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Clinical Practice
Clinical exercise stress testing --
Safety and performance guidelines*
The Cardiac Society of Australia and New Zealand
Clinical exercise testing has wide application in medicine,
including the assessment of functional capacity, ventilatory
function, gas exchange, muscle function, and endocrine and
metabolic function, and as a test for claudication in peripheral
vascular disease. The major use of exercise testing, however, is as a
stress test in patients with known or suspected coronary artery
disease. This article outlines the minimum safety and performance
guidelines for exercise stress testing with electrocardiography,
although many of the safety guidelines are common to other types of
exercise tests, particularly exercise stress scintigraphy and
echocardiography.
MJA 1996; 164: 282-284
| Introduction |
Clinical exercise stress testing with exercise
electrocardiography is usually performed in patients with known or
suspected coronary artery disease (see Box 1). It is thus not without
risk: one in 10 000 people will die, and two to three in 10 000 will have a
major morbid event such as myocardial infarction, a major arrhythmia
requiring resuscitation, severe hypotension, severe heart failure
or unstable angina pectoris. (The complication rates may be higher in
some laboratories because of the mix of referred patients.) Those who
perform exercise stress testing must thus be able to recognise and
exclude patients at high risk, and have the clinical skills and
equipment to recognise and deal effectively with complications.
They should also obtain informed consent from the patient before
performing the test.
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Exercise equipment | |
Energy expenditure is best quantified by measurement of oxygen
consumption (Vo2), expressed in METS, during
exercise. A MET unit is the energy expenditure at rest, equivalent to
an oxygen uptake of approximately 3.5 mL O2 per kilogram
bodyweight per minute. This is the most precise measurement of
metabolic load, and therefore cardiovascular load, and can vary
considerably between individuals with differing exercise
efficiency working at the same treadmill or cycle ergometer setting.
Vo2 is not usually measured directly; energy
expenditure in METS can be estimated from nomograms1 which assume
that energy expenditure can be quantified as watts (cycle ergometer)
or as speed and grade (treadmill).
Treadmills must be motorised and calibrated, and
should be capable of providing measured increases in speed and
gradient. The treadmill speed can be easily checked by measuring the
visible length of belt, multiplying by two, and multiplying this by
manually counted belt revolutions/ minute to give km/hour.
Treadmill inclination can be checked by a protractor.
Cycle ergometers must be able to vary the external
workload and quantify it in watts. Preference is for electrical or
mechanical braking, although wind-braking is probably adequate.
Thumb-screw braking is not adequate as the load cannot be quantified
and is not reproducible.
Simple step devices (including "Masters two-step"), or any other
form of non-quantified and unmonitored exercise, are not adequate
for clinical exercise stress testing. Equipment should be serviced
on a regular basis to ensure performance within specifications.
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Electrocardiograph (ECG) | |
Use 12-lead ECG equipment, recording on a 3-channel device with
adequate low frequency and phase response. Devices which record only
one or three ECG leads, even if these are bipolar chest leads, are not
adequate. If the device provides computer-averaged complexes, raw
ECG traces should also be inspected at each stage of exercise, or at
least every three minutes, to avoid incorrect interpretation
resulting from noise or artefact.
Electrodes must be firmly fixed to the patient's skin with adhesive or
continuous suction, and have good contact with the ECG lead, to
prevent movement artefact in the ECG trace. Use an alcohol solution to
remove oil from the patient's skin and abrade the horny layer of the
epidermis with fine sandpaper or a disposable abrasive device.
Record a standard supine ECG (with limb leads on the limbs) for each
patient, and an additional supine ECG with the limb electrodes on the
torso if this is where they will be placed during exercise. Monitor the
ECG continuously during the exercise period and for five minutes
after the cessation of exercise on a video display of two or three
leads, preferably selected to be semiorthogonal (i.e., an inferior
lead, V5, and V1 or V2). Monitoring a single lead is suboptimal for
detecting arrhythmias and ischaemic patterns during exercise.
Monitoring devices should have a memory loop capable of providing
hard copy or storing rhythm traces on request by the operator. Record
further ECGs with the patient upright; during each stage of exercise
(or at least every three minutes); at peak exercise; immediately upon
cessation of exercise; and at least twice during the post- exercise
period.
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Blood pressure measurement | |
Measure blood pressure before, during (ideally every minute but at
least every three minutes, coinciding with each stage of exercise)
and after exercise (at least two measurements). If possible, a
measurement should be made at peak exercise. Additional
measurements may be required depending on clinical circumstances.
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Documentation |
Document the resting and peak heart rate and blood pressure, and any
abnormalities of these or the ECG. The peak rate-pressure product
(heart rate x systolic blood pressure) should be calculated as this
provides the best estimate of myocardial load. Question the patient
about symptoms such as angina, anginal equivalents, shortness of
breath, presyncope and claudication during and after exercise.
Identify the major symptom which limits exercise and record its
intensity, at least descriptively, but ideally with a quantitative
measure such as the Borg scale2 (see Box 2). Also record the
duration of exercise and the maximum workload achieved.
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Postexercise period | |
Patients should be observed for at least 10 minutes after cessation of
exercise. Continue ECG monitoring for at least five minutes, or
longer if clinically indicated. The duration of ECG monitoring may be
abbreviated to three minutes in special circumstances, such as
thallium scintigraphy, when imaging must commence as soon as
possible after exercise. In such cases, the patient should be closely
observed for the first 10 minutes after exercise.
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Resuscitation equipment | |
Exercise stress test laboratories must be adequately equipped to
provide advanced life support in the event of a cardiac arrest (see Box 3). The exercise room must be sufficiently large to allow the patient
to be removed from the treadmill or cycle and be placed on the ground for
resuscitation if complications occur. All resuscitation equipment
must be easily accessible and maintained and tested on a regular
basis.
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Personnel |
Two people (at least one of whom is a registered medical practitioner,
see Box 4) should be present in the exercise room at all times during
exercise stress testing and the immediate postexercise period. Both
should be trained in cardiopulmonary resuscitation and in the
recognition of the major arrhythmias and ischaemic patterns on the
ECG. No regular specific courses are currently available in exercise
stress testing.
The assistant for exercise stress testing should be a professional
person with training in an area related to health (e.g., ECG
technician, graduate of a course approved by the Australian
Association for Exercise and Sports Sciences, coronary
care-trained nurse, physiotherapist, occupational therapist). He
or she must be able to perform cardiopulmonary resuscitation, obtain
a high quality ECG trace, and recognise the major arrhythmic and
ischaemic ECG and clinical manifestations likely to occur during
exercise stress testing. He or she should also have observed exercise
stress tests under the supervision of a cardiologist and performed
tests under supervision of an experienced assistant. A retraining
program in cardiopulmonary resuscitation should be undertaken
every two years.
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References | |
- The Committee on Exercise, American Heart Association. Exercise
testing and training of apparently healthy individuals: a handbook
for physicians. Dallas, TX: American Heart Association, 1972: 13.
-
Noble BJ, Borg GAV, Jacobs I, et al. A category-ratio perceived
exertion scale: relationship to blood and muscle lactates and heart
rate. Med Sci Sports Exerc 1983; 15: 523-528.
* Adapted from a Cardiac Society guideline document, copies of which
are available from Professor Freedman. |
| | Authors' details |
145 Macquarie Street, Sydney, NSW 2000.
The Cardiac Society of Australia and New Zealand.
No reprints will be available.
Correspondence: Professor Ben
Freedman, Honorary Secretary.
©MJA 1998
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© 1998 Medical Journal of Australia.
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