Download Significance of the QX/QT Ratio and the Electrocardiogram

Significance of the QX/QT Ratio and the
QT Ratio (QTr) in the Exercise
Electrocardiogram
By LAURIAN ROMAN, M.D.,
AND
mHE exercise electrocardiogram is a fairly
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relatively reliable criterion for the differentiation of a "true-positive" from a "false-positive"
test. However, they found QX/QT 5 50 per
cent in 13 per cent of a control normal group.
An additional criterion is the QT ratio
(QTr) .4, 6 The QTr is determined by dividing
the actual QT by the ideal QT calculated
for the respective heart rate by the formula
proposed by Bazett.9 Master and Rosenfeld6
assume that in an ischemic heart, the electrical
systole, measured by the QT interval, is prolonged and therefore the QTr is increased in
coronary heart disease, especially after exercise. In the postexercise test, they consider
a QTr > 1.08 as a significant finding reflecting
myocardial ischemia.
Since these relatively recent criteria have
been considered controversial, we thought it of
interest to study the QX/QT ratio and the
QTr in the electrocardiogram after exercise
in 150 normal young subjects. In this group,
coronary arteriosclerosis, even latent, has the
least probability of existing and is therefore
most suitable for studying the normal electrocardiographic response to exercise.
well established and frequently used
procedure as an adjunct in the diagnosis of
symptomatic or latent coronary insufficiency.
Many authors have confirmed its value.'-"
The criteria for a positive test, however, still
remain somewhat controversial.
The value of "ischemic" type ST-segment
depression is well documented, but the problem of the significance of various degrees of
junctional-type depression is still controversial. Recently, Master and Rosenfeld3-6 introduced among their criteria the QX/ QT
ratio and QT ratio (QTr). They state that
a J depression of less than 2 mm., but with a
QX/QT ratio of 50 per cent or more, represents a positive or an equivocal test.4,6 The
possible value of the QX/QT ratio was first
advanced by Lepeschkin and Surawicz.7 8 X
represents the point where the depressed
ST segment returns to the baseline. In order
to express the ST-segment depression in a
quantitative manner independent of the heart
rate, these authors studied the ratio QX/QT
in an attempt to distinguish a "true-positive"
from a "false-positive" ST-segment depression.
It was assumed that the duration of the ST
depression due to a current of injury produced
by subendocardial ischemia should persist
longer than the depression associated with
simple tachycardia or with changes in the
ventricular gradient. These authors proposed
a QX/ QT ratio of 50 per cent or more as a
Methods and Material
A double two-step exercise test was performed
on a total of 150 normal, young college students
and nursing students between 17 and 21 years of
age, with no clinical evidence of heart disease; all
of them had normal resting electrocardiograms.
The electrocardiograms were recorded by the
technic of radioelectrocardiography during and
after exercise. The principle involved, the apparatus, the type of electrodes used and their placement have been discussed in previous communications.10-12 Studies have shown that our apparatus,
with proper standardization of the electrocardiogram, is comparable to that of the conventional
electrocardiogram.'2' 14 Leads L2, V4, and V6 were
studied; these were taken immediately after and
at 1, 3, and 5 minutes after exercise. All of these
From the Division of Cardiology, Philadelphia General Hospital, Philadelphia, Pennsylvania.
Aided by Grants 65-5615 from the Commonwealth
of Pennsylvania and HE-07364 from the National Institutes of Health, U. S. Public Health Service, and
The Foundation for Cardiovascular Research, Phila-
delphia, Pennsylvania.
Circulation, Volume XXXII, September 1965
SAMUEL BELLET, M.D.
