Clinical implications of mismatched uptakes of beta-methyl fatty acid analogue and thallium in infarcted myocardium: Correlations with coronary stenosis and regional wall motion abnormality

Myocardial perfusion and fatty acid metabolism were assessed by using myocardial single-photon emission computed tomography with thallium and beta- methyl-p-iodophenyl-pentadecanoic acid (BMIPP) during acute and/or late stages of myocardial infarction in 157 infarcted segments of 100 patients. The incidence of reduced thallium perfusion relative to BMIPP uptake ('T- type' mismatch) was significantly (p<0.05) lower (9%) compared to that of reduced BMIPP uptake relative to thallium perfusion ('B-type' mismatch) (59%) or non-mismatched segment (32%). In an anteroseptal region, B-type dissociation had a significantly higher incidence compared to no or T-type mismatch; 68% vs. 27% vs. 5%, respectively, whereas the incidence of T-type uptake was relatively high in inferior and posterolateral regions; 13%, 11%, respectively. Severe coronary stenosis was observed in 76% of B-type segments and 72% of non-mismatched segments but in only 43% of T-type segments. The incidence of regional wall motion abnormality was significantly lower (46%) in the T-type mismatch segments when compared to the B-type (91%) or non- mismatched segments (96%). In conclusion, myocardial fatty acid metabolism was more markedly impaired compared to an involved coronary perfusion, resulting in the mismatch of perfusion and fatty acid metabolism. Coronary stenosis and regional wall motion abnormality are more closely related to 'B- type' mismatch but not necessarily to 'T-type' dissociation, probably because of attenuation artifacts in inferior and posterolateral regions in thallium scan.