Maximal Treadmill Stress Testing

for Cardiovascular Evaluation

By MYRVIN H. ELLESTAD, M.D., WILLIAM ALLEN, M.D.,
MAURICE C. K. WAN, M.D., AND GEORGE L. KEMP, M.D.

SUMMARY
Experience with a maximal treadmill stress testing procedure which is relatively safe,
simple, and reproducible is reported. It has been used in normal persons and cardiac
patients with ages ranging from 7 to 83 years. There have been no deaths in our total
experience of 4,028 maximal capacity stress tests. Maximal capacity is predicted
by the patient's peak predicted pulse rate. Sixty-three per cent of those with ischemic
S-T segments did not experience pain of any type.

Additional Indexing Words:

Maximal capacity testing Ischemic S-T changes Peak predicted pulse rates
Monitoring Cardiac diagnosis

ALMOST 40 years ago Master and Oppen- were chosen for detailed analysis. Information
heimer' introduced an exercise test for as to their previous health was only known for
the detection of coronary insufficiency which 284 executives previously examined and thought
to be normal by history and resting ECG. Many
many still consider to be the standard. The of the remainder were sent for evaluation of
significance of exercise induced S-T segment known or suspected angina, and many were sent
depression as indicative of coronary insuffi- for screening prior to embarking on a physical
ciency is accepted by most cardiologists.2 4 fitness program. Careful questioning as to symp-
Master's single and double two-step test is toms, medication, and previous cardiac disease
was done to rule out unstable coronary insuffi-
accepted as the standard submaximal stress ciency and congestive failure. In the group were
test, but there has been no uniform acceptance 205 females and 795 males with ages varying
of a protocol for a maximal stress test. between 7 and 83 years.
It is the purpose of this paper to describe a No special attempt was made to standardize
method which has evolved in our laboratory the time of day or the relationship of the last
meal.
and propose it as a standard maximal stress The patients are prepared by applying gel
test. The procedure is simple to perform and (Lectrocardiographic Gel) to the Telectrode
requires a limited amount of special equip- electrode and affixing these self-adherent electrodes
ment. Experience with it has been extensive to the upper part of the manubrium sterni and
enough to establish norms of performance and the standard left chest V5 position (CM-5).5
The cable attachments are then snapped to the
to demonstrate its safety. electrodes and the cable is connected to a direct-
Methods writing Sanborn electrocardiograph. The electro-
cardiographic complexes are monitored continually
The first 1,000 patients referred to the Division with an oscilloscope. An aneroid sphygmoma-
of Clinical Physiology, of Memorial Hospital of nometer is placed on the right arm for measure-
Long Beach, for maximal treadmill stress testing ments of blood pressure. A cardiotachometer gives
a constant read-out of the heart rate. Oxygen,
From the Division of Clinical Physiology, Memori- emergency drugs, and a DC defibrillator are avail-
al Hospital of Long Beach, Long Beach, California. able in the room.
Work was supported in part by the Long Beach Resting electrocardiograms are taken while the
Heart Association and the Memorial Hospital Re- patient is sitting and also while standing,
search Foundation. before and after hyperventilation, and are used
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S18 ELLESTAD ET AL.
Table 1 after the J-point is measured, and if it is 2 mm
Ages and Mlaximal Pulse Rates (1IIPR)* below a line drawn through the P-Q junction,
the tracing is read as positive for ischemia. De-
Age MPR Age X1I1I1 Age MIPR pressions of lesser magnitude are read as equiv-
(yr) (yr) (yr) ocal for ischemia if the S-T segment is concave,
20 200 41 181 61 167 but are considered as a normal finding if the S-T
21 199 12 180 62 167 segment is convex. T-wave changes by themselves
22 198 43 180 6.3 166 are not considered in the evaluation of ischemic
23 197 44 180 64 165 response to exercise if there are no coexisting
24 196 45 179 65 164 abnormalities in the S-T segment. Precipitation
25 195 46 177 66 163 of frequent premature atrial or ventricular con-
26 194 4i 177 67 162 tractions or an increase in these if present at rest
27 193 48 1 77 68 161 as well as runs of ventricular tachycardia during
28 192 49 176 69 161 or after exercise are considered equivocal findings
29 191 50 175 70 160 not necessarily indicative of myocardial ischema.
30 190 51 174 71 160
31 190 52 173 72 160 Results
32 189 53 172 73 160 Safety
33 188 54 171 74 160
No deaths occurred during the testing in
34 187 55 171 75a 160
35 186 56 170 the 1,000 cases presented herein or from any
36 186 57 170 of the subsequent 3,028 treadmill tests per-
37 185 58 169 formed in our laboratory. Ventricular asystole
38 184 59 168 and ventricular fibrillation were not seen. Tran-
39 183 60 168
40 182
sient ventricular tachycardia, lasting less than
20 sec and reverting spontaneously, occurred
*
These figures are based upon regression figures of nine times. Only one patient required any
Robinson.8a Age groups from 10 to 20 years have been therapy for ventricular tachycardia. He be-
compiled by Astrand and associates, 6-8 and range of came slightly hypotensive and diaphoretic
MPR from 210 to 197, respectively. and was converted to normal sinus rhythm by
as a base line for changes occurring during and
DC countershock. Disturbances in A-V con-
after exercise. Blood pressure is also taken in the duction were precipitated in only two patients.
sitting and standing positions. The patient then No patient fell from the apparatus although
steps onto a treadmill which has a fixed incline physical support was frequently needed at the
of 10% and walks for 3 min at 1.7 mph, 2 min end of walking to assist the patient in sitting
at 3 mph, 2 min at 4 mph and finally, 3 min at down.
5 mph. Blood pressure and electrocardiogram
are recorded at 1-min intervals during exercise Transient vasovagal reactions, that is, mild
and for a period of 8 min following exercise. hypotension and bradycardia in the early re-
The exercise is terminated if the patient be- covery period, occurred in less than 1%; of the
comes exhausted, if the blood pressure falls group. Hypotension during or after exercise
significantly, if there is progressive S-T segment occurred infrequently and was rarely a prob-
depression or pain, or if multiple premature
ventricular contractions or ventricular tachycardia lem. Tvo patients had myocardial infarctions
occurs. If none of these occur, the patient is temporally related to the test, but both sur-
urged to continue until he or she reaches at vived.
least 95% of the predicted maximal pulse rate. A The safety of maximal stress testing has
compilation of maximal pulse rates (MPR) been demonstrated not only by this study but
based upon age is listed from studies by Astrand
and Norris and their associates6-8 (table 1). also by Bruce and others.9-11 It must be em-
Ischemic S-T change in the electrocardiogram phasized that safety requires continuous ob-
occurring during or in the 8-min period of moni- servation by an experienced physician. The
toring after maximal exercise stress testing is test can then be terminated in time to avoid
defined as a 2-mm depression below the iso-
electric line lasting for 0.08 sec from the J-point trouble, or the patient can be encouraged to
(fig. 1). When the depressed S-T segment is not continue long enough for us to obtain definitive
horizontal but slopes upward, a point 0.08 sec data. A careful history, and if indicated, a
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MAXIMAL TREADMILL STRESS TESTING 519

