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Stress Testing

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Stress Testing

  1. 1. Stress testing 1
  2. 2. WHAT IS STRESS TESTING 2  Tests used in Medicine to measure the heart’s ability to respond to external stress in a controlled clinical environment .
  3. 3. TYPES OF STRESS TESTING 3  EXERCISE a. Treadmill b. Bicycle  PHARMACOLOGIC a. Adenosine b. Dipyridamole c. Dobutamine d. Isoproterenol  OTHER a. Pacing
  4. 4. INDICATIONS OF EXERCISE TESTING 4 • Elicit abnormalities not present at rest • Estimate functional capacity • Estimate prognosis of CAD • Likelihood of coronary artery disease • Extent of coronary artery disease • Effect of treatment
  5. 5. INDICATIONS OF PHARMACOLOGICAL STRESS TESTING 5  Patients inability to exercise adequately because of physical or psychological limitations.  The chosen test cannot be performed readily with exercise (e.g. PET scanning).
  6. 6. METHODS OF DETECTING ISCHEMIA DURING STRESS TESTING 6  Electrocardiography  Echocardiography  Myocardial perfusion imaging  Positron emission tomography  Magnetic resonance imaging
  7. 7. 7 ACC/AHA GUIDELINES (American College of Cardiology/ American Heart Association)
  8. 8. Indications for exercise testing to diagnose obstructive coronary artery disease 8  Adult patients with right bundle branch block or less than 1mm of resting ST depression with an intermediate pretest probabilty CAD on the basis of gender , age and symptoms.
  9. 9. 9
  10. 10. Indications in patients with prior history of coronary heart disease 10  Patients undergoing initial evaluation with suspected or known CAD, including those with complete right bundle branch block or less than 1mm of resting ST depression.  Patients with suspected or known CAD , previously evaluated , now presenting with significant change in clinical status .  Low risk (on pretest probability), unstable angina patients 8 – 12 hours after presentation who have been free of active ischemia or heart failure symptoms.  Intermediate risk (on pre test probability),unstable angina patients 2 to 3 days after presentation who have been free of active ischemic or heart failure symptoms.
  11. 11. Indications in patients with Valvular heart disease 11 1. In Chronic Aortic Regurgitation for assessment of functional capacity and symptomatic responses in patients with a history of equivocal symptoms. 2. Aortic stenosis – role of exercise testing in asymptomatic AS patients , with recommendations that aortic valve replacement be considered in those with exercise induced symptoms or abnormal blood pressure response.
  12. 12. Indications in patients with Valvular heart disease 12  Mitral stenosis – class 1 reommendation for stress echocardiography in patients with MS and discordance between symptoms and stenosis severity.  Threshold values proposed for consideration of intervention: a. Mean transmitral pressure gradient >15 mm Hg during exercise. b. A peak pulmonary artery systolic pressure > 60 mm Hg during exercise.
  13. 13. Indications in patients with Valvular heart disease 13  Mitral regurgitation – In asymptomatic patients with severe MR, exercise stress echo helps identify: a. Patients with subclinical latent LV dysfunction b. Worsening of MR severity c. Marked increase in pulmonary arterial pressure d. Impaired exercise capacity
  14. 14. Indications in patients with Valvular heart disease 14  Prosthetic heart valves – Stress echocardiography used in confirming or excluding the presence of hemodynamically significant prosthetic valve stenosis or Patient prosthesis mismatch (PPM).
  15. 15. RHYTHM DISODERS 15  Evaluation of congenital complete heart block in patients considering increased physical activity or participation in competitive sports .
  16. 16. CONTRAINDICATIONS FOR STRESS TESTING 16  Acute myocardial infarction ( within 2 days )  High risk(on pretest probability) unstable angina  Uncontrolled cardiac arrthymias causing symptoms or hemodynamic compromise  Symptomatic severe aortic stenosis  Acute pulmonary embolus or pulmonary infarction  Acute myocarditis or pericarditis  Acute aortic dissection
  17. 17. EXERCISE PHYSIOLOGY 17 • Patient position – supine or upright. • At rest CO and SV more in supine position than in upright position. • Change from supine to upright position causes , CO as a result of in SV and HR. • The net effect on exercise performance is an approx. 10 % increase exercise time cardiac index, heart rate, and rate pressure product at peak exercise in the upright as compared with the supine position.
