Scintigraphic evaluation of myocardial ischaemia using a new fatty acid analogue: iodine-123-labelled 15-(p-iodophenyl)-9-(R, S)-methylpentadecanoic acid (9MPA)

Iodine-123-labelled 15-(p-iodophenyl)-9(R,S)-methylpentadecanoic acid (9MPA ) is a branched fatty acid analogue for myocardial imaging, which has been recently designed for medium washout rates from the myocardium. The purpose of this study was to assess the clinical feasibility of use of 9MPA for th e evaluation of myocardial ischaemia. Twenty-one patients were injected wit h 9MPA at rest, and sequential single-photon emission tomography (SPET) acq uisitions were performed 5, 45 and 240 min after administration to calculat e washout rates from the myocardium. The findings of 9MPA images were analy sed in comparison with those of perfusion images with thallium-201 or sesta mibi, coronary angiography and left venticulography. In general, reduction of 9MPA uptake was more remarkable than that of perfusion tracers. The find ings of 9MPA early images correlated better with those of exercise perfusio n images than with the rest images. Measured washout rates of 9MPA from isc haemic myocardium were significantly slower than those from normal myocardi um. The majority of areas with abnormal 9MPA distribution manifested wall m otion abnormality, while all areas with normal tracer distribution presente d normal wall motion. The detectability of myocardial ischaemia was improve d by adding mid and delayed images in six cases. However, both washout and fill-in patterns were encountered in ischaemic lesions, rendering the inter pretation of images difficult. In conclusion, the results of this study ind icated that 9MPA has acceptable myocardial uptake, that its use is feasible for the detection of ischaemia and that the abnormal distribution of the t racer correlates well with wall motion abnormality reflecting metabolic dis orders.