Changes in renal artery dimensions are associated with clinical response to radiofrequency renal denervation: a series of studies using quantitative angiography and intravascular ultrasound

OBJECTIVE

Renal denervation (RDN) can cause focal (notches) and global (spasms) changes in renal artery dimensions. We quantified these changes and related them to renal norepinephrin tissue content in animals and to blood pressure (BP) changes in patients.

METHODS

We measured renal artery dimensions pre-RDN and post-RDN, utilizing quantitative renal angiography (QRA) in a porcine model and in a retrospective patient cohort, and intravascular ultrasound (IVUS) in a prospective patient cohort. Focal and global measurements were minimum and mean diameter/area/volume with QRA, minimum lumen/vessel/wall area and volume with IVUS. BP was assessed with 24-h ambulatory monitoring, norepinephrin content with liquid chromatography.

RESULTS

In 36 pigs treated unilaterally with RDN, norepinephrin content of the treated right kidney was 48.2% of the untreated left kidney. QRA measurements following RDN were associated with norepinephrin content only of the (treated) right kidney. In the human QRA study (n = 43 patients), mean 24-h BP fell by 8/4 and 12/6 mmHg at 1 and 12 months, respectively. More pronounced changes in QRA measurements were associated with a more pronounced BP drop. In multiple regression models, the change in minimum diameter was independently associated with BP changes at 12 months. In the prospective IVUS study (n = 17 patients), a larger decrease in minimum lumen/vessel area and larger increase of wall area/volume were associated with a larger BP drop.

CONCLUSION

Focal and global changes in renal arteries following RDN can be quantified, using QRA or IVUS, and may serve as markers of a successful procedure.

Influence of pseudo-resistance on the effect of renal denervation on 24-hour ambulatory blood pressure levels

BACKGROUND

Renal denervation (RDN) is a promising treatment option in addition to medical antihypertensive treatment in patients suffering from resistant hypertension. Despite the growing interest in RDN, the negative result of the Symplicity HTN-3 trial led to a debate on the efficacy of RDN.

METHODS

We systematically investigated the effects of RDN, evaluated by 24-hr ambulatory blood pressure measurements (ABPM), in a consecutive series of patients with resistant hypertension, which was defined by a mean office systolic blood pressure (SBP) >160 mm Hg (>150 mm Hg in patients with diabetes). Patients with a mean 24-hr SBP of less than 130 mm Hg at baseline were classified as pseudo-resistant, while all other patients were classified as true-resistant. After six months, we analyzed the response rates in true-resistant and in pseudo-resistant patients, respectively, by the means of 24-hr ABPM. Thereby, patients with a reduction of more than 5 mm Hg in 24-hr SBP were classified as responders.

RESULTS

RDN was performed in 106 patients. By 24-hr ABPM, 20 patients (18.9%) were classified as pseudo-resistant patients. In this cohort, we only found two responders (response rate 10%) six months after RDN. By contrast, in true-resistant patients, the response rate was almost 60% and the mean BP reduction was -18.6/-9 mm Hg in 24-hr ABPM.

CONCLUSIONS

We found a significant BP reduction in almost 60% of patients with true-resistant hypertension, but only in 10% in patients with pseudo-resistant hypertension. According to our results, patient selection seems to be crucial for acceptable response rates after RDN.