Iodine-123-free fatty acid analogs, such as beta-methyliodophenylpentadecanoic acid (BMIPP), allow for myocardial metabolic studies with SPECT. The goal of this investigation was to determine whether BMIPP uptake can be used to differentiate viable myocardium from scar tissue soon after coronary thrombolysis for acute myocardial infarction.
Methods: BMIPP and 99mTc-sestamibi (MIBI) myocardial distribution after injection at rest were analyzed in 22 patients 4 to 10 days after coronary thrombolysis. The relative uptake of the two tracers was compared on a segmental basis to the regional wall motion and to the inotropic reserve assessed by two-dimensional echocardiography and low-dose dobutamine stimulation.
Results: Three segmental patterns were identified in the infarct-related coronary artery territory. Segments with normal BMIPP and MIBI uptake showed normal wall motion. Segments with more reduced BMIPP uptake than MIBI uptake (mismatching) showed either normal wall motion or demonstrated inotropic reserve during dobutamine stimulation. Segments with matched defects always showed abnormal wall motion and did not demonstrate inotropic reserve, regardless of the MIBI uptake.
Conclusion: In patients with subacute myocardial infarction, combined imaging of BMIPP and MIBI at rest might be more sensitive than MIBI or wall motion at rest alone to demonstrate myocardial areas that have been acutely ischemic. Mismatching is due to more severely depressed fatty acid metabolism than expected on the basis of the flow and is indicative of jeopardized, but viable myocardium. In dysfunctional segments, mismatching may correspond either to stunned or to hibernating myocardium. Matched defects are associated with scar tissue.