Difference between revisions of "Cardiac viability"

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*Distinguishes hibernating myocardium from scar (i.e. candidates for revascularization)
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Distinguishes hibernating myocardium from scar (i.e. candidates for revascularization)
*Rest-Rest TI 201 with radiatracter activity on delays
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 +
Matched defect on perfusion and viability indicates non-viable myocardium
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 +
 
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Mismatched defect (no perfusion, but positive viability) indicates viable myocardium
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Reverse mismatched defect (perfusion, but no viability) can be seen with stunning, LBBB or pacer
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== F18 FDG PET ==
 +
*Myocytes prefer fatty acids in a fasting state when glucose and insulin are low
 +
**This is why a fasting protocol (6-12 hrs) is preferred when evaluating for cardiac sarcoid
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*Glucose Loading
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**50 mg of oral glucose
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**Measure blood glucose and administer sliding scale insulin after 1 hour
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**High insulin state will make myocytes prefer glucose
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== Thallium ==
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Rest-Rest TI 201 with radiotracer activity on delays
 
:Highest first-pass extraction fraction of any commonly used perfusion tracer, extraction efficiency 90%
 
:Highest first-pass extraction fraction of any commonly used perfusion tracer, extraction efficiency 90%
 
:K analog tha uses ATPase NA-K pump
 
:K analog tha uses ATPase NA-K pump
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::Ischemic myocardium will fill in on delayed imaging
 
::Ischemic myocardium will fill in on delayed imaging
 
*Often performed after Stress-Rest demonstrates fixed defect
 
*Often performed after Stress-Rest demonstrates fixed defect
*F18 FDG-PET is also used
 
  
  

Latest revision as of 14:14, 11 July 2011

Distinguishes hibernating myocardium from scar (i.e. candidates for revascularization)

Matched defect on perfusion and viability indicates non-viable myocardium


Mismatched defect (no perfusion, but positive viability) indicates viable myocardium


Reverse mismatched defect (perfusion, but no viability) can be seen with stunning, LBBB or pacer


F18 FDG PET

  • Myocytes prefer fatty acids in a fasting state when glucose and insulin are low
    • This is why a fasting protocol (6-12 hrs) is preferred when evaluating for cardiac sarcoid
  • Glucose Loading
    • 50 mg of oral glucose
    • Measure blood glucose and administer sliding scale insulin after 1 hour
    • High insulin state will make myocytes prefer glucose

Thallium

Rest-Rest TI 201 with radiotracer activity on delays

Highest first-pass extraction fraction of any commonly used perfusion tracer, extraction efficiency 90%
K analog tha uses ATPase NA-K pump
Undergoes redistribution - as TI clears from myocardium, it's replaced by circulating TI
Cold defects on early images are due to decreased flow
Ischemic myocardium will fill in on delayed imaging
  • Often performed after Stress-Rest demonstrates fixed defect


Stunned Myocardium

  • Reperfused myocardium after occlusion
  • Normal blood flow, but decreased contractility, will regain function in a few weeks


Hibernating Myocardium

  • Chronic myocardial ischemia with reduction of blood flow and contractility
  • Although myocardium is viable
  • Perfusion defect will be mild or moderate, severe fixed defect compatible with infarct