New insights into spinal cord ischaemia after thoracic aortic procedures: the importance of the number of anterior radiculomedullary arteries for surgical outcome

OBJECTIVES: Anterior radiculomedullary arteries (ARMAs) link dorsal segmental arteries and the intraspinal compartment of the spinal collateral network. The number of thoracic ARMA is highly variable from one person to another. The impact of the number of ARMAs on spinal cord perfusion during thoracic aortic procedures is unknown. We investigated the influence of the number of thoracic ARMAs on spinal cord perfusion in an aortic surgical large animal model. METHODS: Twenty-six pigs were included (20 treatment animals, 6 sham animals, weight 34 +/- 3 kg). The animals underwent ligation of the left subclavian artery and the thoracic segmental arteries via a left lateral thoracotomy with normothermia. After sacrifice, complete body perfusion with coloured cast resin was performed and the number of thoracic ARMAs was documented at autopsy. End points were spinal cord perfusion pressure, cerebrospinal fluid pressure, spinal cord blood flow (microspheres) and neurological outcome. Observation time was 3 h post-ligation. RESULTS: The numbers of thoracic ARMAs ranged between 3 (n = 1) and 13 (n = 1). The mean number was 8. Animals were grouped according to number of thoracic ARMA: 6-7 (5 animals), 8-10 (8 animals) and 11-13 (5 animals). A large number of thoracic ARMAs was linked to (i) a lower drop in spinal cord blood flow from baseline to post-clamp, (ii) the presence and increased magnitude of hyperaemia evident 3 h post-clamp (P < 0.001) and (iii) the presence of early hyperaemia starting immediately post-clamp in animals with 11 or more ARMA (P < 0.001). CONCLUSIONS: We showed that a large number of thoracic ARMA protects against spinal cord injury during descending aortic surgical procedures.1