Inability of the Submaximal Treadmill Stress Test to

Predict the Location of Coronary Disease

By MARVIN A. KAPLAN, M.D., CLIFFORD N. HARRIS, M.D., WILBERT S. ARONOW, M.D.,

DAVM P. PARKER, M.D., AND MYRVIN H. ELLESTAD, M.D.

SUMMARYTwo hundred patients had submaximal treadmill stress tests (STSTs) and selective coronary

arteriography performed within 2 months of each other. An attempt was made to assess thepredictability of disease isolated to any given coronary vessel by performance on the treadmill.This was not possible for disease isolated to the right coronary, the left anterior descending, thecircumflex branch of the left coronary, or a combination of right coronary and circumflex arteries.Eleven patients had disease in the left main coronary artery; all had associated disease of some

other branch as well. One of these patients had a negative submaximal treadmill stress test but was

unable to reach 90% of his maximum predicted heart rate. The remaining 10 patients had positiveSTSTs. Patients with 26-50% narrowing of any branch had treadmill results similar to those with51-75% narrowing. There was a large number of patients with single-vessel disease in the study andmost of the negative STSTs occurred in this group. Nevertheless, within this group no one vesselgave a higher incidence of positive STSTs than any other. It is concluded that (1) a positiveSTST is more likely to be associated with increased severity and extent of coronary artery disease;(2) a negative STST is more likely to be found in disease limited to a single vessel; and (3)within the latter group, the STST is of no value in predicting the specific coronary artery involved.

Additional Indexing Words:Exercise test Coronary artery disease

A VOLUMINOUS literature has accumulateddescribing the value of exercise stress testing

in patients with coronary artery disease.1-5 Amongthe well-accepted varieties of exercise stress testingis the submaximal treadmill stress test (STST)which has become established as a useful methodfor the production of significant S-T-segmentchanges which are most commonly secondary tocoronary artery disease. With the advent ofselective coronary arteriography it has becomepossible to correlate anatomic compromise of thecoronary arterial lumen with the performance onstress testing.6-9 Thus, a strong criterion for the

From the Cardiology Section, Medical Service, VeteransAdministration Hospital, Long Beach, California, theUniversity of California, Irvine, California, the MemorialHospital Medical Center of Long Beach, Long Beach,California, and the Anaheim Memorial Hospital, Anaheim,California.

Address for reprints: Marvin A. Kaplan, M.D., CardiologySection, St. Vincent's Hospital, 2131 West Third Street, LosAngeles, California 90057.

Received April 7, 1972; revision accepted for publicationSeptember 25, 1972.

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Coronary arteriography

sensitivity (percentage of true positives) andspecificity (percentage of true negatives) of the testhas evolved.Most of the studies correlating exercise perfor-

mance with coronary arteriography have addressedthemselves to such parameters in patients withnormal resting electrocardiograms;4 6, 8 some inves-tigators have included patients with abnormalresting tracings,8' 10-12 and others" 13 have reportedon hemodynamic parameters correlated with coro-nary arteriograms as related to postexercise electro-cardiograms. However, only one abstract'4 hasappeared attempting to relate the anatomic site ofdisease with the STST performance. The presentstudy was undertaken to assess the relation of STSTperformance to each of the following anatomicparameters of coronary artery disease (CAD) asevaluated by selective coronary arteriography:(1) specific branch of the coronary tree involved;(2) severity of luminal narrowing, i.e., the maximalnarrowing of any branch of the coronary tree; and(3) extent of vascular involvement, i.e., number ofbranches narrowed.

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Materials and MethodsTwo hundred patients were selected at random from

our several institutions; 156 were men and 44 werewomen. All of the patients studied had chest painwhich was interpreted as definite or possible angina inthe opinion of the consulting cardiologist. The criteriafor selection were availability of an adequate coronary

arteriogram and an STST performed within 2 months ofthe angiogram. Patients with visible occlusive CADwere retained in the study regardless of the results oftheir STST; those without visible CAD were excludedunless their STST was positive.

Coronary arteriography was performed by either theJudkins'"5 or the Sones"6 method. Films of poortechnical quality were excluded. In well over 90% ofcases two views of each vessel (right and left anterioroblique) were required before a patient was included inthe study; an occasional patient was included if a singleview showed either an obviously widely patent or

severely narrowed vessel. This circumstance occurredrarely and only with regard to the right coronary artery.All coronary arteriograms were reviewed separately bytwo independent observers who had no knowledge ofthe results of the STST, and the given vessel was

graded into quartiles, based on the following percent-age narrowing of the worst lesion: 0-25% first quartile;26-50% second quartile; 51-75% third quartile; 76-100%fourth quartile.