  18. 18. 18  The main types of exercise are isotonic or dynamic exercise, isometric or static exercise, and resistive (combined isometric and isotonic) exercise.  Isometric a. Holding a static pushup position; b. Holding a dumbbell in one hand; c. Pushing against an immovable object, such as a wall.
  19. 19. 19  Isotonic a. Weight lifting b. Swimming c. Rock climbing d. Cycling
  20. 20. CARDIOPULMONARY EXERCISE TESTING 20 • Involves measurements of respiratory oxygen uptake (VO2),carbon dioxide production (VCO2), and ventilatory 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. • The VO2 max decreases with age, is usually less in women than in men, and diminished by degree of cardio-vascular 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.
  21. 21. METABOLIC EQUIVALENT 21 • 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. • 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.
  22. 22. METHODS 22  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
  23. 23. SAFETY PRECAUTIONS AND EQUIPMENT 23 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.
  24. 24. TMT ROOM 24
  25. 25. TREADMILL 25
  26. 26. Emergency stop button 26
  27. 27. PRETEST PREPARATION 27 Any history of light headed or fainted while exercising sholud 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
  28. 28. Preparation for exercise testing include the following- 28 1. The subject should be instructed not to eat or smoke atleast 2 hours prior to the test . 2. Unusual physical exertion should be avoided before testing. 3. Specific questioning should determine which drugs are being taken. The labeled medications should be brought along so that medications can be identified and recorded. 4. Because of a greater potential for cardiac events with the sudden cessation of -blockers , they should not be automatically stopped prior to testing but done so gradually under physician guidance, only after consideration of the purpose of the test.
  29. 29. EXERCISE PROTOCOLS 29  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. 30. VARIOUS PROTOCOLS 30  Treadmill protocols a. Bruce b. Cornell c. Balke ware d. Acip e. mAcip f. Naughton g. Weber  Bicycle ergometer
  31. 31. TREADMILL PROTOCOL 31  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 work-load is increased for next stage.  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.
  32. 32. BRUCE PROTOCOL 32
  33. 33. 33
  34. 34. The 6-Minute Walk Test 34  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. 35. MEASUREMENTS 35  ECG  Exercise capacity (METS – metabolic equivalent)  Symptoms  Blood pressure  Heart rate response & recovery
  36. 36. 36  Positive test a. 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 a. Target heart rate (85% of maximal predicted heart for age and sex ) is not achieved .
  37. 37. 37  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.  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.  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
  38. 38. 38  Bruce protocol. lead V4, the exercise electrocardiographic (ECG) result is abnormal early in the test, reaching 0.3mV (3mm) of horizontal ST segment depression at the end of exercise.  The ischemic changes persist for at least 1 minute and 30 seconds into the recovery phase.  The right panel provides a continuous plot of the J point, ST slope, and ST segment displacement at 80msec after the J point (ST level) during exercise and in the recovery phase. Exercise ends at the vertical line at 4.5 minutes (red arrow). The computer trends permit a more precise identification of initial onset and offset of ischemic ST segment depression.  This type of ECG pattern, with early onset of ischemic ST segment depression, reaching more than 3mm of horizontal ST segment displacement and persisting several minutes into the recovery phase, is consistent with a
  39. 39. 39  A 48-year-old man with several atherosclerotic risk factors and a normal resting electrocardiographic (ECG) result, developed marked ST segment elevation (4 mm [arrows]) in leads V2 and V3 with lesser degrees of ST segment elevation in leads V1 and V4 and J point depression with upsloping ST segments in lead II, associated with angina.  This type of ECG pattern is usually associated with a full-thickness, reversible myocardial perfusion defect in the corresponding left ventricular myocardial segments and high-grade intraluminal narrowing at coronary angiography.
