THE USE OF T H E C A T H O D E RAY FOR RECORDING H E A R T

SOUNDS AND VIBRATIONS

I [ I . TOTAL CARDIAC VIBRATIONS IN ONE HUNDRED NORMAL SUBJECTS

JOH~ R. S~ITH, M.D., JOSEP~ C. EDWARDS, M.D., A~,'D WILLIAM B. Kou~¢z, M.D.

S¢. Louis, Mo.

I N RECENT years phonoeard iography has acquired a definite place in the diagnosis of hear t disease. The regis t ra t ion of the hear t sounds

for clinical purposes was greatly facili tated by the introduction of electrical stethographs, whose convenience of use and superior ac- curacy in recording are signally superior to the older methods. 1 However, these s te thographs have usual ly been constructed in such a way as to emphasize murmurs and other adventi t ious sounds. Such records may be of dist inct value in s tudying certain adventi t ious sounds, especially as regards their re la t ion to the cardiac cycle. Litt le, if any, a t tent ion has been paid to the general character of all of the vibrat ions produced by the hear tbeat , the audible l requeneies of which make up the hear t sounds. As was pointed out ~n a previous com- munication, ~ certain lundamenta l changes in the hear t tones may occur in various kinds and stages of hear t disease; it would seem ad- vantageous to record all of the vibrat ions set up by the hear tbeat , both audible and inaudible, so tha t these fundamenta l changes, which may be obvious to the ear, can be recorded and studied.

The object of this communication is to present a composite s tudy oil t racings of total cardiac vibrat ions which were obtained from 100 normal young adults.

PROCEDURE

The subjects were medical s tuden ts and nurses~ whose ages ranged ~rom 20 to 35 years. All of them had previously had complete physical examinat ions , in-

eluding roen tgenograms of the chest, and were presumed to be in good health. The ins t rumen~ used for recording the hear t v ibra t ions was the vibrocardiograph. A detailed descript ion of the device has been presented.a In most eases the vibroeardiographle t rac ings were recorded s imul taneously wi th Lead I I of the electrocardiogram, and the records were .synchronized by flashing lamps which played on the two records simultaneously.a Dur ing the procedure the subject lay

supine for ten to fif teen minutes , un t i l s tab i l i ty of the hear t ra te was assured. The blood pressure, which was recorded during the period of rest, was wi th in normal range in each case. Tracings were obta ined f rom the aortic, trienspid~ mitral , and pulmonie areas. In some cases the pickup uni t was placed at other locations on the anter ior chest wall, in an effort to discover whether there were var ia t ions i~ wave forms and in tens i t ies outside of the usual auscul ta t ion areas.

From tile Department of Internal Medicine, Washington University School of Medicine and Barnes Hospital.

l:~eeeived for publication Nov. 12, 19~0.

228

S M I T t I E T A L . : U S E O F C A T H O D E R A Y 229

DESCRIPTION OF T[-IE RECORDS

The dominant vibrat ion groups iu normal v ibrocardiograms are those incident to the onset of systole (embodying the audible fre- quencies of the first hear t sounds) and those incident to closure of the semilunar valves. In analyzing the first (systolic) v ibra t ion com- plex, a group of small pre l iminary waves (one to three in number) could usual ly be seen in reeords f rom all of the four auscul tat ion areas. They were interposed between the P wave and the crest of the R wave, and immediate ly preceded the large prineipal vibrat ions of which the first sound is a part . The time of occurrence of the pre- l iminary waves would seem to be just pr ior to the rise of in t raventr icu- lar pressure at the onset of systole; they correspond in time to the "p r e l im ina ry v ib ra t ions" noted by 3/IeKeeY I t is possible tha t these ripples are caused by the forcible ejection of blood f rom the auricles into the ventricles dur ing auricular systole. I t is likewise possible that they ma y be induced by movements in the vent r icu lar nmscle when it is fu r the r dis tended by the force of aur icular systole.

