Advertisement
Advertisement
November 2010 Supplement
Next-Generation Devices for TEVAR
The Valiant Stent Graft: 30-day results from the VALOR II study.
Originally modeled on devices for endovascular abdominal aortic repair (EVAR), devices for thoracic endovascular aortic repair (TEVAR) have evolved toward ever greater anatomic specificity, and the latest generation of thoracic stent grafts promises improved performance with respect to the unique characteristics of the aortic arch and descending thoracic aorta—extreme tortuosity, greater hemodynamic forces, remoteness from the sites of vascular access, and risk of iatrogenic injury.1,2 The potential for complications (stent graft collapse, migration, fracture, endoleak, and retrograde type A aortic dissection) due to poor proximal alignment and apposition of the stent graft is better understood, and the risks for neurologic embolic complications and spinal cord ischemia with attendant paraplegia and paraparesis are better defined (along with the indications for adjunctive procedures such as left subclavian artery bypass and cerebrospinal fluid drainage).3-7 Vascular access for large-diameter thoracic devices has remained a major challenge, particularly in elderly women with small, calcified, stenotic external iliac arteries.3,8,9
The Valiant Thoracic Stent Graft (Medtronic, Inc., Minneapolis, MN) (Figure 1) is an evolution of the Talent Thoracic Stent Graft (Medtronic, Inc.),9 with new features specifically addressing TEVAR issues identified by earlier studies. Since 2005, when the device received Conformité Européenne (CE) Mark, the Valiant Thoracic Stent Graft has been employed for repair of thoracic aortic lesions in clinical practice outside the United States.10-12 In the United States, the Valiant Thoracic Stent Graft is currently being investigated under an investigational device exemption (IDE) in the VALOR II prospective, multicenter, single-arm trial.
THE VALIANT THORACIC
STENT GRAFT SYSTEM
The Valiant is a modular device consisting of a woven
monofilament polyester graft sutured to a self-expanding
nitinol wire stent. The nitinol scaffolding of the stent
graft is composed of a series of serpentine 5-peaked
springs stacked in a tubular configuration and sewn to
the outside (not the inside, as with the Talent Thoracic
Stent Graft) of the graft material, the raised surface of the
springs providing additional mechanical interference as
the device is modeled into the vessel wall. The proximal
and distal stents have an 8-peak configuration (as compared
to the 5-peak configuration of the Talent device)
that distributes radial force across more points of contact
with less stress per point, allowing for excellent sealing
characteristics while offering a softer interface with the aortic wall. To increase graft flexibility and conformability,
the longitudinal connecting bar of the Talent device
has been eliminated in the Valiant, and the spring spacing
has been redesigned to allow adjacent peaks to contact
each other and provide the necessary column
strength for deployment. To facilitate tailoring of the
device to particular aortic pathologies, the proximal
stent graft is available in FreeFlo configuration, and the
distal grafts are available in closed-web, straight, tapered,
and bare-spring configurations. The FreeFlo configuration
has a bare proximal spring extending beyond the edge of
the fabric, whereas the closed-web design does not have
bare proximal springs.
The Valiant Thoracic Stent Graft has been evaluated most extensively in the real-world TRAVIATA (Thoracic Repair Analysis Using Valiant in Indications of the Thoracic Aorta) retrospective multicenter registry, from which 3-year results have been published.12 In TRAVIATA, 92 patients underwent TEVAR for degenerative aneurysm (60.8%), aortic dissection (34.8%), and traumatic injury (4.4%) at four German centers between June 2005 and March 2008. The technical success rate was 86.9%. Periprocedural complications included endoleak (6.5%), systemic complications (6.5%), arterial rupture or dissection (6.5%), device-related complications (5.4%), retrograde aortic dissection (1.1%), aortic rupture (1.1%), spinal cord ischemia (1.1%), and stroke (1.1%). Through 30 days there were three deaths (3.3%). The rate of aneurysm-related mortality was 2.2%. Cumulative survival was 95.5% at 1 year, 87.4% at 2 years, and 76.4% at 3 years. No patients were converted to open surgery during the 3-year follow-up.
VALOR I I : PRELIMINARY
30-DAY RESULTS
VALOR II is a prospective, multicenter, single-arm IDE
trial conducted in the United States to evaluate the safety
and effectiveness of the Valiant Thoracic Stent Graft
System for treating thoracic aortic aneurysms (TAAs) in
the descending thoracic aorta. Enrollment of 160
patients occurred from December 2006 to September
2009 at 24 institutions across the United States. Eligible
patients were considered candidates for open surgical
repair of TAA with low to moderate risk (0, 1, and 2) per
the modified Society for Vascular Surgery/American
Association for Vascular Surgery criteria. Indications for
inclusion in the trial were fusiform TAA ≥ 5 cm or ≥ 2
times the diameter of the nonaneurysmal thoracic aorta
and/or focal saccular TAA (penetrating atherosclerotic
ulcers). Anatomical eligibility criteria included TAA ≥ 20
mm distal to the origin of the left common carotid artery
and ≥ 20 mm proximal to the celiac artery, proximal and
distal nonaneurysmal aortic neck diameter of between 20 and 42 mm, and proximal and distal nonaneurysmal
aortic neck lengths of > 20 mm. VALOR II exclusion criteria
included planned placement of the covered portion
of the stent graft in zone 0 or 1 of the aortic arch, TAA
with contained rupture, and connective tissue disease.
