This analysis of tissues from human autopsies hints that further BP reductions can be achieved with this approach.
Ablating the sympathetic nerves in accessory renal arteries might help enhance the blood pressure-lowering effects of renal denervation, a study of tissues from human cadavers suggests.
Though accessory renal arteries were smaller in diameter and had about two-thirds the number of nerves found in the main arteries, the size of the nerves running through them was similar, Yu Sato, MD (CVPath Institute, Gaithersburg, MD), reported during the virtual TCT Connect 2020 meeting.
As the diameter of the arteries increased, so too did the number of nerves per section based on an angiographic analysis—from 24.5 in accessory arteries smaller than 3 mm, to 38 in accessory arteries 3 mm or larger, to 53 in dominant renal arteries.
The results, also published online in JACC: Cardiovascular Interventions, “suggest that renal denervation for accessory renal arteries should result in an additional blood pressure reduction,” Sato concluded. “Further renal denervation clinical trials should consider including patients with accessory renal arteries.”
To TCTMD, senior author Aloke Finn, MD (CVPath Institute), said there has been a question about whether nerves in accessory renal arteries—which are found in about 30% of patients—need to be ablated as part of the renal denervation procedure. “But it’s not really been systematically studied, and it remains kind of a murky area in this . . . field.”
Some renal denervation trials have excluded patients with accessory arteries, whereas the trials that allowed them excluded those with smaller accessory arteries (less than 3 or 4 mm in diameter). But there is some evidence from prior research that ablating the nerves in the accessory arteries may lead to greater BP reduction with renal denervation.
An analysis of the RADIANCE-HTN SOLO trial, for instance, showed that patients with untreated accessory arteries had less of a BP response to denervation with the Paradise ultrasound system (ReCor Medical).
The larger the accessory renal artery, the more nerves, and the more worthwhile that is for denervation. Aloke Finn
To gain a better understanding of the sympathetic nerves’ anatomic distribution around accessory renal arteries, Sato, Finn, and colleagues examined renal arteries from eight human cadavers (mean age 60.3 years; 75% men). Five of the individuals had suffered a sudden cardiac death, and the other three died from noncoronary causes. Five had hypertension.
The study included examination of 23 renal arteries, including 14 accessory and nine dominant (supplying blood to more than 50% of the kidney). An accessory artery was one that arose from the aorta above or below the main renal artery (n = 10) or that bifurcated within 20 mm of where the main artery originated (n = 4). Those arteries included a total of 7,287 nerves.
Histologic analysis showed that accessory arteries were smaller in diameter compared with the dominant arteries (median 3.72 vs 3.99 mm; P = 0.0045) and had fewer nerves per section (median 30 vs 49; P < 0.0001). However, the median shortest nerve diameter did not differ by artery type (0.088 mm in both groups; P = 0.57). Nerves in the accessories were closer to the arterial lumen than those in the dominant arteries (median 1.55 vs 2.19 mm; P < 0.0001).
Using postmortem angiography, the researchers divided arteries into three groups: small accessories (less than 3 mm), large accessories (3 mm or greater), and dominant arteries. Average arterial diameters were 2.61 mm, 3.57 mm, and 4.47 mm, respectively, across the three groups. The corresponding average proportions of perfused kidney area were 20.1%, 36.5%, and 60.2%. Larger arteries had more nerves.
“We found that accessory renal arteries did have significant periarterial nerve distribution and that . . . probably makes them worth going after in terms of the [renal denervation] procedure,” Finn said, adding that “the larger the accessory renal artery, the more nerves, and the more worthwhile that is for denervation.”
He pointed out that current renal denervation technologies can get into arteries as small as about 3 mm, suggesting that modifications would have to be made to treat smaller accessories.
After Sato’s presentation, Sahil Parikh, MD (NewYork-Presbyterian/Columbia University Irving Medical Center, New York, NY), one of the moderators, said “that anatomic insight also suggests that there may be a role for complementary techniques” for treating different vessel sizes. “Whereas we’ve been trying heretofore to try one device per individual patient, I suspect we’ll have a superior effect if we were to use multimodality treatment,” he said.
Panelist Robert Lookstein, MD (Icahn School of Medicine at Mount Sinai, New York, NY), said these data contribute to the idea “that the concept of renal denervation is nowhere near as simple as we originally thought. And while everyone is desperately looking for a technology that can handle resistant hypertension, we’re really going to have to think outside the box, and the role of accessory renal arteries is without question going to play a role. We don’t have the devices right now that can, off the shelf, tackle all the different anatomic substrates we’re going to see.”
The clinical translation of these findings will be critical, Finn said. “Obviously, just by knowing the nerve distribution we can’t tell you the additional effect in terms of blood pressure-lowering of denervating these nerves around these arteries. But this suggests that in terms of standardized protocols, patients with accessory renals shouldn’t be excluded and that accessory renals that are amenable to the technology, whatever technology that is, should be a target for ablation.”