Myocardial infarction (PYP imaging)

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Myocardial infarction(PYP imaging)
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Anatomy

• Myocardial Infarction
• Left Ventricle
• Areas affected
• Anterior wall and septum
• Inferior wall and posterior third of septum
• Right ventricle
• involved in 25 to 50 of pt with inferior wall
  infarction

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Classification of infarction

• Thickness of necrosis
• Transmural or Q wave- full thickness myocardial
  wall
• Nontransmural, non-Q wave- less than full
  thickness of wall
• Subendocardial infarction- less than one-half
  thickness of wall.

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Causes for Infarction

• Coronary thrombosis
• Present in half of infarcts
• Intramural hemorrhage 40
• Most frequent arteries
• LAD (56)
• Right coronary (25)
• Circumflex (14)
• Tans mural infarction
• Coronary artery spasm
• Some primary cause of infarction

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Physiology

• Myocardial Infarction
• Intramural infarctions
• Reduced blood flow to center of infarction
  endocardium

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• Technitium 99m pyrophosphate
• Determinants of Uptake in infarction.
• Blood Flow
• Tc 99m PYP must reach damaged tissue to be taken
  up.
• Highest concentration of 99mTc pyrophosphate
  occurs when local blood flow reduced by 20 to
  40
• Flow reduces, concentration falls in regions of
  severely reduced flow
• Concentration of pyrophosphate greater in
  epicardial than endocardial segments
• PYP ratio of 18 to 20 infarcted tissue/ normal
  myocardium possible.

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• Extraction
• Extraction fraction
• Total amount tracer extracted decreases at low
  flow.
• Calcium influx
• Key role in T99m PYP binding acute infarction
• Intracellular calcium phosphate and is present in
  3 forms in cell
• Amorphous uniformly
• Crystalline
• Hydroxyapatite- mitochondria
• PYP binds to both amorphous and hydroxyapatite
  deposits
• 99mTc PYP concentration parallels calcium
  phosphate concentration.

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• Necrotic Tissue
• Pyrophosphate
• Acutely necrotic myocardium
• Other Diseases unstable angina, multifocal
  lesions of necrosis and myocytolysis
• Uptake in ventricular aneurysm

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Timing

• Earliest uptake 4 hours after coronary artery
  occulsion
• Peak uptake _at_ 48 hours
• Diminish over next 5 to 7 days
• Time course varies depending on
• Size of infarction
• Extension of infarction

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CAD
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CAD
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MI
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Myocardial Infarction
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PYP