Stress Echocardiography: A Brief Overview and Some Cases

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Stress Echocardiography A Brief Overview and
Some Cases

• Manitoba College of Family Physicians Annual
  Scientific Assembly April 30, 2009
• Amrit Malik MD FRCPC
• Assistant Professor
• Echocardiography and Heart Failure
• Dept of Cardiology

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• Cardiac ultrasound was first established in the
  1960s
• used to evaluate valvular and pericardial disease
• Once 2D imaging platforms were developed, it was
  used to detect CAD

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• Initially detected only infarcts and LV function
• A patient developed spontaneous angina during a
  study, and developed new wall motion
  abnormalities
• observation came at a time when other modalities
  (ECG alone) demonstrated shortcomings

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• The impetus for development of stress echo was
  the drive to gain an equivalent degree of
  clinical relevance (and superiority) over other
  competing techniques for detection and prognosis
  of CAD

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• initial studies were largely feasibility studies
• imaging was limited to 30 degree scanners with
  limited gray scale resolution and low frame rates
• This, combined with imaging the heart during
  exercise presented obstacles

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• The pioneers included investigators from Indiana
  University Echo lab who began studying patients
  during supine bicycle exercise
• In a landmark article in 1979 Wann et al
  demonstrated the feasibility of identifying
  exercise induced wall motion abnormalities with
  2D echo and their resolution after successful CABG

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• one of the first proposed solution was to image
  immediately post treadmill exercise
• This was a natural add-on to the usual stress
  test which was the traditional method of
  evaluating CAD

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• Images were recorded on videotape, but could only
  be viewed sequentially, not side by side for
  direct pre and post exercise comparison.
• Because of this, stress echo took a backseat
  until the mid 1980s

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• Offline digital acquisition systems became
  available, and images were compared side by side
• One of the first studies (1986) showed stress
  echo as a superior tool when added to GXT with a
  non diagnostic ECG

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• Today we know that any imaging modality lends an
  improved sens and spec to the standard GXT, no
  matter what the ECG response is to exercise

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• technical difficulties of imaging pts immediately
  post exercise, other non exercise forms of stress
  were introduced
• Hand grip
• Dobutamine (/- atropine)
• Dipyridamole (/- atropine)

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• standardized protocols for stress echo with
  images acquired at baseline, and varying stages
  or stress and recovery
• Exercise Stress (treadmill, bicycle, handgrip)
• Pharmacologic Stress

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Dobutamine Stress Echo

• Baseline images are acquired
• Dobutamine is infused at 10, 20, 30, and 40
  ug/kg/min
• Addition of atropine at peak dose to achieve THR
• Inducibility of new wall motion abnormalities

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Detection of CAD

• Several studies published
• Majority suggest a higher sensitivity for
  detecting pts with multivessel disease compared
  to single vessel disease
• Bicycle exercise (which allows imaging at peak
  exercise) increases sensitivity

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• Thresholds of stenoses are between 50 and 70
  luminal narrowing on angiography
• In general stress echo has a slightly higher
  specificity than radionuclide imaging which is
  slightly more sensitive for detection of CAD

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Assessing Prognosis

• Prognostic implications of a normal exercise echo
  and perfusion study were compared in a
  meta-analysis of available studies between 1990
  and 2005
• NPV for the hard end points of MI and cardiac
  death of 98.8 for perfusion imaging, and 98.4
  for echo imaging during 33-36 month f/up

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Viability

• The ability of dysfunctional myocardium to
  recover either spontaneously or after
  revascularization is known as viability
• Suggests the potential for functional improvement
  implying either stunned or hibernating myocardium

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• Using DSE to assess augmentation of contractility
  in response to beta adrenergic stimulation
• A biphasic response (improvement at los dose with
  worsening at higher doses of dobutamine) was most
  predictive of functional recovery
• Sens for predicting recovery 74-88
• Spec 73-90
• DSE is less sensitive, but more specific than
  radionuclide imaging

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39 yo female with CP
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45 yo male with IDCM
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68 yo male with CDM
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