Measurement of regional myocardial blood flow in rats by unlabeled microspheres and Coulter channelyzer

Abstract

A relatively inexpensive, expeditious, new nonradioactive microsphere method for measuring regional myocardial blood flow (RMBF) was developed with unlabeled microspheres and a Coulter Channelyzer. To validate the efficiency of this method, hearts from rats were perfused ex vivo by retrograde aortic cannulation. Unlabeled microspheres of varying size were injected into a side arm in the aortic cannula or added to blood samples collected from the rats. Microspheres were then recovered from the cardiac tissue and blood samples. It was found that > 97% of perfused microspheres (diam > 9.4 microns) were retained in the myocardium and that 94.8 +/- 2.2% of the trapped microspheres were recovered and counted successfully using a Counter Channelyzer. The percent recovery of microspheres from 2- and 0.5-ml blood samples were 95.4 +/- 2.3 and 95.3 +/- 3.1%, respectively. Blood flow to the anterior and posterior halves of the ventricular free walls and septum were measured in six rats; excellent agreements were found between the results yielded by 10-, 15-, and 20-microns unlabeled microspheres injected simultaneously. The transmural flow gradients in the left ventricular free wall estimated by 10- and 15-microns spheres did not significantly differ from each other. Thus the method developed here provides a new alternative for measurement of RMBF, which currently allows at least three measurements for nontransmural gradient RMBF and at least two measurements for transmural gradient RMBF.

Biological and Optical Properties of Fluorescent Nanoparticles Developed for Intravascular Imaging

“…Previous attempts to define local velocity fields in the blood circulation have used nonbiologic particulate tracers because of their economy and convenience (Austin et al, 1989;Baer et al, 1984;Bernard et al, 1996;Buckberg et al, 1971;Luchtel et al, 1998;Van Oosterhout et al, 1995;Wang et al, 1996). The disadvantages of these tracers have included rapid plasma clearance and poor signal isolation.…”