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

Background: This study was designed to assess the impact of obesity and acquisition protocol on I-123-metaiodobenzylguanidine (MIBG) indexes of cardiac sympathetic innervation. Methods: Forty-five patients with heart failure (HF) (38 men, age 58 +/- 15 years) underwent I-123-MIBG cardiac imaging. Of these patients, 10 were obese [ body mass index (BMI) = 30 kg/m(2)]. 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 I-123-MIBG heart-to-mediastinum (H/M)ratios and washout rate were computed. Results: In overall study population, early and late I-123-MIBG H/M ratios and washout rate were comparable between supine-and prone-position acquisitions. Obese patients had a lower early and late I-123-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 I-123-MIBG indexes of cardiac sympathetic innervation. Prone-position did not change early and late I-123-MIBG H/M ratios and washout rate compared to supine position both in obese and non-obese HF patients.