Cath Lab Digest

Review of Previous and Current Clinical Trials
Currently, there are several thoracic endografts available for the treatment of descending thoracic aortic aneurysms. They are the TAG device made by WL Gore (Flagstaff, Arizona), the TX2 device by Cook, Inc. (Bloomington, Indiana), the Talent and Valiant devices by Medtronic (Santa Rosa, California), and the Relay device by Bolton Medical (Sunrise, Florida). At this time, the only thoracic endograft approved by the FDA for use in the United States is the TAG device. The TX2 device and Talent device have completed their initial enrollment and have been submitted to the U.S. Food and Drug Administration (FDA) for approval. They are expected to gain FDA approval in late 2007 or early 2008. The Valiant and Relay devices are also in clinical trial and currently enrolling patients. Tables 1 and 2 list both the inclusion and exclusion criteria, respectively, for each of the major trials.

TAG Device (WL Gore and Associates)
The TAG device is a symmetrical expanded PTFE tube with an external nitinol self-expanding stent along the entire graft surface. A circumferential PTFE sealing cuff is located on the external surface of the endograft at the base of each flared, scalloped end. This device is currently the only device commercially available at this time.

The TAG device was investigated in the Pivotal trial completed in 2001. This was a nonrandomized, controlled clinical trial. There were two arms in the study. The first arm was the control group, which consisted of 94 patients treated by open surgical repair. The second arm was the device treatment group, which consisted of 142 patients treated with the TAG device. As shown in Table 1, at least 2 cm of the normal descending thoracic aorta was required distal to the left common carotid artery and proximal to the celiac artery in order to be enrolled in the trial. A left subclavian artery revascularization procedure was mandated by the trial design.

Of the 142 patients, 139 (98%) had a successful implantation of the device. The 3 failures were attributed to inadequate arterial access. The mean size of the treated descending thoracic aneurysm was 64.1 ± 15.4 mm. The average age of patients treated was 71 years. The majority of the patients were male (57.7%). Single graft therapy was achieved in 44% of patients and the additional 56% of patients required two or more devices to exclude the aneurysm. Of the patients 90% were American Society of Anesthesiologists category III or IV. In 28 patients, repair of the aneurysm required covering the left subclavian artery.

The procedure time averaged 150 minutes, and the estimated blood loss averaged 506 ml for the endovascular treatment arm. The post-procedure hospital stay for the TAG device patients averaged 7.6 days, with an average of 2.6 days in the intensive care unit. The 30-day morbidity rate was 32%, which included 45 patients who had at least 1 adverse event. Of those 45 patients, 5 (4% of the total patient pool) experienced a stroke, 4 (3%) demonstrated temporary or permanent paraplegia, 20 (14%) experienced vascular trauma or thrombosis, and 2 (1.5%) died.

The mean length of follow-up was 24 months. Four of the patients had aneurysm-related deaths during this period. Three patients underwent endovascular procedures to correct endoleaks. No ruptures were reported. Of note, 20 wire fractures were identified in 19 patients (13%). Of these wire fractures, 18 (90%) occurred in the longitudinal spine, and only 1 patient required treatment, due to a type 3 endoleak. At 2 years, aneurysm-related and overall survival rates were 97% and 75%, respectively. Of the three patients that expired within the first 30 days, one death was secondary to a postoperative stroke. The second death was attributed to a cardiac event on postoperative day 11. A third death occurred outside the 30-day period, but during the same admission after a long hospital course (7 months), secondary to anoxic brain injury after a respiratory arrest. In comparison, 6 (6.4%) deaths occurred in the surgical control group. Spinal cord ischemia (SCI) was noted in 4 patients in the TAG group (3%). Three patients recovered function, but one patient’s deficit persisted. In the surgical control group, the incidence of SCI was significantly higher at 14%. Cerebrovascular incidents were equal among the two groups, both at 4.3%. Endoleaks occurred in 5 (3%) of the TAG patients. Vascular injury in the TAG group was higher at 14% as compared to 4% in the open surgical group. This significantly higher rate of vascular injury was associated with the passage of large introducer sheaths through the iliac arteries. A comparison of complications is illustrated in Figure 1.

As stated earlier, there were 20 wire fractures in the original TAG device (99-01) in the Pivotal trial and 19 of these were in the longitudinal spine. This prompted a redesign of the TAG device, which included the removal of the longitudinal spine and the addition of a low permeability film layer. These changes provide longitudinal stiffness for deployment accuracy and the change is also an attempt to decrease the permeability of the device and prevent endotension. Below is a picture of both the original and the modified TAG devices. (Figure 2)

The modified device (TAG 03-03) was then evaluated in the TAG Confirmatory trial. The Confirmatory trial consisted of 51 patients treated with the Modified Tag Device and the open surgical controls were used from the original Pivotal Trial (99-01). The 51 patients were enrolled by June 2004 and the 5-year follow up is currently ongoing.