Risk Stratification and Cardiac Sympathetic Activity Assessment Using Myocardial [I-123] MIBG Imaging in Renal Denervation

Hyperactivation of the sympathetic nervous system plays a central role in the pathophysiology of hypertension. The aim of this study was to assess cardiac sympathetic activity and investigate the role of myocardial I-123-labelled meta-iodo benzyl guanidine ([I-123] MIBG) scintigraphy in cardiovascular risk stratification of patients with resistant hypertension treated with renal denervation (RDN). Eighteen patients were included in this prospective study (mean age 56 +/- 10 years old, 27.8% females). Transthoracic echocardiogram, general blood analysis and myocardial ([I-123] MIBG scintigraphy were performed before and six-months after RDN. A patient was considered a responder (R) if a drop >= 5mmHg on mean systolic ambulatory blood pressure (BP) monitoring was observed at the six-month follow-up. 66.7% of patients were R (drop in systolic BP of 20.6 +/- 14.5mmHg, vs minus 8 +/- 11.6mmHg in non-responders (NR), p=0.001). Early heart-mediastinum ratio (HMR) was significantly lower at baseline in the R group (1.6 +/- 0.1 vs 1.72 +/- 0.1, p<0.02) but similar at six months. Considering both instants in time, the R group had lower early HMR values than the NR group (p<0.05). Both the late HMR and the washout rate were identical and no significant correlation between response to RDN or any MIBG imaging index was found. Renal denervation effectively lowered blood pressure in the majority of patients but [I-123] MIBG was not useful in predicting the response. However, there was evidence of sympathetic overdrive and, both early and late HMR were overall reduced, probably putting this population at a higher risk of adverse events.