Pharmacologic stress-induced regional myocardial blood flow heterogeneity and left ventricular wall thickening abnormality: comparison of intravenous adenosine with dipyridamole in a model of critical coronary stenosis.

Variations in reported sensitivity of myocardial perfusion scans or wall motion abnormalities during pharmacologic stress with intravenous adenosine and dipyridamole may be caused by differences in myocardial oxygen demand or myocardial blood flow redistribution induced by each agent. To investigate the physiologic correlates of functional abnormalities during pharmacologic stress testing, regional myocardial blood flow (radiolabeled microsphere technique) and left ventricular segmental wall thickening (quantitative two-dimensional echocardiography) were measured in 9 dogs with an open chest model of critical stenosis of the left circumflex coronary artery. Data were obtained at baseline and peak drug infusion for intravenous adenosine (0.42 mg/kg over a 3-minute period) and for intravenous dipyridamole (0.56 mg/kg over a 4-minute period). Adenosine and dipyridamole induced regional flow abnormality in 7 (77%) of 9 dogs. Myocardial segments with decreased endocardial/epicardial flow ratio were similar for both agents (2.9 +/- 1.8 vs 2.7 +/- 1.3, p = [NS]). Segments with myocardial flow heterogeneity (ratio of endocardial flow to control left anterior descending/left circumflex endocardial flow) were similar for both agents (2.7 +/- 0.9 vs 2.3 +/- 1.0, p = NS). Adenosine-induced wall thickening abnormality (77% vs 55% with dipyridamole) correlated with regional flow abnormality. Significantly lower mean arterial pressure (53 +/- 1.7 mm Hg vs 64 +/- 1.9 mm Hg, p < 0.01) and more prolonged drug effect (18 +/- 6.4 min vs 3 +/- 1.4 min, p < 0.001) were seen for dipyridamole compared with adenosine. Adenosine induces regional flow abnormality similar to dipyridamole but with less hemodynamic perturbation, and adenosine-induced wall thickening abnormality more closely parallels regional flow abnormality.

Significance of diffuse cardiac activity on In-111 labeled leucocyte scans.

To assess the significance of diffuse cardiac activity (DCA) seen on In-111 labeled leukocyte scans, we reviewed 87 studies performed over the last 4 years. Inflammatory cardiac conditions were seen as frequently in patients with DCA (15%) as those without (7%, P = 0.3). There was a higher ratio of RBC:WBC in the final WBC preparation in the false-positive DCA group than the true positive DCA and no DCA groups. False-positive studies showing DCA are most likely due to residual blood pool activity.

Tropolone: a lipid solubilizing agent for cationic metals.

Lipid soluble agents which chelate radioactive cations have several potential uses in nuclear medicine including: brain imaging, labeling of blood elements, and identifying fatty infiltration of organs. A tropolone-gallium complex has been characterized by the determination of in vitro partition ratios correlated with in vivo organ distribution in the rat. Partition ratios were determined for gallium-67 citrate, indium-114m chloride, and iron-59 chloride cations complexed with tropolone in chloroform + water, octanol + water, olive oil + water, and olive oil + plasma two-phased systems. Tropolone proved to be highly effective in the lipid solubilization of these metal cations. Distribution studies in animals of these cations complexed with tropolone demonstrated an increased concentration of these cation complexes in tissues of high lipid content when compared with appropriate controls.