The main deflections follow the pre l iminary waves and consist of spikes of h igher ampli tude and frequency. These main deflections be- gin immediately a f te r the peak of R and then taper into lower-fre- quency, lower-ampli tude waves which finally disappear at, or just after, midsystole. Since the principal deflections inelude the audible components which comprise the first hear t sound, the sound itself, therefore, falls on the descending limb of the R wave. The total durat ion of the first vibrat ion complex, including the pre l iminary waves and the main deflections, with the audible frequencies, ranges from 0.19 to 0.29 second and averages 0.22 second when the heart rate ranges froln 70 to 85 pet' minute. The dura t ion of the main wave complex (i.e., deflections fol lowing the peak of R, including the audible portions) is f rom 0.08 to 0.19 second, and averages 0.1] second in the entire series of eases. The wide var ia t ion in the dura t ion of the first vibrat ion complex possibly depends on several factors, such as r ap id i ty of rise of in te rvent r ieu la r tension, thickness of the aur iculoventr ieular valves, and the blood pressure level. I t is in teres t ing that , a l though subtle differenees in the hear t sounds may be detected in normal per- sons by auscultation, there may be striking' variat ions in the shape of the waves of the first sound complexes a m o n g n o r m a l persons, as recorded by the cathode-ray oscillograph. Such changes appear to be caused by al terat ions in the lower-f requency components, wi thout much visible modification in the sharp waves which produce the sound. i t is likewise of interest tha t the shapes of successive waves f rom a given subject are r emarkab ly constant, so long as the basal s tate re- mains undisturbed. The significance of the low-frequency components and other variat ions in the curves will be discussed later.

230 T t I E AMERICAN H E A R T J O U R N A L

I t is general ly thought tha t the second hear t sound is caused by the closure of the pulmonic and aortic valves. In the records obtained with the vibroeardiograph, or by ordinary phonoeardiography, the see- ond sound is sharper in profile and shorter in durat ion than the first sound complex. In this series, the second sound complex, both at the pulmonic and aortic areas, consisted of one to three sharp waves which ranged f rom 0.04 to 0.09 second in dura t ion (averaging 0.06 see.), wi th frequencies of approximate ly 80 to 90 d.v. per second. This is in agreement with the results obtained by most workers. The second sound complex falls on the descending limb of the T wave of the electrocardiogram. The ampli tude of the deflections (sound intensi ty) is p robab ly direct ly related to the level of the aortic and pulmonie pressure, as noted by Wiggers and Dean2

General analysis of the durat ion of the vibrocardiographic curves with relat ion to the dura t ion of systole, diastole, aJld the first and second sound complexes showed variable results. I t is known that accelerat ion of the hear t ra te shortens diastole, and, occasionally, systole. A rise in blood pressure caused an increase in the dura t ion of the first sound complex, apparen t ly by prolonging tha t pa r t which fol lowed the peak of R. Age had some effect on the dura t ion of the first sound. As a rule, the younger the subject, the shorter were the systolic vibrat ion complexes, and, the older the subject, the longer were the systolic vibrations. The dura t ion of the first vibrat ion complex was general ly shorter in female than in male subjects. The ratio of the dura t ion of the first and second vibrat ion complexes was roughly two to one, although, when the hear t rate was fast, the two sounds f requent ly tended to be of the same duration. The point of contact also affected the vent r icu la r complex; general ly the vibra- tions at the aortic and t r icuspid areas were more prolonged than at the pulmonic and mitral areas.

i t is said that a th i rd hear t sound may occasionally be audible in ear ly diastole, but none of our 100 subjects had a diastolic th i rd hear t sound. However , in 7 per cent of the tracings, there was, following the second sound complex, a large wave at the time when the th i rd hear t sound might be expected to occur (i.e., approximate ly 0.1 see. af ter the second sound). The deflection was of too low a f requency to be heard. There is a general feeling tha t rapid vent r icular filling' in early diastole, producing' sudden distension of the ventr icular walls, cre- ates vibrat ions which sometimes may be heard. ~ Hirsch and Gubner, 5 who studied cardiac movement by means of roentgenkymography, found that a sharp break occurs early in the diastolic wave f rom normal hearts. They in te rpre ted this as represent ing sudden vent r icu lar dis- tension caused by rapid filling of the vent r icu la r cavities. I t would thus seem possible tha t sudden vent r ieu lar distension in early diastole

SMITH ET AL. : USE OF CATIIOi)E RAY 23i

might produce a single movement which would register as a single,

low-frequency wave. Another group of subjects (5 per cent of the series) showed low-

frequency, low-amplitude waves (below acoustic level) in diastole. There were usually three waves, although occasionally only two were

evident. The phenomenon occurred principally in persons who had

been athletes. It is curious that the diastolic waves were usually most

marked in tracings made from the tricuspid or aortic areas. Oc- casionally they were more conspicuous when the receiver was placed at some point along the right sternal border. They appear to be the result of myocardial motion, as will be discussed later.

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Fig. l.--Diagrammatic sketch of typical vibrocardiographic curves in relation to Lead II of the electrocard]ogram. The vertical line (/~) represents the time of oc- currence of the I% wave. The preliminary waves (A) occur between I J and R of the electrocardiogram. B intimates the "main deflections" at the onset of systole which embody the audible frequencies of the first heart sound. The peaked deflections (C) comprise the second heart sound. /9 and E are the low-frequency, inaudible waves which occur in systole and diastole.

