| Summary: | Aims: (1) Explore the physiological effect of renal denervation (RDN) (2) Explore the efficacy of distal denervation on blood pressure (BP) reduction in patients undergoing directly observed anti-hypertensive therapy (DOT) to minimise measurement bias (3) Evaluate the 6-month safety of distal denervation Methods: Patients with resistant hypertension were recruited and underwent assessment of drug compliance by assaying urinary drug levels. All subsequent measurements were recorded under DOT. Pre-denervation, office and ambulatory BP were measured, and patients underwent bilateral renal angiography and invasive measurement of aortic and renal arterial pressure and blood flow velocity. RDN was performed using the Symplicity Spyral catheter, denervating in the main renal arteries and each distal branch >3mm diameter. Invasive and non-invasive measurements were repeated 6-months post denervation under DOT. Results: 16 patients underwent denervation (age 63±12 years) with referral office SBP 180±18 mmHg. In total each patient received 22.6±5.0 ablations, 9.3±2.9 ablations in the main trunk and 13.3±4.8 ablations distally. At 6-months follow-up, overall unblinded 24-hour SBP reduction was -5.1±7.5 mmHg (p=0.020), with DBP reduction -3.4±4.9 mmHg (p=0.018). At 6-months follow-up an overall increase in renal blood flow velocity occurred at rest (1.91±3.51cm/s, p=0.04) and under identical sedation states (1.81±3.44 cm/s, p=0.05). Patients with the largest reduction in ambulatory SBP at 6-months had the largest increase in renal blood flow acutely after RDN (R 2=0.60, p < 0.001) and the largest decrease in renal resistance (R2=0.56, p < 0.001). Quantitative vessel angiography showed no significant change in any main or distal renal artery dimensions at 6-months. Conclusion: This unblinded study of distal RDN showed a significant reduction in ambulatory systolic and diastolic BP with no safety concerns at 6-months. These exploratory results suggest that acute changes in renal hemodynamics may be predictive of blood pressure response at 6-months follow-up.
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