Treadmill Stress Testing for the Primary Care Physician

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Treadmill Stress Testing for the Primary Care
Physician

• Francis G. OConnor, MD,MPH,FACSM
• Medical Director, Human Performance Lab
• Associate Professor of Family Medicine
• Uniformed Services University of the Health
  Sciences

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Objectives

• Review essential Exercise Stress Test (EST)
  background, resources and terminology.
• Describe the performance of the EST.
• Describe common normal and abnormal responses to
  exercise testing.
• Discuss interpretation of the EST.

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Exercise Stress Test Essentials
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Exercise Stress Testing and Family Physicians

• Frequency of Utilization Estimated that 13 of
  family physicians perform and interpret
  treadmills in their office.
• American Academy of Family Physicians. Facts
  about Family Practice. Kansas City, Mo American
  Academy of Family Physicians 1998.  
• Credentialing Recent guidelines suggest that a
  physician acquire 50 exercise stress tests to
  qualify for privileges, and should perform
  atleast 25/yr to maintain clinical competency.
• Schlant et al Clinical competence in exercise
  testing a statement for physicians from the
  ACP/ACC/AHA task force on clinical privileges in
  cardiology. Circulation 1990821884-1888.

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Safety and Exercise Stress Testing

• The risk of death during or immediately after an
  exercise test is less than or equal to 0.01.
• The risk of an acute MI during or immediately
  after an exercise test is less than or equal to
  0.04.
• The risk of a complication requiring
  hospitalization is less than or equal to 0.2.

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References

• ACC/AHAQ Practice Guidelines
• Fletcher GF et al Exercise Standards a
  statement for healthcare professionals from the
  American Heart Association Writing Group Special
  Report. Circulation 199591580-615.
• ACC/AHA Guidelines for Exercise Testing. A Report
  of the ACC/AHA Task Force on Practice Guidelines.
  JACC Vol. 30 (3)260-311.
• Gibbons RJ et al ACC/AHA 2002 guideline update
  for exercise testing a report of the American
  College of Cardiology/American heart Association
  Task Force on Practice Guidelines 2002.
  www.acc.org/clinical/guidelines
• ACSM References
• ACSMs Guidelines for Exercise Testing and
  Prescription, Seventh Edition.
• ACSMs Resource Manual for Exercise Testing and
  Prescription, Seventh Edition.

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The Electrocardiogram

• PR segment isoelectric line from which the J
  point and ST segment are measured from rest. PQ
  junction is the point of reference.
• J Point point that distinguishes the QRS complex
  from the ST segment measuring point for ST
  segment depression.
• ST segment ST segment is measured relative to
  the PQ junction, 80 ms from the J point, or 60 ms
  in rates over 145 bpm.

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Exercise Physiology

• METs oxygen uptake is conveniently expressed in
  METs 3.5 ml O2/kg/min
• 1 METrest 5 METADLs10 METs medical therapy
  equivalent to CABG 18 METSelite athlete.
• Myocardial Oxygen Consumption
• Double product of HRxSBP correlates with
  myocardial oxygen consumption.
• VO2 MAX
• Fick Equation VO2max (HRmax x SV max) x
  (CaO2max CvO2max)
• Gold standard for aerobic fitness.

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The Fick Equation
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Performance of the Exercise Stress Test
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Equipment and Protocols

• Equipment
• Treadmill
• Cycle
• Arm Ergometery
• Monitor and EKG Recorder
• Thallium, Echocardiography
• Protocol
• Maximal
• Bruce Protocol is the most commonly used test.
  Vigorous with the first stage commencing at 5
  METs. Speed and grade is increased every three
  months. Generally symptom-limited adequate tests
  reach 85 of MPHR.
• Sub-Maximal
• Tests that involve termination at a
  pre-determined heart rate. Post-MI patients
  generally are set at 60 of MPHR, 5 METs or 120
  bpm.

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Treadmill Protocols
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Indications

• ACC/AHA Guidelines for Exercise Testing
• Class I general consensus/evidence that testing
  is justified.
• Class II divergence of opinion on utility. IIa
  in favor IIb less evidence.
• Class III agreement that testing is not
  warranted.

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Indications Diagnose Obstructive CAD

• Class I
• Adult patients (including those with RBBB and 1mm
  resting ST depression) with an intermediate
  pre-test probability of disease.
• Class IIa
• Patients with vasospastic angina.
• Class IIb
• Patients with a high or low pre-test probability
  of disease.
• Patients with less than 1mm ST depression and
  taking digoxin.
• Patients with LVH by voltage and less than 1mm of
  baseline ST depression.
• Class III
• WPW paced rhythm gt1mm ST depression LBBB.