S-T Segment Change With Exercise

A B C
Figure 1
(A) This QRS-T complex demonstrates a normal configuration noted during or after maximal
stress. f-point depression is associated with a convex J-X curve. (B) The J-point depression is
associated with a slow return of the S-T segment to the base line. By measurement, a point
0.08 sec after the J-point is projected upward to bisect the S-T segment. If this intersection is
2 mm or more below the iso-electric line, the tracing is considered positive for ischemia. The
J-X curve is concave. (C) This complex demonstrates the typical ischemic S-T segment de-
pression seen after maximal stress. The S-T segment is depressed 2 mm or more below the
iso-electric line and there is usually straightening of the S-T segment.
REPEATABILITY OF MAXIMAL EFFORT resting ECG should be repeated to prevent
& ISCHEMIC S-T CHANGES exercising a patient with recent infarction or
100 - unstable angina.
90 -
Reproducibility
8o
To evaluate the reproducibility of a pa-
( 70 tient's response to maximal treadmill stress
60 - testing, 25 males, 40 to 68 years old, had repeat
50 -
stress tests within 1 to 90 days. Twenty-two
40 -
of the patients had angina pectoris or a his-
tory of myocardial infarction, or both, and
30 -
three did not. Fifteen patients (60%) per-
20 - formed for an identical time, eight (32%)
I walked 1 min less or 1 min more than they had
on their previous treadmill test, and only two
Duration of
MAXIMAL
ISCHEMIC
S-T
(8%) had a difference in duration of effort
EFFORT CHANGES greater than 1 min on repeat study. Thus, in
9s3
i ,N.-;
- IDENTICAL
T ME :5: : : WITHIN
MI NUTE
ONE- 92% the duration of exercise was within 1 min
on the repeat study (fig. 2). The hypothesis
Figure 2

Of a total of 25 males who were retested by maximal

treadmill exercise within a 90-day period, 92% per- and 95% developed S-T segment abnormalities at a
formed for a similar length of time (within 1 min) similar time interval (within 1 min).
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520 ELLESTAD ET AL.

