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JariLaukkanen

Exercise Stress Test

Essentials

  • Exercise stress testing can be used for investigating cardiorespiratory performance. The test is most commonly done with a bicycle ergometer, and it can well be done in primary care.
  • Exercise stress testing can be used for the diagnosis of coronary heart disease (CHD) or arrhythmia and for assessing treatment response, functional capacity and prognosis.
    • In the diagnosis of CHD, in particular, the pretest probability of the disease is highly significant for interpreting the results of the exercise stress test. Therefore, when assessing the indications for the test, it is essential to review symptoms and risk factors.
  • The exercise ECG provides an assessment of ischaemia and, additionally, important information on
    • the association between symptoms and stress
    • exercise capacity
    • the response of blood pressure to exercise
    • pulse behaviour
    • any arrhythmia
    • prognosis.

Indications for the test

  • Chest pain, dyspnoea or abnormal fatigue and malaise on exertion, when the pretest probability of CHD is increased (15-85%)
  • Acute coronary syndrome / chest pain
    • The need for an early exercise stress test in these patients is very low since all patients with myocardial infarction, if eligible for the procedure, undergo coronary angiography and revascularization (balloon angioplasty or bypass surgery).
    • If acute chest pain is not associated with ECG changes or release of cardiac markers but the pretest probability for CHD is increased (> 15%), either an exercise stress test or an imaging study should be performed as considered appropriate, unless (non-urgent) angiography is already planned.
  • Evaluation of exercise capacity to assess the patient's ability to work
    • The test should be performed under optimal medication.
  • Investigation of arrhythmias
    • Evaluation of exercise-related arrhythmia or syncope
    • Suspicion of an inadequate increase in the heart rate during exercise (disorders of the conduction system)
    • Adequate or excessive rate control (ventricular response) in atrial fibrillation
    • Investigation of exceptionally frequent extrasystoles
  • Assessment of exercise capacity and haemodynamics during exercise in association with valvular diseases
  • Assessment of response to rehabilitation
  • If considered necessary, in asymptomatic men aged over 40 years
    • with particular occupations
    • with several risk factors for CHD and high-risk occupation
    • if previously sedentary and wishing to start strenuous physical exercise.

Conditions where the interpretation is problematic

  • When exercise stress testing is used as a diagnostic test to confirm CHD, it should be performed before starting antianginal medication (long-acting nitrates or beta blockers, certain calcium channel blockers) or the medication should be paused for 3-5 half-lives before the test (often for 2 days).
  • For diagnosis of CHD, digoxin should be paused for 7-10 days before the test. However, this is not always possible.
  • If the patient is incapable of pedalling, an option is to carry out pharmacological stress testing in a hospital, combined with radioisotope myocardial perfusion scanning or echocardiography.
  • A clearly abnormal ECG at rest. In this case the test should not be performed for diagnostic purposes.
    • LBBB
    • WPW syndrome
    • ST segment depression > 1 mm at rest (significant LVH)
    • Permanent ventricular pacing
  • Other conditions
    • Diagnosis of CHD in women with atypical cardiac symptoms or symptoms suggestive of functional heart disease
    • If the patient is on digitalis or a phenothiazine (ST changes).

Contraindications

Absolute

Relative

  • Untreated, rapid atrial fibrillation
    • Atrial fibrillation may also be an indication for exercise testing if it is suspected that the exercise-induced ventricular response is either too slow or too fast.
  • High blood pressure (systolic pressure > 220 and/or diastolic pressure > 120 mmHg)
  • Pulmonary insufficiency (pO2< 8 kPa or pCO2> 6 kPa)
  • Untreated or severe asthma Long-Term Management of Asthma or COPD Chronic Obstructive Pulmonary Disease (COPD)
  • Other physical or psychological cause preventing the full performance of the test

Performing the test

  • The age-adjusted target heart rate for both men and women is calculated by the formula: 220 - age. This is one of the most frequently used methods for calculating target heart rate.
  • In the exercise stress test, the aim is to reach the age-appropriate target heart rate, as this is significant for interpretation of the test. Carrying out the test maximally should be aimed at, limited by symptoms.

Workload increments

  • For a stepwise protocol, the initial workload is chosen individually based on the patient's age, sex, height, weight and estimated exercise capacity (usually 10-20 W).
    • During the test, the workload is increased once a minute by the amount of the initial workload.
    • The aim of the chosen stepwise protocol is to achieve the maximum workload in 8-12 minutes.
    • Smaller increments (10-15 W) are preferred if the patient's exercise capacity before the test is assessed as impaired (in the elderly, for example).
  • Alternatively, the workload can be increased in 50 Watt (W) increments in men, in 40 W increments in women and in 25 W increments in patients who are aged or in poor physical condition; increasing the workload every 3 minutes. Large increments may be problematic and are therefore not recommended for the elderly or for patients who are in poor physical condition.
  • The recovery phase is usually monitored for 5 minutes; monitoring can be prolonged if needed (ST segment depression, arrhythmias, chest pain).

