The relationship between lung mibg uptake and clinical response to renal denervation

Objective: Renal denervation (RDN) attenuates the sympathetic nervous system overactivity that characterizes patients with elevated blood pressure (BP). Given that accurate predictors of BP response to RDN remain to be identified and that metaiodobenzylguanidine (MIBG) scintigraphy allows non-invasive assessment of sympathetic nerve activity, we explored if the kidney, heart and lung MIBG uptake predict BP response to RDN. Design and method: Thirteen patients with difficult-to-treat hypertension underwent radiofrequency-based RDN. Before the procedure, clinical and pharmacological history, office and ambulatory BP values and cardiovascular risk factors were recorded. Patients also underwent preprocedural rest echocardiography and MIBG scintigraphy. After RDN, a follow-up visit was performed at 3 months, with registration of office and ambulatory BP values. We considered as responders (R) those patients showing a reduction of office BP values on unchanged BP-lowering treatment and those who reduced the number and/or dosage of BP-lowering medications while maintaining optimal control of office BP. Results: Seven patients were classified as R (1 woman, mean age 48±11 years), while 6 were non-responders (NR) (2 women, mean age 50±8 years). The reduction in office systolic and diastolic BP values from baseline to 3 months was significantly larger in R vs NR (p=0.01). Furthermore, the burden of BP-lowering medications after the procedure was reduced more significantly in R (-44%) than NR (-16%), p<0.01. Baseline heart rate was the only clinical parameter significantly different between R (median 82, IQR [67-98]) bpm vs NR (median 62, IQR [60-72]) bpm, p<0.05. In early MIBG acquisitions, the lung/mediastinum ratio on both sides showed higher MIBG uptake in R vs NR (p<0.05). In late acquisitions, only the left side showed a significant difference between R and NR (p<0.05). There was a higher MIBG uptake in the right vs. left lung in the whole population and in R vs NR. All other MIBG scintigraphy parameters were similar between groups. Conclusions: Among patients with difficult-to-treat hypertension, those responding to RDN showed a higher lung/mediastinum ratio at MIBG scintigraphy and a higher heart rate before the procedure. Further studies are needed to confirm these preliminary results.