Production of Heart Sounds by the Cardiac CatheterBy FREDERIC L. ELDRIDGE, M.D., AND HERBERT N. HULTGREN, M.D.

Extra heart sounds are frequently produced by the cardiac catheter in the human subjectduring routine cardiac catheterization. They are associated with a characteristic pressure

artefact, which suggests that the sound is produced by back-and-forth movement of thecatheter tip across the pulmonic valve. Similar sounds, and also murmurs, can be pro-

duced by catheter passage across pulmonary or aortic valves in excised canine hearts.The fact that such artificial sounds can be produced by the intracardiac catheter sug-gests that some caution must be used in interpreting phonocardiograms obtained duringcardiac catheterization.

INCREASED interest in the heart sounds inrecent years has led to attempts to obtain

better correlation between the sounds and me-chanical events within the heart than can beprovided by external recording of pulses andsounds. One method is the simultaneous re-cording of external heart sounds and intracar-diac pressures during cardiac catheterization.Recently the recording of intracardiac soundsby means of the intracardiac phonocatheterhas been used in an attempt further to refineinterpretation. 2 Such methods have provedto be very useful.For the past year we have been recording

simultaneously external heart sounds and in-tracardiac pressures in a large proportion ofroutinely catheterized patients. We have ob-served that heart sounds may be produced bymovement of the cardiac catheter within theheart, and that such sounds may lead to errorsin interpretation of the phonocardiogram ob-tained during catheterization. Because of theincreasing use of phonocardiography duringcardiac catheterization, especially with theintracardiac phonocatheter, we think it ofsome value to report our findings regardingthe incidence, characteristics, and mechanismof production of such catheter-induced heartsounds.

MATERIAL AND METHODSOf a total number of 132 patients catheterized

in this laboratory over a period of a year, 57 willbe considered. All these subjects had simultaneous

From the Department of Medicine of the StanfordUniversity School of Medicine, San Francisco, Calif.

Dr. Eldridge is Scholar in Medical Science of theJohn and Mary R. Markle Foundation.

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recording of intracardiac pressures and heartsounds during withdrawal of the cardiac catheterfrom the pulmonary artery to right ventricle andatrium.

Intracardiac pressure pulses were recordedphotographically by means of a multichannel mir-ror oscillograph via the catheter and a Stathamstrain-gage transducer (P23D). The heart soundswere received by a microphone (Cambridge Ini-strument Co.) placed on the anterior chest wall inthe pulmonic area or along the left sternal border,amplified by means of a low-level amplifier (Tek-tronics, Inc., Type 122), and recorded by the sameoscillographic recorder. With this equipmentpressure events on the recording have a delay ofno more than 0.01 second in relation to the phono-cardiographic events, even with the smallest andlargest catheters used.

CLINICAL OBSERVATIONSThe records of 18 of the 57 patients studied

were found to show an extra heart sound. Inall cases, this was loudest along the left ster-nal margin at the second or third intercostalspaces. The sound was clearly audible to aus-cultation over this area.

In 17 of the 18 cases, the extra sound hadthe following characteristics: 1. It had thesame pitch and duration as a second heartsound. 2. It was noted only when the cathetertip appeared to be in the right ventricularoutflow tract, or during withdrawal of thecatheter from pulmonary artery to right ven-tricle. In 7 cases, the extra sound was notedonly in 1 or 2 heart cycles during the with-drawal, but in the other 10 cases it occurredrepeatedly during the period in which thecatheter tip seemed to be in the right ventricle.3. It occurred in early diastole as shown inthe example in figure 1. There was no fixed

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FIG. 1. The extra heart sound (x) in diastole is induced by the cardiac catheter in a humansubject. The pressure tracing represents a combination of pulmonary artery pressures (inlater systole and in early diastole before the sound) and right ventricular pressures (indiastole following the extra sound and in the first portion of systole). The sharp drop inpressure coincident with the extra sound is due to the sudden pulling back of the cathetertip into the right ventricle.

