Experimental simulated staged repair of extensive thoracoabdominal aneurysms significantly reduces paraplegia risk

Aims: In a pig model, we compared spinal cord injury (SCI) and collateral network (CN) perfusion pressure after extensive segmental artery (SA) sacrifice in a single-stage with recovery after a two-stage procedure: lumbar followed by thoracic SA-sacrifice.

Methods: Juvenile Yorkshire pigs (N=20) were randomly assigned to undergo extensive SA-sacrifice at 32°C either in a single operation (group-A; N=10), or in two, staged operations with thoracic SA-ligation 7 days after lumbar SA-sacrifice (group-B; N=10). The CN-pressure was monitored using a catheter placed in the distal stump of the first lumbar SA. Intraoperatively, spinal cord function was evaluated using motor-evoked potentials (MEP), and for 5 days postoperatively using a modified Tarlov score.

Results: MEPs were intact in all pigs until 1h after surgery. All pigs in group-B fully recovered hind limb function, whereas 40% in group-A experienced paraplegia (median modified Tarlov scores 9 vs. 7; p=0.004). In group-A CN-pressure fell to 28±6mmHg after single-stage operation, compared with 44±8mmHg in group-B (p<0.0001). After completed SA-sacrifice CN-pressures in group-B remained significantly higher than in group-A from end clamping until 72h postoperatively (p=0.0002); histopathologic analysis showed more severe ischaemic damage to the lower thoracic (p<0.001) and lumbar spinal cord (p=0.01) in group-A.

Conclusions: In contrast with the single-stage approach, the two-stage procedure lead to only a mild drop in CN-pressure and stimulated vascular remodeling, minimizing the impact of subsequent SA-sacrifice on spinal cord function. The greater safety of extensive SA-sacrifice when undertaken in two stages has important implications for endovascular and hybrid aneurysm repair.