title: Technetium 99m-Q12 kinetics in perfused rat myocardium: effects of hypoxia and low flow.
abstract: Technetium 99m-Q12 is a new cationic myocardial perfusion imaging agent that produces excellent images in human beings. The purpose of this study was to examine the separate effects of hypoxia and low flow on myocardial clearance kinetics. After a 1 mCi bolus injection, myocardial 99mTc-Q12 clearance was monitored for 1 hour by using an Nal detector in 24 isolated perfused rat hearts. In 6 control hearts, flow was 12 ml/min, and oxygenation was normal. In 6 hypoxic hearts, flow was normal, but oxygenation was reduced (<5% 02). In 6 low-flow hearts, flow was 3 ml/min, and oxygenation was normal. In 6 very low flow hearts, flow was 1 ml/min, and oxygenation was normal. 99mTc-Q12 myocardial clearance was biphasic in all four groups, consisting of a rapid early phase and a second slow phase that began after 10 minutes. Myocardial retention between 1 and 10 minutes was 56.8% +/- 1.8% for control, 49.2% +/- 2.2% (p < 0.05 compared with control) for hypoxic, 56.8% +/- 2.6% (p = NS compared with control) for low flow (3 ml/min), and 63.7% +/- 2.1 % (p < 0.05 compared with control) for very low flow hearts (1 ml/min). Myocardial retention between 10 and 60 minutes was 90.5% +/- 0.2% for control, 90.2% +/- 1.6% for hypoxic, 90.0% +/- 0.8% for low-flow hearts (3 ml/min), and 87.6% +/- 0.3% (p < 0.05 compared with other groups) for very low flow hearts (1 ml/min). In conclusion, 99mTc-012 demonstrates biphasic clearance from normal, hypoxic, low-flow, and very low flow ischemic myocardium. Early-phase myocardial retention is decreased by hypoxia and increased by very low flow.
authors.affiliation: William K Warren Medical Research Institute of the University of Oklahoma Health Sciences Center, Tulsa, OK 74136, USA.
authors.forename: R D
authors.initials: RD
authors.lastname: Okada
authors.forename: K N
authors.initials: KN
authors.lastname: Nguyen
authors.forename: M
authors.initials: M
authors.lastname: Lauinger
authors.forename: I L
authors.initials: IL
authors.lastname: Allton
authors.forename: G
authors.initials: G
authors.lastname: Johnson
mesh_terms: D000818:Animals; D009202:Cardiomyopathies / Q000378:metabolism*; D003326:Coronary Circulation; D005663:Furans / Q000008:administration & dosage / Q000493:pharmacokinetics*; D000860:Hypoxia / Q000378:metabolism*; D007267:Injections; D008297:Male; D008657:Metabolic Clearance Rate; D009203:Myocardial Infarction / Q000378:metabolism; D017202:Myocardial Ischemia / Q000378:metabolism*; D009206:Myocardium / Q000378:metabolism*; D015609:Organotechnetium Compounds / Q000008:administration & dosage / Q000493:pharmacokinetics*; D010101:Oxygen Consumption; D051381:Rats; D017207:Rats, Sprague-Dawley; D013997:Time Factors; D016277:Ventricular Function, Left
chemical_list: D005663:Furans; D015609:Organotechnetium Compounds; C078496:technetium Tc 99m Q12