The basic premise of aortic stent grafting involves introduction of a stent graft that is constrained on a delivery catheter through the femoral arteries, advancement of the catheter to the area of the aneurysm, and deployment of the stent graft within a cylindrical aortic neck to seal the aneurysm from chronic systemic pressures in order to reduce rupture risk. Unfortunately, this oversimplified description does not account for the many anatomic challenges encountered by the vascular specialist during an endovascular aneurysm repair (EVAR) procedure.

In the decade following US Food and Drug Administration (FDA) approval of the first stent graft for EVAR, a variety of stent grafts were introduced with comparable anatomic requirements for use. Typical guidelines included neck length ≥ 10 to 15 mm, neck diameter of 18 to 32 mm, angulation < 45º to 60º, and access vessels > 6 to 7 mm in diameter. Although these requirements were adequate to execute clinical trials for the purposes of regulatory approval, these criteria excluded many abdominal aortic aneurysm (AAA) patients in need of intervention (Table 1).

Given the complex anatomies of typical patients with AAA disease, achieving minimally traumatic vascular access and durable seal with commercially available stent grafts across a wide range of anatomies remains an elusive therapeutic goal. Over the last several years, many stent graft manufacturers have introduced next-generation devices intended to address the therapeutic gap in patients with small-diameter access vessels and challenging aortic neck anatomy. However, recent advancements in EVAR have been incremental at best, and many patients in need of EVAR continue to be denied treatment due to anatomic constraints. The Ovation Prime stent graft system (TriVascular, Inc.) was specifically developed to significantly expand patient eligibility for EVAR by identifying, addressing, and overcoming the major barriers to EVAR today—namely, access, fixation, and seal—for long-term, durable results.

ACCESS

The Ovation Prime stent graft is delivered via a 14-F outer- diameter delivery system, which is a comparably much smaller profile than the typical 18- to 22-F delivery systems used with other stent grafts. This lower profile is achieved by adding polymer material over time, thereby minimizing the region of fabric and metal overlap within the catheter. The advantages of a lower-profile delivery system are obvious. More than 50% of women and nearly 20% of men with AAAs present with bilateral iliac diameters of < 6 mm,1 and these patients would be denied EVAR with other stent grafts based solely on inadequate access. In contrast, at least four out of five of these patients could be treated with the Ovation Prime system. Additionally, the ultra-low-profile delivery system facilitates percutaneous access. A growing body of evidence shows that totally percutaneous vascular access results in higher technical success rates, less blood loss, fewer complications, and shorter hospital stays compared to surgical cutdown.2-9

When comparing outcomes in patients who underwent bilateral percutaneous access (n = 69) or surgical cutdown (n = 92) in the global pivotal trial of the Ovation® stent graft,10 anesthesia (149 vs 191 minutes) and procedure (98 vs 118 minutes) times were shorter; hospital stays were shorter (1 vs 2 days); the 30-day major adverse event rate was lower (1.4% vs 3.3%); and treatment success at 1 year was higher (100% vs 98.9%). The Ovation Prime system is approved by the FDA for use via percutaneous access, which has become our preferred access method. Based on these access-related advantages alone, the Ovation Prime system is well positioned to broaden EVAR eligibility and improve perioperative outcomes.

FIXATION

The Ovation Prime system employs a suprarenal stent to engage healthy tissue proximal to the site of the more diseased aneurysm using integrally formed anchors. This allows for reliable fixation in the most stable part of the aorta. Anchoring into healthy tissue area increases pullout forces and may prevent migration. In the global pivotal trial, there were no reported migrations at the 1- and 2-year follow-up intervals. The Ovation Prime stent graft is delivered via a progressive, staged delivery. The first stage releases the midcrown, which centers and aligns the suprarenal stent and graft in the lumen. Eight radiopaque markers allow for an orthogonal view to be achieved, enabling precise placement. Once positioned, the second stage releases the proximal crown with integral anchors, which are deployed radially, with no longitudinal displacement. This ability allows for controlled deployment and precise placement, especially in short-neck anatomies.

SEAL

The Ovation Prime stent graft utilizes an O-ring sealing mechanism that is a truly game-changing innovation. The O-rings create a custom seal by injection of a low-viscosity polymer that conforms to the aortic wall without exerting chronic radial force and insulating the aortic neck from circulation. These effects are particularly beneficial in the presence of irregular anatomies resulting from calcification, thrombus, or reverse taper. This is in sharp contrast to conventional, self-expanding wire and fabric grafts that seal by exerting outward radial force against the luminal surface. The implications for this novel sealing mechanism are tremendous in maintaining a durable seal, preventing neck dilatation, and minimizing risk for late complications such as endoleak or migration.

