Anatomic Assessment of Sympathetic Peri-Arterial Renal Nerves in Man

BACKGROUND Although renal sympathetic denervation therapy has shown promising results in patients with resistant hypertension, the human anatomy of peri-arterial renal nerves is poorly understood. OBJECTIVES The aim of our study was to investigate the anatomic distribution of peri-arterial sympathetic nerves around human renal arteries. METHODS Bilateral renal arteries were collected from human autopsy subjects, and peri-arterial renal nerve anatomy was examined by using morphometric software. The ratio of afferent to efferent nerve fibers was investigated by dual immunofluorescence staining using antibodies targeted for anti-tyrosine hydroxylase and anti-calcitonin gene-related peptide. RESULTS A total of 10,329 nerves were identified from 20 (12 hypertensive and 8 nonhypertensive) patients. The mean individual number of nerves in the proximal and middle segments was similar (39.6 +/- 16.7 per section and 39.9 +/- 1 3.9 per section), whereas the distal segment showed fewer nerves (33.6 +/- 13.1 per section) (p = 0.01). Mean subject-specific nerve distance to arterial lumen was greatest in proximal segments (3.40 +/- 0.78 mm), followed by middle segments (3.10 +/- 0.69 mm), and least in distal segments (2.60 +/- 0.77 mm) (p < 0.001). The mean number of nerves in the ventral region (11.0 +/- 3.5 per section) was greater compared with the dorsal region (6.2 +/- 3.0 per section) (p < 0.001). Efferent nerve fibers were predominant (tyrosine hydroxylase/calcitonin gene-related peptide ratio 25.1 +/- 33.4; p < 0.0001). Nerve anatomy in hypertensive patients was not considerably different compared with nonhypertensive patients. CONCLUSIONS The density of peri-arterial renal sympathetic nerve fibers is lower in distal segments and dorsal locations. There is a clear predominance of efferent nerve fibers, with decreasing prevalence of afferent nerves from proximal to distal peri-arterial and renal parenchyma. Understanding these anatomic patterns is important for refinement of renal denervation procedures. (C) 2014 by the American College of Cardiology Foundation.