Comparison of Iodine-125-BMIPP and Thallium-201 in Myocardial Hypoperfusion

Radiolabeled fatty acids such as 15-(p-iodophenyl)-3-R,S-methylpentadecanoic acid (BMIPP) have unique metabolic properties of potential use as myocardial perfusion tracers. Accordingly, we compared the in vivo pattem of uptake of BMIPP and 201 Tl in hypoperfused rabbit myocardium. Methods : Animals were intubated, ventilated and their arterial pressures monitored. A left thoracotomy was performed. After ligation of a major branch of the circumflex artery, an intravenous injection of BMIPP or BMIPP/ 201 Tl was given. Radiolabeled microspheres were used to document the area of risk. After the circulation period, the animals were killed. Tracer deposition within the hearts was determined by either dual-tracer autoradiography (Protocol I) or by segmental tissue analysis (Protocol II). Results : Dual-tracer autoradiographic activity profiles for BMIPP were comparable to those of 201 Tl. Moreover, the two tracers yielded similar values for normal-to-defect contrast and defect size. The myocardial activity concentration of BMIPP for both protocols correlated strongly with coronary blood flow and compared favorably with 201 Tl. Conclusion : BMIPP and 201 Tl accurately delineate areas of hypoperfusion distal to a coronary occlusion. Therefore, differences in the myocardial distribution of BMIPP and 201 Tl in clinical studies may be related to cellular fatty acid metabolism.