Covered Stents Show Promise in Patients With Aortic Coarctation: COAST II

Implantation of a covered stent results in high procedural success and good short-term outcomes for the treatment of patients with a congenital narrowing of the aorta, according to results of the COAST II trial published online February 17, 2016, in JACC: Cardiovascular Interventions. 

“Our data suggest that [covered] stent placement is safe with a very low rate of acute complications related to the stent itself,” investigators led by Nathaniel W Taggart, MD, of Mayo Clinic (Rochester, MN) write.

Coarctation of the aorta occurs in approximately 4 in 10,000 live births and accounts for up to 8% of all congenital heart disease diagnoses. Although surgery was the primary means of dealing with the condition in the past, reports of bare-metal stents being used began to appear in the literature in the 1990s.

Since that time, bare metal stents have been advocated by the American College of Cardiology/American Heart Association Task Force as the preferred strategy for patients with recurrent coarctation. However, in those with native, complex and long segment coarctation, the Task Force maintains that there is a paucity of safety data to support stent use. Aortic wall injury as a result of bare metal stent implantation, or as a late complication, remains a concern and is the primary appeal of a covered stent.

According to Taggart et al, prior to their study, there have been no standardized clinical trials of aortic coarctation treated with covered stents.

High Success, But Some Complications

For the single-arm COAST II trial, which enrolled patients treated at 19 pediatric cardiac centers in the US, Taggart and colleagues examined 30-day safety and efficacy in 158 patients (median age, 19 years; 65% male). All had coarctation of the aorta and either pre-existing aortic wall injury (treatment group), or were at increased risk for it (prevention group). All patients received the balloon-expandable covered Cheatham-platinum stent (NuMED, Inc., Hopkinton, NY). The vast majority of those enrolled were “legacy” patients, who received the covered stent during the original COAST trial under FDA Emergency Use or Compassionate Use guidelines, or “continued access” patients, who were treated after the COAST trial enrollment had closed.

Overall, the rate of technical success was 100%, and complete coverage of pre-existing aortic wall injury was achieved in 92%. In this group, final angiography showed minor residual endoleak in 8% that was unlikely to require additional therapy. Median length of hospital stay for the entire cohort was 1 day. Serious or somewhat serious adverse events attributable to the stent, catheterization, or implantation procedure occurred in 13 patients (8%). At 30 days, no re-interventions, deaths, new aortic wall injuries, strokes, or episodes of bacteremia/endocarditis had occurred in either the treatment or prevention group.  

Of significance, however, was the incidence of arterial access site injury. Suspected femoral artery injury occurred in 9 patients (4 serious, 5 mild), while 10 additional patients had borderline femoral artery injury.

Substantial improvements from baseline in resting systolic BP and systolic BP gradient were seen in patients in both the treatment and prevention groups at 30 days. Additionally, only 13% of the total cohort had a systolic BP ≥ 140 mmHg compared with 46% at baseline. In 60% of patients systolic BP decreased by more than 10 mm Hg, and nearly three-quarters of patients had an upper-lower extremity systolic BP gradient ≤ 10 mmHg.

Injuries and Patient Selection Issues

In an editorial accompanying the study, Damien Kenny, MD, of Our Lady’s Hospital for Sick Children (Dublin, Ireland), and Ziyad M. Hijazi, MD, MPH, of Sidra Medical and Research Center (Doha, Qatar), note that despite CE mark approval since 2003, and 12 years of research outside the US, there remains no FDA approval for the covered stent used in COAST II.

“Arguably, this has led to unacceptable risk for US patients and interventionalists, limiting their therapeutic options,” they write.

Despite the overall good results, Kenny and Hijazi say the serious and subclinical femoral artery injuries in COAST II are more than 50% higher than that reported in the original COAST trial and argue for careful patient selection. In fact, the true incidence of those injuries, they say, is unknown given the lack of systematic radiological evaluation after treatment or at follow up.

Another issue of concern, according to Kenny and Hijazi, is the 8% rate of residual endoleak, which raises the issue of whether a self-expanding stent graft may be more suitable in patients with “a dominant aneurysm without significant residual coarctation.”

Continued research in these patient groups is important, they say, adding that “approval of a covered stent in the US will have a significant impact on patient care” but will put the responsibility on operators to use them prudently.

Sources: 
1. Taggart NW, Minahan M, Cabalka AK, et al. Immediate outcomes of covered stent placement for treatment or prevention of aortic wall injury associated with coarctation of the aorta (COAST II). J Am Coll Cardiol Intv. 2016;Epub ahead of print.
2. Kenny DP, Hijazi ZM. COAST-ing towards covered stents for aortic coarctation – not all plain sailing! J Am Coll Cardiol Intv. 2016;Epub ahead of print. 

Disclosures:

• COAST II was funded by NuMED Corp. 
• Taggart, Kenny, and Hijazi report no relevant conflicts of interest.