studies of electrocardiographic changes exercise...

Studies of Electrocardiographic Changes

during Exercise (Modified Double

Two-Step Test)By PAUL N. G. Yu, M.D., AND ALFRED SOFFER, M.D.

A method of recording electrocardiograms during the performance of a double two-step exercisetest is described. Data obtained from 32 normal subjects and 54 patients are analyzed, and changesin heart rate, S-T segment, T wave and Q-T interval and the occurrence of premature beats de-scribed. Criteria for an abnormal response indicating coronary insufficiency are defined. Thismethod retains the merits of Master's original test and in addition has several distinct advantages.

STUDIES of the electrocardiogram duringand after exercise (walking on a tread-mill ergometer at standard speed and

grade) in normal subjects have shown adefinite pattern of change in the Q-T intervaland no evidence of coronary insufficiency." 2On the other hand, a large percentage ofpatients with various cardiopulmonary diseasesshowed definite and striking abnormal changes.

Since Master's "two-step" test3' 4 has beenwidely used in different clinics, similar studiesof the electrocardiogram during exercise wereundertaken with modification of the originalmethod. It is the purpose of this report todescribe the procedure and to present theresults obtained in 32 normal subjects and 54patients with various cardiovascular disease.These studies suggest that the modifiedmethod can be used wherever the exerciseelectrocardiogram is indicated and that itcontributes significantly to its sensitivity andsafety.

METHODAn exploring precordial electrode connected with

the chest wire was placed over the fifth intercostalspace along the left midelavicular line or slightlyto its left. An indifferent electrode connected withthe left leg wire was placed just below the tip of

From the Department of Medicine, University ofRochester School of Medicine and Dentistry, andthe Medical Clinics of the Strong Memorial Hospital,Rochester Municipal Hospital and Genesee Hospi-tals, Rochester, N. Y.

This study has been SlUoPrt.ed in part by theHochstetter Fund.

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the right scapula. A third electrode connected withthe right leg wire, placed over the right precordium,served as the ground. The exploring and indifferentelectrodes constitute the so-called "CB4" lead whichwas first introduced by Wolferth and Wood5 andlater modified by Lieberson and Liberson.6 Allthree electrodes were tightly applied to the chestwall by a rubber chest strap* so that during exer-cise there was no change in the position of the elec-trodes. The control knob was switched to CF torecord lead CB4 or CB5.A portable direct-writing electrocardiograph

(Edin) was used throughout the study. Changes inthe electrocardiogram during and after exercisecould be observed minute by minute. Lead CR4was standardized so that 1 mv. caused a deflectionof 10 mm. If the QRS complex was too high, itwas standardized at a deflection of 5 mm. per milli-volt.A short strip of lead C3 swas taken before the ex-

ercise w as performed. If the R wave wsas low and Swave deep (rS), the precordial electrode was movedfurther to the left until an Rs, or qRs complex wasobtained. (Depression of the S-T segment is usuallymore marked with a high R wave than with a deepS wave, because the presence of a high R waveindicates that the electrode is facing the left ven-tricular surface.) The subject was instructed totake several deep inspirations and expirations whilea tracing was being recorded. Marked shifting ofthe baseline or muscular interference indicated theneed for tightening of the rubber chest strap andreapplication of the electrode paste. During exer-cise the baseline often wandered slightly due torespiratory movement. In some women it was neces-sary to place the exploring electrode in the anterioraxillary line (CBs) in order to obtain full phase con-tact of the electrode.

* Obtained from Sanborn Company, Cambridge,Mass.

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ELECTROCARDIOGRAPHIC CHANGES DURING EXERCISE

The performance of the step test was the sameas that described by Master and associates3' 4 exceptfor the following modifications: (a) The CB4 orCB5 lead was used throughout the test and notracings from limb leads were made. (b) A doubletwo-step test lasting three minutes was performedon every subject unless it was interrupted by theappearance of symptoms or marked electrocardio-graphic abnormalities. (c) The tracings were madeat rest, at the end of each minute during exercise,30 seconds, 90 seconds, and 150 seconds aftertermination of exercise and 8 minutes after exerciseor later.The test was arbitrarily divided into four periods:

(1) Resting-before exercise, (2) Exercise-threeminutes or less. (3) Early recovery first threeminutes of recovery. (4) Late recovery-eighthminute of recovery or later.The heart rate was obtained by measuring the

number of QRS complexes in a period of six secondsand multiplying by 10. Depression or elevation ofthe S-T segment was measured from the iso-electriclevel (P-R or P-Q level). It was essential to measurethree or four beats on a horizontal level in order toavoid simulation of S-T depression or elevation bya wandering baseline. The amplitude of the T wavewas measured from the baseline to the peak of thewave in each individual complex. If there was dis-tinct variation of the amplitude of the T wave, theaverage of the amplitude of an equal number ofhigh and low T waves was recorded. Usually threeor more consecutive Q-T intervals and correspond-ing cycle length were measured to the nearest 0.05second. Their average values were used to computethe Q-T/T-Q ratio and the corrected Q-T interval(Q-T). The T-Q interval is the difference betweenthe cycle length and its Q-T interval. The correctedQ-T interval (Q-TJ) was calculated from the modi-fied Bazett's formula,7

Q-T - Q-T interval/cycle length

RESULTS IN NORMAL SUBJECTS

Thirty-two normal individuals between ages21 and (66 years served as controls. They weremainly physicians, medical students, nurses,and technicians. There were 26 males and 6females. None had a history of cardiovasculardisease. Each had a normal physical exami-nation and resting electrocardiogram. A roent-genogram of the chest was obtained in mostof the subjec ts and was normal in each instance.Changes in the heart rate varied greatly in

different individuals. The maximum heartrates during exercise and early recovery were,respectively, 158 and 125 per minute, and these

were recorded in the same subject. The heartrate returned to within 10 points of theresting value during the second minute ofrecovery in 25 of the 32 normal subjects.In several subjects the heart rate was theslowest in the second minute of recovery.The Q-T/T-Q ratio at rest was usually less

than 1. It always increased during exerciseand promptly returned to the resting valuebefore the third minute of recovery. In noneof the normal subjects did the Q-T/T-Q ratioexceed 2 during exercise. The increase inaverage exercise Q-T/T-Q ratio was usuallyless than 100 per cent of the average restingvalue.The pattern of changes of the Q-T, interval

was the same as that observed in treadmillwalking, that is, prolongation during exercise,shortening during early recovery and returnto the resting value during late recovery.'The Q-T0 interval was usually highest in thefirst minute of exercise. In no case duringexercise did the Q-T0 interval decrease belowthe average resting value. Shortening of theQ-T0 interval during early recovery wasdefinite, especially during the second minuteof recovery.There was no significant change in the P

wave during and after exercise. Some in-dividuals showed slight decrease in the ampli-tude of the R wave and a concomitant deepen-ing of the S wave during exercise. The T wavebecame lower or remained unchanged duringexercise in all of the instances, while in somesubjects it increased slightly during earlyrecovery. High T waves during exercise orearly recovery, with an increase in amplitudeof more than 50 per cent of the resting value,were not observed. Slight S-T depression of lessthan 1 mm. during or immediately after ex-ercise occurred in four subjects. In a greatmajority of normal subjects the S-T segmentremained iso-electric throughout the test.In two normal subjects a slightly elevatedS-T segment at rest became iso-electric duringand after exercise. We agree with Master4that this change should be considered asnormal, unless the depression is below the iso-electric level. No S-T elevation has ever beennoted in normal controls. None of the normal

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PAUL N. G. YU AND ALFRED SOFFER

subjects showed ventricular premature beats,auriculoventricular or intraventricular block,or the appearance of a Q wave during or afterexercise.

Typical traciings of control subjects withnormal response to exercise are illustrated infigure 1. The composite data of the heart rate,

D.MC. A.C.

iso-electric, or from inverted to upright).(b) Increase in the amplitude of the T wavegreater than 50 per cent of the resting value.(3) Q-T/T-Q ratio of more than 2.2 duringexercise. (4) Shortening of the Q-T, intervalduring exercise or prolongation of Q-T, intervalduring early recovery. (5) The appearance ofventricular premature beats during exercise orearly recovery.We have not encountered intraventricular

or auriculoventricular block.

