Combined thallium-201 and dynamic iodine-123 iodophenylpentadecanoic acid single-photon emission computed tomography in patients after acute myocardial infarction with effective reperfusion

Background Considerable derangements of energy metabolism are to be expecte d during ischemia and reperfusion. In ischemic myocardium, the oxidative de gradation of carbohydrates is shifted toward the anaerobic production of la ctate and the oxidation of fatty acids is suppressed. Hypothesis: The aim of this study was to examine the uptake and metabolism of iodine-123 (I-123) iodophenylpentadecanoic acid (TPPA) in stunned myocar dium. Methods: In 15 patients, SPECT with Tl-201 and I-123 IPPA as well as echoca rdiography with low-dose dobutamine stimulation were performed 12 +/- 5 day s after myocardial infarction with reperfusion. Follow-up echocardiography was carried out 24 +/- 8 days later for documentation of functional improve ment. Uptake of Tl-201 and I-123 IPPA were obtained in five left ventricula r segments, and dynamic SPECT imaging was used for calculation of the fast and the slow components of the biexponential myocardial I-123 IPPA clearanc e. Results: Wall motion improved in 14 of 26 dysfunctional segments (54%). Stu nned segments were characterized by a reduced I-123 IPPA extraction, a shor ter half-life of the fast, and a longer half-life of the slow clearance com ponent. All parameters of the combined Tl-201/I-123 IPPA study predicted fu nctional recovery with similar accuracies (area under the receiver operator characteristic curves between 0.68 and 0.76; p = NS). Analysis of Tl-201 u ptake alone could not predict functional recovery in this study. Conclusions: Stunned myocardium is characterized by a disturbance of fatty acid metabolism. For prediction of functional improvement, I-123 IPPA imagi ng added significant diagnostic information.