  40. 40. 40  False positive : a. In asymptomatic men < 40 years. b. In patients taking cardioactive drugs c. In patients with intraventricular conduction disturbances,ventricul ar hypertrophy , abnormal potassium levels.  False negative : a. In patients with obstructive diseases limited to circumflex coronary artery(lateral portion is not well represented on the surface 12 lead ECG.)
  41. 41. 41  Bruce protocol. The exercise electrocardiographic (ECG) result is not yet abnormal at 8:50 minutes but becomes abnormal at 9:30 minutes (horizontal arrows, right) of a 12-minute exercise test and resolves in the immediate recovery phase.  This ECG pattern in which the ST segment becomes abnormal only at high exercise workloads and returns to baseline in the immediate recovery phase may indicate a false-positive result in an asymptomatic individual without atherosclerotic risk factors.  Vertical arrow indicates termination of exercise.
  42. 42. T WAVE CHANGES 42 Influenced by:  Body position  Respiration  Hyperventilation  Drug Rx  Myocardial ischaemia  Necrosis Pseudonormalisation of T wave:  Usually non-diagnostic and consider ancillary imaging in such cases.
  43. 43. 43  Pseudonormalization of T waves in a 49-year-old man referred for exercise testing.  The resting electrocardiogram in this patient with coronary artery disease shows inferior and anterolateral T wave inversion, an adverse long-term prognosticator.  The patient exercised to 8 METs, reaching a peak heart rate of 142 beats/min and a peak systolic blood pressure of 248 mm Hg. At that point, the test was stopped because of hypertension. During exercise, pseudonormalization of T waves occurs, and it returns to baseline (inverted T wave) in the postexercise phase. Transient conversion of a negative T wave at rest to a positive T wave during exercise is a nonspecific finding in patients without prior myocardial infarction and does not enhance
  44. 44. MAXIMAL WORK CAPACITY 44 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.
  45. 45. BLOOD PRESSURE RESPONSE 45  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 compliant vascular systems.  Failure to increase systolic blood pressure beyond 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 .
  46. 46. HEART RATE RESPONSE 46  Peak HR > 85% of maximal predicted for age  HR recovery >12 bpm (erect)  HR recovery >18 bpm (supine)
  47. 47. 47 Chronotropic incompetence is determined by decreased heart rate sensitivity to the normal increase in sympathetic tone during exercise and is defined as inability to increase heart rate to atleast 85 percent of age predicted maximum. Heart rate reserve is calculated as follows – % HRR used = (HRpeak- HRres) / (220-age-HRres) Abnormal heart rate recovery refers to a relatively slow deceleration of heart rate following exercise cessation. This type of response reflects decreased vagal tone and is associated with increased mortality.
  50. 50. PROGNOSTIC VALUE OF STRESS TESTING 50 Parameters associated with adverse prognosis or multi- vessel disease :  Duration of symptom-limiting exercise <5 METs  Failure to increase sBP ≥120mmHg, or a sustained decreased ≥ 10mmHg, or below rest levels, during progressive exercise  ST segment depression ≥2mm, downsloping ST segment, starting at <5 METs, involving ≥5 leads, persisting ≥5 min into recovery  Exercise-induced ST segment elevation (aVR excluded)  Angina pectoris at low exercise workloads  Reproducible sustained (>30 sec) or symptomatic ventricular tachycardia
  51. 51. LIMITATIONS OF TREADMILL STRESS TEST 51  Non-diagnostic ECG change  Women – false positives  Elderly – more sensitive/less specific  Diabetics – autonomic dysfunction  Hypertension  Inability to exercise  Drugs – digoxin; anti-anginals
