Exercise stress testing
- 7. WHAT IS STRESS TESTING Tests used in Medicine to measure the heart’s ability to respond to external stress in a controlled clinical environment
- 8. DEFINITION MULTISTAGE TEST THAT DETERMINES THE CARDIOVASCULAR CAPACITY OF THE INDIVIDUAL Individual undergoing stress testing should have physical examination , be monitored by the ECG and be closely observed at rest , during exercise , during recovery
- 9. PRINCIPLE Changing the workload by increasing the speed or grade on treadmill or resistance on the bicycle An initial work load that is low in terms of the individual anticipated aerobic threshold Maintain each work load for 1 min or longer up to 3 min Terminating the programme by onset of symptoms or a definable abnormality in ECG
- 10. TYPES OF STRESS TESTING EXERCISE A)Treadmill I. 6 minute walk test II. 12 minute walk test III.Bruce protocol B) Bicycle
- 11. TYPES OF STRESS TESTING PHARMOCOLOGICAL A)Adenosine B)Dipyridamole C)Dobutamine D)isoproterenol
- 12. TYPES OF STRESS TESTING OTHER A) Pacing (thallium imaging)
- 13. INDICATIONS & USES OF EXERCISE TESTING Elicit abnormalities not present at rest Estimate functional capacity Estimate prognosis of CAD Extent of coronary artery disease Effect of treatment
- 14. INDICATIONS OF PHARMACOLOGICAL STRESS TESTING Patients inability to exercise adequately because of physical or psychological limitations. The chosen test cannot be performed readily with exercise (e.g. PET scanning). Patient who cannot exercise.
- 15. CONTRAINDICATIONS FOR STRESS TESTING Acute myocardial infarction ( within 2 days ) High risk(on pre-test probability) unstable angina Uncontrolled cardiac arrhythmias causing symptoms or hemodynamic compromise Symptomatic severe aortic stenosis Acute pulmonary embolus or pulmonary infarction Acute myocarditis or pericarditis Acute aortic dissection
- 18. MEASUREMENTS ECG Exercise capacity (METS – metabolic equivalent) Symptoms Blood pressure Heart rate response & recovery
- 19. SAFETY PRECAUTIONS AND EQUIPMENT The treadmill should have front and side rails for subjects to steady themselves. It should be calibrated monthly. An emergency stop button should be readily available to the staff only. Exercise test should be performed under the supervision of a physician who has been trained to conduct exercise tests
- 20. METHODS OF DETECTING ISCHEMIA DURING STRESS TESTING Electrocardiography Echocardiography Myocardial perfusion imaging Positron emission tomography (PET) Magnetic resonance imaging (MRI)
- 21. CARDIOPULMONARY EXERCISE TESTING Involves measurements of respiratory oxygen uptake (VO2),carbon dioxide production (VCO2), and ventilator parameters during a symptom-limited exercise test. VO2 max is the product of maximal arterial-venous oxygen difference and cardiac output and represents the largest amount of oxygen a person can use while performing dynamic exercise involving a large part of total muscle mass.
- 22. The VO2 max decreases with age, is usually less in women than in men, and diminished by degree of cardiovascular impairment and by physical inactivity. Peak exercise capacity is decreased when the ratio of measured to predicted VO2 max is less than 85 to 90 percent
- 23. METABOLIC EQUIVALENT Metabolic equivalent (MET) refers to a unit of oxygen uptake in a sitting, resting person. 1 MET is equivalent to 3.5 VO2 ml 02/kg/min of body weight. Measured VO2 in ml 02/kg/min divided by 3.5 ml 02/kg/min determines the number of METs associated with activity.
- 24. Work activities can be calculated in multiples of METs; this measurement is useful to determine exercise prescriptions, assess disability, and standardize the reporting of submaximal and peak exercise workloads when different protocols are used
- 25. METHODS General concerns prior to performing an exercise test include :- • Safety precautions and equipments needs. • Patient preparation • Choosing a test type • Choosing a test protocol • Patient monitoring • Reasons to terminate a test • Post test monitoring
- 26. PRETEST PREPARATION Any history of light headed or fainted while exercising should be asked. The physician should also ask about family history and general medical history, making note of any considerations that may increase the risk of sudden death. A brief physical examination should always be performed prior to testing to rule out significant outflow obstruction
- 27. Preparation for exercise testing include the following The subject should be instructed not to eat or smoke at least 2 hours prior to the test . Unusual physical exertion should be avoided before testing. Specific questioning should determine which drugs are being taken. The labeled medications should be brought along so that medications can be identified and recorded.