FIG. 2. Extra heart sounds (x) induced by the cardiac catheter, occurring at variableintervals after the second heart sound. Note the variable contour of the "right ventricular"pressure pulse contour, with a, sharp drop in pressure occurring at the time of each extra sound.

interval between the second heart sound andthe extra sound. From subject to subject andeven in the same individual there was oftena varying relationship between the secondsound and the extra sound (fig. 2). 4. Thesound was always associated with a character-istic pressure tracing. This was an artifactin the right ventricular tracing which con-sisted of prolonged elevation and a sharp dropof pressure in diastole to the diastolic levelof the right ventricle (figs. 1 to 4). In everycase the extra sound coincided exactly withthis pressure drop.

WTe have interpreted these findings as fol-lows. Durin(g end-diastole the catheter tip isin the right ventricular outflow tract, ven-tricular diastolic pressure being recorded.Systolic contraction of the ventricle pushesthe catheter tip through the opened pulmo-nary valve, so that pressure in the pulmonaryartery is recorded. After the second heartsound, in early diastole, the catheter tip re-mains in the pulmonary artery for a time; butthen, as the ventricular cavity enlarges dur-ing diastole, it is pulled back through the nowclosed pulmonary valve into the ventricle, so

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FIG. 3. An extra sound is absent when the(first 2 cycles), but it appears when catheterartery and right ventricle.

that the recorded pressure drops suddenly.The sound is related to the same events. Thepresence of the catheter does not prevent a

normal second pulmonic heart sound, butwithdrawal of the catheter produces an extravalvular sound.We have on several occasions noted such

a back-and-forth movement of the cathetertip across the pulmonary valve during high-speed cineangiocardiographic studies.

Other factors that might have affected theproduction or incidence of this extra soundwere considered. The sound occurred with allsizes (5F to 1OF) of cardiac catheters. Ageseemed to be no factor, since the range was

from 4 to 47 years. The extra sound occurredwith a variety of cardiac abnormalities, in-cluding 6 with atrial septal defect, 5 withinterventricular septal defect, 4 with mitralstenosis, and 2 with primary pulmonary hy-pertension. There seemed to be no relationshipto left-to-right intracardiac shunts, since 6patients had no shunts, 7 had moderate-to-large shunts, and 4 had balanced left-to-rightand right-to-left shunts. The 1 factor thatappeared to be of some importance was thatof pulmonary hypertension, a pulmonary ar-

tery systolic pressure of greater than 40 mm.

Hg being present in 12 of the 17 cases, a

greater incidence than would be expected from

the material usually studied in this laboratory.Nevertheless, the existence of pulmonary hy-pertension was not essential for the produc-

catheter tip is fully in the pulmonary arterytip passes back and forth between pulmonary

FIG. 4. Sounds and "right ventricular" pressuretracings from 3 human subjects showing appearanceof extra heart sound ($) and pressure artifact coin-cident with sound.

tion of the extra sound, 1 subject having a

systolic pulmonary pressure of only 26 mm.Hg.None of the 10 patients with moderate to

severe pulmonic stenosis developed this dias-

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ELDRIDGE, HULTGREN

FIG. 5. Sounds and pulmonary artery pressure tracing from a patient with pulmonic stenosis.Note systolic extra heart sound (x), whichartery.

tolic sound. It is therefore of interest thatthe eighteenth patient, who had severe val-vular pulmonic stenosis, did show a midsys-tolic sound (fig. 5). This sound occurred onlywhen the catheter tip was located in the pul-monary artery several centimeters beyond thevalve.

In spite of the occasional appearance of apressure artifact due to the catheter tip 'spassing from the ventricle to the atrium dur-ing systole, no coincident extra sound wasnoted in any case.

EXPERIMENTAL OBSERVATIONSIn view of the findings in patients, we

thought it desirable to attempt the experimen-tal production of heart sounds by means ofthe cardiac catheter, and to verify the valvu-lar origin of the sound.