GLOBAL EXPERIENCE WITH OVATION AND OVATION PRIME SYSTEMS

The pivotal trial of the Ovation stent graft system demonstrated excellent safety and device effectiveness through 1 year.10 Based on recent reports, the 2-year data are similarly impressive, with no type I or III endoleaks, migration, AAA rupture, or surgical conversion. These impressive patient outcomes are not confined to the clinical trial setting alone. The ongoing OVATION Post-Market Registry has enrolled more than 500 patients with similarly promising outcomes. To date, the Ovation and Ovation Prime systems have been implanted in more than 4,500 patients worldwide. A summary of published reports on the clinical experience with the Ovation and Ovation Prime systems is shown in Table 2.

ARIZONA HEART HOSPITAL AND CHAMPAIGN-URBANA EXPERIENCES WITH OVATION PRIME SYSTEM SINCE FDA APPROVAL

After the much-anticipated FDA approval of the Ovation Prime stent graft system in late 2012, we quickly incorporated this device into our practice as our go-to stent graft in patients who could not be treated with EVAR otherwise. This early experience mainly included patients with small-caliber access vessels and short aortic necks. However, with continued experience, we quickly realized that the Ovation Prime system was well-suited for challenging and straightforward anatomies alike.

Our combined commercial experience with the Ovation Prime system includes 156 cases with an average follow-up of 8.5 months (range, 1–19 months). Most patients (78%) were men, and the mean age was 74.5 years. As a whole, these patients presented with very challenging anatomy: 41% had narrow (< 7 mm) access vessels, 39% had short (< 15 mm) proximal necks, and moderate/severe neck calcium and thrombus was observed in approximately half of all patients. Totally percutaneous access was achieved in 66% of patients, with the majority undergoing general anesthesia. Procedural blood loss was minimal (mean, 82 mL).

The overall mean hospital stay was 1.9 days, with only three patients with severe comorbidities being admitted to the intensive care unit (unrelated to the procedure). In this combined series, we have experienced no technical failures. There were seven intraoperative type Ia endoleaks. Four patients were successfully treated with Palmaz stent (Cordis Corporation) placement, one with coiling; one case resolved before the 30-day follow-up, and another patient was treated with extension of the proximal landing zone.

Over a mean 8.5-month follow-up period, there have been no late type I, III, or IV endoleaks; no migrations; no AAA enlargements; and no limb occlusions. For patients at 1-year follow-up, there have been no AAA ruptures, no surgical conversions, no secondary interventions, and no migrations.



 



Venkatesh G. Ramaiah, MD, FACS, is a vascular surgeon at the Arizona Heart Institute and Hospital in Phoenix, Arizona. He is Director of Research at the Arizona Heart Institute and Medical Director of the Arizona Heart Hospital. He has disclosed that he is a consultant to TriVascular and National Principal Co-Investigator of the LIFE study..

Syed M. Hussain, MD, is Chairman, Vascular/Endovascular Surgery, Christie Clinic; and Assistant Clinical Professor of Surgery University of Illinois College of Medicine in Champaign, Illinois. He has disclosed that he is a consultant to TriVascular and National Principal Investigator of the Ovation and Ovation Prime postapproval study. Dr. Hussain may be reached at msyhussain@yahoo.com.

Jennifer L. Ash, MD, is with the Vascular/Endovascular Surgery Department, Christie Clinic; and Assistant Clinical Professor of Surgery, University of Illinois College of Medicine in Champaign, Illinois. She disclosed that she is a consultant to TriVascular. .

Ayman Jamal, MD, is a consultant interventional cardiologist at the Arizona Heart Institute and Hospital in Phoenix, Arizona. He has disclosed that he is a consultant to TriVascular.

Ravi Hasanadka, MD, is with the Vascular/Endovascular Surgery Department, Christie Clinic; and Assistant Clinical Professor of Surgery, University of Illinois College of Medicine in Champaign, Illinois. He stated that he has no financial interests related to this article.

Thomas King, DO, is an attending vascular surgeon at CGH Hospital in Sterling, Illinois. He stated that he has no financial interests related to this article.

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