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General Inpatient Medicine




Infectious Disease








Outpatient & Preventative Medicine


Palliative Care




Pulmonary/Critical Care



Cardiac Stress Testing


  • Rationale: noninvasive means to diagnosis high-grade epicardial stenoses (typically >50%)
    • Does not detect subclinical CAD, ruptured plaque, or viable myocardium
    • Physiologic, not anatomic test – does not actually image coronaries
  • Modalities:
    • Exercise ECG (ETT)
      • Physiology: patient exercises which monitored continuously via ECG, and repolarization changes/symptoms are noted
      • Advantages: widely available, cheap, provides information on functional status
      • Disadvantages: poor performance (sensitivity 68%, specificity 77%), cannot be used with certain baseline ECG abnormalities (LBBB, preexcitation, baseline ST depression, LVH)
      • Based on this, ETT should only be used to gauge a patient’s exercise capacity, and if one is truly interested in ischemia, an imaging modality should be ordered
    • Radionuclide myocardial perfusion imaging (single photon emission computed tomography)
      • Physiology: radiolabeled isotopes (e.g. thallium, technetium-labeled compounds) are injected, and when uptaken by cardiac myocytes, are indicative of perfusion (delivery of tracer), and viability (uptake)
        • Image at rest → absence of uptake typically indicates infarcted myocardium
        • Image under stress → absence of uptake indicates either ischemic or infarcted myocardium
        • Mismatches in uptake are ischemic regions
        • In addition to mismatched perfusion, transient ischemic dilation (marker of multivessel disease) and post-stress LVEF are prognostic factors
      • Advantages: performance (sensitivity 88%, specificity 77%), can measure LV size and EF, vasodilator MPI can be used in setting of existing LBBB
      • Disadvantages: radiation exposure, measures only relative blood flow between regions (can miss “balanced ischemia”), artifacts from breast/diaphragmatic tissue
      • Tracers:
        • Thallium: redistribution properties allow for viability assessment, but given long half-life can only use lower doses, which compromises image quality, and lower energy increases artifact
        • Technetium: does not redistribute, thus allowing for gated imaging and LVEF estimation, but limited ability to evaluate viability
      • Method of stress:
        • If possible, exercise patient, as it provides additional prognostic information:
          • Exercise capacity
          • Exercise BP: drop in BP suggests severe 3-vessel disease
          • Chronotropic competence
          • Post-HR recovery: impaired vagal tone is poor prognostic sign
          • Ventricular ectopy
        • Pharmacologic:
          • Vasodilator to cause relative increase in flow to non-diseased coronary arteries (adenosine, dipyridamole): caution in reactive airway disease
          • Dobutamine: not typically used in MPI, as performance is inferior, but may be indicated in patients with severe COPD or asthma
    • Stress echo
      • Physiology: regional ischemia provokes by stress is evidenced by wall motion abnormalities
      • Advantages: performance similar to MPI (sensitivity 76%, specificity 88%), provides structural information, cheaper and faster than MPI, no radiation, dobutamine stress can be used in setting of existing LBBB
      • Disadvantages: subjective interpretation
      • Method of stress:
        • As above, exercise if possible
        • Pharmacologic
          • Dobutamine: increases HR/contractility and myocardial oxygen demand, thus inducing wall motion abnormalities in ischemic regions
          • Vasodilators: not used, as sensitivity is inferior
  • Impact of medications:
    • Given their anti-ischemic effects, beta blockers, calcium channel blockers, and nitrates can result in false negative results and should be held for 4-5 half lives
    • Beta blockers and calcium channel blockers can also prevent peak HR from being reached in exercise tests
    • Caffeine can interfere with pharmacologic MPI (adenosine receptor antagonist)


(Christopher Woo MD, 4/19/11)