high-frequency components in the...

High-Frequency Components in the

Electrocardiogram

A Comparative Study of Normals and Patients with

Myocardial Disease

By ERNEST W. REYNOLDS, JR., M.D., BERNARD F. MULLER, CAPTAIN, M. C.,

GARY J. ANDERSON, M.D., AND BRUCE T. MULLER

SUMMARYExpanding the frequency response of the electrocardiogram and its derivative to

1,000 cps revealed notching in certain parts of the QRS complex which correlateswith the presence of primary myocardial disease. Chi-square analysis of data from169 patients with myocardial involvement indicated that notching on the downstrokeof leads X, V4, and V6 separated abnormal from normal patients at the 1% level of sig-nificance, whereas fine and coarse slurring showed reverse correlation at the 1% levelof significance. This suggests that notching and not slurring is the important evidenceof disease. Neither notching nor slurring was significant at the peak of the R wave

in any lead. Study of individual cases revealed that complete right and left bundle-branch blocks do not mask high-frequency components caused by myocardial diseasenor do they produce high-frequency components. Conclusions regarding specific diag-nostic criteria, however, should serve only as guidelines.

ADD,ITIONAL INDEXING WORDS:Bundle-branch blockRight ventricular hypertrophy

M UCH of the clinically useful informa-tion derived from the electrocardio-

gram comes from gross alterations in the QRScomplexes and T waves. These changes in-volve frequencies mostly below 100 cps' or inthe low-frequency range, but patients withdiffuse myocardial disease often will show re-duced voltage and many high-frequency com-ponents in the QRS complexes. Oppenheimerand Rothschild2 first correlated these changeswith a disseminated patchy sclerosis involvingthe subendocardial layer of the heart, and

From the Department of Internal Medicine (HeartStation), University of Michigan Medical Center, AnnArbor, Michigan.Study was supported by Research Grant HE-

07406-04 from the National Institutes of Health,U. S. Public Health Service.

Presented at the Thirty-eighth Scientific Sessions,American Heart Association, October 1965, Bal Har-bour, Florida.

Circulation, Volume XXXV, January 1967

Intraventricular conduction defect

they concluded that the abnormal electrocar-diograms were due to lesions in the Purkinjenetwork. They suggested that the conditionbe known as arborization block.

Unfortunately, conventional electrocardio-graphic equipment with its poor high frequen-cy response and slow paper speed is incapableof recording these phenomena.3 Recognizingthis, Langner and associates4-10 have used thecathode-ray oscilloscope and an expanded timescale to demonstrate these high-frequencywaves in patients with coronary artery dis-ease. Franke and associates"1 have shown fre-quency components up to 3,000 cps, whichwas well above the noise level in some sub-jects, and have noted abnormal power spec-tra in ischemic heart disease. The two largestudies reported to date8 11 have dealt sole-ly with coronary artery disease. The pres-ent study was designed to determine criteriawhich permit separation of three abnormal

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REYNOLDS ET AL.

groups of patients from a normal githree groups of patients studied haddiseases affecting the heart, noncorcdiomyopathy, and coronary artery dis

MethodsTwo techniques giving comparable r(

used for expanding the frequency respcelectrocardiogram and its derivative tolimit of 1,000 cps. In the first 80 stECG and its derivative were recorctaneously on a tape recorder employingtronics at 30 inches per second andsequently reproduced on an oscillogrinches per second. In more recentpatients were studied by simply phothe QRS complex on the face of an osusing a sweep speed of 500 mm/secortronix 502 dual beam oscilloscope alC-12 Tektronix Polaroid oscilloscopwere used. The technique of recordingative of the electrocardiogram to accehigh frequency components was used band associates.9' 10 The circuit diagrarified by the authors to give a frequenc1,000 cps is shown in figure 1. In prderivative aids in distinguishing a notslur in the electrocardiogram, since the

10080

60

40-

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0

Ihiz

4D

20-

10-

8-

6-

4.

