Stunned myocardium

Radiopaedia • CC-by-nc-sa 3.0 • de

Stunned myocardium refers to a situation in which an acute transient myocardial ischemic event results in a prolonged wall motion abnormality which eventually resolves.

The term is usually distinguished from "hibernating" myocardium, in which a chronic ischemic process leads to chronic left ventricular dysfunction.

Pathology

The term "stunned" myocardium originally arose from observing the wall motion of canine hearts after occluding coronary blood flow shorter than necessary to cause cell death (5-15 minutes) .

The myocardium at risk of being stunned in a more typical human clinical situation is myocardium which has a low fractional flow reserve at rest. Between 40-80% stenosis, there is normal coronary blood flow, but a decrease in maximal coronary blood flow. Myocardium in this territory is at risk of being "stunned" with a maximal effort.

Some think that the difference in stunned myocardium and hibernating myocardium is one of degree rather than of kind, and that the two conditions may often coexist . In addition, some think that hibernating myocardium is a result of repeated episodes of stunning .

Radiographic features

Nuclear medicine
Cardiac MRI
  • appearance is similar to hibernating myocardium
    • ​quantitative perfusion assessment gives an indication of myocardial viability
  • quantitative cutoffs for appropriate wall thickness, with or without dobutamine challenge, have problematic specificity
  • presence of delayed enhancement / scar likely best indication that the myocardium is no longer viable in that region

Differential diagnosis

  • hibernating myocardium
    • the two entities may exist on a spectrum and imaging findings are similar
  • myocardial infarction
    • matched rest and stress perfusion abnormality in nuclear medicine SPECT studies
    • decreased uptake in FDG-PET/CT
    • wall thinning and postcontrast delayed enhancement in regions of infarct and scar on cardiac MRI