Abstract 18099: Renal Sympathetic Denervation Increases Renal Artery Blood Flow: a Serial MRI Study in Resistant Hypertension

Background: Pre-clinical studies to date have demonstrated potential improvements in renal blood flow after renal sympathetic denervation, however such effects are yet to be confirmed in patients with resistant hypertension. We assessed the effects of renal sympathetic denervation in these patients on renal artery blood flow and diameter at multiple time points. Methods and results: Patients (n = 15) with systolic blood pressures ≤ 160mmHg despite taking ≥ 3 antihypertensive medications concurrently at maximum tolerated dose were recruited into this single centre, prospective, non-blinded study. MRI indices included renal blood flow and renal artery diameters at baseline, 1 month and 6 months. In addition to significant decreases in blood pressures (p < 0.05) renal blood flow (total volume per cardiac cycle) increased 20% from (6.9 ± 2 mls) at baseline to (8.7 ± 2 mls; p=0.001) at one month and (8.0 ± 2mls; p=0.01) six months post procedure. There was a significant decrease in renal artery diameters from (6.8 ± 2 mm) at baseline to (6.2 ± 1 mm; p<0.03) at 1 month post procedure and this decrease was associated with increases of maximum velocity of blood flow from (73 ± 19 cm/sec) at baseline to (78 ± 19 cm/sec) at one month post procedure and notably, both parameters revert to 6.9 ± 2 mm and 72 ± 18 cm/sec respectively. Thus, this study is the first to provide evidence of an early reduction in renal artery diameters (potentially due to oedema and inflammation) post intervention that has resolved by 6 months. Conclusion: Renal sympathetic denervation improves renal physiology as evidenced by significant improvements in renal blood flow. Additionally, this study for the first time identifies a transient decrease in renal artery diameters immediately after procedure and further demonstrates that these changes revert to baseline values six months post procedure.