In most situations both observers independentlyagreed on the quartile score; where the two interpreta-tions fell into different quartiles the film was reviewedjointly and a decision reached. For the purpose ofanalysis, the overall pattern of coronary disease (asassessed angiographically) in each patient will besubsequently categorized on the basis of the quartilerating of the worst lesion in any of the coronary arteries(without regard to equivalent or lesser lesions in thesame or other coronary arteries).The STSTs were performed as previously de-

scribed.3 17 Three different methods were utilized inthe performance of the STSTs: (1) In 68 cases,17 leadsI, aVF, and V5 were recorded in the supine andstanding positions before exercise. A multistage uninter-rupted treadmill test similar to that described by Doanand associates2 was then performed. The patients were

monitored with lead V5 throughout exercise with an

oscilloscope. Leads V5, aVF, and I were recorded in

that order each minute during exercise, continuouslyafter 75% of the predicted maximal heart rate18 was

reached, immediately after exercise in the upright andsupine positions, and in the supine position every

minute after exercise for at least 6 min. (2) In 120cases,3 the electrodes were affixed to the upper part ofthe manubrium sterni and the standard left chest V5position. The multistage treadmill test was performed ata constant 10% grade. Monitoring and recording were

performed as above with lead V5. (3) In 12 cases,

modified leads II and V4 were utilized with exerciseand recording performed as above in (2).

Tests were classified into three groups: positive,negative, or test stopped because of angina or othersymptoms before 90% of the maximal predicted heartrate (MPHR) was achieved or significant S-T-segmentchanges occurred.

For a test to be read as positive, one of the followingcriteria had to be met: (1) S-T-segment elevation of> 1.0 mm above the resting level; (2) S-T-segmentdepression of 1.0 mm below the resting level, with theS-T segment extending horizontally for at least 0.08sec; (3) S-T-segment depression of -: 1.0 mm below theresting level, with downward sloping of the S-Tsegment, persisting for at least 0.08 sec.

All tests were read independently by two of theauthors. In all but five of the 200 cases, there was

agreement between the two readings. Where theinterpretations differed, the test was submitted to a

third author whose reading was taken as the finalone.

The data were analyzed using a chi-square test. Inthose instances where the frequencies were small, an

exact test for a 2 x 3 contingency table was alsodone.

ResultsNineteen of the 200 patients (9.5%) with 25% or

less (first quartile) narrowing of any branch of thecoronary arterial tree had positive STSTs. Of theremaining 181 patients, 104 (57%) had positive and48 (27%) negative STSTs. Twenty-nine patients(16%) stopped the test prior to developing a

positive STST or achieving 90% of their MPHR.These patients were not included in the statistical

Table 1

Analysis of Patients with Negative STST

Patients (no.)Vessels involved QII QIII QIV Total Total

(no.) N = 15 N = 20 N = 117 observed expected

1 9 7 14 30 162 0 3 7 10 163 0 1 7 8 16

Total 9 11 28 48 48% of all patients

in quartile 60 55 23.9 P < 0.001

Abbreviations: QII = second quartile, 26-50% narrowing of worst lesion; QIII = 51-75% narrowing;QIV = 76-100% narrowing.

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Table 2

Analysis of Patients with a Positive STST

Vessels Patients (no.)involved N = 104

(no.) QII QIII QIV

1 5 3 1.52 1 4 233 0 2 454 0 0 6

Total 6 9 89

Abbreviations: QII = 26-50% narrowing; QIII = .51-75%/ narrowing; QIV = 76-100%7 narrowing.

analysis. These patients who stopped prior toachieving 90% of their MPHR did so because ofangina, fatigue, claudication, or dyspnea. Thus,there was a total of 152 patients who either had apositive STST or reached 90% or more of theirMPHR; 68% of these 152 patients had positiveSTSTs, and 32% of these 152 patients had negativeSTSTs.Table 1 shows the distribution of patients with

negative STSTs. Table 1 also shows that there is adisproportionate number of patients with single-ves-sel disease who have negative STSTs (P < 0.001).

Table 2 shows the distribution of patients with apositive STST. It is evident that both increasingextent and increasing severity of disease increasethe probability of a positive STST.