TABLE 1.-The Heart Rate, Q-T/T-Q Ratio, and Q-7'Tin 32 Normal Subjects

Period of Observation

RestingExercise

1st minute

2nd minute

3rd minute

Early recovery1st minute

2nd minute

3rd minute

Late recovery8th minute

10th minute

Heart RatePer Minute

Average andRange

7857-98114

79-140124

102-150127

107-158

9873-125

8054-109

8355-116

8360-108

8266-113

Q-T/T-Q Q-Tc

Average and Average andRange Range

0.90 .408.62-1.17 .358-.453

1.58 .441.81-2.00 .367-.5001.61 .430

1.03-2.00 .384- .4811.63 .430

1.16-2.00 .372-.454

1.020.60-1.40

0.900.54-1.20

0.920.56-1.36

0.970.66-1.38

0.950.64-1.36

.393.342-.431

.400.369-.442

.405.367-.456

.415.360-.456

.409.375-.448

FIG. 1. Normal Subjects: D. Mc., male, age 46;A. C., male, age 30. A-Rest. B, C, D-Three minutesof exercise. E, F, G-First three minutes of recovery.H-Eighth minute of recovery.

Q-T/T-Q ratio and Q-T, interval are presentedin table 1.On the basis of the electrocardiographic

findings in normal subjects, abnormal responses

in lead CB4 or CBri were judged according to thefollowing criteria: (1) Depression of S-Tsegment of more than 1 mm. below the iso-electric level. (2) (a) Partial or complete re-

version of T wave (from upright to inverted or

RESULTS IN PATIENTS

Fifty-four patients ranging in age from 18to 69 years were studied. There were 35 malesand 19 females. They were classified into threemain groups according to diagnosis. (a)Group I-21 patients with a typical history ofangina pectoris. (b) Group 11-21 patientswith arteriosclerotic and hypertensive heartdiseases (ASHD and HCVD) who had nohistory of angina. (c) Group III-12 patientswith miscellaneous diseases including fivewith rheumatic heart disease, two with con-genital heart disease, two with intermittent

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claudication, two with atypical chest pain andtwo with abnormal ballistocardiogram.The resting electrocardiogram was normal in

each instance except for minimal T waveabnormalities in six patients and slight S-Tdepression in one patient. Eleven patients ingroup I and four patients in group II did notcomplete the double two-step test because ofprecordial pain, severe dyspnea, or markedelectrocardiographic changes. At least oneexercise electrocardiogram was recorded for

TABLE 2.-The Heart Rate, Q-T/T-Q Ratio, and Q-T,in 54 patients

Period of Observation

Resting

Exercise1st minute

2nd minute

3rd minute

Early Recovery1st minute

2nd minute

3rd minute

Late Recovery8th minute

10th minute

Heart RatePer Minute

Average andRange

8252-100

12378-166

13490-172

14291-182

11269-166

9967-133

9159-124

9065-118

8864-122

Q-T/T-Q

Average andRange

0.96.61-1.56

1.911.00-4.422.16

1.13-5.002.16

1.07-4.00

1.50.62-4.001.22.67-2.601.17.62-.2.26

1.11.63-1.701 .19.74-1.78

Q-T,

Average andRange

.417.348-.486

.447.385-.545

.447.399- .534

.438.375-.490

.425.364- 505

.426.342- .495

.430.370-.510

.430.375-.490

.437.394-.490

each patient. Two or more exercise tests were

performed at regular intervals on nine patients.

Pulse and Q-T ChangesThe average value and range of the heart

rate, Q-T/T-Q ratio, and Q-T0 interval duringrest, exercise and recovery are presented intable 2. The over-all heart rate in the cor-

responding minutes was higher in the patientsthan in the normal subjects. During exercisethe heart rate of 15 patients exceeded 158 per

minute which is the maximum rate obtainedin the normal subjects. The heart rate failed

to return to within 10 points of the restingvalue during the second minute of recovery inmore than 75 per cent of the patients.

