Renal sympathetic denervation: MDCT evaluation of the renal arteries

Quantitative angiographic anatomy of the renal arteries and adjacent aorta in the swine for preclinical studies of intravascular catheterization devices

Swine are the most common animal model in preclinical studies of cardiovascular devices. Because of the recent trend for development of new devices for percutaneous catheterization, especially for the renal arteries (RAs), we examined the quantitative anatomical dimensions of the RAs and adjacent aorta in swine. Angiographic images were analyzed in 66 female Yorkshire/Landrace crossbred swine. The diameter of both the right and left main RA was 5.4 ± 0.6 mm. The length of the right main RA was significantly longer than that of the left (29.8 ± 7.5 mm vs. 20.6 ± 5.4 mm, respectively; P<0.001). The diameter of both the right and left branch RA with diameters ≥3 mm (the target vessel diameter of recently developed devices) was 3.8 ± 0.5 mm. The right branch RA was significantly longer than that of the left (18.9 ± 7.8 mm vs. 16.4 ± 7.4 mm, respectively; P<0.05). The branching angle of the right RA from the aorta was significantly smaller than that of the left (91 ± 12° vs. 103 ± 15°, respectively; P<0.001). The diameters of the suprarenal and infrarenal aorta were 10.6 ± 1.1 mm and 9.7 ± 0.9 mm, respectively. In conclusion, because of their similar dimensions to human, swine are an appropriate animal model for assessing the safety of, and determining optimal design of, catheter devices for RAs in simulated clinical use. However, there were species differences in the branching angle and adjacent aorta diameter, suggesting that swine models alone are inadequate to assess the delivery performance of catheter devices for RAs.

Innervation patterns may limit response to endovascular renal denervation

BACKGROUND

Renal denervation is a new interventional approach to treat hypertension with variable results.

OBJECTIVES

The purpose of this study was to correlate response to endovascular radiofrequency ablation of renal arteries with nerve and ganglia distributions. We examined how renal neural network anatomy affected treatment efficacy.

METHODS

A multielectrode radiofrequency catheter (15 W/60 s) treated 8 renal arteries (group 1). Arteries and kidneys were harvested 7 days post-treatment. Renal norepinephrine (NEPI) levels were correlated with ablation zone geometries and neural injury. Nerve and ganglion distributions and sizes were quantified at discrete distances from the aorta and were compared with 16 control arteries (group 2).

RESULTS

Nerve and ganglia distributions varied with distance from the aorta (p < 0.001). A total of 75% of nerves fell within a circumferential area of 9.3, 6.3, and 3.4 mm of the lumen and 0.3, 3.0, and 6.0 mm from the aorta. Efficacy (NEPI 37 ng/g) was observed in only 1 of 8 treated arteries where ablation involved all 4 quadrants, reached a depth of 9.1 mm, and affected 50% of nerves. In 7 treated arteries, NEPI levels remained at baseline values (620 to 991 ng/g), ≤20% of the nerves were affected, and the ablation areas were smaller (16.2 ± 10.9 mm(2)) and present in only 1 to 2 quadrants at maximal depths of 3.8 ± 2.7 mm.

CONCLUSIONS

Renal denervation procedures that do not account for asymmetries in renal periarterial nerve and ganglia distribution may miss targets and fall below the critical threshold for effect. This phenomenon is most acute in the ostium but holds throughout the renal artery, which requires further definition.