of more than chance reproducibility of per- Discussion

formance was tested using the standard nor- When considering an exercise stress test,
mal deviate, Z. The frequency categories were several objectives should be kept in mind:
split into performance within 1 min and great- (1) It should be safe, (2) should require a
er than 1 min, and were significant at less limited amount of special equipment, (3)
than the 0.01 level. should not be too time consuming, (4) should
Twenty-two patients, all of whom had a pos- be adaptable enough in design so that it does
itive history, exhibited ischemic S-T changes. not overstress some and understress other
Fifteen patients (68%) developed ischemic cardiac patients, (5) should use a familiar
S-T changes at the identical time interval, six form of exercise, and (6) results should be
(27%) within 1 min of the previous time, and reproducible.9, 12-14
one (5%) had his S-T changes at a time inter- The reproducible association between the
val greater than 1 min. The onset of ischemic exercise work load and the onset of S-T seg-
S-T changes was separated by only 1 min or ment depression has been documented by
less in 95% of the patients. By splitting the Areskag,12 Burkart and their associates,13 and
frequency categories into less than 1 min and others.9' 1 The product of systolic blood pres-
greater than 1 min, a Z test indicated signifi- sure multiplied by the pulse rate has been
cant reproducibility (less than 0.01 level of found by others to be even more predictive of
significance). the end point in patients with coronary in-
Incidence of Chest Pain sufficiency.16 It has been our impression that
Of 284 apparently normal executives referred the more severe the disease, the more re-
for treadmill stress testing as part of a routine producible the test.
Since the cardiac output and oxygen con-
physical examination, 30 (11%) developed sumption increase in nearly a linear relation-
ischemic S-T changes, and 10 (3.5%) had ship with the pulse, the peak pulse response
equivocal S-T changes during or after exercise. allows us to estimate the maximal cardiac
All of the executives were males, aged 30 to
59 years, and in none was heart disease pre- output.6-8 Many patients with coronary dis-
viously suspected. It was surprising that in no ease do not reach their predicted maximal
instance was chest pain associated with ischem- pulse rate; however, in those with normal
tests only 6% failed to reach a pulse rate of at
ic abnormalities. This executive group will be least 80% of predicted value.
the subject of a subsequent report. The advantage of our procedure over the
A detailed analysis of the remaining 716
Bruce procedure is based mainly on its sim-
patients is not presented, since they were re- plicity and the fact that it takes less time to
ferred for various reasons, some of which were perform. The 10% incline is kept constant in
not apparent at the time of the test. However,
the relationship between positive tests and our test in contrast to their changing inclines.
chest pain in the total group is of interest. However, if one wishes to study the well-
Only 88 (37%) of the 236 patients with posi- trained athlete, the Bruce test has the advan-
tive tests had chest pain. Sixty-three per cent tage of requiring much higher levels of energy
had ischemic changes without pain. The fe- expenditure toward the end of the test.
males had a 16% higher incidence of chest The timing of the work periods has been
pain than the males (50% and 34%, respectively) arbitrarily set for convenience. The initial 3-
with Z significant at less than 0.01 level. The min period functions as a warm-up and allows
younger males (31 to 40 years of age) stand the patient to become acquainted with the
out as the group which had the lowest per- uphill grade. When the speed reaches 4 mph,
centage of chest pain (13%). Of the 88 pa- some subjects must jog and almost all must
tients who developed chest pain as well as do so at 5 mph. It has been suggested that in-
ischemic S-T patterns, 61 (69%) experienced creasing the grade would be a more satis-
pain within the first 5 min. factory method of increasing the work load,
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MAXIMAL TREADMILL STRESS TESTING 521