Heart rate

  • Heart rate should be recorded throughout the test.
  • The commonly applied definition "85% of the age-adjusted maximum (220 - age)" alone should not be used as an indication of maximal testing and particularly not as an indication for stopping the test.
  • A rapid heart rate before introducing the initial workload is often due to nervousness associated with the test situation.

ECG recording

  • Continuous ECG recording is recommended.

Blood pressure measurements

  • Blood pressure should be measured
    • With the patient lying down
    • With the patient sitting on the bicycle
    • During exercise at the end of every second minute (more often if necessary)
    • Immediately after exercise
    • During the recovery phase at 1 and 3 minutes, at least

Respiratory rate

  • Respiratory rate should be monitored during the test.

Measurement of PEF or FEV1

  • Should be performed
    • At the start of the test
    • Immediately after exercise
    • After recovery

Indications for stopping the test

  • Symptoms reported by the patient
    • Atypical feeling of exhaustion
    • Severe dyspnoea
    • Severe angina pectoris
    • Severe limb fatigue
    • Severe calf pain (claudication)
    • Dizziness, disturbed consciousness or nausea
  • Test supervisor's observations
    • The required information has been obtained
    • ECG recordings or blood pressure measurements of technically poor quality
    • Significant ST segment depression of (2-)4 mm
    • ST segment elevation ≥ 2 mm in association with a pathological Q wave; otherwise ST segment elevation ≥ 4 mm (rare finding)
    • Ataxia (poor coordination)
    • A decrease in systolic blood pressure of > 20 mmHg (absolute indication for stopping) or failure of systolic pressure to increase
    • Ventricular tachycardia
    • Rapid supraventricular tachycardia or too rapid atrial fibrillation
    • Development of third degree AV block (absolute indication for stopping), second degree AV block or pronounced bradycardia
    • Arterial oxygen saturation falls below 90%
    • Development of pale or cyanotic skin
    • Excessive blood pressure increase
      • systolic pressure > 280 mmHg
      • diastolic pressure > 130 mmHg.
  • During an early exercise test (post acute coronary syndrome), the above principles apply except
    • systolic blood pressure increases higher than 200 mmHg
    • heart rate increases to over 150 bpm (if the patient is on beta blockers to over 130 bpm).

Interpretation and measurement of ECG changes

ST segment depression

  • Should be measured
    • in the lead with the most pronounced depression at the end of the test
    • in a horizontal part of the ECG tracing
    • in at least three complexes
    • usually in chest leads (V1-V6).
  • The PQ junction is used as the base line.
  • The measurements are taken 0.08 and 0.06 seconds from the J point (defined as the point in the ECG that marks the end of the S wave and the beginning of the ST segment; typically forms nearly an angle.
  • Types of ST segment depression
    • Junctional (rapidly upsloping)
    • Slowly upsloping
    • Horizontal
    • Downsloping

Abnormal findings (suggestive of ischaemia)

  • ST segment depression ≥ 1 mm, measured 0.08 s from the J point (if the heart rate is > 130 bpm ST segment depression is measured 0.06 s from the J point).
  • The most reliable (most significant) change is ST segment depression that develops during exercise and returns to normal during the post-exercise period. Follow-up should be continued longer (more than 5 minutes), as necessary.
  • Symptom of cardiac origin with concomitant ST segment depression appearing during the test
  • It should be noted that ST segment depression suggestive of ischaemia will usually not resolve immediately after exercise.

Factors suppressing the increase of pulse rate or ST segment depression

Interpretation of the test

  • In order to make a reliable interpretation, also in the event of a test showing normal results, the heart rate should be at least 85% of the age-adjusted maximum heart rate during the test, provided that indications for stopping the test do not appear before that.
  • Factors restricting maximal exercise capacity should always be considered and reported. Conclusions from a submaximal exercise stress test are unreliable.
  • Beta-blockers affect pulse behaviour. It should be noted that beta-blockers should not be withdrawn if the patient has been diagnosed with CHD before the exercise stress test or if the test is done for a purpose other than the diagnosis of CHD.

Exercise capacity (Wmax)

  • Wmax = the workload during the second to last stage of exercise + that portion of the workload added during the last stage which corresponds to the amount of exercise completed (for example, the test is stopped 2 minutes after the workload has reached 150 W: 100 W + 2/3 × 50 W = 133 W).
  • Ergometric performance = Wmax/body weight (kg); check local reference values
    • <1 W/kg or < 5 METs: severe disease, poor prognosis
    • 2-3 W/kg or 8-10 METs: moderately good prognosis with medication, without invasive procedures
    • >3 W/kg: good prognosis; ECG changes are of lesser significance
  • METs (metabolic equivalents) express the multiples of resting oxygen uptake during maximal exertion.

