Radiofrequency Sympathetic Renal Denervation

Sympathetic renal denervation (SRD) has emerged as a therapeutic alternative for patients with resistant hypertension (1-2). Resistant hypertension is defined as a systolic blood pressure of 140mmHg or higher despite the adherence to at least three maximally tolerated doses of antihypertensive medication from complementary classes, including a diuretic at an appropriate dose (3), after the exclusion of any possible cause of secondary hypertension (4-5).

The promising results of SRD performed with radiofrequency were based on several studies that yielded a significant and sustained reduction on office blood pressure (OBP) after ablation of the sympathetic renal nerves with radiofrequency. In particular the HTN I (6) and HTN II (7-8) studies revealed a significant reduction of the systolic and diastolic OBP of 22mmHg and 10,2mmHg respectively at 6 months for HTN-I and of 32mmHg and 12mmHg respectively at 6 months for HTN-II with the use of the Medtronic Symplicity Flex monopolar radiofrequency catheter (Medtronic Inc, Santa Rosa, CA, USA). However, these results could not be replicated when the treatment was compared to a sham procedure and optimized medical treatment, as designed in the multi-center, double-blind, randomized Hypertension III study (HTN-III) (5). Indeed, HTN-III did not confirm such a substantial blood pressure reduction with the same catheter, and as a consequence, the anti-hypertensive effect of the SRD catheter was not significantly different as compared to the results of the medically treated group. Although a significant change from baseline to 6 months systolic OBP and ambulatory blood pressure was observed in sham and denervation group, the group difference did not meet a test of superiority with a margin of 5mmHg for OBP (-2,39 mmHg, p= 0.98) and 2mmHg for ambulatory blood pressure (ABP) (-1,96 mmHg, p= 0.98) (5). Although the trial confirmed the safety endpoint, the lack of efficacy casted doubts on the real value of the SRD treatment, and the therapy was almost abandoned after the publication of HTN-III trial on March 29th 2014 (5).

Several interpretations have been speculated to analyze the possible causes of the negative results of HTN-III (9-10). Based on some anatomical observations related to the innervation of the renal arteries (11-12), a different pattern and technque of radiofrequency delivery in the renal arteries with a new SRD tetrapolar Spyral catheter has reopened the interest on the technique.

This webinar is aimed at showing the differences between the previous and the present radiofrequency systems, and to discuss how the new device may be more effective maintaining safety.