435
ROMAN, BELLET
436
Table 1
Junctional Depression in the Postexercise Electrocardiogram for Normal Subjects
Total with J depression
Normal QX/QT and QT ratio
Abnormal QX/QT5 50 per cent
Abnormal QT ratio (QTr 5 1.08)
Abnormal QX/QT and QT ratio
Abnormal QX/QT or QTr (equivocal)
86
53
22
20
9
24
(61.6%)
(25.5%)
(23.2%)
(10.5%)
(27.9%)
patients had a negative exercise test according to
our criteria.12
Results
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Of the 150 persons studied there were 83
and 67 females; the ages varied between 17 and 21 years. From this total of 150
subjects, 86 (57.7 per cent) displayed a junctional depression of less than 2 mm. The
findings in these 86 subjects are given in
table 1.
Therefore, according to the most recent
criteria of Master and Rosenfeld, for this
group of 86 young, normal individuals with
postexercise J depression (which represent
57.3 per cent of the total of the normal subjects
studied), the results can be interpreted as
follows: in 61.6 per cent the test was clearly
negative according to these criteria, and in
38.4 per cent of the group with a J depression
there was a positive or equivocal result. In
other words, as the group with J depression
represents 57.3 per cent of the total of 150
subjects studied, 22 per cent of the total
group of 150 normal, young subjects have a
positive or equivocal exercise test.
males
Discussion
Initially, Master and Rosenfeld3 4 considered a small J depression, of less than 2 mm.,
to be representative of a positive criterion for
the exercise test if the QX/QT ratio was > 50
per cent or if the QTr was 5 the 1.08. More
recently, in their latest publication6 they have
changed their criteria and now consider a
positive result for the exercise test a J
depression that fulfills both conditions, having
a QX/QT ratio > 50 per cent and a QTr
> 1.08; the J depression in which only one of
these ratios is increased, the other being below
the critical level, is considered "equivocal";
the J depression with both QX/QT ratio less
than 50 per cent and QTr less than 1.08 is
considered a negative finding.
The accurate measurement of the QT
interval, particularly at high rates, is often
difficult. With tachycardia, which usually appears immediately after the exercise test, the
end of the T wave is often difficult to determine, since it may not reach the baseline
and may be followed by a superimposed "U"
wave or "P" wave. Furthermore, exercise is
nearly always accompanied by hyperventilation, which may produce considerable T-wave
changes, particularly QT prolongation and
ST-segment depression even in normal subjects. These changes add to the difficulty in
determining the significance of slight grades
of ST-segment depression and QT-segment
prolongation.
There is no general agreement concerning
the significance of QTr prolongation in coronary heart disease. Yu et al.15 found that the
QTr is slightly diminished in patients with
coronary heart disease after exercise in comparison with the resting value. Friedberg et
al.,13 using the QX/ QT ratio and QTr as
proposed by Rosenfeld and Master, found 32
per cent "false-positive" or equivocal results
in their noncardiac patients. In addition, Robb
and Marks' from their long-term study, concluded that the QX/QT and QT ratios are
unreliable methods of evaluating the electrocardiogram after exercise.
In contrast with our results and with those
of Robb and Marks' and Friedberg et al.,'3
Rosenfeld and Master,6 according to their
latest criteria, observed only 13.2 per cent
positive or equivocal results in their functional
(noncardiac) patients with J depression in
the electrocardiogram after exercise.
In conclusion, our data, like those of other
authors who studied the problem, do not
support the validity of the assumption that
a small J depression (of less than 2 mm. )
associated with a QX/QT ratio > 50 per cent
or a QT ratio 5 1.08, or both, should be considered a positive or equivocal result for an
electrocardiographic exercise test.
Circulation, Volume XXXII, September 1965
EXERCISE ELECTROCARDIOGRAM
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Summary
Recently, a junctional depression of small
amplitude (less than 2 mm.) of the ST
segment was considered to be a positive or
equivocal result for the electrocardiographic
exercise test if the QX/QT ratio was 5 50
per cent or the QTr > 1.08.
In 150 normal, young students with no clinical evidence of heart disease, a junctional
depression of the ST segment with a QX/QT
ratio 5; 50 per cent or a QTr 5; 1.08 or both,
was observed in 22 per cent.
