Impact of obesity and acquisition protocol on 123I-metaiodobenzylguanidine indexes of cardiac sympathetic innervation

Background: This study was designed to assess the impact of obesity and acquisition protocol on 123I-metaiodobenzylguanidine (MIBG) indexes of cardiac sympathetic innervation. Methods: Forty-five patients with heart failure (HF) (38 men, age 58±15 years) underwent 123I-MIBG cardiac imaging. Of these patients, 10 were obese [body mass index (BMI) >=30 kg/m2]. Ten-minute planar images of the thorax in anterior view were performed 15 minutes ("early" image) and 3 hours and 50 minutes ("late" image) after tracer administration in both supine- and prone-position. Early and late 123I-MIBG heart-to-mediastinum (H/M) ratios and washout rate were computed. Results: In overall study population, early and late 123I-MIBG H/M ratios and washout rate were comparable between supine- and prone-position acquisitions. Obese patients had a lower early and late 123I-MIBG H/M ratios both in supine (P<0.01) and prone (P<0.05) positions compared to non-obese subjects. Conclusions: Our results indicate that in HF patients, obesity has a significant impact on 123I-MIBG indexes of cardiac sympathetic innervation. Prone-position did not change early and late 123I-MIBG H/M ratios and washout rate compared to supine position both in obese and non-obese HF patients.