Radionuclide Assessment of Stunned Myocardium by Alterations in Perfusion, Metabolism and Function

A method for the diagnosis of stunned myocardium has not yet been establishied, although it has been retrospectively demonstrated in patients after intracoronary thrombolysis, unstable angina, and coronary revascularization. In this study, radionuclide cardiac imaging was carried out to evaluate the existence of stunned myocardium. 1) Gated blood pool scanning was performed in patients undergoing intracoronary thrombolysis both at the time of reperfusion (Rp) and 10 days later. In the Rp<4 h group, about half of the initially abnormal segments showed complete improvement on quantitative wall motion analysis, which was more than in the Rp>4 h and control groups. 2) In patients with acute myocardial ischemia, the correlation between thallium perfusion and regional wall motion was assessed semiquantitatively. In unstable angina, 5.8% of the ventricular wall segments showed dissociation between perfusion and wall motion (well-perfused asynergy). These segments had abnormal wall motion although perfusion was maintained, and were thought to be areas of stunned myocardium. 3) Fourteen dogs were studied using thallium and ¹²³I-β-methyl-iodophenyl pentadecanoic acid (BMIPP) fatty acid imaging to evaluate the relationship of perfusion to metabolism. In the reperfusion model, mismatching of the pattern of thallium and BMIPP uptake was observed. Reperfused myocardium probably has an increased triglyceride content, which is related to the degree of myocardial viability. In conclusion, stunned myocardium may be correctly diagnosed acutely on the basis of alterations in its perfusion, metabolism, and function by using radionuclide cardiac imaging.