1. The intact hearts and great vessels from2 recently killed normal dogs were used. Ineach, the pulmonary artery was cannulatedand attached by means of plastic tubing to asmall reservoir of water. A pressure of ap-proximately 25 to 30 mm. Hg was maintainedin the pulmonary artery, which kept the pul-monary valve cusps tightly closed.

Pressures within the right ventricle and pul-monary artery were recorded by means of acardiac catheter inserted through the rightventricular wall. Sounds were recorded bymeans of the equipment described above, themicrophone being carefully placed over themain pulmonary artery. During the proce-dure, pressures and sounds were recorded si-

occurred only when catheter was in pulmonary

multawieously while the catheter tip was beingmoved slowly or rapidly in and out of thepulmonary artery, through the pulmonicvalve.

In both hearts the passage of the cathetertip through the pulmonary valve, in either di-rection, caused loud sounds to occur. Anexample is shown in figure 6. The high in-tensity of sound at the pick-up site is demon-strated by comparison with the apex sounds ofa normal human adult taken with the sameequipment and at the same amplifier setting.The main factor in the production of the

sound seemed to be the setting of the tensedvalve cusps into vibration by insertion orwithdrawal of the catheter tip. The size ofthe catheter was unimportant as far as soundproduction was concerned, as was the position(lateral or central) of the catheter in thevalve. The speed of withdrawal was impor-tant: when fast, a sharp sound was generated;when slow, no sound was recorded but thepresence of the catheter tip in the valve pro-duced pulmonic insufficiency and the associ-ated murmur (fig. 7).

2. A similar experiment was performed withanother excised canine heart with use of theaorta valve. Here again, passage of the cathe-ter tip across the valve yielded sharp, loudsounds.

DIscussIoN

It is apparent from these findings that thepresence of a catheter in the heart can bringabout the production of true valvular heart

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CATHETER PRODUCED HEART SOUNDS

FIG. 6. Sounds generated at the pulmonic valve inan excised dog heart when catheter tip passed rapidlyback and forth between right ventricle and pulmo-nary artery. Pressure tracing shows abrupt fall inpressure as catheter tip passes across closed pulmonicvalve. Lower tracing of normal adult human apexsounds taken with same equipment and amplificationshows the high intensity of the sounds induced in thedog heart.

sounds. The coincidence of the pressure arte-fact and the extra heart sound, and the ex-perimental findings are strong evidence infavor of the postulated mechanism as thecause of the diastolic extra sound found inlmost of our subjects. Further support comesfrom the demonstration by high-speed cine-angiocardiography of a back-and-forth move-ment of the catheter tip across the pulmonaryvalve.

Since sounds were caused in the excisedhearts both by insertion and by withdrawal ofthe catheter across the pulmonary valve, itmay be questioned why only withdrawalcaused a sound in the human subjects. Theexplanation undoubtedly lies in the fact thatin the excised heart the valve was closed dur-ing both insertion and withdrawal, and wastherefore capable of producing sound withboth, whereas in the beating heart, systolicopening of the valve occurred before ventric-ular contraction pushed the catheter through,and therefore no sound could be generated.

It is interesting that no diastolic soundswere produced in cases with pulmonic valvu-lar stenosis. We have no definite explanationfor this observation, but there are 3 possibili-ties: 1. The pressure in the pulmonary arteryis insufficient to tense the valve cusps enoughto produce sound. 2. The rigid valve cusps are

FIG. 7. Tracing showing the murmur of pulmonicinsufficiency generated in an excised dog heart byslow withdrawal of the catheter tip from pulmonaryartery to right ventricle.

not able to vibrate sufficiently to cause au-dible sound. 3. Because of the narrow valveorifice the catheter tip cannot easily moveinto and out of the pulmonary artery, andthe conditions for the production of the soundare not established. Cineangiocardiographicstudies on suitable patients might help tosettle this point.The experimental findings, and the 1 patient

with pulmonic stenosis who had a systolicsound, suggest that other sounds and mur-murs can be produced by a catheter in theheart. No murmurs attributable to the cathe-ter were recorded externally in any of ourhuman subjects, but it may be that any mur-murs produced were of insufficient intensity.The experimental findings demonstrated thestriking loudness of the diastolic sound, whichwas easily recorded in patients.