but we have found that the stretch in the with S-T depression should be considered
soleus muscles is very uncomfortable for un- when the absence of angina is used to rule
trained individuals at the higher inclines. out the likelihood of coronary insufficiency.
More study on the range of oxygen con- Exercise is often prescribed to the point of
sumption at each speed is underway, but some pain on the grounds that it is a reliable indi-
preliminary data collected with the Webb cator of myocardial ischemia. Our experience
metabolic rate monitor are available. At a indicates that more often than not ischemia,
speed of 1.7 mph the oxygen consumption is often associated with ventricular irritability,
equivalent to 4 to 5 times the basal consump- will develop unannounced by pain or any
tion of oxygen, at 3 mph to 6 to 7 times basal, other symptom easily recognizable by the
at 4 mph to 9 to 10 times basal, and 5 mph to patient.
15 times basal. Vo2/kg/min for 10 middle- The fact that the incidence of pain is higher
aged males averaged 4.2 at rest, 5 at 1.7 mph, in patients manifesting S-T segment depression
7 at 3 mph, 9 at 4 mph and 16 at 5 mph.17 early in the test suggests that it may be partly
These data are consistent with that presented related to the degree of ischemia. In those
by Gordon,18 Rowell and associates19 and Ford with S-T depression at or near peak pulse
and Hellerstein20 and would suggest that 3 rate it was invariably absent. On the other
mph at a 10% grade is roughly equivalent to hand, typical coronary pain in the absence of
Master's single-step test and 4 mph is equiva- S-T depression is rare, and we have not seen
lent to Master's two-step test. We do not be- it more than a few times. While we were able
lieve that it is practical to strive for a steady to discover 11% positive ischemic responses
state at each work load. to the treadmill stress test in a group of execu-
The controversy over ECG criteria for diag- tives without clinical heart disease, in no case
nosis of ischemia by exercise has yet to be were these ischemic changes associated with
settled. We have used more stringent criteria pain in the chest, even though each man was
for ischemia than those used by Master and exercised to his maximal capacity.
Rosenfeld21 in order to avoid false positives as Using maximal stress testing in the younger
reported by Mattingly.14 Friedberg and asso- age groups seems particularly important. Sixty
ciates22 found no false positives only when the per cent of our males, aged 31 to 40 years with
S-T segment was depressed 2 mm or more. positive tests, would have been missed by
However, we believe that the criteria listed submaximal testing.
by us may be established eventually as too We have used treadmill stress testing to
strict. Robb and Marks,23 using the standard discover subclinical coronary artery disease
double Master's test, have shown that even and to clarify the etiology of chest pain, to
minimal S-T depression is associated with a evaluate the results of cardiac surgery, and to
higher mortality risk. This may not be as valid assess medical management of coronary dis-
with maximal stress testing, however, because ease. It may also be helpful in developing ex-
many young, seemingly healthy males and ercise prescriptions for patients with coronary
females have minimal S-T depression with this disease.*
technic. Sensitivity might also be increased
by using more than one ECG lead.'2 References
It should be stressed that little is known 1. MASTER, A. M., AND OPPENHEIMER, E. T.: Simple
about the specificity and prognostic signifi- exercise tolerance test for circulatory deficiency,
with standard tables for normal individuals.
cance of ischemic S-T changes during and Amer J Med Sci 177: 223, 1929.
after maximal exercise. A recent paper by 2. MASTER, A. M., AND ROSENFELD, I.: Can the
Most and co-workers24 supports the view, how-
ever, that relative ischemia is the most likely
*Note: Pulse response graphs for untrained normal
cause. individuals, male and female, age 20 to 70 years, are
The infrequent occurrence of pain associated available on request from M. H. Ellestad.
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5u,2d2 ELLESTAD ET AL.
amount of S-T segment depression after the capacity: ECG reaction to work test and
"two-step" test be correlated with the severity coronary angiogram in coronary artery disease.
of ischemic heart disease? Amer J Cardiol Acta Med Scand 472: 9, 1967.
15: 139, 1965. 13. BURKART, F., BAROLD, S., AND SOWTON, E.:
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sis of angina pectoris. Circulation 32: 477, 14. MATTINGLY, T. W.: Post exercise electrocardio-
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E. V., AND DAYRTrr, C.: Evaluation of some with special reference to surgical treatment.
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electrocardiogram in diagnosing coronary in- 16. ROBINSON, B. F.: Relation of heart rate and
sufficiency. Amer J Cardiol 13: 310, 1964. systolic blood pressure to the onset of pain
5. BLACKBURN, H., TAYLOR, H. L., VASQUEZ, C. L., in angina pectoris. Circulation 35: 1073, 1967.
AND PUCHNER, T. C.: Electrocardiogram dur- 17. KEhip, G. L.: Rapid analysis of oxygen consump-
ing exercise. Circulationi 34: 1034, 1966. tion during treadmill exercise. A.C.C. course,
6. SHOCK, N. W., ANDRES, R., LANDOWNE, M., Instrumental Acquisition of Cardiological Data,
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HALLEN, A., AND STROM, G.: Physical work men. Arch Intern Med 121: 225, 1968.

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 Maximal Treadmill Stress Testing for Cardiovascular Evaluation
MYRVIN H. ELLESTAD, WILLIAM ALLEN, MAURICE C. K. WAN and
GEORGE L. KEMP

Circulation. 1969;39:517-522
doi: 10.1161/01.CIR.39.4.517
Circulation is published by the American Heart Association, 7272 Greenville Avenue, Dallas, TX 75231
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