Vibrations of low frequency over the precordium.

A method for taking tracings which represent actual movements of the precordium (displacement curves) or records which show waves proportional to the velocity of movement of the chest wall (velocity curves) is described. The equipment employed is readily available, and the method is easy to use. The displacement curves are nearly identical with cardiograms taken with a good optical setup, and they may have diagnostic value. The velocity curves are more closely related to the functional status of the myocardium. The clinical significance of these tracings, especially the former, is pointed out. V IBRATIONS of many different kinds are produced by mechanical activity of the heart, and these may be transmitted through the chest wall and be detected by inspection, palpation, auscultation or by more elaborate instrumental methods. The heart sounds, murmurs and other auscultatory findings heard with the stethoscope are due to vibrations within the audible range (average frequency, 20 to 30 cycles per second or more), and much information relative to structural defects or functional disorders of the heart is, of course, obtained from these phenomena. Few physicians realize that these audible vibrations are usually insignificant in amplitude compared with those of low frequency. The latter may be seen and felt, but they are not heard on auscultation, and comparatively little attention has been paid to them. It is true that the apex beat or point of maximal impulse (PMI) is often referred to in a cursory fashion, but rarely is the character of the low frequency pulsations that cause it studied in any detail, and vibrations that may be seen or felt elsewhere over the precordium are often completely neglected. 579 Instruments for recording vibrations over the precordium have been available for many years in the form of tambours connected with levers arranged to write on smoked paper, and records (apex cardiograms) taken with such equipment may still be found in some text books of physiology. The poor frequency response and great mechanical lag inherent in such apparatus make these tracings nearly valueless, but optical methods developed by Frank,' Frank and Hess,2 and refined by Wiggers3 make it possible to record vibrations occurring over the precordium or elsewhere with a high degree of accuracy. Weitz,4 using the optical method of Frank with a somewhat different pickup device, recorded vibrations from the cardiac apex in normal subjects and in patients with different types of heart diesase and claimed …