Abnormal increase in heart rate

  • Poor cardiorespiratory fitness and overweight
  • Heart failure
  • Anaemia
  • Latent infection
  • Hyperthyroidism
  • Sympathicotonia
  • Atrial fibrillation, other arrhythmia

Abnormally slow increase in heart rate

  • An inadequately increased heart rate (chronotropic incompetence) is an abnormal finding in a maximal exercise stress test.
  • Sinus node disorder
  • Cardiac conduction disorder
  • Medication that inhibits the increase in heart rate (beta-blockers)
  • Good cardiorespiratory fitness may slow down the increase in heart rate (at submaximal workload).

Exercise-induced blood pressure reaction

  • Normal blood pressure response
    • Systolic pressure increases up to the level of 200 mmHg.
    • Diastolic pressure does not change or increases slightly.
  • Abnormal blood pressure response
    • Systolic pressure decreases or fails to increase (suggestive of severe myocardial ischaemia, left ventricular failure, aortic stenosis or an effect of blood pressure medication).
    • Repeated blood pressure measurement is warranted if an abnormal blood pressure response is suspected.
  • Changes suggestive of hypertension:
    • systolic pressure increases to > 240 mmHg
    • diastolic pressure increases to > 100 mmHg
    • slow fall of blood pressure after exercise.

Respiratory rate

  • More than 40 breaths/minute is abnormal.

Diagnostic conclusions

Normal findings

  • Maximal or submaximal heart rate has been achieved.
  • No ST segment changes
  • Junctional ST segment depression (”rapidly upsloping ST depression”); seen particularly in women and often in association with rapid heart rate.
  • Isolated T wave inversion
  • Isolated ectopic beats, short episodes of atrial arrhythmias
  • A normal test result predicts a low risk of cardiac events.
  • The rather low sensitivity of the exercise stress test increases the number of false negative results especially in patients who have a high pretest probability of CHD (> 65%), typical chest pain or high-risk signs.
    • A specialist consultation should be considered in such cases for further investigations even if there are no abnormal findings during the test.

Abnormal findings in the diagnosis of CHD (ischaemia)

  • ST segment depression > 1 mm 0.08 s or 0.06 s from the J point
    • The sooner the ST segment changes appear, the deeper the depression, and the higher the number of leads showing the changes, the more extensive the myocardial ischaemia is likely to be.
    • Ischaemic ST segment depression that persists for several minutes after the exercise has ended suggests a significant CHD.
    • An upward sloping, mild ST depression that appears during high heart rate, only, and disappears quickly during rest may be a false positive finding.
    • In women, a slight change (0.5-1-mm ST depression) does not usually suggest CHD. However, more marked ST changes are more likely to be related to ischaemia. The assessment of the ST segment always depends on the pretest probability.
  • Decreased exercise capacity measured either by maximal heart rate, by total (ergometric performance) or as metabolic equivalents (MET)
  • Poor exercise capacity measured in the exercise stress test impairs the prognosis greatly and is associated with risk of a cardiac event.
    • Exercise capacity is poor if the Wmax reached is < 1 W/kg or MET is < 5.
    • Check local sources for more specific reference values according to age and sex.
  • Effort angina pectoris appearing at a low workload and low rate-pressure product
  • An exceptionally high increase, no increase at all or a decrease in systolic blood pressure on exertion.
    • Decreased blood pressure may be a sign of severe myocardial ischaemia.
    • An excessive blood pressure increase may predict a risk of cardiac events (as may elevated resting blood pressure, see above).
  • Frequent extrasystoles of atrial or ventricular origin or tachycardia occurring during exercise may reflect myocardial ischaemia.
    • This normally requires further investigations.

References

  • Laukkanen JA, Isiozor NM, Kunutsor SK. Objectively Assessed Cardiorespiratory Fitness and All-Cause Mortality Risk: An Updated Meta-analysis of 37 Cohort Studies Involving 2,258,029 Participants. Mayo Clin Proc 2022;97(6):1054-1073. [PubMed]
  • Chronic coronary artery syndrome. A Current Care Guideline. Working group appointed by the Finnish Medical Society Duodecim and Finnish Cardiac Society. Helsinki: Finnish Medical Society Duodecim, 2022 (referenced 17 Nov 2022). (In Finnish only) http://www.kaypahoito.fi/hoi50102
  • Knuuti J, Wijns W, Saraste A et al. 2019 ESC Guidelines for the diagnosis and management of chronic coronary syndromes. Eur Heart J 2020;41(3):407-477. [PubMed]
  • Ross R, Blair SN, Arena R et al. Importance of Assessing Cardiorespiratory Fitness in Clinical Practice: A Case for Fitness as a Clinical Vital Sign: A Scientific Statement From the American Heart Association. Circulation 2016;134(24):e653-e699. [PubMed]
  • Fletcher GF, Ades PA, Kligfield P et al. Exercise standards for testing and training: a scientific statement from the American Heart Association. Circulation 2013;128(8):873-934. [PubMed]