2-

6N

004 .0015

K OK

EIN P2j EOUT

ALL CAPACITANCE IN Mfd, RESISTANCE IN OHMS

0

-900- 0

Iz

+9 0°

*

0

0

0

0

0

0

0

0

0

0

FREQUENCY (CPS)

Figure 1

Circuit diagram (above) for obtaining thcfrom the electrocardiogram. The frequen((open circles) and phase shift (closed cir(were measuremenets carried out using thisThe gain (Eout/E n) is approximately douloctave (doubling in frequency) up to 1,001

roup. TheI collagenmary car-sease.

esults werense of thean upper

tudies, theled simul-FFM elec-were sub-aph at 17work, 169tographingscilloscope,-d. A Tek-nrl >i fx-np

z

Figure 2

Bipolar X, Y, and Z lead connections.

iC camera in the case of a notch must pass through the baseicecaerav line.

ntuate the Special bipolar leads (X, Y, and Z) were re-corded in the first 80 patients, and conventionaly Langner leads (V2, V4, and V0) were added in the second

y cutoff at group of 169 patients. The bipolar leads (X, Y,cti,the and Z), shown in figure 2, were used to minimizeactice, th artifacts due to somatic muscle tremor, which are:c from a

a more serious problem when electrodes are

placed on the extremities. For practical purposes,bipolar lead X is similar to lead I, lead Y is sim-ilar to lead aVF, and lead Z is similar to V2. Thesimilarity between leads Z and V2 was found tobe so close that lead Z was omitted in the studvof the final 169 patients.

000 0 The studies on the first 80 patients served as a° check on the accuracy of the recording methods0 and as a test of reproducibility of notching in

one QRS complex compared with another. At0 least two QRS complexes were recorded in every

lead and, except for expected slight phase shifts,reproducibility was excellent between two QRScomplexes taken at the same time or at a later

o time when the leads were reattached. In all ofthe later studies reproducibility was checked byexamining the oscilloscope during several QRScomplexes before any photographs were made.

Artifacts on the records were kept to a mini-mum by the use of the special leads mentionedby careful preparation of the skin with electrode

N paste, and by efforts to keep the patient relaxedand comfortable. A foam-padded bed with ablanket to cover the patient helped to reducemuscle tremor. Differential amplifiers were used

e derivative for both the electrocardiogram and its derivative,cy response and the center ground point of the amplifier wascles) shown attached to the patient to reduce a-c interference.equipment. Synchronization of the QRS complex on thedle for each oscilloscope was accomplished bv attaching a spe-0 cps. cial lead to the chest wall, giving an initial

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HIGH-FREQUENCY COMPONENTS IN ECG

positive deflection, and connecting this lead afterappropriate amplification to the external syn-chronization connection of the 502 oscilloscope.It was important that this lead have no Q wave,since even a small negative deflection delayedappearance of the QRS complex, causing part ofthe complex to be missed. Where such a leadcould not be found, an alternative procedure wasto use one QRS complex to trigger the sweepand display of the next QRS complex. Becauseof variations in heart rate, this technique resultedin some difficulty in centering the QRS complexon the screen.

Standardization was accomplished by intro-ducing a 0.5 mv, 60 cycle sine wave into bothamplifier channels and adjusting the gain of theelectrocardiographic channel to 1.1 cm deflec-tion, and that of the derivative channel to 2.2cm. With a 0.9 reduction of image size by thecamera, this resulted in approximately 0.5 mv =I cm (ECG) and 2 cm (dv/dt) at 60 cps on thefinished print.The records from the 169 patients were studied

by one of the investigators counting the numberof slurs and notches on the upstroke (U), peak(P), downstroke (D), and from the nadir of Sto the base line (S) in each of five leads. Thesedata and available clinical information were codedon IBM cards, and the statistical analyses wereprogrammed in MAD for an IBM 7090 computerat the University of Michigan Computing Cen-ter.

