Anatomical predictors for blood pressure outcome after endovascular ultrasound renal denervation

Aims: Renal denervation for hypertension shows broad variety in blood pressure (BP) reduction. Anatomical factors as renal artery diameter or course of renal veins might reduce the efficacy of renal denervation procedures due to incomplete ablation patterns. Furthermore, the relation between renal arteries’ length and the distance between aorta and kidney, which is associated with the presence of late arriving renal nerves, might affect completeness of denervation. We aimed to investigate the influence of anatomical factors on ultrasound renal denervation (uRDN) in a prospective cohort.

Methods and results: Eighty patients with treatment resistant arterial hypertension underwent magnetic resonance imaging (MRI) of the renal vasculature before uRDN. Ambulatory blood pressure measurements were taken before and 3 months after uRDN. Patients with a systolic BP drop of >5 mmHg on 24h average after 3 months were classified as responders, all other patients as non-responders. MRI was used to measure a) the diameter of three segments of both main renal arteries, b) the minimal arterial venous distance (AVD) and c) main renal arteries' lenght, the distance between the aorta and both kidneys’ hilum as well as the lenght-to-distance ratio (LTDR).

After 3 months, 24h ambulatory BP was reduced by -18.0 ±9.7 mmHg in responders and was unchanged in non-responders (+0.6 ±5.0 mmHg). Three-months BP responders had a) comparable renal artery diameters throughout all renal arteries’ segments (mean renal artery diameter responders vs. non-responders right 5.7 ±0.7 mm vs. 6.0 ±0.9, left 5.9 ±0.9 and 5.9 ±0.7 mm, p = 0.16 and 0.96 respectively); b) no significant difference in AVD (right 2.0 ±1.7 vs. 1.4 ±0.7 mm, left 3.7 ±3.6 vs. 3.6 ±2.6 mm, p=0.34 and 0.79 respectively) and c) a significantly smaller distance between the right renal hilum and the aorta (78.7 ±8.7 vs. 84.7 ±11.3 mm, p = 0.009), with no significant differences for the left aortic-hilum distance or LTDR. Area under the curve for the prediction of a BP response for the right aortic hilum distance was 0.69. Youden-index allowed to classify patients with a poor BP response relatively accurate: Mean 24h BP reduction  was -12.0 ±12.6 vs. -3 ±7.3 mmHg for patients below vs. above the cut-off of 89.6 mm.

Conclusions: Renal artery diameter, vein-artery distance and LTDR did not influence BP reduction after uRDN. In contrast, the right-renal aortic-hilum distance was correlated with BP outcome and might serve as a predictor for BP outcomes following uRDN after confirmation in future prospective studies.