Intrinsic washout rates of thallium-201 in normal and ischemic myocardium after dipyridamole-induced vasodilation
Infusion of dipyridamole has been suggested as an alternative to exercise stress for myocardial perfusion imaging for detection of ischemia, but the mechanism and significance of thallium-201 (/sup 201/Tl) redistribution after administration of dipyridamole are uncertain. If disparate intrinsic cellular efflux rates of /sup 201/Tl from normal and relatively underperfused myocardium in response to dipyridamole-induced vasodilation were observed, this could explain delayed /sup 201/Tl redistribution. We investigated the effect of an intravenous infusion of 0.15 mg/kg dipyridamole on the intrinsic myocardial washout rate of /sup 201/Tl as measured with a gamma-detector probe after intracoronary injection (50 muCi) of the radionuclide in open-chested anesthetized dogs. In six normal dogs the t 1/2 for intrinsic /sup 201/Tl washout from the myocardium was 89 +/- 11 min (SE) at control conditions and became more rapid at 59 +/- 10 min (p . .0001) after dipyridamole. This corresponded to a significant increase in microsphere-determined epicardial (0.95 +/- 0.11 to 2.23 +/- 0.46 ml/min/g; p . .01) and endocardial (0.86 +/- 0.10 to 1.53 +/- 0.27; p . .029) flows. In 12 dogs with a critical coronary stenosis, the /sup 201/Tl intrinsic washout rate slowed from 70 +/- 5 to 104 +/- 6 min (p . .0001) after production of the stenosis and slowed even further to 169 +/- 21 min (p . .003) after dipyridamole.
- Research Organization:
- Univ. of Virginia Medical Center, Charlottesville
- OSTI ID:
- 5777763
- Journal Information:
- Circulation; (United States), Journal Name: Circulation; (United States) Vol. 71:2; ISSN CIRCA
- Country of Publication:
- United States
- Language:
- English
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59 BASIC BIOLOGICAL SCIENCES
ANIMAL TISSUES
ANIMALS
BETA DECAY RADIOISOTOPES
BIOLOGICAL EFFECTS
BLOOD FLOW
BODY
CARDIOVASCULAR AGENTS
CARDIOVASCULAR DISEASES
CARDIOVASCULAR SYSTEM
DAYS LIVING RADIOISOTOPES
DISEASES
DISTRIBUTION
DOGS
DRUGS
ELECTRON CAPTURE RADIOISOTOPES
HEART
HEAVY NUCLEI
ISOMERIC TRANSITION ISOTOPES
ISOTOPES
MAMMALS
MICROSPHERES
MUSCLES
MYOCARDIUM
NUCLEI
ODD-EVEN NUCLEI
ORGANS
PERFUSED TISSUES
RADIOISOTOPES
SECONDS LIVING RADIOISOTOPES
THALLIUM 201
THALLIUM ISOTOPES
TISSUE DISTRIBUTION
TISSUES
VASODILATION
VASODILATORS
VERTEBRATES