REST

EXERCISE S eLV{ST MIN

:2ND M A 8 X

3RD MIN

FIG.~~~~~~'25....J. S A 58 year old wman wit severehypertensioanhitor of anin petois. Note~I

RECOVERY 1w i -IST Ml

2ND MINX

ILd3RD MINK f

cant increase in the amplitude of the T wave duringboth exercise and early recovery. J. D. A 44 year oldman with typical history of angina pectoris. Notesignificant increase in the amplitude of the T waveduring exercise and early recovery. The Q-T/T-Qratio during exercise exceeds 4.0. Distinct S-T de-pression occurs during the first three minutes of re-covery. V. B. A 54 year old woman with no evidenceof cardiovascular disease. Although the increase inthe heart rate during exercise (158 per minute) iscomparable with that in case J. D., yet the Q-T/T-Qis less than 2.0. Furthermore, no significant changesin either the T wave or the S-T segment were ob-served.

The average Q-T/T-Q ratio in the cor-responding minutes was higher in the patientsthan in the normal subjects. In 23 patients

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the Q-T/T-Q ratio was more than 2.2 in one ofthe three minutes of exercise. In severalpatients who showed marked symptoms anddistinct electrocardiographic changes, the ex-ercise Q-T/T-Q ratio reached 4 or 5 (fig. 2,J. D).Although the averaged Q-T, interval was

prolonged during exercise, it did not shortenduring early recovery. This abnormal responsewas observed in almost half of the patients.

three patients. In one patient multiple pre-mature ventricular beats developed during thefirst minute of exercise and the patient did notcomplain of precordial pain until the end of thethird minute (fig. 7).Of the 21 patients in Group II, four showed

distinct S-T depression during recovery andnot during exercise, and eight exhibited similarchanges both during exercise and recovery.Two patients had significantly high T waves

TABLE 3.-Incidence of Abnormal Changes During Exercise and Recovery in 54 Patients

S-T Depression

|DuringExercise

only

5GROUP IAngina Pectoris

(21 cases)

GROUP ILASHDHCVD(non-angina)

(21 cases)

GROUP IIIMiscellaneous

(12 cases)

1

DuringDuringReRecovery and Re-

2

4

1

covery

10

8

Changes in T Wave*

During Exercise During Recoveryonly only

42 inverted2 high

22 high

11 high

* Inverted-from an upright to an inverted T wave.High-from an upright to a high T wave.Diphasic-from an upright to a diphasic T wave.Paradoxic-from an inverted to an upright T wave.

S-T and T ChangesThe incidence of the abnormal electro-

cardiographic changes observed in 54 patientsis summarized in table 3.

Of 21 patients in group I, abnormal S-Tdepression was recorded only during exercisein five (figs. 3 and 4, S. G.), only during recoveryin two and during both exercise and recovery

in 10 (fig. 5). Four patients showed abnor-malities in the T wave only during exercise:two with inversion of the T wave (fig. 4,M. T.) and another two with the developmentof high T waves (fig. 6). T-wave changesoccurred during both exercise and recovery in

six patients (figs. 2, 6). Ventricular prematurebeats occurred during exercise and recovery in

11 diphasic

During Exerciseand Recovery

63 paradoxical2 inverted1 high

55 diphasic or

inverted

Ab-normalQ~T/T-QAbove2.2

Ab-normalQ-T,

13 9

10

3

7

3

Ven-tric-ularPre-ma-tureBeats

3

1

1

during exercise and five patients showed eitheran inverted or diphasic T wave during bothexercise and recovery. Ventricular prematurebeats were registered during exercise andrecovery in one patient.

In group III the incidence of S-T and T-wave abnormalities was low. One patientshowed abnormal S-T depression and anotherhigh T waves only during exercise. The thirdpatient had S-T depression and diphasic Twaves only during early recovery.

Abnormalities of the S-T segment and Twave which developed during exercise usuallypersisted through the first three minutes ofrecovery and returned to the resting patternby the eighth minute of recovery.

1- .iila

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Elevation of the S-T segment occurred inone case during exercise and early recovery.The case is not included in this series. Pro-

two-step test has been reported. Movementsof the extremities preclude recording anysatisfactory tracings during exercise by usingMaster's original .,method. With precordial

FIG. 3. F. B. A 37 year old man with history ofangina pectoris. He did not complain of any pre-cordial pain during both double two-step tests. Notemarked S-T depression during exercise on 3/9/50 andless marked S-T depression during exercise on 6/6/50.In either instance the changes are not significant dur-ing recovery. This case illustrates three points: (1)No constant parallel exists between precordial painand electrocardiographic abnormalities. (2) Changesindicative of coronary insufficiency may occur onlyduring exercise and not after exercise. (3) Similarchanges may be reproduced even after a period ofthree months.

longation of P-lt interval or widening ofQRS complex were not observed.