Patient SelectionIn the group of 169 patients having five or

more leads recorded, there were 76 normalpatients with a mean age of 26 years. Six ofthese patients showing questionable evidenceof incomplete right bundle-branch block wereretained in the study, but separate evaluationof the 70 normal patients without this condi-tion was carried out.The 93 patients with abnormal hearts were

selected if there was reasonable clinical evi-dence of myocardial involvement by somepathological process. Forty-two patients hadnoncoronary cardiomyopathies. In this groupthere were 12 with scleroderma with systemicinvolvement, five with Friedreich's ataxia, andseveral patients with each of the following:myocarditis, acromegalic heart disease, amy-loid heart disease, polyarteritis, muscular dys-trophy, idiopathic cardiomyopathy, hemachro-matosis, myotonia congenita, systemic lupuserythematosus, allergic vasculitis, sarcoid heartCirculation, Volume XXXV, January 1967

disease, and alcoholic cardiomyopathy. Four-teen patients had hypertensive or rheumaticheart disease, and 12 had complete right orleft bundle-branch block. The remaining 25patients had various stages of coronary arterydisease, though patients with frank infarctionby electrocardiogram were generally omittedfrom the study, except where peri-infarctionblock or left bundle-branch block complicatedthe infarction pattern.

ResultsA notch was defined as a change in direc-

tion of the trace. These were most easilyrecognized by counting the spikes in the de-rivative which crossed the base line, omittingthe primary spikes caused by the peaks of theQ, R, and S waves. The difference betweenfine and coarse slurring was more difficult toquantitate. The former produced beading inthe trace and occurred in groups whichcaused several spikes in the derivative, ex-ceeding 1.5 cm with normal standardization.Only the presence or absence of fine slurringwas noted. Coarse slurring was more oftengrossly visible in the electrocardiographictrace as a single slur with the derivative fail-ing to cross the base line.For each portion (U, P, D, and S) of the

QRS complex of each lead, a table was pre-pared giving the number of patients in thenormal and abnormal groups having nonotches, one notch, two notches, and so onup to nine or more notches. Similar tableswere prepared for coarse and fine slurs. Thisserved as the basis for a chi-square test. Be-cause the number of patients having more thanone or two notches (slurs) was too small forapplication of the chi-squ-re test to the fulltable, the groups having the higher numberof notches (slurs) were lumped to give a 2 by2 table (zero notches versus one or more) or

a 2 by 3 table (zero notches, one notch, andtwo or more notches). The results are given intable 1. Notching on the downslope of the Rwave of leads X, V4, and V6, and in the S waveof lead V4 discriminated either the 73 or 93abnormal patients from 70 normal patientsat the 1% level of significance in the expected

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Table 1Significance of Notching and Slurring of the QRS Complex in DiscriminatingNinety-three Abnormal Patients

Seventy-six Normal frown

Wave

UpD

QRS

76N/93Anotching

525

52

U

(2)(1)(1)

(2)W(1)W

70N/93Anotching*

2(1)5(1)

5(2)W2(1)W

% of significance70N/73Anotching*

15252

(1)(2)(1)(2)W(1)W

pDS

QRS

U

pDS

QRS

UpD

SQRS

U

pDS

QRS

1 (2)W1 (1)W

5 (2)W1 (2)W1 (1)W1 (2)W1 (1)W

1 (2)1 (1)2 (1)

0.1(1)

2 (2)5 (1)

1(2)W1(1)W

2(2)W5(1)W1(1)W1(1)W

1(2)1(1)1(1)

1(1)

2(2)

1 (2)W1 (1)W

2 (2)W1 (1)W

1 (2)1 (1)0.1(1)5 (1)

1 (1)

2 (2)5 (1)

Coarseslurring

5 (1)W

5 (1)W

0.1(2)WO.l(l)W

1 (I)W

2 (1)W2 (2)W1 (1)W

1 (2)WI (1)W

Fineslurring

0.1(1)W

5 (1)W0.1(2)W0.1(1)W5 (1)W

0.1(1)W

1 (2)W1 (1)W1 (1)W

1 (1)

