

This Transactions ceased publication in 1960. The current retitled publication is Biomedical Engineering, IEEE Transactions on

Full Aims & Scope