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Clinical Practice

New Zealand
Med J Aust 1996; 164 (5): 282-284.
Published online: 4 March 1996

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.


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.


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.


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.


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.


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.


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.


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.


References

  1. 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.
  2. 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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1: Indications for exercise stress testing*

  1. As a diagnostic test in patients with suspected coronary artery disease (e.g., men with symptoms that are atypical for myocardial ischaemia, patients with symptoms consistent with recurrent exercise-induced cardiac arrhythmias).
  2. To assist in identifying patients with documented coronary artery disease who are at high risk (e.g., due to advanced disease and/or left ventricular dysfunction).
  3. To evaluate patients after coronary artery bypass surgery or angioplasty.
  4. To quantify a patient's functional capacity, prognosis or response to therapies, and to follow the natural course of disease at appropriate intervals (e.g., after uncomplicated myocardial infarction, in selected patients with congenital heart disease).

General contraindications

  1. Unstable angina prior to a period of stabilisation
  2. Untreated life-threatening arrhythmias
  3. Uncompensated severe congestive heart failure
  4. Advanced atrioventricular heart block
  5. Acute myocarditis
  6. Critical aortic stenosis

* Adapted from: Guidelines for exercise testing. A report of the American College of Cardiology/American Heart Association Task Force on Assessment of Cardiovascular Procedures (Subcommittee on Exercise Testing). J Am Coll Cardiol 1986; 8: 725-738.
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2: Borg scale2 for ratings of
perceived exertion

0Nothing at all
0.5 Very, very weak
1 Very weak
2 Weak
3 Moderate
4 Somewhat strong
5 Strong
6
7 Very strong
8
9
10 Very, very strong
(maximal)
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3: Essential resuscitation equipment

  1. Defibrillator with electrogel or electrode pads
  2. Suction (motor driven or gas cylinder [Venturi] device with appropriate plastic or metal suckers)
  3. Airway plus self-inflating ventilation bag
  4. Oxygen and appropriate masks
  5. Drugs, intravenous cannulas and giving sets, including atropine, lignocaine, adrenaline, and sotalol or amiodarone for intravenous use, a β2-agonist inhaler (e.g., salbutamol), and short-acting nitrates (e.g., sublingual glyceryl trinitrate or isosorbide dinitrate, or glyceryl trinitrate spray)
  6. Alarm to summon nearby personnel and a telephone to call an intensive care ambulance in the event of an emergency
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4: Medical practitioners supervising exercise stress tests should be able to:

  1. Evaluate indications for exercise stress testing and recognise contraindications.
  2. Interpret all the major abnormalities that can be detected on 12-lead electrocardiography, particularly those associated with ischaemic heart disease; those likely to preclude interpretation of the exercise ECG; those which might indicate deferral of the exercise test; and the tachy- and bradyarrhythmias that may occur during exercise.
  3. Differentiate ischaemic from non-ischaemic symptoms during exercise.
  4. Perform basic and advanced life support with skill in an emergency situation, and show evidence of continuing competence by, for example, attending retraining courses at two-yearly intervals.
  5. Demonstate previous experience in exercise stress testing supervised by a cardiologist, including determination of the most appropriate protocol for individual patients.
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  • New Zealand


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