The Colt Device for Treating Thoraco-Abdominal Aneurysms - Concept and Clinical Results

To report results of application a new stent graft design for the treatment of patients with thoraco-abdominal aneurysms (TAAAs), which was co-invented by a vascular surgeon. This is a retrospective observational study.

The Colt is a self-expanding stent graft, composed of nitinol metal stents creating a special exoskeleton with asymmetric springs covered with polyester material. The Colt device offers some advantages over existing stent graft options. The main body is available in two different diameters on both ends and in three different lengths. It has four branches pointing downward and coming from the main stent graft at two levels. It offers the physician an opportunity to decide which branch to choose for the target vessel. It may be implanted alone or extended proximally and distally. Balloon expandable and/or self-expanding stent grafts are used to create the visceral branches. In complex extensive aneurysms, the procedure is divided into two or three stages to minimize the risks of spinal cord ischemia.

Between August 2015 and December 2021, twenty-two Colt stent grafts were implanted in twenty males and two females (aged 56-81) with TAAAs (eight Type II; twelve Type III; two Type IV). The mean aneurysm diameter was 73.4 mm (range 64-83). All patients were asymptomatic. Eighty-five target vessels were reconstructed using either self-expanding or balloon-expandable stent grafts. Fourteen bifurcated, six custom-made tubes and two aortouniiliac (AUI) stent grafts were used as distal extensions to the Colt device. Completion angiography revealed no type I endoleaks. Five patients had Type II endoleaks which were treated conservatively. There were no intraoperative deaths. One patient died on the 7th postoperative day from multiorgan failure. We did not observe any other complications within 30 days after implantation. One patient died from Covid-19 two months after discharge. Follow-up ranged from three to 75 months. There was no migration or dislocation of the docking station or proximal and distal extensions. All Colt device prostheses remained patent, however, two branches leading to the coeliac trunk were found occluded at the time of the 12-month CTA, without any symptoms. In two patients, there were late problems with three renal bridging stent grafts. One of the Type II endoleaks resolved spontaneously after one year, while four others remain under observation. No patient had an increase in sac diameter.

Results from the current series are promising. The Colt stent graft can be applied to a large variety of TAAA anatomies, which may facilitate the development of new "off-the-shelf" devices in the future.