1 (2)WI (1)W

*These two columns represent a selection removing certain normals whose standard ECG showed secondary Rwaves in V1, thus suggesting incomplete right bundle-branch block. The third column removes 20 abnormals inwhich cardiac involvement was minimal.Abbreviations: N - normals; A = abnormals; U - upstroke; P = peak; D - downstroke; S = nadir to base line;W = reverse correlation, notching, or slurring being less frequent in the abnormal; (1) = one degree of freedom,a 2 by 2 table (normals and abnormals versus no notching [or slurring] and one or more notches [slurs]);(2) - two degrees of freedom, a 2 by 3 table (normals and abnormals versus no notching [slurring], one notch[slur], and more than one notch [slur]), and -= significance less than at the 5% level.

direction; that is, more notches were foundin the abnormal patients. The 73 abnormalpatients represent a selection from the 93 ab-normal patients in which cardiac involvementwas more certain as manifested by such find-ings as definite rather than borderline cardiacenlargement by x-ray examination. Since the

significance of notching did not change great-ly by this selection, and data from both select-ed and unselected groups are presented, thedetails of selection are not discussed.

Table 1 shows that in certain parts of QRSnotching discriminates the abnormal from thenormal group of patients with a high level of

Circulation, Volame XXXV, January 1967

Lead

x

y

V2

V4

V6

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confidence, but in the unexpected direction.Notching thus tends to disappear in leads Y-U, V2-U, V2-D, V2-S, and V2-total in the ab-normal group of patients when compared tothe normal group. Table 1 also shows that bothfine and coarse slurring show a similar re-verse correlation, as they are present morefrequently in the normal group of patients.This reverse correlation was unexpected, anduntil this is better understood, the absence ofnotching or slurring should not be used as adiagnostic criterion. It is apparent from exam-ination of the tracings that, when notching isexcessive, as shown in leads X or V6 of figure3, slurs are less easily recognized and alsothere appear to be fewer of them even in thissituation; whereas, slurring of mild extent iscommonplace in certain leads taken on normalpatients as shown in figure 4. Since slurringof both fine and coarse types shows this re-verse correlation, except for the isolated cor-relation in lead V4-D (where fine slurring isin the expected direction), for the time beingall slurring has been ignored in setting up di-agnostic criteria.Table 1 indicates that notching and slurring

at the peak of the R wave are not significant,and in fact are found with equal frequency in

A. S. AGE 42 FRIEDREICH 'S ATAXIA

both normal and abnormal groups of patients.For this reason, the part of the QRS complexat the peak of the R wave has not been in-cluded in the diagnostic criteria for thesestudies, and it would seem wise to omit thepeak of R waves from any program for spec-tral analysis.From a practical point of view, leads Y and

V2 are not very helpful because of the highincidence of normal notching and reverse cor-relation with slurring. Since notching in leadsV4 and V6 gave better discrimination betweenthe abnormal and normal groups of patients,it would be wise to take additional left-sidedchest leads.Table 2 compares the percentage of pa-

tients in the three categories who show notch-ing in parts of the QRS complex consideredmost significant. It is probable that notching isnonspecific and is unrelated to the type ofdisease which affects the myocardium, al-though a higher percentage of patients shownotching among the cardiomyopathies thanamong the groups of patients with coronaryartery disease or collagen disease. This maybe due to the fact that patients in the lasttwo groups are selected at an earlier stageof their disease because of specific symptoms;

D 96

Figure 3

Reduced voltage of the QRS complex (above) with abnormal notching and loss of R-wavevoltage in V6 and increased voltage of the derivative (below) suggest extensive myocardialchanges in this patient.

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A.C. AGEt 19 NORMAL D 128

Figure 4

The typical normal ECG (above) and derivative (below) in this normal patient show normalslurring in Y-upstroke and downslope, notching and slurring in Z-S wave, and a notch inV2-S wave. The downslopes of leads X, V,,, and V6 are free of notching and slurring.

the cardiomyopathies are detected later intheir course, presenting such late signs as car-diac enlargement and congestive heart failureas the first recognizable manifestations.