Standard follow-up evaluations were performed at 1, 6,
and 12 months, and annually thereafter. Follow-up visits
included a computed tomography (CT) scan, chest radiograph,
and physical examination.
The primary safety endpoint of VALOR II is 12-month all-cause mortality. The primary effectiveness endpoint is 12-month successful aneurysm treatment, defined as the absence of (1) > 5-mm aneurysm growth between 1 and 12 months and (2) type I and/or type III endoleak for which a secondary procedure was performed or recommended. The 30-day secondary endpoints included perioperative mortality, paraplegia, paraparesis, secondary procedures due to endoleak after discharge, and major adverse events.
The mean age of VALOR II patients at baseline was 72.2 ± 9.1 years, and 59.4% were men. The baseline risk profile of the VALOR II patients was similar to that for other TEVAR trials, including the VALOR trial of the Talent device9 and the report on 443 TEVAR procedures in the EUROSTAR and United Kingdom Thoracic Endograft registries.13 Concomitant vascular conditions included abdominal aortic aneurysms (AAAs) in 38.8%, previous AAA repair in 20.6%, ascending thoracic aneurysm in 8.1%, and peripheral vascular disease in 25%. At enrollment, 50 of the 160 patients (31.3%) had aneurysm-related symptoms. Core laboratory preimplant mean anatomical dimensions included maximum aneurysm diameter 57 ± 11.03 mm and aneurysm length 123.25 ± 73.02 mm. Vessel access was successful in 98.1% of patients, and device delivery and deployment in 96.3%. Three patients did not receive the study device because of access failure. There were two instances of misaligned deployment (bare spring flip). A mean number of 1.8 ± 0.8 stent graft devices (range, 1–4) were implanted per patient.
Through 30 days postimplantation, five of 160 VALOR II patients (3.1%) died; three of these deaths (1.9%) were adjudicated (by the clinical events committee) as aneurysm related. Causes of deaths included aortic rupture, aortic dissection, multiorgan failure, pneumonia, and respiratory failure. Through 30 days, there were no conversions to open surgery, and no patient experienced aneurysm rupture. One secondary procedure was performed at day 9 postimplantation to resolve a type I endoleak. One or more major adverse events occurred in 38.1% (61 of 160) of the VALOR II patients ≤ 30 days after implantation. Four VALOR II patients had a periprocedural stroke (2.5%). Postoperative paraplegia and paraparesis ≤ 30 days occurred in one patient (0.6%) and three patients (1.9%), respectively. Through 30 days, the rates of site-reported endoleak were type I, 0.7%; type II, 3.4%; type III, 0.0%; and type IV, 0.0%.
THE NEXT-GENERATION CAPTIVIA
TEVAR DELIVERY SYSTEM
For both TRAVIATA and VALOR II, the Valiant Stent
Graft was compressed and preloaded on the Xcelerant
Delivery System (Medtronic, Inc.), consisting of a flexible
single-use disposable catheter, compatible with a 0.035-
inch guidewire, with an integrated handle intended to
provide a mechanical advantage and lower user deployment
force. The Valiant System is inserted through the
femoral or iliac artery via surgical incision and advanced
to the lesion site, where upon withdrawal of the delivery
sheath, the stent graft self-expands to conform to the
vessel morphology and exclude the aneurysm.
The next-generation Captivia Delivery System (Medtronic, Inc.) adds to the Xcelerant feature set a novel tip capture mechanism for more controlled deployment of the FreeFlo proximal stent grafts to avoid the windsock effect and to stabilize the graft at the targeted landing zone. With the tip capture mechanism, deployment occurs in two stages: (1) deployment of the stent graft with the FreeFlo stent still constrained, then (2) release of the FreeFlo stent. A hydrophilic coating has also been applied to the graft cover of the delivery system to facilitate vascular access and enhance stent graft delivery through tortuous iliac and aortic courses.
The Captivia Delivery System received CE Mark in October 2009 and is currently under investigation in two trials. In the United States, it has been evaluated with the Talent Thoracic Stent Graft in 20 high-risk patients as a continuation of the high-risk arm of the VALOR study, the pivotal trial of the Talent Thoracic Stent Graft as compared with retrospective surgical data.9 The Talent Thoracic Stent Graft with the Captivia Delivery System has received FDA clearance and introduction to the US market is planned. Outside the United States, the Captivia Delivery System is being evaluated with the Valiant Thoracic Stent Graft in 100 patients in more than 20 sites across Europe.
Ronald M. Fairman, MD, is the Clyde F. Barker-William Maul Measey Professor of Surgery, Chief of the Division of Vascular Surgery and Endovascular Therapy, and Vice Chairman for Clinical Affairs of the Department of Surgery at the Hospital of the University of Pennsylvania in Philadelphia. He has disclosed that he holds no financial interest in any product or manufacturer mentioned herein. Dr. Fairman may be reached at ron.fairman@uphs.upenn.edu.
Advertisement
Advertisement