In ordinary phonocardiography, lnurmurs and other adventitious sounds may appear particularly clear because of dalnphlg out of lower vibration frequencies and anlplification of the higher; therefore,

232 T I I E AMERICAN H E A R T J O U R N A L

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234 THE AMERICAN HEART JOURNAL

the defiectious representing a murmur may be out of al1 proport,ion to the intensity at which they actnally occur, as eompa.red with the in- tensity of th.e heart sounds. Tracings obtained by this method will show that the vibrations incident to the murmur are of low a~~~lit~~de if the intensity of the murmur is small in comparison with other sounds produced by the heartbeat. If, however, a murmur is loud, as in. wcll- marked aortic stenosis, the sound may he registered as a series of tall,

high-frequency, systolic waves. One frequently encouvrters pulmonic systolic murmurs in normal persons, especially when the subject is

Fig. 4.--Vibrocardliograghic curves, synchronized with Lead II of the electrocardio- gram, picked at random from the series of cases. A, Curve obtained from the tricuspid area of a subject who showed low-frequency systolw and diastohc waves (marked bg curved arrows). B, Curve obtained from the mitral wea of a subject with a func- tiona.1 mitral systolic murmur. Note the high frequency systolic w&ves which represent the murmur. The mtenslty of the murmur is proportionate to that of the first and second sounds. e, Vibrocardiogram taken from the tricuspid area of a subject who had “splitting” or reduplication of the first heart sound. Note the two, tall, peaked witves, separated by a short segment : each wave has steep, audible slopes.

in the reclining position. This is best shown in Fig:. 3; small, high- frequency waves are noted in the systolic intewals of the tracings obtained at the base of the heart. In this instance the murmur wn.s faint; consequently, in the curve it is diminutive in comparison with the other waves.

S M I T H ET AL. : USE OF CATHODE RAY 2 3 5

An interest ing occurrence in some normal hearts is spli t t ing of the fi~'st or second sounds. In tracings recording total hear t vibrations, thi~ appears as a redupl ica ted or doubled series of tall deflections, with steep slopes as the audible port ions (Fig. 4).

COMMENT

Curves were obtained from 100 normal subjects under as near ly uniform conditions as possible, and the t racings were general ly similar. As noted before, the wave shapes may va ry widely, a]though, to auscultation, the heart sounds may seem to differ but little. These variations in contour appear to be dependent largely on modification of the lower-frequency vibrat ions incident to vent r icular systo]e. A sm'vey of the mater ia l shows that the sharpness of the first vibrat ion complex is not re la ted to the dura t ion of systole or diastole, for there may be shortened first sound vibrat ion complexes when either systole or diastole is prolonged or shortened. However, it is recognized that the quali ty and intensi ty of the sounds may change in normal subjects, depending on the conditions under which the hear t must work. Wig- gers 6 found that, within certain limits, a change in the vibrat ions produced by the beat ing hear t was an indication of a change in the rate of rise of in t ravent r icu la r tension during the isometric phase of contractio11. Thus, the speed and force with which the ventricle con-

tracts, whether the subject is at rest or active, may determine the sharpness and intensity of the heart sounds. The heart tones may

likewise be influenced by the size of the chest and the thickness of the chest wall. Obesity or a well-developed thoracic musculature may di-

minish the intensi ty of the vibrations, whereas in slender subjects the vibrations may seem par t ieu lar ly clear.

Of greater interest, we believe, than the recording of sound in- tensities and murmurs, are the low-frequency, inaudible defleetions i~eident to the systolic and diastolic phases of vent r ieu lar eontraetion. The main vibrat ions of the first hear t sound, or the taper ing vibrat ions themselves, often embody such low-frequency waves. The cause of these systolic waves is not ye t clear. Smith, Kountz, and Gilson, 7 working with hearts of dogs, noted that, when the aur iculoventr icular valves were immobilized, the vibrat ions produced by contract ion of the myoeardium alone were large and of low frequency, with slopes as steep as those of the audible vibrations. Such waves, as recorded from the beat ing dog heart , of ten bear a s tr iking similari ty to the low-frequency waves which are par t of the first vibration complex in tracings from normal subjects. I t is possible that these low-frequeney waves indicate myocardial motion per se, and that they may result from additional contracti le motions of the hear t dur ing systole.