Table 3 shows how the number of notchesin the significant leads helps discriminate theabnormal from the normal patients. The maxi-mum number of notches in the normal groupwas one in leads X-D, V4-S, and V6-D andtwo notches in lead V4-D. In the abnormal pa-tients, as many as five to eight notches werefound in these leads. The high number of ab-normal patients failing to show notching in

these leads suggests that notching may bepresent only in the later stages of disease.Many questions could not be answered by

the statistical methods because there were in-sufficient examples available for study. Ten-tative answers to some of these questions aregiven by study of single patients.

Since endocardial fibrosis and the assumedarborization block have been shown capable ofcausing notching in the QRS complex, it isproper to determine what effect completeright and left bundle-branch block would havein producing high frequency components or

Table 2Analysis of Notching: Per Cent of Normals and Abnormals That Show Either No orSome Notching in Most Significant Parts of the QRS Complex

Lead /QRS

X-D 0*

V4-D 0

V4-S 0+

V,-D 0

*No notching.tNotching.

76 Normals 70 Normals

94.75.3

88.211.896.13.9

97.42.6

95.74.3

88.611.498.61.4

97.12.9

24 Coronary 18 Collagen

70.8 88.829.2 11.275.0 61.225.0 38.870.8 100.029.2 0.083.3 72.316.7 27.7

16 Cardiomyopathy

75.025.043.656.475.025.075.025.0


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Table 3Portions of the QRS Complex Where Notching Shows Disc;-imination Between Abnormaland Normal at 1% Level in Seventy Normals and Ninety-three Abnormals.

Numberof X-downstroke

rnotches N A

0

2345678

Total

6730000000

70

777322011093

V4-downstrokeN A

(

Number of patients

32 64 695 9 13 9 00 5 00 3 00 1 00 0 00 1 00 1 070 93 70

V4-S waveN A

78112011000

93

Vs-downs rokeN A

68 752 110 20 3o o0 1o 00 1o 0

70 93

Abbreviations: N = normals, and A = abnormals.

in masking underlying disease. Study of asingle patient with transient left bundle-branch block who had a normal electrocardio-gram at other times and no clear evidenceof heart disease shows no high frequencychanges during the period when left bundle-branch block was present (fig. 5). Uncompli-cated right bundle-branch block shows a fewnotches in leads Y, Z-S, and V2-S (fig. 6).Notching in leads Y and V2-S shows reversecorrelation, being present more often in theseleads from the normal patient and is consid-

ered normal in these studies (table 1.). On theother hand, when right bundle-branch blockwas observed in a patient with systemic scle-rosis and cardiac enlargement (fig. 7), therewere abnormal high-frequency changes, es-pecially in lead V4-D, where notching wassignificant. Peri-infarction block (fig. 8) pro-duces extensive notching in agreement withthe observation of Oppenheimer and Roths-child.2 Thus, the individual studies to datesuggest that complete right or left bundle-branch block does not mask high frequency

R. P. AGEt 7 IKANSIENT CUMPLEIt LBBB, NO UOlTK EVIDENCE V CIriAt UI CtAH,t

Figure 5

D 188

Transient complete left bundle-branch block (LBBB) in this patient without other evidence ofheart disease produced no high frequency changes.


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D.Y. NORMAL MALE AGE 20 COMNPLETL RBBB U1)

Figure 6The standard ECG (not shown) is interpreted as complete right bundle-branch block (RBBB).The high fidelity ECG (above) and its derivative (below) confirm RBBB as manaifest by pro-longation of the QRS interval and broad S waves in leads X and V6. It is significant that noabnormal high frequency components have been produced by the conduction defect. Thenotches seen in leads Y-U, Y-D, Z-S, and V2-S are present more frequently in electrocardio-grams of normal than of abnormal patients.

D. S. AGE 47 SCIERODERMA HEAKI UIStASt CUMPLEiT KRBB u ClU

Figure 7Complete RBBB in this patient with systemic sclerosis has not masked the abnormal highfrequency components shown in lead V4-D. This tracing suggests that the heart is involvedwith systemic sclerosis in addition to the presence of RBBB.

components which are produced by diseaseand neither do these major conduction de-fects add greatly to the high-frequency com-ponents normally present.

