Technetium-99m-tetrofosmin to assess myocardial blood flow: experimental validation in an intact canine model of ischemia.
Technetium-99m-tetrofosmin is a 99mTc-labeled perfusion tracer demonstrating promise for myocardial perfusion imaging. To determine if 99mTc-tetrofosmin tracks myocardial flow over a pathophysiologic range, the initial myocardial uptake and clearance of 99mTc-tetrofosmin relative to microsphere flow were evaluated in a canine model of ischemia during pharmacological vasodilatation.


METHODS
Six open-chest dogs were subjected to complete left anterior descending coronary artery occlusion. Dogs were injected with 99mTc-tetrofosmin and radiolabeled microspheres during pharmacological stress. Coincident with radiotracer injection, dynamic planar imaging and arterial sampling were performed to assess 99mTc-tetrofosmin clearance from blood, myocardium, lung and liver. Fifteen minutes after injection, hearts were excised for well counting of myocardial 99mTc-tetrofosmin activity and flow.


RESULTS
Myocardial 99mTc-tetrofosmin activity correlated linearly with microsphere flow (r = 0.84). Relative 99mTc-tetrofosmin activity underestimated flow at higher flow ranges (> 2.0 ml/min/g) and overestimated flow in low flow ranges (< 0.2 ml/min/g). Technetium-99m-tetrofosmin cleared rapidly from the blood and was retained in the myocardium. Resting target-to-background activity ratios (heart:lung = 3.57 +/- 1.01; heart:liver = 0.58 +/- 0.04) were acceptable 10 min after injection.


CONCLUSIONS
Our experimental data support both the validity of 99mTc-tetrofosmin as a myocardial perfusion tracer and the use of early poststress 99mTc-tetrofosmin imaging for the assessment of myocardial perfusion in man.
Sinusas
A J
AJ
Department of Internal Medicine, Yale University, School of Medicine, New Haven, Connecticut 06510.
Shi
Q
Q
Saltzberg
M T
MT
Vitols
P
P
Jain
D
D
Wackers
F J
FJ
Zaret
B L
BL
D000241:Adenosine / Q000494:pharmacology; D000818:Animals; D003326:Coronary Circulation / Q000187:drug effects; D004285:Dogs; D006321:Heart / Q000000981:diagnostic imaging; D017202:Myocardial Ischemia / Q000000981:diagnostic imaging* / Q000503:physiopathology; D009943:Organophosphorus Compounds / Q000493:pharmacokinetics; D015609:Organotechnetium Compounds / Q000493:pharmacokinetics; D011877:Radionuclide Imaging
D009943:Organophosphorus Compounds; D015609:Organotechnetium Compounds; C078700:technetium tc-99m tetrofosmin; D000241:Adenosine