Stress testing Stress tests Performed on patients with

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Stress testing
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Stress tests

• Performed on patients with intermediate pretest
  probability of coronary artery disease.
• In patients with low pre-test probability, a
  stress tests does not help to further clarify
  diagnosis or prognosis.
• In patients with very high pre-test probability
  of CAD, a cardiac catheterization provides
  definitive information about coronary anatomy and
  the opportunity for intervention.
• Provides diagnosis but more importantly prognosis.

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Bayesian Theory
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Source of stress

• Exercise
• Pharmacologic
• Adenosine
• Dobutamine
• Pharmacologic stress tests will be addressed in
  another lecture.

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Detection of Ischemia

• EKG
• Nuclear perfusion imaging
• Echocardiography
• Later two methods will be addressed in another
  lecture.

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Exercise

• Prefer method of stress
• Reproduce symptoms in real-life context.
• The amount of exercise one can perform provides a
  lot of prognostic information.
• Bruce, modified Bruce (3 minutes of easy time
  Bruce), Naughton/Gervino protocols.
• Usually, ask the patient to exercise close to
  their maximal effort. Would like them to reach
  85 MPHR or RPP gt20,000. Stop if there are very
  high risk features (hemodynamic compromise,
  signs/symptoms of severe ischemia, serious
  arrythmias)

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Fitness strong predictor of survival

• 6213 men referred for exercise testing who were
  followed for a mean of 6.2 years., M, Froelicher,
  V, et al, N Engl J Med 2002 346793
• In both subject with and without cardiovascular
  disease, exercise capacity strongly predicts
  survival (in fact, more than the presence or
  absence of CVD).
• For each one MET increase in exercise capacity
  there was a 12 percent improvement in survival.

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Why not always exercise the patient?

• Often, patients cannot exercise to the workload
  necessary for a diagnostic test due to arthritis,
  PVD, poor functional statusetc.
• Sometimes useful to assess just how poor is the
  functional status.
• Exercise stress test is contraindicated
• Within 2 days of myocardial infarction or high
  risk unstable angina (known ST depressionetc).
• Decompensated heart failure, acute PE, known or
  suspected dissecting aneurysm.
• Severe stenotic valvular disease relatively
  contraindicated.

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Hemodynamic response

• With exercise, both the blood pressure and heart
  rate goes up.
• Failure to increase the SBP gt120, sustained
  decrease gt10mmHg or decrease in BP below standing
  value during exercise is a high risk feature
• Usually reflects LMCA, 3vd, or severe AS where
  cardiac output declines with stress

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Hemodynamic response

• For diagnosis of CAD, would like the patient to
  reach 85 of maximal predicted heart rate or rate
  pressure product of gt20,000
• Maximal predicted HR (220-age)
• Rate pressure product (BP x HR)
• Should medicines (beta-blockersetc.) be withheld
  prior to the test?
• For the diagnosis of CAD, yes
• For the assessment of the efficacy of medical
  mngt, no need to withhold drugs.

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EKG response

• ST depression (0.8ms after the J point- usually
  read on 3 consecutive beats)
• Shape (upsloping, flat, down-sloping)
• Amount
• Positive test considered 1mm horizontal or
  down-sloping depression in 2 neighboring leads.
• Location does not localize ischemia.
• ST elevation-
• In leads with prior q waves, not a concern
• In leads with no q waves- ACS, sent to cath lab,
  location predicts ischemia. Uncommon- 1

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EKG response

• Can also develop arrythmias-
• VT can develops in setting of ischemia.
• Supraventricular tachycardia
• Heart block in the case of infranodal conduction
  disease.
• The heart rhythm abnormalities can sometimes
  explain the patients symptoms.

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Diagnosis and prognosis

• Sensitivity and specificity in patients selected
  for angiography is 68 and 77, respectively
• referral bias exaggerate false positives,
  eliminates false negatives (falsely improves
  sensitivity and worsens specificity)
• Duke Treadmill score
• Exercise time- (5x ST deviation)- 4x treadmill
  angina index)
• Angina index- 0 none, 1 typical angina, 2
  angina reason patient stopped exercising.

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Duke Treadmill Score

• Low risk- gt5
• Intermediate- 4 to -10
• High risk- lt-11
• The five year survival was
• 65 percent in high risk patients
• 90 percent in moderate risk patients
• over 97 percent in low risk patients
• A study with 70 men
• Shaw, LJ, Peterson, ED, Shaw, LK, et al.
  Circulation 1998 981622

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Some limitations of EKG

• Uninterpretable in the setting of LBBB or IVCD.
• Accuracy goes down in the setting of LVH or
  otherwise abnormal resting EKG.
• Less accurate in women compared to men (more
  false positives)

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Potential complications

• In general, exercise stress test is a very safe
  test.
• 1 cardiac arrest per 565,000 person/hour of
  exercise, about 10 fold higher in the population
  with CAD (still very low).

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How to interpret a stress test?

• Look for
• Duration of exercise
• High risk hemodynamic features- fall in blood
  pressureetc
• Symptoms
• Heart rate and blood pressure response (HR 85
  MPHR and RPP gt20000)
• EKG results- presence of ischemic changes, ectopy
• Can calculate Duke treadmill score

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Case 1

• 53 year old man with hyperlipidemia was referred
  to an exercise stress test for chest pain. He
  exercised 13 minutes of the Bruce protocol,
  developing mild chest pain at minute 11, EKG
  shows 1mm ST horizontal ST depression that
  resolved 5 minutes after recovery. What do you
  think of is his
• Diagnosis?
• Prognosis?

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Case 2

• 74 year old woman with diabetes, hypertension,
  and hyperlipidemia who exercised for 2 minutes of
  the Bruce protocol and developed severe, crushing
  chest pain. EKG monitoring shows 4mm downsloping
  ST depression and intermittent NVST. What is her
• Diagnosis?
• Prognosis?