THE USE of modern recording devices to supplement subjective impressions with objective determinations constitutes an important aspect of current progress in clinical diagnosis. For example, many types of cardiac arrhythmia may be recognized from clinical signs, but electrocardiography has become the final court of appeals in most cases. Similarly, the size and configuration of the cardiac silhouette can be determined more accurately from teleroentgenograms than by percussion. It is generally recognized that an objective record, examined visually, is more reliable than subjective sensations, such as tactile, temperature, or auditory perception. In view of the limitations of auditory acuity and the difficulty in distinguishing the temporal sequence of sounds, stethocardiography represents another opportunity to supplement subjective sensations with objective records. Sensitive and reliable stethocardiographs have been available for many years, but their use has been very limited. The advent of direct-writing electrocardiographic equipment, using high-inertia, low-frequency galvanometers, presages further reduction in
RUSHMER RF, BARK RS, ELLIS RM. DIRECT-WRITING HEART-SOUND RECORDER(The Sonvelograph). AMA Am J Dis Child. 1952;83(6):733–739. doi:10.1001/archpedi.1952.02040100031002
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