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Pre-Test Probability of Disease
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ACSM Recommendations for Exercise Testing Prior
to Exercise Participation

• CAD Risk Factors
• FH MI in 1st degree male relative before 55
  female before 65.
• Smoker or quit within 6 months.
• Hypertension
• Hypercholesterolemia TCHOL gt 200 HDL lt35 LDL gt
  130.
• Impaired fasting glucose gt110.
• Obesity BMI gt30.
• Sedentary
• HDL gt60 is a negative risk factor.

• CAD Signs/Symptoms
• Pain in the chest, neck, jaw, arms that may be
  due to ischemia
• SOB at rest or exertion
• Dizziness or syncope
• Orthopnea/PND
• Ankle edema
• Claudication
• Known heart murmur
• Unusual fatigue or SOB with usual activities

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ACSM Recommendations for Exercise Testing Prior
to Exercise Participation

• Initial ACSM Risk Stratification
• Low Risk younger individuals who are
  asymptomatic and have no more than one risk
  factor.
• Moderate Risk older or those who meet the
  threshold for two or more risk factors.
• High Risk individual with signs or symptoms of
  CAD, or known cardiovascular, pulmonary, or
  metabolic disease
• Old versus Young
• Men lt 45 years of age Women lt 55.
• Moderate versus Vigorous Exercise
• Moderate 3-6 METs, 40 to 60 maximal oxygen
  uptake.
• Vigorous gt6 METs, or 60 maximal oxygen uptake.

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ACSM Recommendations for Exercise Testing Prior
to Exercise Participation
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Contraindications

• Absolute
• Acute myocardial infarction (within 2d)
• High risk unstable angina
• Uncontrolled arrhythmias causing symptoms or
  hemodynamic compromise
• Symptomatic severe aortic stenosis
• Acute PE, myocarditis or pericarditis
• Acute aortic dissection

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Contraindications

• Relative
• Left main coronary stenosis
• Moderate stenotic valvular heart disease
• Electrolyte Abnormalities
• Severe arterial hypertension (200/110)
• Tachy/Bradyarrhythmias
• Hypertrophic cardiomyopathy
• Mental or physical impairment leading to
  inability to exercise adequately
• High degree AV block

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Special Considerations

• Medications
• Beta blockers blunt HR response short acting
  held the day of the test long acting held two
  days.
• Calcium channel blockers delay ischemia,
  decreasing sensitivity of the test.
• Digoxin produces abnormal ST depression with
  exercise.
• Diuretics may cause ST depression with
  hypokalemia.
• Conduction Disturbances
• High degree AV block (Mobitz II and third degree
  block) should not be tested.
• LBBB and WPW preclude interpretation of ischemia
  and should not be tested.
• Special Clinical Situations
• Severe arthritis/Obesity consider pharmacologic
  stress testing.
• Hypertension dont test 200/120
• Q waves in post MI pts, ST elevation can
  indicate a hypokinetic ventricle.

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Physician Responsibilities During the Test

• Patient Evaluation and Clearance
• Careful history of symptoms and past medical
  history typical vs. atypical.
• Risk factors
• Family history
• Informed Consent
• Physical Examination
• Vital signs
• Cardiovascular murmurs, gallops
• Lungs
• Selection of Protocol
• Maximal vs. Sub-Maximal
• Treadmill vs. Cycle

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Performing the Test

• Preparing the Patient
• Monitoring the Patient
• Terminating the Test
• Recovery of the Patient

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Preparing the Patient

• Instructions
• No eating two hours before test no consumption
  of alcohol, caffeine, or tobacco three hrs
  before.
• Comfortable clothing.
• Medications determined by functional vs.
  diagnostic testing.
• Skin Preparation
• Hair shaved abrasive rub tap test.
• Appropriate Blood Pressure cuff.
• Consent.

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Preparing the Patient

• Pre-Test Checklist
• Equipment and safety check
• Informed Consent
• Pre-test history and physical examination
• Electrode skin preparation
• Resting ECG reviewed
• Standing ECG and BP
• Patient Demonstration
• Patient Questions

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Monitoring the Patient

• Pre-Test
• 12 lead ECG supine and standing.
• BP supine and standing.
• Exercise
• 12 lead last 15 sec of each stage.
• BP and RPE at the end of each stage.
• Post-Test
• 12 lead ECG immediately after exercise, then
  every 1 to 2 minutes until return to baseline.
• BP immediately after exercise, then every 1 to 2
  minutes until return to baseline.
• Follow symptoms.