DISCUSSION

No previous study of electrocardiographicchanges during the performance of Master's

FIG. 4. S. G. A 59 year old man with history ofangina pectoris and also evidence of anemia. He wasunable to exercise for more than two minutes becauseof precordial pain and dyspnea. The electrocardio-gram shows distinct S-T depression only duringexercise and not after exercise. M. T. A 57 year oldman who had had an attack of anterior myocardialinfarction five years ago and since then frequentlycomplained of precordial pain after exertion. TheCB4 lead shows a low T wave which becomes invertedonly during the second and third minutes of exercise.Note the upright T wave in the recovery period.

lead (CB4 or CB5) it is possible to record theelectrocardiogram during exercise without dif-ficulty or interference. Most investigatorsagree that the precordial lead is more sensitivethan any of the three standard limb leads.4 10

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This is understandable according to theprinciple that "regions close to the exploringelectrode influence the pattern obtained to agreater degree than do areas remote from it.""

REST

EXERCISEIST MIN

2ND MIN

3RD MIN

RECOVER'IST MIN

2ND MIN

3RD

8TH M

FIG. 5. K. S. A 39 year old man with typical his-tory of angina pectoris. Patient died of an attack ofacute myocardial infarction two weeks after this testwas performed. P. A. A 56 year old man with typicalhistory of angina pectoris.

The exercise electrocardiogram in these two cases

shows marked depression of the S-T segment duringboth exercise and recovery Note that the S-T de-pression actually occurs early in the first minute ofexercise.

The potential of the right scapular region, on

which the indifferent electrode is placed,varies through a relatively small range."

Other investigators4' 8, 12 have pointed outthat the double tw-o-step test demonstrates

FIG. 6. E. P. A 59 year old man with typicalhistory of angina pectoris. On 4/12/50 he was able toexercise for only two minutes because of dyspneaand precordial pain. The exercise electrocardiogramshows a so-called paradoxical response. The diphasicor inverted T wave at rest becomes upright duringexercise and early recovery. After dietary manage-ment for a period of six months, his condition wasimproved and his precordial pain was less frequent.On 10/20/50 another exercise test was performed.This time he completed the double two-step test withonly slight discomfort, and the resting electro-cardiogram (lead CB4) shows an upright T wave.During the second and third minutes of exercise,there is a distinct increase in the amplitude of theT wave associated with S-T depression. Both theparadoxic response and increase in the amplitude ofT wave are the result of subendocardial ischemia.

abnormalities ill many patients ill wvhom theelectrocardiogram is normal in the standard

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test. For this reason, we used the double two-step test as standard procedure in our study.If severe symptoms develop or if markedabnormalities appear in the electrocardiogramthe test may be interrupted immediately.Indeed, unlimited exertion in order to producepain may be hazardous. In, some cases elec-trocardiographic abnormalities may occur with-

FIG. 7. The patient is a 52 year old woman whomanifests classic symptoms of angina pectoris. Be-ginning in the recovery period the patient experiencedsomewhat marked though temporary symptoms, butnote that an arrhythmia is recorded earlier thanthis in the second minute of exercise. A Rest. B,C and D Exercise. E, F and G-Early recovery.H-Late recovery.

out symptoms, since no constant parallelexists between pain and electrocardiographicchanges.4' 13Abnormal findings in the exercise electro-

cardiogram have been demonstrated in normalsubjects under unusual stresses.2 Therefore, we

believe that any exercise for the diagnosis ofcoronary insufficiency should be standardized.Changes of heart rate may be observed by

taking electrocardiogram during the exerciseperiod. The average heart rate during exercisewas considerably higher in the patients thanthat in the normal subjects for the correspond-ing minute. Furthermore, the heart rate in atleast one of the three minutes of exerciseexceeded the maximum rate recorded in thenormal subjects in 15 of the 54 patients.Changes of the Q-T interval in normal