Analysis of the STSTs in the second quartile (fig.1) revealed that six of 15 individuals (40%) hadpositive STSTs. This figure compares to the 45%positive tests in the next quartile of disease.Comparing positive with negative STSTs in those

patients with disease isolated to the left anteriordescending artery (LAD) regardless of severity

COMPARISON OF 2nd AND 3rd QUARTILE PATIENTS

2nd Quartile

= 55%

3rd Quartile

45%

Figure 1

Posterior wall disease. Crosshatched bars = negative sub-maximal treadmill stress test. Clear bars = positive submaxi-mal treadmill stress test.

(table 3) revealed no significant difference(P 0.2). Here, fourth-quartile patients had an

almost equal number of positive and negativeSTSTs.Comparison of positive with negative STSTs in

isolated right coronary artery (RCA) disease (table4) again reveals no significant difference (P = 0.68).

Isolated circumflex disease gave an equal numberof positive and negative STSTs (table 5).There were 38 patients with disease limited to

two vessels who either had a positive STST or

achieved at least 90% of their MPHR and had a

negative STST. In 13 of these individuals, the twovessels involved were those supplying the posteriorwall of the heart, viz., the right coronary artery(RCA) and the circumflex branch of the leftcoronary artery. The remaining 25 patients haddisease of some combination of two vessels otherthan the RCA and circumflex. Comparisons were

made to determine whether two-vessel diseaselocalized to vessels of the posterior wall produced a

percentage of positive STST results which differedfrom that produced by disease in any other two

vessels (fig. 2). Nine of the 13 patients (69.2%) withtwo-vessel disease involving the posterior wall had a

positive STST. Of the 25 individuals with two-vesseldisease involving a combination other than the RCAand circumflex, 19 (76%) had a positive STST. Thisdifference was not statistically significant. Thus,posterior wall disease produced no significantlydifferent incidence of positive STST than did any

other combination of two-vessel disease.Increasing severity of disease (table 6) caused a

marked increase in the yield of positive STSTs(P = 0.00098).That increasing extent of vessel involvement

produces more positive STSTs can be seen fromtable 7. Increasing degrees of statistical significanceare reached as one-, two-, and three- and four-vesselinvolvement are analyzed.

Table 3

Analysis of Patients with Isolated LAD Disease*

Patients (no.)Quartile Positive STST Negative STST Total

II 1 .o 6III 1 2 3IV 9 7 16

Total 11 14 2.5

*P = 0.2.

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Table 4

Analysis of Patients with Isolated RCA Disease*

Patients (no.)Quartile Positive STST Negative STST Total

II 2 2 4III 1 4 5IV 4 ,) 9

Total 7 11 18

*P = 0.68.

No patient with significant narrowing in the leftmain coronary artery who reached 90% of hisMPHR had a negative STST. There was a total of11 patients in this group, one of whom failed toreach at least 90% of his MPHR and had a negativeSTST. The remaining 10 patients had positiveSTSTs. Of these 11 patients, one had one othervessel involved (two-vessel disease), four had twoother vessels involved (three-vessel disease), andsix had three other vessels involved (four-vesseldisease). There was no case of disease isolated tothe left main branch; all patients with diseaseinvolving this branch had disease in at least oneother branch. However, patients with disease inthe left main coronary artery fell into quartilesII-Iv.

All patients were evaluated for the presence ofintercoronary collaterals. These vessels were identi-fied only when one coronary vessel was opacified inretrograde fashion following injection of contrastmaterial into one of the other two arteries. Thirty-nine of the 181 patients (21.5%) with angiographi-cally documented coronary artery disease werefound to have such intercoronary collateral vessels.These were found only when obstruction of at leastone vessel was greater than 75%. There was anincreasing incidence of collateral vessels as theextent of coronary disease increased from one- tofour-vessel involvement. When comparisons weremade between those patients with collaterals andthose without collaterals but with comparableextent and severity of disease, it appeared that the

Table 5

Analysis of Patients with Isolated Circumflex Disease

Patients (no.)Quartile Positive STST Negative STST Total

II 2 2 4III 1 1 2IV 2 2 4

Total ,5 5 10

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POSTERIOR WALL DISEASE COMPARED WITH OTHER 2-VESSEL INVOLVEMENT

9 + 21-

6- .- 14 - ,E

3 n 30.8% ;.69,2% 724% T7A

Posterior Wall 2-Vessel Disease other than RCA & Cx

Figure 2

Comparison of patients in second and third quartile. Clearbars = negative submaximal treadmill stress test. Stippledbars = positive submaximal treadmill stress test.

collaterals afforded no protection against myocar-dial ischemia as measured by treadmill stress tests.The detailed analysis of this comparison is thesubject of a separate communication.19

DiscussionThe results of the present study have corrobo-

rated reports from other investigators. The finding of9.5% of patients with positive STSTs having lessthan 25% narrowing of any branch of the coronarytree agrees with the work of others.9' 11 Whetherany of these "false positives" was influenced bymyocardial disease cannot be evaluated sinceparameters of contractility and end-diastolic pres-sure measurements were not evaluated in thisstudy.