• Borg RPE Scale
• 6
• 7 Very, very light
• 8
• 9 Very light
• 10
• 11 Fairly light
• 12
• 13 Somewhat hard
• 14
• 15 Hard
• 16
• 17 Very hard
• 18
• 19 Very, very hard
• 20

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Terminating the Test

• All treadmill stress tests should be completed to
  a symptom-limited endpoint, if possible.
• 85 of maximal predicted heart rate is required
  to identify a test as adequate.

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Indications for Test Termination

• Absolute
• Drop in SBP of gt10 mmHg from baseline, despite
  increased workload, when accompanied by other
  ischemia
• Moderate to severe angina
• Increasing ataxia, dizziness, or pre-syncope
• Signs of poor perfusion
• Technical difficulties
• Subjects desire
• Sustained Vtach
• ST elevation in leads without diagnostic Q waves

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Indications for Test Termination

• Relative
• Drop in SBP of gt10 mmHg from baseline, despite
  increased workload
• ST depression gt2mm from baseline
• Multifocal PVCs, triplets, SVT, heart block
• Fatigue, shortness of breath, wheezing, leg
  cramps
• Bundle branch block
• Increasing chest pain
• Hypertensive response

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Recovery of the Patient

• Have the patient lie down and continuously
  observe.
• Auscultate for abnormal heart and lung sounds.
• Monitor until clinically stable and
  electrocardiogram has returned to normal.
• ECG changes in recovery just as ominous as those
  occurring during exercise.

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Common Normal Responses to Exercise Testing

• Symptoms
• Typical anginal symptoms can be produced by
  testing and increase the prognostic value of a
  test.
• Symptoms, however, do not define a positive test,
  and define a test suggestive of ischemia.
• Opportunity for anginal threshold determination
  and use of Borg Scale for exercise prescription.

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Electrocardiographic Responses to Exercise

• P wave
• Superimposition of P and T p wave may increase
  in inferior leads.
• PR segment
• Shortens and downslopes in the inferior leads.
• QRS complex
• Increases in septal q waves slight decreases in
  R wave amplitude minimal shortening of interval.
• J junction
• Decreases with exercise in subjects with resting
  J junction elevation, this normalizes to
  baseline.
• ST segment
• Demonstrates positive upslope that returns to
  baseline by 80ms.
• T wave
• initially a gradual decrease in amplitude.
• QT interval
• Rate-related shortening.

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Heart Rate

• Normal Heart Rate Response
• Increase in HR as a result of vagal tone
  withdrawal.
• Standard deviation for peak HR determination is
  15 BPM.
• Chronotropic Incompetence
• Peak heart rate less than 120 BPM.
• Failure to achieve 85 of age-predicted maximum.
• Heart Rate Recovery

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Heart Rate Recovery and Treadmill Exercise Score
as Predictors of Mortality in Patients Referred
for Exercise ECG Nishime EO, et al JAMA,
September 20, 2000.Vo 284, No 11, 2000.
Heart Rate Recovery

• Following the GXT, patients walked for 2 minutes
  at 1.5 mph and at a grade of 2.5.
• Heart rate recovery was the difference in heart
  rate at peak exercise and one minute into
  recovery 12/min or less was considered abnormal.
• 9454 patients were followed for a median of 5
  years 20 had abnormal heart rate recovery
  they represented 8 of deaths vs. 2 hazard
  ratio of 4.16.
• Heart rate recovery is an independent predictor
  of mortality.

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Blood Pressure

• Normal
• Systolic increases during exercise returns to
  baseline by five to six minutes in recovery.
• Hypotensive Response to Exercise
• A drop in BP to baseline levels during exercise
  poor prognosis.
• Hypertensive Response to Exercise
• Systolic greater than 220mmHg, or rise in
  diastolic of gt 10mmHg, or Stage II age predicted
  95 DBP.
• Singh et al BP response during treadmill testing
  as a risk factor for new-onset hypertension.
  Circulation. 1999991831-1836.
• Blood Pressure in Recovery
• 3 Minute Systolic BP Ratio SBP 3 min/ SBP Peak gt
  0.91 is abnormal.
• Taylor et al Postexercise systolic BP response
  clinical application to the assessment of
  ischemic heart disease. American Family
  Physician. Vol 58(5).

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Common Abnormal Responses to Exercise Stress
Testing
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ST Depression and Elevation

• Measurement
• Three Continuous beats
• Baseline is the junction of downsloping PR and
  QRS complex
• Depression
• If ST elevated at rest c/w early repolarization,
  measure from baseline.
• If ST depressed at rest, measure deviation from
  the baseline depression.
• Elevation
• ST elevation is c/w transmural ischemia, however
  needs to be classified by whether it occurs over
  Q waves.
• Over Q waves ST elevation may occur in the
  presence of prior infarct, and may or may not
  represent ischemia.

