To evaluate the relationship between the reversible defect of 123I-15-(p-iodophenyl)-9-(R,S)-methylpentadecanoic
acid (
9MPA) and residual viability within an
infarct-related area, we performed resting single photon emission computed tomography (SPECT) with
9MPA and positron emission tomography (PET) with 18F-deoxyglucose (FDG) and 13N-ammonia (NH3) in 7 patients with prior
myocardial infarction. 9MPA-SPECT was obtained 2 min (early) and 50 min (delayed) after tracer injection. Tomographic images of the left ventricle were divided into 13 segments to correlate the regional uptake of each tracer. Residual viability within an
infarct-related segment was confirmed by NH3- and FDG-PET. Twenty-six
infarct-related segments, confirmed by NH3-PET, showed reduced uptake of
9MPA on early images. In these 26 segments, 6 showed reversible defect of
9MPA and 20 showed fixed defect on delayed images. Residual viability was present in all segments exhibiting reversible
9MPA defect and 7 segments (35%) exhibiting fixed defect (p < 0.05). The sensitivity, specificity and accuracy of reversible
9MPA defect for the detection of myocardial viability were 46%, 100%, and 73%, respectively. Myocardial clearance of
9MPA was significantly slower in non-viable segments than in ischemic but viable segments (4.9+/-5.1% vs. 10.1+/-5.3%; p < 0.05). These data suggest that a reversible
9MPA defect indicates residual viability within the
infarct-related area.