TEVAR Still a Challenge; But These Tips May Help

By Kerri Wachter

NEW YORK -- While stent grafting of thoracic aortic aneurysm has become more routine, the procedure still has a number of limitations, Martin Malina, Ph.D., said at the Veith symposium on vascular medicine sponsored by the Cleveland Clinic.

Currently-available thoracic endografts are limited by issues related to access, hostile neck, deployment, and durability. Dr. Malina, a consultant vascular surgeon at Malmö (Sweden) University Hospital, offered his thoughts on these limitations and some tips for overcoming them.

Access. While access remains a problem for thoracic stent grafts, "we do have many quite simple tricks to get around this problem," said Dr. Malina.

He recommends using an ultra-stiff guidewire. In addition, don't push the graft in. "The more you push, the more the wire buckles," he said. To avoid this, use a brachial wire to pull the graft by placing a clamp at the lower end of the wire. "This way, the more you pull, the more the wire will get straightened out."

Iliac stenosis poses an access problem. One alternative is to make an incision in the groin and to advance the sheath outside of and parallel to the external iliac artery, inserting the graft at a more favorable angle.

"Actually, nowadays I feel access is very rarely a limiting factor," said Dr. Malina.

The neck. "Very often there is no neck," said Dr. Malina. One option in these cases is to push the stent graft farther around the arch, covering the left subclavian artery. Contraindications to this technique include right vertebral stenosis, aberrant right subclavian artery lusoria, or left internal mammary artery coronary bypass.

"In these cases, you still can cover the left subclavian, if you do it first," said Dr. Malina. This can be followed by transposition of the subclavian or carotid-subclavian bypass.

Deployment. "It is actually very hard to assess where the stent graft will be deployed," said Dr. Malina. Whether the carotid artery will be covered is of particular concern, even after the stent has been deployed. Some projections used to view the stent may give the appearance that the carotid artery is not covered, when in fact it is or vice versa. "You have to find the ideal projection ... to really prove that you have not covered the vessel," he said.

Durability. When the stent is deployed at the vertex of an elongated aortic arch, "the blood will hit the upper surface of the stent-graft and you will end up having a flapping motion, which is clearly bad," said Dr. Malina. The flapping motion contributes to material fatigue and possibly stent collapse, leading to occlusion or migration and high risk of death. "Also this flapping motion may erode the arch and cause immediate rupture and hemorrhage," he said.

Motion also should be avoided when telescoping the various components. Otherwise the stent-graft can disintegrate. Also, without sufficient overlap, the stent can migrate upward. "So wherever you place the stent-graft, you must make sure that you have enough overlap and secure the position of the stent-graft without any motion," said Dr. Malina. Usually this means going beyond the vertex of the arch to get a secure deployment.

Dr. Malina disclosed that he had no conflicts of interest.