These observations, supported by other
published reports concerning the QX/QT
ratio and the QTr, indicate that these criteria
are not reliable for the determination of a
positive electrocardiographic exercise test.
References
1. ROBB, G. P., AND MARKS, H. H.: The postexercise
ECG in the detection of coronary disease: A
long-term evaluation. Tr. A. Life Insur. M.
Dir. America 45: 81, 1962.
2. MATTINGLY, T. W.: Postexercise electrocardiogram. The value in diagnosis and prognosis
of coronary artery disease. Am. J. Cardiol.
9: 395, 1952.
3. MASTER, A. M., AND ROSENFELD, I.: Interpretation of the Master two-step exercise ECG by
quantitative analysis of RS-T segment. Proc.
Soc. Exper. Biol. & Med. 103: 320, 1962.
4. MASTER, A. M., AND ROSENFELD, I.: Criteria for
clinical application of two-step exercise test:
Obviation of false-negative and false-positive
responses. J. A. M. A. 178: 283, 1961.
437
5. ROSENFELD, I., AND MASTER, A. M.: Recording
the ECG during the performance of the Master two-step test: II. Circulation 29: 212, 1964.
6. MASTER, A. M., AND ROSENFELD, I.: Monitored
and postexercise two-step test. J. A. M. A.
190: 494, 1964.
7. LEPESCHKIN, E., AND SURAWICZ, B.: Characteristics of true-positive and false-positive results
of ECG Master two-step exercise tests. New
England J. Med. 258: 54, 1958.
8. LEPESCHKIN, E.: Exercise tests in the diagnosis
of coronary heart disease. Circulation 22: 986,
1960.
9. BAZETT, H. C.: An analysis of the time relations
of electrocardiograms. Heart 6: 353, 1920.
10. BELLET, S., DELIYIANNIS, S., AND ELIAKIM, M.:
Electrocardiogram during exercise as recorded
by radioelectrocardiology. Am. J. Cardiol. 8:
385, 1961.
11. BELLET, S., ELIAKIM, M., DELIYIANNIS, S., AND
LAVAN, D.: Radioelectrocardiography during
exercise in patients with angina pectoris. Cir-
culation 25: 5, 1962.
12. BELLET, S., MULLER, O., LAVAN, D. W., NiCHOLS, G., AND HERRING, A. B.: Radioelectrocardiography during exercise in patients with
the anginal syndrome. Circulation 29: 366,
1964.
13. FRIEDBERG, C. K., JAFFE, H. L., PoRDY, L., AND
CHESKY, K.: The two-step exercise electrocardiogram. A double-blind evaluation of its
use in the diagnosis of angina pectoris. Circulation 26: 1254, 1962.
14. BELLET, S., AND MULLER, O.: The electrocardiogram during exercise: Its value in the diagnosis
of angina pectoris. Circulation 32: 477, 1965.
15. Yu, P. N., BRUCE, R. A., LovEjoY, F. W., AND
PEARSON, R.: Observation on the change of
ventricular systole (QT interval) during exercise. J. Clin. Invest. 29: 279, 1950.
Cumulative Knowledge
Our debt to tradition through reading and conversation is so massive, our protest or
private addition so rare and insignificant-and this commonly on the ground of other
reading or hearing-that in a large sense, one would say there is no pure originality.
All minds quote.-RALPH WALDO EMERSON.
Circulation, Volume XXXII, September 1965
Significance of the QX/QT Ratio and the QT Ratio (QTr) in the Exercise
Electrocardiogram
LAURIAN ROMAN and SAMUEL BELLET
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Circulation. 1965;32:435-437
doi: 10.1161/01.CIR.32.3.435
Circulation is published by the American Heart Association, 7272 Greenville Avenue, Dallas, TX 75231
Copyright © 1965 American Heart Association, Inc. All rights reserved.
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