The question whether routine electrocardio-grams taken with direct writing instrumentscan be used to predict either a normal or ab-normal high fidelity tracing was studied by

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A. K. AGE 72 RKI - INFAKRICIUN BLUOC D 216

Figure 8Anterolateral myocardial infarction with peri-infarction block is present with marked notching,especially in leads V4 and V5. Lesions of this kind which perhaps block the peripheral branchesof the Purkinje system regularly produce high frequency changes; block of either of the mainbundle branches does not.

_ . .-. .-

V4 MAGNIFIED D-166

Figure 9

Amplification of part of the lead V4-R wave showsfine notching which is not revealed by the direct

Circglation, Volame XXXV, Janmary 1967

reading the standard tracings in terms of slur-ring, notching, beading, and the presence oflow voltage which might indicate a positiveor negative high fidelity electrocardiogram,without knowledge of the result of the latter.Of the 169 high fidelity electrocardiograms an-alyzed in this manner, 71% were correctly pre-dicted by reading the standard electrocardio-gram. Thus, 50% of 60 abnormal high fidelitytracings and 83% of 109 normal high fidelityelectrocardiograms were correctly predicted.The fact that more of the normal than the ab-normal records were correctly predicted sug-gests that there is, indeed, additional informa-tion in the high fidelity electrocardiogram. Anexample illustrating this situation is shown infigure 9, where the standard lead V4 showsonly blunting at the top of the R wave, but anamplified high fidelity lead V4 shows manyfine notches in the upper part of the R wave,which were reproducible in successive trac-ings, and this is almost certainly an abnormal

writer EGC. These changes, which were reproduciblein successive tracings, are abnormal and suggest myo-cardial involvement in this patient with systemicsclerosis. See figure 10 also.

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Figure 10Thtis 42-year-old woman with history acnd findinigs of systemic sclerosis of 2 years' durationdwied suddenly. The heart was enlarged and showed patchy fibrosis with normal large coronaryarterics. Compare with figure 9 (sanme case).

B.H. AGE 53 PRIMARY PULMONARY HYPERTENTION D186

Figure 11

Uncomnplicated right ventricular hypce trophy dtue to pr-itnary palmtonairy hypertentsionl. Asingle niotch which appears in the same location in leads V2-D, Y-D, and V6-D is the onlyabnormiiality. This suggests that unicomplicated right venttricular hypertrophly is probably notresponsible for the high-frequency chaniges whicht are correlated with disease reported here.

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result. Figure 10 shows a microscopic sectiontaken from this patient's heart at autopsy. Finescarring surrounded most of the large coro-nary arteries and invaded the myocardium.The clinical diagnosis was systemic sclerosis,and this was supported by the finding ofcardiac fibrosis in the presence of patency ofthe large coronary arteries.

It is difficult to find patients with "pure"ventricular hypertrophy, since most conditionsthat produce cardiac enlargement are apt tocause some additional myocardial fibrosis. Afew patients with probable "pure" right ven-tricular hypertrophy who were studied, suchas the example shown in figure 11, show littlenotching. In this instance, the single notch ap-pearing on the downslope of several leads inapproximately the same location suggested acommon origin for this notch. Since so fewhigh frequency changes have been observedin uncomplicated right ventricular hyper-trophy, this suggests that hypertrophy aloneis not responsible for notching. This was nottrue in patients with left ventricular hyper-trophy, but in all of these instances, the asso-ciated lesion producing hypertrophy, such ashypertension or aortic stenosis, was also capa-ble of causing subendocardial fibrosis.

