Cerebral embolization, silent cerebral infarction and neurocognitive decline after thoracic endovascular aortic repair

Background

Silent cerebral infarction is brain injury detected incidentally on imaging; it can be associated with cognitive decline and future stroke. This study investigated cerebral embolization, silent cerebral infarction and neurocognitive decline following thoracic endovascular aortic repair (TEVAR).

Methods

Patients undergoing elective or emergency TEVAR at Imperial College Healthcare NHS Trust and Guy's and St Thomas' NHS Foundation Trust between January 2012 and April 2015 were recruited. Aortic atheroma graded from 1 (normal) to 5 (mobile atheroma) was evaluated by preoperative CT. Patients underwent intraoperative transcranial Doppler imaging (TCD), preoperative and postoperative cerebral MRI, and neurocognitive assessment.

Results

Fifty-two patients underwent TEVAR. Higher rates of TCD-detected embolization were observed with greater aortic atheroma (median 207 for grade 4–5 versus 100 for grade 1–3; P = 0·042), more proximal landing zones (median 450 for zone 0–1 versus 72 for zone 3–4; P = 0·001), and during stent-graft deployment and contrast injection (P = 0·001). In univariable analysis, left subclavian artery bypass (β coefficient 0·423, s.e. 132·62, P = 0·005), proximal landing zone 0–1 (β coefficient 0·504, s.e. 170·57, P = 0·001) and arch hybrid procedure (β coefficient 0·514, s.e. 182·96, P < 0·001) were predictors of cerebral emboli. Cerebral infarction was detected in 25 of 31 patients (81 per cent) who underwent MRI: 21 (68 per cent) silent and four (13 per cent) clinical strokes. Neurocognitive decline was seen in six of seven domains assessed in 15 patients with silent cerebral infarction, with age a significant predictor of decline.

Conclusion

This study demonstrates a high rate of cerebral embolization and neurocognitive decline affecting patients following TEVAR. Brain injury after TEVAR is more common than previously recognized, with cerebral infarction in more than 80 per cent of patients.

Fenestrated TEVAR Using a Guidewire Fixator for Anchoring in Aortic Arch Target Vessels

Purpose: To report a new facilitated method for securing target vessel access during single fenestrated and branched thoracic endovascular repair using a guidewire fixator. Technique: The Liungman Guidewire Fixator (LGF) includes a 0.035-inch guidewire that is fitted with a stopper close to the distal end and a self-expanding anchoring element that is freely movable over the guidewire to the point of the stopper. The technique of using a LGF for anchoring in a target vessel is described in a 75-year-old woman with a 53-mm saccular arch aneurysm. She was treated with a fenestrated Zenith stent-graft that had a catheter-preloaded fenestration for the left subclavian artery (LSA) and a scallop for the left common carotid artery. To avoid through-and-through wire and brachial access, the LGF was used to secure the guidewire in the LSA during stent-graft deployment. Conclusion: The use of an LGF for anchoring in the target LSA during fenestrated arch endografting was feasible and safe.

Air bubbles are released by thoracic endograft deployment: An in vitro experimental study

Purpose:

Embolic stroke is a dreaded complication of thoracic endovascular aortic repair. The prevailing theory about its cause is that particulate debris from atherosclerotic lesions in the aortic wall are dislodged by endovascular instruments and embolize to the brain. An alternative source of embolism might be air trapped in the endograft delivery system. The aim of this experimental study was to determine whether air is released during deployment of a thoracic endograft.

Methods:

In an experimental benchtop study, eight thoracic endografts (five Medtronic Valiant Thoracic and three Gore TAG) were deployed in a water-filled transparent container drained from air. Endografts were prepared and deployed according to their instructions for use. Deployment was filmed and the volume of air released was collected and measured in a calibrated syringe.

Results:

Air was released from all the endografts examined. Air volumes ranged from 0.1 to 0.3 mL for Medtronic Valiant Thoracic and from <0.025 to 0.04 mL for Gore TAG. The largest bubbles had a diameter of approximately 3 mm and came from the proximal end of the Medtronic Valiant device.

Conclusion:

Air bubbles are released from thoracic endografts during deployment. Air embolism may be an alternative cause of stroke during thoracic endovascular aortic repair.

Air Embolism During TEVAR

Purpose: To investigate the amount of gas released from Zenith thoracic stent-grafts using standard saline flushing vs the carbon dioxide flushing technique. Methods: In an experimental bench setting, 20 thoracic stent-grafts were separated into 2 groups of 10 endografts. One group of grafts was flushed with 60 mL saline and the other group was flushed with carbon dioxide for 5 minutes followed by 60 mL saline. All grafts were deployed into a water-filled container with a curved plastic pipe; the deployment was recorded and released gas was measured using a calibrated setup. Results: Gas was released from all grafts in both study groups during endograft deployment. The average amount of released gas per graft was significantly lower in the study group with carbon dioxide flushing (0.79 vs 0.51 mL, p=0.005). Conclusion: Thoracic endografts release significant amounts of air during deployment if flushed according to the instructions for use. Application of carbon dioxide for the flushing of thoracic stent-grafts prior to standard saline flush significantly reduces the amount of gas released during deployment. The additional use of carbon dioxide should be considered as a standard flush technique for aortic stent-grafts, especially in those implanted in proximal aortic segments, to reduce the risk of air embolism and stroke.