oa Cardiovascular Journal of Africa - Comparison of the uptake of radiolabelled fatty acid (123I-paraphenyl-pentadecanoic acid) with 99mTc-MIBI in patients with established transmural infarction
Single photon emission computed tomography (SPECT) metabolic imaging of the heart can be undertaken with I23I-labelled fatty acids. Among these, 123I-paraiodophenyl pentadecanoic acid (pIPPA) was used to detect myocardial ischaemia and to study viability. The purpose of this study was to compare the distribution of locally produced 123I-pIPPA (National Accelerator Centre, Faure) with the perfusion tracer 99 mTc-hexakis-2-methoxyisobutyl isonitrile (MIBI) in patients with established transmural infarction. Nine male patients scheduled for resting myocardial perfusion imaging with 99mTc-MIBI were also studied with 123I-plPPA. Tomographic short-axis slices of the left ventricle were used to obtain circumferential profiles for comparison. The percentage uptake index for 123I-pIPPA was higher than that of .9mTc-MIBI in 5 patients, while the opposite pattern was observed in 4 patients. The mean uptake of 123I-plPPA (60.2% ï¿½ 9.7%) did not differ from the 59.6% ï¿½ 9.4% obtained for 99 mTc-MIBI. The individual variations in distribution of the tracers are consistent with previous reports. Reduced 123I-pIPPA uptake (less than 99mTc-MIBI uptake) may suggest greater sensitivity to detect residual grey zone ischaemia. Better uptake in scar tissue implies maintained cytosolic uptake, i.e. viability. Different locally produced 123I-labelled fatty acids are now available to study cardiac fatty acid metabolism with SPECT.
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