Bolton Medical (Sunrise, Florida), now owned by Terumo (Tokyo, Japan), introduced the Relay thoracic endovascular aortic repair (TEVAR) endograft in 2005, with Phase II trials for approval in the United States beginning in 2007. In 2009, RelayPlus was introduced, which is now one of Bolton Medical’s main TEVAR endografts. While the endograft itself remained the same, the delivery system was updated. RelayPlus is the company’s only endograft approved for use in the United States by the Food and Drug Administration (FDA), receiving this approval on September 21, 2012.
Bolton Medical also manufactures RelayNBSPlus, an alternative to RelayPlus. Although the delivery system is the same, the RelayNBSPlus does not feature an uncovered fixation portion proximally. The company also offers customizable options for unique anatomy. As these two endografts lack FDA approval, this chapter will only focus on RelayPlus.
RelayPlus ( Fig. 22.1 ) is indicated for the treatment of thoracic aorta aneurysms (TAAs) and penetrating atherosclerotic ulcers (PAUs). Treatment of aortic dissections or traumatic aortic injuries is currently an off-label use. The endograft consists of nitinol stents sutured to a polyester fabric. More unique to RelayPlus is a curved bar of nitinol, called an “S-bar”, which runs along the length of the graft. This provides longitudinal and torsional stability, theoretically allowing for better graft apposition along the aortic arch. In the literature, it remains unclear whether this S-bar translates to lower endoleak and migration rates. Proximally, the device has a bare stent that provides alignment to the graft and is 13–21 mm long, depending on endograft length. Radial force is primarily achieved through the first and last covered stents, with additional radial force achieved by the second covered stent. Sizes for the endografts are shown in Table 22.1 .
|Endograft lengths||100, 150, 200, 250 mm|
|Endograft diameters||22–46 mm with diameters available every 2 mm|
|Tapered endograft lengths||150, 200, 250 mm|
|Tapered endograft diameters||28–46 mm proximally, with proximal diameters available every 2 mm. Distally, diameter is 4 mm less than proximal end.|
Tapered endografts are also available, with the distal end 4 mm narrower than the proximal end. Sizes are more limited, however, and can accommodate proximal necks from 24 to 42 mm. Instructions for use (IFU) for the endograft are shown in Table 22.2 . Be cognizant that proximal and distal sealing zone lengths differ depending on endograft size.
|Pathology||Thoracic aorta aneurysms and penetrating atherosclerotic ulcers|
|Proximal aortic diameter||19–42 mm|
|Proximal landing zone|
|Distal landing zone|
|Other||Ability for iliofemoral system to accommodate 22–26 French sheaths|
The delivery system ( Fig. 22.2 ) is a hydrophilic coaxial construct with the endograft mounted inside a secondary sheath, which is mounted inside a primary sheath. The secondary sheath can be left behind if additional procedures (balloon angioplasty, angiography, etc.) are needed after deployment. The system is available from 22 to 26 French outer diameter, comparable to other TEVAR delivery systems. The endograft is deployed by retracting the secondary sheath over the endograft (a “pin-and-pull” deployment system). The proximal bare-stent portion is attached to a tip-capture mechanism, mitigating bare stent eversion on deployment.
RelayPlus is MRI conditional, allowing patients to undergo MRI if the MRI is in normal or first level controlled operating modes, with a 1.5 or 3 T magnetic field, a 720 G/cm or less magnetic field spatial gradient, and a maximum whole-body averaged specific absorption rate of 4 W/kg for 15 minutes of scanning. These recommendations are based on nonclinical trials.
The main study evaluating outcomes is the Bolton Relay Thoracic Aorta Endovascular Pivotal Trial, which evaluated 133 patients treated with the original Relay endograft (with the RelayTransport delivery system) for TAAs and later for PAUs. Between January 2007 and May 2010, 120 patients received surgery, with an additional 13 recruited between May 2010 and FDA approval. For the final 38 patients RelayPlus was used instead. Patients were also compared with 60 open surgical control patients. The two groups were statistically similar, although in the Relay group there were more patients with saccular aneurysms and PAUs.
Successful endograft deployment was achieved in 96.9% without damage to the endograft, intraoperative deaths, or the need for conversion to an open procedure. One patient had kinking and twisting of the endograft without compromised flow. Of the four patients who had an unsuccessful implantation, three were unsuccessful because of severe atherosclerotic disease, and one because of the inability to rotate endograft to correct alignment per IFU. After 30 days, there were 5.3% aneurysm related deaths in the Relay group, with 10% in the surgical group. A total of 20.3% of Relay patients and 48.3% of surgical patients suffered from a major adverse event (defined as stroke, paralysis, myocardial infarction, respiratory failure, renal failure, wound healing issues, and aneurysm related mortality). Over 1 year, 25.6% of Relay patients and 50% of surgical patients had at least one of these events. Over a 5-year postoperative period, freedom from major adverse events was higher in the Relay group (65.7% versus 44.7%). The surgical group also experienced higher rates of respiratory failure and procedural bleeding.
Outcomes for the endograft itself were also good. Among the RelayPlus subset, there was a 0% stroke rate at 30 days and a 2.6% overall stroke rate, no Type I or III endoleaks, no migrations, and no stent fractures. All endografts remained patent during the study period. Only 15% of patients had an increase of their aneurysm size of more than 5 mm. Of these patients, only one underwent another procedure 2 years later, with no further expansion. Overall, 7.5% of patients required a secondary intervention.
Planning for placement of the RelayPlus endograft follows the same general principles for the placement of any thoracic endograft, described in Chapter 18 . Specific to this device, aortic diameter should be measured from outer wall to outer wall.
The deployment steps for the RelayPlus endograft are demonstrated in Fig. 22.3 . To ensure adequate and safe deployment, all steps should be followed closely and measures should be taken not to deviate from protocol.