As any specific disease becomes more ad-vanced, the number of notches appears to in-crease, making it comparatively easy to recog-nize the abnormality. Records from patientswith extensive disease are shown in figures3 and 12. In each case, the voltage of thederivative is markedly increased from normalin most leads. Such examples unfortunatelysuggest that one of the chief uses of the highfidelity electrocardiogram may be in recog-nizing the end stages, rather than the earlychanges, of cardiac disease. Such tracings are,nevertheless, useful in many clinical situations.Thus, one might not elect to do coronaryartery surgery or replace an aortic valve inthe presence of such evidence pointing toextensive fibrosis of the myocardium. Attemptsto detect early stages of disease, as in anginapectoris or familial hypercholesterolemia, havebeen somewhat unrewarding because thenumber and location of notches tend to over-lap the high frequency changes found in thenormal group.

AcknowledgmentWe thank Dr. John A. Jacquez and Miss Frances

J. Mather of the Biomedical Data Processing Train-ing Program for their help in carrying out the statis-tical analyses and the computations, and Dr. Franklin

I

A.S. AGE 29 POLYARTERITIS D 104

Figure 12

This 29-year-old woman has findings compatible with polyarteritis. The tracing is unusual inthat no portion of the QRS complex in any lead is entirely free of notching. This would suggestextensive myocardial disease.


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D. Johnston for help with the project and the criticalreview and revision of the manuscript.

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analysis of the electrocardiogram. CirculationResearch 8: 344, 1960.

2. OPPENHEIMER, B. S., AND ROTHsCHILD, M. A.:Electrocardiographic changes associated withmyocardial involvement. JAMA 69: 429, 1917.

3. KERWIN, A. J.: Effect of the frequency responseof electrocardiographs on the form of electro-cardiograms and vectorcardiograms. Circula-tion 8: 98, 1953.

4. LANGNER, P. H.: Value of high fidelity electro-cardiography using the cathode ray oscillo-graph and an expanded time scale. Circula-tion 5: 249, 1952.

5. LANGNER, P. H.: High fidelity electrocardiog-raphy: Further studies including the com-parative performance of four different electro-cardiographs. Amer Heart J 45: 683, 1953.

6. LANGNERn, P. H.: Further studies in high fidelity

electrocardiography: Myocardial infarction.Circulation 8: 905, 1953.

7. LANGNER, P. H., AND GESELOWrrZ, D. B.: Char-acteristics of the frequency spectrum in thenormal electrocardiogram and in subjects fol-lowing myocardial infarction. Circulation Re-search 8: 577, 1960.

8. LANGNER, P. H., GESELOWITZ, D. B., AND MAN-suRE, F. T.: High-frequency components inthe electrocardiograms of normal subjects andof patients with coronary heart disease. AmerHeart J 62: 746, 1961.

9. LANGNER, P. H., AND GESELOWITZ, D. B.: Firstderivative of the electrocardiogram. Circula-tion Research 10: 220, 1962.

10. GESELOWITZ, D. B., LANGNER, P. H., AND MAN-suRE, F. T.: Further studies on the first deriva-tive of the electrocardiogram, including in-struments available for clinical use. AmerHeart J 64: 805, 1962.

11. FRANKE, E. K., BRAUNSTEIN, J. R., AND ZELLNER,D. C.: Study of high frequency components inelectrocardiogram by power spectrum analysis.Circulation Research 10: 870, 1962.

Generalizations on a Few Observations:Valsalva Procedure in Wind Instrument Players

It has been shown that the degree of intrathoracic pressure rise is related to thepitch and loudness of the note blown. Trumpet players reach the highest pressures,160 mm Hg on an arpeggio and 80 mm Hg on a sustained note. Oboe players rarelyreach 60 mm Hg and French horn players, 40 mm Hg. Although occasional attacksof dizziness are common among trumpet players, there is no evidence that prolongedplaying predisposes to respiratory disease.-E. P. SHARPEY-SCHAFER: Effect of Respira-tory Acts on the Circulation. In Handbook of Physiology, sec. 2, Circulation, vol. 3.Washington, D. C., American Physiological Society, 1965, p. 1880.


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ANDERSON and BRUCE T. MULLERERNEST W. REYNOLDS, JR., BERNARD F. MULLER, CAPTIAN, GARY J.

Normals and Patients with Myocardial DiseaseHigh-Frequency Components in the Electrocardiogram: A Comparative Study of

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