Stenting for Aortic Coarctation Can Have Late Complications: COAST

Young patients who receive stents to treat coarctation of the aorta see good hemodynamic results over the long term, combined data from the COAST and COAST II trials show, but late follow-up from these two studies also suggests that their complication risk doesn’t remain static—stent fractures, reinterventions, and aortic aneurysms can arise 4 to 5 years after treatment.

This knowledge doesn’t mean that surgery is preferable, researchers say, but it does mean that clinicians should keep an eye out for potential problems that may develop.

COAST and COAST II, as reported by TCTMD, assessed the safety and efficacy of the balloon-expandable Cheatham-Platinum (CP) stent (NuMED). The device, available in both bare-metal and covered versions, was specifically designed to address aortic coarctation.

When addressed in infancy, the condition is best served by surgery, said Ralf J. Holzer, MD (NewYork-Presbyterian Komansky Children’s Hospital, Weill Cornell Medicine, New York, NY), lead author of the new analysis published in Circulation: Cardiovascular Interventions. Thereafter, options also include balloon angioplasty, which isn’t durable but can be used in growing children, and stent implantation once the devices can be expanded to adult size, he told TCTMD.

For Holzer, these latest results indicate that coarctation of the aorta requires long-term attention. “Over the last many decades, whether you’re talking about surgical or transcatheter therapy, we’ve seen over and over again that this condition is a lifelong condition, with significant morbidity to go with it. You can’t just stop following these patients. You have to keep following them up and be vigilant that problems happen,” he stressed.

He added, however, that the time frame captured by this analysis isn’t yet long enough to get the whole picture. “Nowadays we would hope that patients with coarctation would have a long life. Four to 5 years doesn’t even touch the surface for long-term follow-up,” Holzer stressed.

COAST to COAST II

Holzer et al combined data from the COAST and COAST II trials, as well as their continued-access extensions, arriving at a total of 248 patients. Late follow-up data at 48 or 60 months were available for 180 patients (73%), all of whom had fluoroscopy and aortic imaging with MRI, CT, or angiography. Not all had undergone fluoroscopy and/or aortic imaging at the intermediate (1-month) and early (12-month) follow-up periods.

Median age at implant was 17 years in the 180 patients, who had a median weight of 66.3 kg. Half had native coarctation, while approximately one-quarter had developed their condition after surgery and the remainder after catheterization. Minimum coarctation diameter was a median of 8.0 mm, and the median aortic diameter at the diaphragm was 16.0 mm. Covered stents had been implanted in 52% and bare stents in 48%, with a median minimum stent diameter of 14.4 mm. The minimum ratio of stent diameter to aorta at the diaphragm was 0.87.

Over time, the researchers point out, there was a “notable decrease” seen in the use of antihypertensive medications but no increase in the proportion of patients who had elevated systolic BP (around 20% at each follow-up). Yet the cumulative incidence of stent fractures and of reintervention did rise over time.

Aortic Coarctation Outcomes After CP Stent

Additionally, by late follow-up, 13 patients had signs of aortic wall injury (aneurysm or pseudoaneurysm), for a cumulative incidence of 6.3%, up from 1.2% at 12 months.

Stent fractures at 48/60 months were independently predicted by age < 18 years, male sex, minimum stent diameter ≥ 12 mm, and bare-metal stent use. For reintervention, predictors also included age < 18 years and stent diameter ≥ 12 mm, joined by postimplantation systolic arm-leg BP gradient ≥ 10 mm Hg and initial coarctation minimum diameter < 6 mm.

Some good news, said Holzer, is that “the stent fractures we’ve seen have not actually been significant. We have not seen a loss of structural integrity. The caveat here is we just have this 4- to 5-year follow-up.”

Compared with bare-metal stents, “covered stents appear to confer some protection from the development of stent fractures but do not provide complete protection from late aneurysm formation,” the authors note.

What’s the Clinical Impact?