In view of the increasing use of phonocar-diographic technics during cardiac catheteri-zation, one should be aware of the possibilityof catheter-induced extra sounds, for undersome circumstances the diastolic sound de-scribed could be interpreted as a late pul-monic second sound. Although the presenceof the pressure artifact, which to our knowl-edge has not been described before, is helpfulin making the proper distinction, many of thephonocatheters in use at the present time donot have a separate lumen for measurementof intracardiac pressures, making this check.o0l the sound events unavailable.

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Lewis aud co-workers,2 who have reportedoil the use of the phonoeatheter iu mail, didnot discuss the development of the extrasounds reported here, but did iuention thatwhen the catheter tip was ill contact with

the inner wall of the heart or valves, loudklnockincg sounds were obtained."The fact that such artificial sounds as

those described call be produced by the intra-cardiac catheter suggests that some cautionuiiust be used in interpreting the findings ofinitracardiae phonoeardiography in other re-sl)eets. It is l)ossible, for example, that sys-tolic murmurs recorded in the pulmonary ar-tery could be produced or accentuated by thecatheter. In1 1 )atient, studied in this labora-tory, with a steiiosis of the right branch of thepulmonary artery, the presence of a catheterin the area of stenosis led to all accentuationof the murmur.The frequency of extra sounds noted in

this study indicates that the back-and-forthmovement of the catheter tip across the pul-monary valve is not an unusual occurrencedurilig cardiae catheterization, and, in fact,ani additional 5 patients of the 57 studiedshowed the pressure artifact without record-able sound production. This catheter move-ment is of some practical importanee ill rou-tine cardiac eatheterization, for what isthought to be a high right ventricular bloodsample may ill reality be a mixture of ven-tricular and pulhonary artery bloods. Such afinding ill a patient with patent duetus arteri-osus might lead one to suspect wrongly aventricular septal defect or pulmionie insuf-fieienev.

SUMMARY

In 18 of 57 patients who had phonocardio-granms recorded during diagnostie cardiaccatheterization, an extra heart sound was re-corded. Ill 17 of the 18, the extra sound wasin diastole, and could be identified by its tim-ing and its association with a characteristiclressure tracing. Movement of the cathetertil) baek and forth across the pulmuonie valveduring the heart cycle is thought to be re-

sponsible for production of the sound and the

pressure artifact. Experimental studies inexcised canine hearts showed that catheterpassage across the pulmonary or aortic valvesinduced similar sounds, and also murmurs.

In an eighteeinth patient, one with valvularpulmonic stenosis, catheter movement in thepulmonary artery appeared to be the causeof an extra heart sound in systole. The dias-tolic sound was heard in none of the 10 pa-tients with pulmnonic stenosis.The fact that such artificial sounds can

be produced by the intracardiac catheter sug-gests that some caution must be used in in-terpreting phonocardiograims obtain ed duringcardiac catheterization.The frequency of the back-and-forth move-

ment of the eatheter across the pulmonaryvalve suggests that not uncomnIlo y w-hat isthought to be a highli righlt ventricular bloodsample is in reality a mixture of ventricularand pulmonary artery bloods. This would beof some importallce in the cardiac (athleteri-zation of patiemmts with lpatent (Iichtus arterio-sus.

