Differentiation of regional perfusion and fatty acid uptake in zones of myocardial injury

The relative myocardial distribution of²⁰¹T1 and modified fatty acid (¹²³I-labelled 3-methyl-p- [iodo]-phenyl pentadecanoic acid, MFA) was determined in eight patients with unstable angina (UA) and six patients with acute myocardial infarction treated with reperfusion therapy within 4.1 h (MI). The results of radionuclide imaging were correlated with coronary angiography and quantitative left ventriculography performed within 10 days of the radionuclide procedures. Zones of injury were identified as areas with diminished 201T1 uptake distal to sites of coronary narrowing. A nearly parallel reduction in regional fatty acid concentration was observed in these areas. Comparison of the regional distributions of the two agents revealed subtle differences in their distributions in the ischaemic zones. Three patterns were recognized: MFA uptake greater than Tl (MFA > Tl), (b) matched decrease of MFA and T1 (MFA = Tl), (c) MFA uptake less than Tl (MFA < Tl). Seven of eight patients with UA had normokinesis or hypokinesis on quantitative left ventriculography. Five of the seven showed the MFA > Tl pattern, while one had the MFA < Tl pattern and one had the MFA = Tl pattern. The eighth patient with UA had akinesis and the MFA = Tl pattern. All six patients with acute infarction had akinesis on ventriculography. One of these patients had the MFA > Tl pattern, two had the MFA = Tl pattern and three had the MFA < Tl pattern. These results suggest that fatty acid and thallium have grossly similar distributions in areas of acute myocardial ischaemia. On careful inspection, zones of slight relative excess fatty acid concentration are observed more often in areas of acute ischaemia with normal wall motion.