Circulation, Vol 56, 1029-1034, Copyright © 1977 by American Heart Association
RM Schneider, JP Hayslett, SE Downing, HJ Berger, RK Donabedian and BL Zaret
Repeat DC countershock reproducibly results in myocardial necrosis in dogs.
In this model, myocardial technetium-99m pyrophosphate (PYP) uptake
correlates linearly with tissue creatine kinase depletion (r = - 0.83). The
effect of pretreatment with methylprednisolone (MP) was studied with PYP in
25 dogs. In myocardium damaged by countershock, 12 MP dogs had higher
tissue radioactivity sample:normal (S:N) ratios than control (P less than
0.05), suggesting increased tissue injury. However, by several other
measures of tissue damage, the two groups did not differ. MP-elevated PYP
S:N ratios were explained by reduced PYP activity in normal myocardium of
MP dogs. Further experiments in 21 dogs revealed that renal PYP clearance,
which correlated with glomerular filtration rate (GFR) as measured by
creatinine clearance, was increased in Mp dogs, resulting in accelerated
urinary excretion of PYP (46.9+/-3.6 vs 35.8+/-2.4 percent injected dose in
one hour, P less than 0.01), and reduced blood PYP. Thus MP does not modify
countershock- induced myocardial injury. However, by increasing GFR, MP
increased PYP excretion, resulting in lowered blood and normal zone
myocardial PYP, thereby spuriously affecting myocardial PYP tissue uptake
data.
ARTICLES
Effect of methylprednisolone upon technetium-99m pyrophosphate assessment myocardial necrosis in the canine countershock model