SM-LMAR1o IN INTERLIN(JGA

In 18 ex 57 patientes, in qui phonocardio-grammnas esseva registrate durante diagmiosticeatheterismo cardiac, un supranumerari sonoeardiac esseva registrate. In 17 del 18 casos,ille sono esseva in diastole e poteva esser iden-tificate per le tempore de su occurrentia e persu association con un characteristic curva detension. Mlovimientos del lpuncta del catheterin avante e in retro a triansvxeroso le valvulapulmonic durante le cyclo cardiae es conside-rate Como responsabile pro le ploductioll delsono e le artefacto de tension. Studios ex-perimental in excidite cordes canin ionstravaque le passage de un catheter a traiisverso levalvula pulmonar o le valvuiila aortiec indueevasimile sonos e etiamin murmnures.

In le dece-octave patiente, qui habeva ste-nosis del valvula pulmonic, le movimento delcatheter in le arteria pulmonar pai eva esserle causa de un supernumerari sono cardiac insystole. Le supra-discutite sono diastolic es-

seva audite in nulle de 10 patientes con ste-nosis pulmonic.

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Le constatation que tat sonos$ artificial poteesser producite per le catheter intracardiacsuggere que (erte preeautiones debe esser usa-te in interpretar p)hon1ocardiograsninas obte-nite dturante catheterisino eardiac.

be fre(luentia (del novienieito in ante e

retro que le catheter exeenta a transvers) leval vula pillolal suggere que il oeunrre noninfrequentemente (ue un specimen de sangu-ine regnardate (0o11o (te origine dextero-veii-tricular alte es in realitate hi mixtura (le

sanguine ventricular con sanguine de arteriapulnionar. Isto esserea de alicun importantiain le application de catheterismo cardiac atstudio patientes con patente ducto arteriose.

REFERENCES1. \AMAKA-WA, K., SILIONOYA, Y., KITAMURA, K.,

YAMAMOTO, T., AN-D OHTA, S.: Intracardiacphonoeardiography. Amn. Heart J. 47: 424,1954.

2. LEwis, D., DEITZ, G., VALLACE, I., AND)BROWN, I. : Intracardiae phonocairdiogrla phyin man. Circulation 16: 764, 1957.

9lIncidence of the Disease.-As noted long ago by Sir Gilbert Blaine, angina pectoris is

a rare affectiouI in hospital practice. Gairdner criticises this statement rather sharply,and yet I think that a Illajority of hospital physicians would be found to support it.During the ten years in which I lived in Montreal, I did not see a case of the diseaseeither in private practice or at the Montreal General Hospital. At Blockley (Philadel-phia Hospital), too, it was an exceedingly rare affection. I do not remember to havehad a case under my personal care. There were two cases in my service at the Uni-versity hospital. During the seven years in which the Johns Hopkins Hospital has beenopened, with an unusually large "material" in diseases of the heart and arteries, andwith many cases of heart pain of various sorts, there have been only four instances ofangina pectoris. You will find the statement in Fagge's Practice (third edition, vol. ii,p. 26) that the "writer has never seen classical angina in hospital practice."On the other hand, an individual consultant may see within a year more cases than

occur in all the hospitals of his town within the same period. In corroboration of thisstriking contrast between the incidence of angina pectoris in hospital and consultingwork I may refer to the statistics of the Edinburgh Royal Infirmary, in which for thetwo years covered by the Hospital Reports, 1893 and 1894, there were five cases among.a total of 8,868 medical cases. Compare with this the personal experience of the dis-tinguished Edinburgh consultant, Dr. Balfour, who, in his recently issued work on theSenile Heart, gives an analysis of ninety-eight cases of angina pectoris seen withinten years. My individual experience embraces a series of sixty cases, forty of whichmay be regarded as true angina.-W\ILLIAM OSLER. Lectures on Angina Pectoris andlAllied States, 1897.

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FREDERIC L. ELDRIDGE and HERBERT N. HULTGRENProduction of Heart Sounds by the Cardiac Catheter

Print ISSN: 0009-7322. Online ISSN: 1524-4539 Copyright © 1959 American Heart Association, Inc. All rights reserved.

75231is published by the American Heart Association, 7272 Greenville Avenue, Dallas, TXCirculation

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