Circulation Journal Official Journal of the Japanese Circulation Society http://www. j-circ.or.jp (Figure A, Left). The EPDM diaphragm is firmly fixed and the force is extended by tightening a lid with a spiral groove, which lifts the center by 1 mm, thus increasing the vibration of the plastic plate, and so the sound volume also increases. The comparative structure of the SDS and EDS is shown in Figure A, Right.As a preliminary test, 2 of the authors investigated the acoustic characteristics of various stethoscopes, both diaphragm and bell type, using an acoustic response test system, and found that the Master Classic II (Littmann) was the best and most suitable for the comparative study ( Figure S1).The acoustic differences of the EDS and SDS were recorded during auscultation testing of 3 patients by 5 physicians. The 3 patients (69-year-old male with angina pectoris; 42-year-old male with hypertrophic cardiomyopathy; 83-year-old male with hypertensive heart disease) gave informed consent. The 5 physicians (4 cardiologists, 1 internist) were not informed about the purpose of the test of listening to S4 sounds using 2 types of stethoscope (EDS and SDS). They were instructed to listen to S4 at a marked point of the apex, in 3 stages (no hand pressure, mild pressure, and moderate pressure), after they were handed an EDS or SDS randomly by an assistant. After listening to S4, all the examiners agreed that the EDS was louder and much clearer (Levine's criteria) when using mild pressure (Figure B), compared with the SDS. Furthermore, to confirm this auscultation test, one of the authors used both the SDS and EDS to test S3 and S4 sounds stored in a cardiology patient simulator, 9 as another comparative study. The examiner turned the sound volume switch down as low as possible, -30 points (lowest: -50). First the SDS, Master Classic II (Littmann), was tested and then the EDS under the same n 1816, Rene T. Laennec, was the first person in the world to use a wooden cylinder as an auscultation instrument. 1 After this, the forms and materials of stethoscopes have been modified, but since information technology such as electronic stethoscopes and echocardiography has been introduced into the medical field, stethoscopes have been gradually losing their significance as an important diagnostic tool. Today, there is some controversy concerning the diagnostic significance of cardiac auscultation in various clinical settings. 2-7We wondered if the reason for declining auscultation skills was related to difficulty in hearing heart sounds or murmurs by examiners, or a structural problem of the stethoscope itself? The most commonly used stethoscopes have double-headed chest pieces and single-headed chest pieces have been popular in the past 3 decades. The suspended diaphragm stethoscope (SDS) is considered able to catch all heart sounds, from low frequency (S3 and S4) to high frequency, 8 but it does not differentiate these sounds well. Therefore, we developed a new extensible diaphragm stethoscope (EDS), which has a different st...

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