Comparison of cardiac sympathetic nervous function with left ventricular function and perfusion in cardiomyopathies by I-123-MIBG SPECT and Tc-99m-tetrofosmin electrocardiographically gated SPECT

The objective of this study was to clarify the relationship between cardiac sympathetic nervous function (CSNF) and left ventricular (LV) function and perfusion in hypertrophic cardiomyopathy (HCM) and dilated cardiomyopathy (DCM). Methods: Thirty-eight cases (32 males, 6 females; mean age, 56 +/- 1 5 y), consisting of 5 healthy control subjects, 15 patients with DCM, and 1 8 patients with HCM, were studied with I-123-metaiodobenzylguanidine (MIBG) and Tc-99m-tetrofosmin SPECT. CSNF was evaluated from cardiac uptake and w ashout of MIBG, whereas LV perfusion and function were evaluated from tetro fosmin uptake and wall thickening on electrocardiographically gated SPECT. As quantitative parameters of global cardiac MIBG uptake and washout, the h eart-to-mediastinum ratio (H/M) and percentage washout were calculated from early and delayed planar images. As quantitative regional parameters, the regional uptake and percentage washout of MIBG were calculated from SPECT i mages dividing the left ventricle into 12 segments. In the tetrofosmin stud y, the H/M and LV ejection fraction were calculated as the parameters of gl obal LV perfusion and function. As quantitative regional parameters, the re gional uptake and wall thickening were also calculated for the 12 myocardia l segments using the quantitative gated SPECT software. Multiple linear reg ression analysis was performed to investigate the correlations between the parameters from the 2 studies. Results: In DCM and HCM, multiple linear reg ression analysis of the regional parameters showed significant correlations between LV function and CSNF (P < 0.0001) and between LV perfusion and CSN F (P < 0.0001), According to the partial correlation coefficients, washout and early uptake of MIBG were the most significant factors for predicting L V function and LV perfusion, respectively. Conclusion: In cardiomyopathies, CSNF was closely related to LV function. The quantitative parameters of MI BG washout could reflect cardiac functional impairment. Early MIBG uptake m ight be determined by myocardial perfusion in cardiomyopathies.