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Is spinal cord ischemia following total aortic arch replacement and endovascular stenting of the descending thoracic aorta (TEVAR) still an issue? Pathophysiological investigations in a porcine model.
Peter Haldenwang1, Lorine Häuser1, Nora Prochnow2, Andreas Baumann1, Dirk Buchwald1, I Schmitz1, Markus Schlömicher1, Justus Strauch1.
1BG University Hospital Bergmannsheil Bochum, Bochum, Germany, 2Department of Neuroanatomy and Molecular Brain Research, Ruhr-University of Bochum, Bochum, Germany.

OBJECTIVE: Open aortic arch replacement and endovascular stenting of the descending thoracic aorta (TEVAR) represent the therapies of choice for complicated aortic diseases.
Aim of our study was to analyze in an established animal model if the combination of open arch replacement with extended selective cerebral perfusion (SCP) and an endovascular stenting of the descending aorta (TEVAR) and may cause spinal cord ischemia.
METHODS: Fourteen pigs (41±3kg) were cooled on CPB to 28°C. After clamping of the aortic arch, SCP was established for 90 min: randomly, in n=7 animals the left sided vertebral artery as well as the T4-T13 thoracic segmental arteries (TSA) were clipped, in order to simulate a TEVAR procedure, whereas the TSA of the other n=7 animals remained untouched. After systemic reperfusion and CPB weaning, hemodynamic data were registered for 120min. Microspheres were injected at baseline, reaching of 28°C, during SCP, respectively at 60 and 120min off-CPB for spinal cord blood flow (SCBF) calculation. Via trans-cranial stimulation motor-evoked potentials (MEP) were assessed at the same time points. After sacrifice, the thoracic and lumbar spinal cord was analyzed histologically using transmission electron microscopy (TEM), for necrosis staging and light microscopy for necrosis grading using a 9-point schematic grading system (Kleinman-Score: 0=normal, 8= total necrosis).
RESULTS: During SCP the SCBF presented physiologic values (5.9 ± 2.4 ml/min/100g) for T4-T13, but showed a significant decrease in the L1-L5 region (from 8.4±4.3 to 1.3 ± 1.5 ml/min/100g). After CPB-weaning a hyperperfusion was seen in both groups. The MEP had a significant deeper amplitude decrease for L1-L5 in the TSA-clipped-animals: 59 ± 7%vs.84 ± 15% (vastus medialis) and 48 ± 6%vs.82 ± 26% (tibialis anterior). MEP-amplitude recovered only in the non-clipped-group. The histologic examination showed early ischemic alterations of the cytoplasm and advanced stages of necrosis (TEM) in 12 of 14 animals. Lumbar ischemia rate was higher in the TSA-clipped-animals (Kleinman-Score: 6.0 ± 0.6vs.2.5 ± 2.3).
CONCLUSIONS: 90min of SCP provide sufficient spinal cord protection during arch replacement at 28°C. In combination with TEVAR of the descending aorta the lumbar spinal cord perfusion may be altered, which causes functional and structural damage.

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