Myocardial imaging with β-methyl-p-(123I)iodophenyl-pentadecanoic acid in patients with dilated cardiomyopathy and its usefulness

To investigate the usefulness of myocardial imaging with β-methyl-p-(123I) iodophenyl-pentadecanoic acid (BMIPP) in the assessment of dilated cardiomyopathy (DCM), we studied 14 patients with DCM and 9 normal subjects. Rest myocardial imaging (tomography and planar whole-body imaging) with BMIPP and 201Tl (Tl) was performed on separate days. From the whole body imaging, cardiac accumulation of the radionuclide compared to the total injected dose was calculated (% Uptake). Uptake Ratio (% Uptake of MIBG divided by % Uptake of Tl) was used as an index of myocardial MIBG uptake which was normalized by myocardial mass. And we also calculated the coefficient of variation (CV) for each isotope as the index of unhomogeniety of isotope distribution within the myocardium. Uptake Ratio was significantly lower in patients with DCM (0.95±0.15) than in normal subjects (1.13±0.08) (p<0.01). In addition, Uptake Ratio correlated well with fractional shortening (% FS) (r=0.69, p<0.01) and left ventricular ejection fraction (r=0.70, p<0.01). CV of BMIPP imaging in patients with DCM was greater than that in normal subjects, but there was no difference between DCM and normal subjects in CV of Tl imaging. CV of BMIPP correlated well with serum norepinephrine level (r=0.59, P<0.05) and atrial natriuretic peptide (r=0.73, p<0.01). In patients with DCM, regional abnormality (defect) appeared in 9 patients (64%) both in BMIPP and Tl imaging, but the size of the defect was generally greater in patients with DCM than in normal subjects. These results suggested that in patients with DCM, disturbance of myocardial fatty acid metabolism appeared before perfusion abnormality and/or myocardial necrosis became apparent. The quantification of BMIPP imaging may be useful for assessing the prognosis for patients with DCM. (author)