Single-vessel disease (SVD) was seen withconsiderable frequency in the patients in this study.Thus, all but one of the second-quartile patients (14of 15, or 93%) and half of the third-quartile patients(10 of 20, or 50%) had disease confined to a singlevessel, and these patients had a large number ofnegative STSTs. Moreover, only 15 of 29 patients(52%) with SVD in the fourth quartile had apositive STST. When viewed in this way, it appearsthat the STST frequently fails to detect SVD,regardless of its severity. Moreover, the presence oflarge numbers of patients with SVD in the secondand third quartiles would seem to restrict anyconclusions that could be made from a comparisonof the frequency of positive STSTs in thesequartiles. However, this bias, i.e., the presence oflarge numbers of patients with SVD, in factoccurred in a group of 200 unselected patients and,therefore, would appear to represent a chancebiologic phenomenon. Furthermore, as can be seenfrom tables 1 and 2, increasing severity of disease

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Table 6

STST vs Quartile*

Patients (no.)Quiartile Positive STST Negative STST Total

II 6 9 15III 9 11 20IV 89 28 117

Total 104 48 152

*P = 0.00098.

appears to correlate with increasing extent ofdisease.

It is of special interest, therefore, that 40% ofpatients having between 26 and 50% narrowing ofany given vessel had a positive STST, since 50%narrowing is frequently considered the criticalamount necessary for the production of angina.Moreover, 45% of patients with 51-75% narrowinghad positive STSTs, a figure very close to that of theless severe group. It might be suspected that thesimilarities in these groups are related to: (1) an

excess number of individuals in the second quartilehaving multivessel disease or (2) a clustering ofsingle-vessel disease in the third quartile. That thesespeculations are not true is clearly shown in table 2.Thus, it is possible that present criteria of "falsepositivity," even though high-quality selective coro-

nary arteriograms are available, are still open toquestion. Stated another way, it may be that either50% narrowing should not be considered the criticalamount or the simple presence of 50% (or more)narrowing should not necessarily be used as "proof"that chest pain is due to the luminal compromise ofthe coronary vessels.The conclusions reached above must, neverthe-

less, remain somewhat limited because of thepreviously mentioned disproportionate amount ofSVD encountered in our patient population. Thus,confirmation of our findings should be sought by

further studies in patients with multivessel involve-ment before impressions derived from the presentinvestigation are generalized to all degrees ofcoronary disease.

Predictability of which branch of the coronarytree is more apt to give a positive STST has beenextensively explored. Fitzgibbon et al.7 in a study of160 male patients analyzed their data with respectto maximal severity of narrowing in any givenbranch of the coronary arterial tree and found no

strong positive correlation. Their study differs fromthe present one in that it was not designed toinvestigate specific vessels and their relation topositive STST; data were analyzed only as tomaximum severity in a given branch, disregardingthe presence of lesions in other branches; and 90 ofthe patients were asymptomatic. Despite thesemajor differences, our results are in agreement withthe conclusions of this group.However, it is of interest that in those of our

patients with single-vessel disease (26.5% of thisseries) there was a high incidence of false-negativeSTSTs. Table 1 shows that 30 of 48 patients (66.7%)having negative STSTs have single-vessel disease(P < 0.005). Moreover, the incidence of positiveSTSTs increases markedly when one examines two-,three-, and four-vessel disease (table 6). This hasalso been reported by others.9 This high incidenceof single-vessel coronary disease in patients withfalse-negative exercise tests may have certainimportant implications. Thus, there is a fairprobability that in patients with a negative STST,even if falsely negative, the disease process may beconfined to a single vessel. Furthermore, it may bethat a false-negative STST is, in part, the result ofsmall areas of ischemia associated with therelatively confined disease. Viewed in this fashion, a

negative STST may suggest a relatively favorableprognosis even if it is a false-negative STST. Thisinterpretation would support the conclusions of

