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 the evaluation of myocardial ischaemia. Twenty-one patients were injected with 9MPA at rest, and sequential single-photon emission tomography (SPET) acquisitions were performed 5, 45 and 240 min after administration to calculate washout rates from the myocardium. The findings of 9MPA images were analysed in comparison with those of perfusion images with thallium-201 or sestamibi, coronary angiography and left venticulography. In general, reduction of 9MPA uptake was more remarkable than that of perfusion tracers. The findings of 9MPA early images correlated better with those of exercise perfusion images than with the rest images. Measured washout rates of 9MPA from ischaemic myocardium were significantly slower than those from normal myocardium. The majority of areas with abnormal 9MPA distribution manifested wall motion abnormality, while all areas with normal tracer distribution presented normal wall motion. The detectability of myocardial ischaemia was improved by adding mid and delayed images in six cases. However, both washout and fill-in patterns were encountered in ischaemic lesions, rendering the interpretation of images difficult. In conclusion, the results of this study indicated that 9MPA has acceptable myocardial uptake, that its use is feasible for the detection of ischaemia and that the abnormal distribution of the tracer correlates well with wall motion abnormality reflecting metabolic disorders.