Myocardial stunning is transient systolic ventricular dysfunction that occurs in the acute post-ischemic period and may persist for several weeks even in the face of normal perfusion.
Myocardial hibernation refers to dysfunctional resting left ventricular contractility associated with a mild to moderate fixed defect. This ventricular dysfunction improves following revascularization.
It is thought that repeated episodes of ischemia result in hibernation by causing repetitive myocardial stunning. Hibernation is seen as a defense mechanism by underperfused myocytes.
18F-FDG-PET imaging is the gold standard for assessment of myocardial viability. Hibernating myocardium will appear as an area of fixed perfusion defect on sestamibi perfusion images. 18F-FDG-PET, on the other hand, will show metabolic activity in areas of hibernating (and viable) myocardium (perfusion/metabolism mismatch). A glucose load 1-2 hours prior to imaging will increase insulin levels and increase myocardial glucose uptake.
Stunned myocardium, on the other hand, will show preserved basal perfusion in a dysfunctional segment of myocardium. 18F-FDG-PET will show preserved metabolism in this area.
Thursday, May 7, 2009
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An increased uptake of18 FDG in relation to perfusion or flow-metabolism mismatch is indicative of hibernating myocardium, whereas matched defects are indicative of scar tissue; values in between these represent healthy myocardial tissue mixed with fibrosis.
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