  52. 52. NON-CORONARY CAUSES OF ST SEGMENT DEPRESSION 52  Anaemia  Cardiomyopathy  Digoxin  Glucose load  Hyperventilation  Hypokalaemia  Intraventricular conduction disturbance  Mitral valve prolapse  Pre-excitation syndrome  Severe aortic stenosis  Severe hypertension  Severe hypoxia  Severe volume overload (aortic or mitral rgurgitation)  Sudden excessive exercise  Supraventricular tachycardias
  53. 53. LIMITATIONS OF TREADMILL STRESS TEST 53  Sensitivity 68%  Specificity 77%
  54. 54. ANCILLARY TECHNIQUES TO ENHANCE CONTENT 54  Echocardiography  Radionuclide imaging
  56. 56. STRESS ECHOCARDIOGRAPHY 56 Compares pre & post: Regional contractility  Overall systolic function  Volumes  Pressure gradients  Filling pressures  Pulmonary pressures  Valvular function
  58. 58. 58  Dipyridamole or Adenosine can be given to create a coronary "steal" by temporarily increasing flow in nondiseased segments of the coronary vasculature at the expense of diseased segments.  Alternatively, a graded incremental infusion of dobutamine may be administered to increase MVO2
  59. 59. STRESS ECHO - LIMITATIONS 59 Factors which effect image quality: Body habitus  Lung disease  Breast implants
  60. 60. 60
  61. 61. 61
  63. 63. NUCLEAR SPECT IMAGING 63  Radio-tracer injection  Isotopes: A) Thallium-201 B) Technetium 99m (sestamibi)  Myocardial uptake  Photon emission captured by gamma camera  Rest & redistribution phases  Pharmacologic protocols available  Digital presentation
  65. 65. THALLIUM- 201 SCAN 65  Myocardial perfusion problems are separated from non viable myocardium by the fact that thallium eventually washes out of the myocardial cells and back into the circulation .  If a defect detected on initial thallium imaging disappears over a period of 3-24 hours , the area is presumably viable .  A persistent defect suggests a myocardial scar.
  66. 66. TECHNETIUM – 99M(sestamibi) 66  The technetium – 99m(sestamibi) based agents take advantage of the shorter half - life ( 6 hours; thallium 201’s is 73 hours)  This allows for use of a larger dose , which results in higher energy emissions and higher quality images.  Technetium 99m’s higher energy emissions scatter less and are attenuated less by chest wall structures, reducing the number of artifacts.
  67. 67. POSITRON EMISSION TOMOGRAPHY 67  Is a technique using tracers that simultaneously emit two high energy photons .  A circular array of detectors around the patient can detect these simultaneous events and accurately identify their origin in the heart.  This results in improved spatial resolution , compared with SPECT .  PET can be used to assess myocardial perfusion and myocardial metabolic activity separately by using different tracers coupled to different molecules.
  68. 68. 68  Agents used-  Oxygen 15(half time 2mins)  Nitrogen -13(half life 10 mins)  Carbon -11(half time 20 mins)  Flourene -18(half 110 mins)  Because Rubidium – 82 with a half life of 75 seconds , does not reqiure a cyclotron and can be generated on site , it is frequently used with PET scanning , especially for perfusion images.
  71. 71. 71 Reversible inferior wall defect Milder reversible inferior wall defect
  72. 72. 72
  73. 73. 73
  74. 74. 74
  75. 75. LIMITATIONS OF NUCLEAR SPECT IMAGING 75  Time-consuming  Artifacts  Radiation
  76. 76. LIMITATIONS OF NUCLEAR SPECT IMAGING 76 Breast attenuation
  78. 78. LIMITATIONS OF NUCLEAR SPECT IMAGING 78  Risk of iatrogenic malignancy  Consider:  age  gender  background
  79. 79. LIMITATIONS OF NUCLEAR SPECT IMAGING 79 Einstein, A. J. et al. Circulation 2007;116:1290-1305
  80. 80. MRI CARDIAC STRESS TEST 80  Useful for:  Patients unable to exercise  ECG uninterpretable  Unsuitable for DSE  And….  No radiation  But…  Not currently available
  82. 82. CARDIAC STRESS TESTING 82  So….which one to choose?
  84. 84. 84
  85. 85. 85
  86. 86. 86 THANK YOU

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