Significant correlation between renal ¹²³I-metaiodobenzylguanidine scintigraphy and muscle sympathetic nerve activity in patients with primary hypertension

Background: Iodine-123 metaiodobenzylguanidine (¹²³I-MIBG) scintigraphy is used as a noninvasive imaging method for assessing cardiac sympathetic nerve activity. We tested the hypothesis that renal ¹²³I-MIBG imaging is correlated with muscle sympathetic nerve activity (MSNA) in patients with primary hypertension. Methods: Thirty-one consecutive patients with primary hypertension were included. Multiunit MSNA was recorded from the peroneal nerve to evaluate direct efferent sympathetic nerve activity. Planar renal and cardiac ¹²³I-MIBG images were acquired. Early and delayed kidney-to-mediastinum ratio (K/M), early and delayed heart-to-mediastinum ratio (H/M), and washout rates (WR) were calculated. Results: In 27 of 31 patients, blood pressure was controlled on antihypertensive medication. Mean systolic and diastolic blood pressures were 118 ± 18 and 67 ± 15 mmHg, respectively. Although early and late K/M and H/M were not significantly correlated with MSNA, both cardiac and average renal WR were significantly correlated with MSNA (r = 0.45, P = .0035 and r = 0.68, P < .001, respectively). Right and left renal WR were similarly correlated with MSNA. Renal WR was significantly higher than cardiac WR (43.2% vs 25.8%, P < .001) in these patients with hypertension. Conclusions: Renal ¹²³I-MIBG WR was significantly associated with multiunit MSNA. Renal ¹²³I-MIBG imaging offers a noninvasive clinical methodology for assessing renal sympathetic nerve function.