Krassi Ivancev, University College and Royal Free Hospital, London, UK, presented at the VEITHsymposium (14-18 November 2012, New York, USA) the experience of complete endovascular graft exclusion of arch aneurysms using a non-custom-made branched arched device.
“The arch is certainly a challenging endovascular environment. It is wide, curved, has branches to the brain, is close to the aortic valve, is far from the femoral arteries and is constantly moving,” he said.
The current design of the branched arch device is based on a stent graft delivered via the transfemoral route, the TX2 thoracic stent-graft (Cook Medical). This device incorporates two internalised sleeves for the innominate and left carotid branches with large funnel openings to facilitate retrograde cannulation. The graft is mounted on a pre-curved cannula (and pre-curved sheath), “which conforms in a reliable fashion to the curvature of the arch,” Ivancev stated.
In addition, he commented, the stent graft is mounted onto the cannula with a spiral trigger wire wound round the cannula, and as such the funnels are reliably delivered to the outer curvature of the arch facilitating orientation.
Trigger wires secure “pro-form” alignment of the first two sealing stents into the curved portion of the ascending aorta. The portion of the graft containing the openings of the internalised sleeves (the funnels) is reduced in diameter which allows continued antegrade cerebral blood flow through the graft during deployment and prior to completion with the innominate and carotid branches. Diameter reducing ties attached to trigger wires are also a standard feature. Multiple gold markers outline the funnels.
Ivancev explained that a surgical conduit is placed to the right subclavian artery and a left carotid-subclavian bypass is performed. A radiopaque tipped sheath marks the innominate artery origin. Once the stent graft has been introduced via the transfemoral route its longitudinal position can be ascertained relative to the innominate artery, with the funnel gold markers fully proximal to the innominate orifice. The graft is then unsheathed under rapid overpacing to minimise aortic movement and reduce wind-socking. All trigger wires are then removed apart from the wire securing the distal stent graft. Both sleeves are retrogradely cannulated and a bridging stent graft is then positioned from the right subclavian conduit preserving the innominate artery bifurcation. The left carotid bridging stent graft is then brought in from the ipsilateral brachial artery. The origin of the left subclavian artery may be embolised from this access to prevent a type II endoleak.
Ivancev said that so far 40 patients have been treated with the device worldwide. He added that the 30-day mortality rates show that there is a learning curve with the device. In the first 10 elective cases, mortality was 40%, and in the second 10 cases it was 10%. There were no deaths in the following 20 cases.
He stated that “this may reflect the increased pre-operative morbidity of the patients selected for this procedure, having been deemed unfit for open surgical repair. However, it also may reflect initial user inexperience with the device, as evidenced by the declining mortality in subsequent cases”. And added, “While there are clear advantages in avoiding a full thoracotomy or cardiac bypass, long-term performance is untested as only a handful of cases have been performed. Furthermore, the device is limited to treatment of arch disease and significant pathologies in the ascending aorta (Ishimaru zone 0) will require alternative approaches.”
Ivancev said that in a the two-branch format, a left carotid-subclavian bypass is still required for preservation of the left vertebral artery though modifications are in progress for placement of a third left subclavian artery sleeve to overcome this, and this clearly adds to the endovascular complexity of the case. “Even with this modification, a surgical cutdown to the neck vessels is required for branch delivery,” he said. “One considered alternative is a minithoracotomy with trans-ventricular antegrade cannulation, pre-loaded wires, and antegrade delivery of the branch stent-grafts to the sleeves with potential reduction in stroke risk and cranial nerve injury. This also permits snaring of a through wire for easier passage of the main stent-graft especially in the tortuous arch, and with highly accurate deployment. As further graft refinements are made and experience grows with the device, more meaning comparisons with current accepted treatments will be possible.”
Ivancev conclude that branch orientation and catheterisation in the arch can be technically challenging. “The current branched arch device has been designed to address these problems. Initial experience is encouraging,” he said.