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Strongly positive exercise stress test is equivalent to a brief episode of unstable angina

Posted Jan 20 2010 9:25am

Exercise stress testing(EST)  is one of the common investigation modality in the evaluation of CAD.he indication for EST  generally fall into two broad categories.

  • Diagnostic in patients suspected to have CAD
  • Prognostic evaluation in patients with established CAD .9Many times after a coronary angiogram)

Currently there is a major shift in our thinking,  patients with  classical angina  may undergo coronary angiogram  directly .This is understandable as the stress test  has little to   improve  diagnostic  sensitivity and specificity in patents with clinically obvious CAD.

So , it is now becoming clear , the diagnostic  value  is  increasingly  restricted in the evaluation of  o atypical chest pain .

What is a strongly positive response ?

  • Gross ST segment depression > 2-3mm
  • Occurring in stage one
  • Fall in blood pressure
  • Prolonged angina into recovery

What is the angiographic  correlates of strongly positive EST?

  • Critical left main disease
  • Near total proximal LAD /LCX
  • A severely compromised bifurcation lesion

Morphological correlation

  • These patients  often have eccentric lesions with irregular margins.
  • unstable  lesions
  • Lack collaterals

What is the effect of vigorous  excercise on a critical flow limiting lesion ?

The shear stress over the plaque  increases  with  exercise  and  the  transcoronary gradient can reach a theoretical 60-90mmhg .One can imagine the what this stress can do to the  unstable lipid core .This is the reason unstable angina is an absolute contraindication  to EST.

What does a strongly positive EST imply for the patient ?

  • It indicates he needs urgent CAG and  most likely an immediate revascularisation.
  • Often , these patients have prolonged angina , and mandates admission in a coronary care unit.
  • there has been many incidence of ACS in these  patients  within 24hours of EST.
  • Lives have been lost  on their  way back    ,   as  these patients are sent home , as EST is a  OP procedure .

Final message

  1. It need to be realised a strongly positive response to EST  could  be a  clinical equivalent of  unstable angina .
  2. The common response  from a   physician or cardiologist    after witnessing  a  gross ST depression to EST  would be   “Had  I known this  I would have sent him straight into cathlab instead of EST ”
  3. If only , we give little ear to our patient’s  history we can pick the high risk clue in 9 out of 10 cases !
  4. It can be argued ,  a strongly   positive  EST  by itself  is  “A  clinical diagnostic  failure”  ,   ie  failure  of the physician  to recognise  the likely hood of strongly  positive EST ie a left main disease.
  5. These patients  should never be sent home immediately  after the EST .This is fraught with a risk SCD
  6. Most of them will require observation in step down unit for 24 hours  and if feasible they should be posted for coronary angiogram in the earliest available slot.
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