- 28. Because of a greater potential for cardiac events with the sudden cessation of -blockers , they not be automatically stopped prior to testing but done so gradually under physician guidance, only after consideration of the purpose of the test
- 29. EXERCISE PROTOCOLS Dynamic protocols most frequently are used to assess cardiovascular reserve, and those suitable for clinical testing should include a low intensity warm-up phase. In general, 6 to 12 minutes of continuous progressive exercise during which the myocardial oxygen demand is elevated to the patient's maximal level is optimal for diagnostic and prognostic purposes. The protocol should include a suitable recovery or cool-down period
- 30. VARIOUS PROTOCOLS Treadmill protocols a. Bruce b. Cornell c. Balke ware d. Acip e. mAcip f. Naughton g. Weber Bicycle ergometer
- 31. TREADMILL PROTOCOL In healthy individuals, the standard Bruce protocol is normally used. The Bruce multistage maximal treadmill protocol has 3- minute periods to allow achievement of a steady state before workload is increased for next stage.
- 32. In older individuals or those whose exercise capacity is limited by cardiac disease, the protocol can be modified by two 3-minute warm-up stages at 1.7 mph and 0 percent grade and 1.7 mph and 5 percent grade.
- 34. The 6-Minute Walk Test Used for patients who have marked left ventricular dysfunction or peripheral arterial occlusive disease and who cannot perform bicycle or treadmill exercise. Patients are instructed to walk down a 100-foot corridor at their own pace, attempting to cover as much ground as possible in 6 minutes. At the end of the 6-minute interval, the total distance walked is determined and the symptoms experienced by the patient are recorded
- 35. Positive test A flat or downsloping depression of the ST segment > 0.1 mV below baseline (i.e. the PR segment ) and lasting longer than 0.08s b. Upsloping or junctional ST segment changes are not considered characteristic of ischemia and do Not constitute a positive test Negative test Target heart rate (85% of maximal predicted heart for age and sex ) is not achieved
- 36. The normal and rapid upsloping ST segment responses are normal responses to exercise. Minor ST depression can occur occasionally at submaximal workloads in patients with coronary disease.
- 37. The slow upsloping ST segment pattern often demonstrates an ischemic response in patients with known coronary disease or those with a high pretest clinical risk of coronary disease.
- 38. Downsloping ST segment depression represents a severe ischemic response. ST segment elevation in an infarct territory (Q wave lead) indicates a severe wall motion abnormality and, in most cases, is not considered an ischemic
- 39. MAXIMAL WORK CAPACITY In patients with known or suspected CAD, a limited exercise capacity is associated with an increased risk of cardiac events and in general the more severe the limitation, the worse the CAD extent and prognosis In estimating functional capacity the amount of work performed (or exercise stage achieved) expressed in METs and not the number of minutes of exercise, should be the parameter measured. Major reduction in exercise capacity indicates significant worsening of cardiovascular status.
- 40. BLOOD PRESSURE RESPONSE The normal exercise response is to increase systolic blood pressure progressively with increasing workloads to a peak response ranging from 160 to 200mmHg with the higher range of the scale in older patients with less complaint vascular system 120mmHg or a sustained decrease greater than 10mmHg repeatable within 15 seconds or a fall in systolic blood pressure below standing resting values during progressive exercise when the blood pressure has otherwise been increasing appropriately, is abnormal.
- 41. HEART RATE RESPONSE Peak HR > 85% of maximal predicted for age HR recovery >12 bpm (erect) HR recovery >18 bpm (supine) Heart rate reserve is calculated as follows – % HRR used = (HR Peak- HR res) / (220-age-HRres)
- 42. LIMITATIONS OF TREADMILL STRESS TEST Non-diagnostic ECG change Women – false positives Elderly – more sensitive/less specific Diabetics – autonomic dysfunction Hypertension Inability to exercise Drugs – digoxin; anti-anginas
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