Changes of microsphere density with time in myocardial infarcts in dogs.

The density of microspheres injected before occlusion of a coronary artery, in the infarcted region [I], was compared with that of healthy, normal myocardium [N], from the same dog. The [I]/[N] ratio was measured at different days after infarction up to 2 weeks. The ratio was below unity before the ninth day and above that thereafter. The changes in microspheres density can be explained on the basis of microsphere loss from necrotic tissue and changes in infarct mass.