subjects performing the double two-step testhave been uniform and consistent. The Q-T/T-Q ratio during exercise was always less than2.2 no matter what the heart rate. In somepatients the ratio reached 4 or 5 and thesevalues were associated with a very rapidheart rate. The Q-T/T-Q ratio is closelyrelated to, but not entirely dependent upon,the heart rate. Therefore, both heart rate andQ-T/T-Q ratio may be a very useful index indetermining myocardial function: The morerapid the rate, the higher the Q-T/T-Q ratioand the poorer the function.The significance of changes in the Q-T0

interval in patients with coronary insufficiencyrequires further study.

This study demonstrates that abnormalelectrocardiographic changes such as S-Tdepression, alteration of the T wave and ap-pearance of ventricular premature beats actu-ally occurred during exercise and persisted tothe recovery period in most cases. Thesechanges are frequently diagnostic, and ab-normalities occurring during exercise may bethe only indication of coronary insufficiency.Our results show that false negative tests maybe obtained in about 20 per cent of the cases ofangina pectoris, if tracings are not madeduring exercise.

It should be noted, however, that electro-cardiographic abnormalities indicating cor-onary insufficiency may be seen during andafter exercise in patients without anginapectoris.'Recent experimental and clinical studies14-'9

have shown that S-T depression in the pre-cordial leads is due to injury in the subendo-cardial layer of myocardium. Inversion of anupright T wave in the precordial leads is prob-ably due to a lesion of the epicardial surface,and reversion of an inverted or diphasic T

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wave (paradoxical positive T wave change)in the same leads may be an indication ofendocardial injury with "delayed repolariza-tion." Experimental evidence also indicatesthat minor injury to the subendocardialmyocardium may result in an increase in theamplitude of an upright T wave."' 20 Webelieve that the abnormal increase in theamplitude of an upright T wave during exerciseis significant in human subjects. This changemay be an indication of early subendocardialischemia. An upright T wave in the precordialleads of some patients may increase in ampli-tude (suggesting subendocardial ischemia)earlier than or in association with the classicdepression of the S-T segment indicating sub-endocardial injury due to coronary insuf-ficiency.

SUMMARY AND CONCLUSION

1. A method for recording precordial elec-trocardiogram (CB4 or CB6) during exercisein performing Master's two-step test is de-scribed in detail. The electrocardiograms wererecorded in four periods: (a) resting, (b)exercise, (c) early recovery, and (d) laterecovery.

2. The double two-step test was performedin 32 normal subjects and 54 patients withvarious cardiovascular diseases. The changesin the electrocardiogram during and afterexercise are reported and discussed.

3. The criteria for an abnormal response inthe modified double two-step test are defined.

4. The significance of an increase in theamplitude of the T wave during exercise isclearly shown.

5. The modified method retains the meritsof Master's original test and has severaldistinct advantages: (a) Changes in heartrate and the Q-T interval are recorded duringexercise. The heart rate and the Q-T/T-Qratio recorded during exercise may serve as auseful index of myocardial function. (b)It demonstrates that the electrocardiographicabnormalities in most cases of coronary in-sufficiency actually develop during exerciseand persist to the recovery period. (c) Incertain instances diagnostic changes are presentonly in the electrocardiograms taken during

exercise, thus the sensitivity of the two-steptest is augmented. (d) Since it makes possibleelectrocardiographic observation during ex-ercise as well as during recovery it enhances thesafety of the exercise test.

ACiKSNOWLEDGEMENTS

The authors wish to express their gratitude toDr. William S. McCann, Professor of Medicine,University of Rochester School of Medicine andDentistry, and to Dr. Jacob D. Goldstein, formerlyChief of Laboratories, the Genesee Hospital, fortheir continuous encouragement. The technical as-sistance of Miss Julia Nichols, Miss Carol Gou-verneur, and Mr. S. T. Moore is acknowledged withthanks.

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PAUL N. G. YU and ALFRED SOFFERTest)

Studies of Electrocardiographic Changes during Exercise (Modified Double Two-Step

Print ISSN: 0009-7322. Online ISSN: 1524-4539 Copyright © 1952 American Heart Association, Inc. All rights reserved.

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