Observer reproducibility of results from a low-dose 123I-metaiodobenzylguanidine cardiac imaging protocol in patients with heart failure.

PURPOSE: Imaging of the cardiac autonomic system with (123)I-metaiodobenzylguanidine (MIBG) is useful in the evaluation of patients with a variety of cardiac conditions, including heart failure (HF), but few data are available about the reproducibility of this technique. We assessed the observer reproducibility of the results from a low-dose (123)I-MIBG cardiac imaging protocol in patients with HF. METHODS: A total of 74 patients (62 men, age 67 ± 10 years) with HF and left ventricular systolic dysfunction (ejection fraction 31 ± 7 %) underwent low-dose (111 MBq) planar and single-photon emission computed tomography (SPECT) (123)I-MIBG cardiac sympathetic imaging. The intraclass coefficient of correlation (ICC), Lin's concordance correlation coefficient, and Bland-Altman analysis were used to evaluate the intraobserver and interobserver reproducibility of early and late heart-to-mediastinum (H/M) ratios and of defect scores on SPECT images. The κ statistic was used to evaluate the concordance rates for the identification of patients with a low H/M ratio (<1.60) on late planar imaging. RESULTS: The differences between measurements obtained twice by the same examiner and by two examiners were negligible for both early and late H/M ratios and for SPECT defect scores. These findings were confirmed by the results of Bland-Altman analysis, and ICC and Lin's coefficient values were excellent (>0.90) for all measurements. For the identification of patients with a low H/M ratio, the κ values were 0.90 for intraobserver concordance and 0.83 for interobserver concordance. CONCLUSION: The present study showed a high observer reproducibility of planar H/M ratios and SPECT defect scores using a low-dose (123)I-MIBG cardiac imaging protocol in patients with HF.

Reduced cardiac 123I-metaiodobenzylguanidine uptake in patients with spinocerebellar ataxia type 2: a comparative study with Parkinson's disease.

PURPOSE: Spinocerebellar ataxia type 2 (SCA2) is an autosomal dominant neurodegenerative disorder characterized by cerebellar ataxia, supranuclear ophthalmoplegia, and peripheral neuropathy. Autonomic nervous system dysfunction is often present. This study evaluated the cardiac sympathetic function in patients with SCA2 using (123)I-metaiodobenzylguanidine (MIBG) in comparison with patients with Parkinson's disease (PD) and control subjects. METHODS: Nine patients with SCA2, nine patients with PD, and nine control subjects underwent (123)I-MIBG imaging studies from which early and late heart-to-mediastinum (H/M) ratios and myocardial washout rates were calculated. RESULTS: Early (F = 12.3, p < 0.0001) and late (F = 16.8, p < 0.0001) H/M ratios were significantly different among groups. In controls, early and late H/M ratios (2.2 ± 0.12 and 2.1 ± 0.20) were significantly higher than in patients with SCA2 (1.9 ± 0.23 and 1.8 ± 0.20, both p < 0.05) and with patients with PD (1.7 ± 0.29 and 1.4 ± 0.35, both p < 0.001). There was also a significant difference in washout rates among groups (F = 11.7, p < 0.0001). In controls the washout rate (19.9 ± 9.6%) was significantly lower (p < 0.005) than in patients with PD (51.0 ± 23.7%), but not different from that in SCA2 patients (19.5 ± 9.4%). In SCA2 patients, in a multivariable linear regression analysis only the Scale for the Assessment and Rating of Ataxia score was independently associated with early H/M ratio (ß = -0.12, p < 0.05). CONCLUSION: (123)I-MIBG myocardial scintigraphy demonstrated an impairment of cardiac sympathetic function in patients with SCA2, which was less marked than in PD patients. These results suggest that (123)I-MIBG cardiac imaging could become a useful tool for analysing the pathophysiology of SCA2.