Of equal interest are the low-frequency, low-amplitude diastolie waves which occur ill some normal subjects, par t icular ly in athletes,

236 THE AMERICAN HEART JOURNAL

As noted before, they are usual ly m a x i m m n at the aort ic or t r icuspid

areas. In cast ing about for an explana t ion of this phenomenon, it first seemed l ikely tha t they migh t resul t f rom gross, pendulous mo- t ions of the heart , made possible by the mobi l i ty of the medias t inmn

and the resilience of the lungs. However, al tering the position of the subjec t nei ther abolished not' accen tua ted the waves, a l though one might have expected a modification of the waves if a pendulous, sway-

ing movemen t of the hear t were a factor . I t was also necessary to consider the possibil i ty tha t the resona t ing proper t ies of the chest

migh t produce low-frequency waves incident to the hear tbeat , bu t the deflections in question were found not to vary with respiration, nor

to be influenced by t ight s t r app ing of the chest, which increased the resona t ing p roper t i es of the chest. I t seems nlost likely, therefore,

t ha t the diastolic waves arise f rom motions of the myoea rd ium itself. H o w such mot ion is produced, or why it occurs, is still a moot point. Recent work s-~° suggests tha t diastolic waves may be caused by the

passage of recoiling' movements over the ven t r ieu la r muscle, g iving the appea rance of a " n o t c h - l i k e " di latat ion, r a the r than a smooth dilata-

tion. I f this were the case, one would expect such a phenomenon to occur universal ly. Jt is possible, however, t ha t under some conditions they m a y be damped out.

SUMMARY

The usual s tudy of hear t sounds is l imited to the recording of the sound vibrat ions only, with little a t tent ion to other vibrations produced by the beat ing heart . In this invest igat ion, all of the cardiac vibra- t ions at the usual auscul ta t ion areas in 100 normal young adul ts wet'e recorded by means of a ca thode-ray v ibroeard iograph . The in tens i ty and dura t ion of the first and second sound v ibra t ion groups were s tudied in re la t ion to the length of the systolic and diastolic phases of the cardiac cycle. Wi th this method, murmm' s are reproduced at the in tens i ty wi th which they occur, and, if faint, m a y appea r diminu- t ive in compar ison with the deflections which represent the hear t sounds. Most in teres t ing are the low-frequency vibrat ions, below the aud i to ry level, which occur in systole and diastole and possibly indi- eate myocard ia l mot ion alone.

The au tho r s wish to express thei r apprec ia t ion to the Burd iek Corporat ion, whose coopera t ion nmde th i s work possible.

REFERENCES

1. K o u n t z , W. B., Gi l sm b A. S., and Smi th , J . R . : The Use of t he C a t h o d e Ray fo r R e c o r d i n g I I e a r t S o u n d s a n d V i b r a t i o n s . I. S tud i e s on the N o r m a l Hea r t , A~L HEART J. 20: 667, 1940.

2. M e K e e , 1~[. H. : t I e a r t S ounds in N o r m a l Chi ldren , AM. I-IEART J. 16: 79, 1938. 3. W i g g e r s , C. J., a n d Dean , A. L.: T he N a t u r e and T i m e R e l a t i o n s of the

: F u n d a m e n t a l H e a r t Sound.s, Am. J . Phys io l . ~12: 416~ 1916.

SMITH ET AL. : USE OF CATIIODE RAY 237

4. Orlas~ O., and Braun-Mendndez, E.: The Hear t Sounds in Normal and Pathological Conditions, 1939, New York, Oxford Univ. Press.

5. Hirseh, I. S., and Gubner, R.: Application of Roentgenkymography to the Study of Normal and Abnormal Cardiac Physiology~ A~r. tIEART J. 12: 413, 1936.

6. Wiggers, C. J.: Factors Determining the Relative in t ens i ty of th~ Heart Sounds in Different Auscultation Areas, Arch. Int. Med. 24: 471~ 1919.

7. Smith~ 5. R., 1,2ountz~ W. B., and Gilson, A. S.: The Use of the Cathode Ray for Recording Hear t Sounds and Vibrations. II. Studies on the 3/fuseular Element of the Fi rs t Heart Sound, A~[. IIE.~aT J. 21: 17, 1941.

8. Landis, C., t tunt , W. A., Moe, G. t,2., and Visseher, 3/[. B.: Color and Super Speed Cinematography of the Isolated Heart-Lung~ Aul. J. Physiol. 129: 400~ 1940.

9. Starr, I., and Schrweder, It. A.: t~Mhstoeardiogram: II. Normal Standards. Abnormalit ies Commonly Found in Disease of the Heart and Circulation, and Their Significane% J. Clin. [nvest igat lon 19: 437, 1940.

]0. Smittb J. R., l{ountz, W. B., and @ilson~ A. S.: Unpublished data.