Relative Myocardial Blood Flow Research Articles

Regional myocardial kinetics of lidocaine in experimental infarction: Modulation by regional blood flow

The regional myocardial concentration of lidocaine after intravenous bolus administration was studied in the setting of myocardial infarction in 27 dogs utilizing a 24 hour old infarct model. Myocardial levels of lidocaine measured by gas chromatography were related to regional myocardial blood flow measured by radioactive microspheres in the same sample. A highly significant positive linear relation was noted between relative regional myocardial blood flow and lidocaine tissue concentration in animals killed 1 and 3 minutes after the injection of lidocaine (R 2 = 0.81 and 0.85, respectively). This positive linear relation was no longer evident at 5 or more minutes after injection of lidocaine. This lack of linear relation resulted from dramatic reductions in myocardial lidocaine concentration in normally perfused zones with much lesser reductions in lower flow zones. Thus the initial distribution of lidocaine after bolus injection is directly proportional to myocardial blood flow within the first 3 minutes of injection. Thereafter, the washout of lidocaine appears to be the dominant factor in myocardial distribution.

Liposome accumulation in regions of experimental myocardial infarction.

The uptake of liposomes bearing positive, negative, or no net charge on their membrane and containing a radioactive tracer, [99mTc]diethylenetriamine pentaacetic acid, was studied in 12 intact dogs 24 hours after the induction of myocardial infarction, and compared to the relative regional myocardial blood flow determined from radioactive microspheres. Positively charged and neutral liposomes concentrate in infarcted regions against a flow gradient, while negative liposomes are passively distributed according to regional blood flow. Because positively charged and neutral lipisomes concentrate in infarct areas and have the ability to incorporate pharmacologic agents in their aqueous or lipid phase, they may serve as vehicles for drug delivery to infarct zones of low flow.