Table 7

Analysis of Extent of Disease

One-vessel Two-vessel Three- and four-vessels(no. patients) (no. patients) (no. patients)

Parameter Observed Expected Observed Expected Observed Expected

STSTnegative 30 26.5 10 19 8 30.5STSTpositive 23 26.5 28 19 53 30.5

Total 53 53 38 38 61 61X2 0.68 7.61 31.74P 0.41 0.006 0.001

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others20 who have noted a greatly decreasedmortality incidence among patients whose coronarydisease is confined to one vessel.McHenry et al.14 reported on 50 patients with

angina pectoris exercised on a treadmill until theonset of chest pain and then subjected to selectivecineangiography to determine the location andseverity of CAD. Forty-two of their patients had anabnormal S-T-segment response to exercise. Six ofthe eight with a negative response demonstratedarteriographic evidence of major CAD (greaterthan 50% narrowing) in only one major coronaryartery. In five of these six, the stenosis was localizedto the RCA. Ninety percent of patients with isolateddisease of the LAD branch had a positive response,and only 50% of those with isolated RCA diseasehad a positive response. These data were inter-preted to indicate that patients with angina pectorisare more likely to have a negative treadmill exerciseelectrocardiogram when stenosis of greater than 50%is localized to one vessel, especially if this vessel isthe RCA. In a later report, McHenry et al.21reported on 85 patients studied in the same manner.All of these patients had a stenosis of one or moremajor coronary arteries of 75% or greater. Eighty-three percent of this group had a positive exerciseresponse. Of the 15 with a negative response, 11(73%) had isolated RCA or left circumflex disease.Again, the incidence of a positive response was highin patients with isolated LAD disease. These datawere interpreted to indicate that the bipolar V5 leadsystem (used in the STST) is more sensitive toischemia rising from disease of the LAD artery andthat additional vertical-axis lead systems mayincrease the sensitivity of treadmill exercise testing.Ten of 11 patients who had left main coronary

artery disease had a positive STST but, except forthis small group, the present study clearly indicatesthe lack of predictability of STST performance withregard to specific vessel location of coronary arterydisease. The disparity between our work and thereports of McHenry et al.'4' 21 may lie partially inhis choice of patients having stenosis of 75% ormore. Such individuals compare to our fourthquartile in which there was a 76% incidence ofpositive STST. The difference between the 85%positivity described by McHenry et al. and ourincidence of 76% positivity may be accounted for bythe end point of the tests: production of angina inthe former study; at least 90% of MPHR in thepresent study. An additional problem may be hiscriteria for an abnormal STST based on computerCirculation, Volume XLVII, February 1973

analysis of the S-T-segment changes. However, thedifference in correlation with location of coronarylesions is more difficult to explain. Analyzing allquartiles of severity in the present study, one finds44, 50, and 38.9% STST positivity in isolated diseaseof the LAD, left circumflex, and RCA, respectively.Thus, no specific vessel gave more than 50%positivity, and none produced a significantly higherpercentage than the others. Analyzing our fourth-quartile patients with single-vessel disease, there are14 individuals with a negative STST. Of these,seven had isolated LAD disease, two had isolatedcircumflex disease, and five had isolated RCAdisease. These results would seem to negate theimplication that RCA disease is preferentiallyundetected by STST.Because of the small number of individuals in this

study with disease in the left main branch, thesignificance of the finding of 100% positivity in theSTST (when the single patient failing to reach 90%MPHR is excluded) within this group cannot beassessed. We have concluded that except in the caseof disease in the left main coronary artery the STSTis of no value in predicting the specific coronaryvessel involved.

AcknowledgmentThe authors wish to thank Dr. Edgar Palarea for

providing the exercise test data on several of the patientsincluded in the study. We would also like to acknowledgeMiss Margaret Thomas for her invaluable technical assistance,the Western Research Support Center for its help withthe statistical analyses, and the help of Mrs. Sophie Ocampoin the preparation of the manuscript.

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and MYRVIN H. ELLESTADMARVIN A. KAPLAN, CLIFFORD N. HARRIS, WILBERT S. ARONOW, DAVID P. PARKER

Inability of the Submaximal Treadmill Stress Test to Predict the Location of Coronary Disease

Print ISSN: 0009-7322. Online ISSN: 1524-4539 Copyright © 1973 American Heart Association, Inc. All rights reserved.

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