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Common Abnormal Responses

• Isolated Inferior Depression
• Atrial repolarization has been demonstrated to
  cause J point depression in the inferior leads.
• Isolated inferior lead ST depression is
  frequently a false positive.
• ST Elevation
• ST segment elevation in the absence of Q waves
  usually indicates transmural ischemia.
• Exercise-Induced Bundle Branch Block
• Ischemia can be interpreted in RBBB, but not
  LBBB.
• The Stress test should be stopped and the patient
  should have further evaluation for structural
  heart disease.
• Exercise-Induced Hypotension
• Always serious symptoms that warrant further
  evaluation for structural heart disease.

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Common Abnormal Responses

• Exercise-Induced Arrhythmias
• Simple PVCs not uncommon low grade ectopy,
  unifocal, and infrequent PVCs during exercise do
  not increase risk.
• Complex Arrhythmias complex arrhythmias at low
  levels, in particular when associated with
  ischemia, warrant further evaluation.
• Ventricular Tachycardia require termination of
  the test, with prognosis based upon status of
  underlying heart disease.
• Paroxysmal Atrial Tachycardia/PSVT treated as
  patients who develop PSVT without exercise.

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Determining Myocardial Ischemia

• Suggestive of Myocardial Ischemia
• Horizontal or downsloping ST depression 0.5 1.0
• ST elevation 0.5 1.0
• Upsloping ST depression gt.7 lt1.5
• Exercise-induced hypotension
• Chest pain that seems like angina
• High grade ventricular ectopy
• A new third heart sound
• Inconclusive
• Patient does not achieve 85 of maximum HR and
  has no ischemia.

• Diagnostic of Myocardial Ischemia
• Horizontal or downsloping ST depression gt1.0 mm
  at 60ms past the J point
• ST elevation gt1.0 mm at 60ms past the J point
• Upsloping ST depression gt1.5 at 80 ms past the J
  point
• Negative for Myocardial Ischemia
• Patient has exercised to atleast 85 of maximal
  predicted heart rate and none of the above are
  present.

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The Final Report

• First Paragraph (General Summary)
• Pts age, indication for testing, cardiac
  medications and protocol.
• Baseline heart rate, BP and resting ECG findings.
• Peak exercise data, BP, HR, peak METs, RPE and
  reason for stopping.
• Description of abnormalities in ECG response,
  hemodynamics, dysrhythmias, or symptoms
• Second Paragraph (Assessment)
• Presence or absence of ischemia
• Normal or abnormal HR/BP response
• Presence of dysrhythmias
• Presence of symptoms
• Maximal aerobic capacity

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Interpretation of the Exercise Stress Test
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Bayes Theorem

• Theory of Conditional Probability
• The predictive value of a test depends upon the
  descriptors of the test accuracy as well as the
  prevalence of disease in the population being
  tested.
• Patients with an abnormal test and a low pre-test
  probability of disease are at risk for a
  false-positive.
• Patients with a normal test and a high pre-test
  probability of disease are at risk for a false
  negative test.
• The treadmill is thought to have a sensitivity of
  70 and a specificity of 80 for diagnosing CAD.

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Pre-Test and Post-Test Probability

• Diamond and Forrester Curves

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Common Errors

• False-Positive Tests
• Pre-existing abnormal ECG
• Cardiac hypertrophy
• WPW and other conduction abnormalities
• Drugs
• Cardiomyopathy
• Hypokalemia
• Vasoregulatory abnormalities
• Mitral valve prolapse
• Pericardial disorders
• Pectus excavatum
• Coronary spasm
• Anemia
• Female gender
• Observer error

• False-Negative Tests
• Failure to reach an adequate workload
• Insufficient number of leads
• Single vessel disease
• Good collateral circulation
• Technical or observer error

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Predicting Severity of Disease

• Electrocardiographic Responses
• ST depression gt 2.5mm
• ST depression beginning at 5 METs or less
• Downsloping ST depression or ST elevation
• ST depression lasting more than 8 minutes into
  recovery
• Serious dysrhythmias at a low heart rate
• ST depression in more than 5 leads
• Nonelectrocardiographic Response
• Chronotropic incompetence
• Exercise-induced hypotension
• Inability to exercise past 5 METs

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Determining Prognosis

• Duke Treadmill Score
• Exercise Treadmill Score Minutes of Exercise
  (5 x max ST depression) (4 x Anginal Index)
• Anginal Index
• 0 no angina
• 1 typical
• 2 terminated test secondary to angina.
• Scoring
• gt5 good prognosis with 5 yr survival of 97
• -10 to 4 intermediate prognosis
• -11 lt - poor prognosis 5 yr survival of 72

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Duke Treadmill Score Nomogram
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Function is Everything!
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Summary