Gregory T. Adamson, MD, and Kyong-Jin Lee, MD (both from Stanford University School of Medicine, Palo Alto, CA), writing in an accompanying editorial, agree that aortic coarctation is “a disease for a lifetime.”

COAST and COAST II data have previously supported the safety and efficacy of stenting, they say, adding that this “latest chapter” indicates that much like “other published studies of endovascular stent therapy, the Cheatham-Platinum stent, bare or covered, is highly effective in maintaining long-term excellent hemodynamic outcomes, that is, minimal blood pressure gradients and progressively reduce the need for antihypertensive medications.”

But it is clear there are long-term considerations, Adamson and Lee note, highlighting late aneurysms, a complication that “raises the specter of aortic rupture.”

What’s unclear is why these aortic wall injuries occur. “The nidus for aneurysm formation is likely multifactorial, hinging on mechanical, hemodynamic, and genetic factors,” the editorialists suggest, adding, “We are confronted with deciphering data of aneurysms occurring in heterogenous coarctation substrates related to variations in the age of the vessel, severity and extent of cystic medial necrosis, stenosis severity relative to the surrounding aorta and degree of vessel wall disruption by various expansion therapies.

“Improvements in surgical techniques have decreased the aneurysm incidence to 9% to 12.5% at late follow-up,” they continue. “For aneurysms occurring after catheter-based therapies, a focused review and analysis which include the specific locations, dimensions, and filling properties may modify technical approach and decrease future incidence.” For now, they urge a systematic approach for aortic imaging, irrespective of patients’ initial treatment.

Subclinical stent fractures and aneurysms, while they appear to occur at high frequency, have unknown significance, the editorialists observe.

For adults and adolescents, the typical COAST patients, endovascular treatment of these complications is “likely to be straightforward,” they say. “However, these complications may have bigger implications and consequences as stents are implanted in younger patients (eg, < 20 kg) as a staged strategy.” It’s not yet known how repeat dilations and layer upon layer of stent material could affect diseased vessels, they note. “Specifically, will this result in additional aortic wall injury and necessitate implantation of another stent?”

You can’t just stop following these patients. You have to keep following them up and be vigilant that problems happen. Ralf J. Holzer

Current US guidelines recommend surgical repair or catheter-based stenting for adults with hypertension and significant native or recurrent aortic coarctation (class I, level of evidence B-NR), while balloon angioplasty can be considered in these patients if stenting isn’t feasible and surgery isn’t an option (class IB, level of evidence B-NR). Medical therapy also is recommended for treatment of the hypertension.

Holzer told TCTMD that, in his opinion, stents are the ideal therapy for larger, adult-sized individuals, but he emphasized patient selection is key. For example, someone in their 40s who has challenging anatomy may be better served by surgery.

“I think the best way to improve longevity in these patients and reduce morbidity is to treat the coarctation efficiently without any residual obstruction,” said Holzer, “and to be vigilant [so you can] identify aneurysms and treat them as needed.”

Looking back across many decades of surgical repair, then stenting since the mid-1980s, clinicians traditionally thought of these as onetime procedures, he said. “Providers thought, ‘Look, I cut out a narrowed area, stitched the aorta back together or put a patch over it. It’s done. You have essentially normal plumbing, normal anatomy, [with] no need for follow-up. You’re completely normal.’ That was the original attitude. That’s why many patients were lost to follow-up.”

A long view shows that, over many years, “there’s significant residual pathology,” like recoarctation, coronary artery disease, or aneurysms, said Holzer. When counseling patients and their families, as well as their healthcare providers, he advised, the key message to convey is the lifelong nature of this disease: “We’re going to treat this as much as we can, fix as much as we can for you, but we need to keep on track with it. We need to be constantly vigilant at identifying potential problems related to the initial coarctation and subsequent therapy, because they do occur. You cannot just discharge the patient—something that looks great now may not look great in 10 years’ time.”

Answers to the open question of how patients fare over 30 or 40 years after intervention could help inform how often to perform imaging—most of the aneurysms found in this study, Holzer pointed out, were discovered during cardiac catheterization, so it’s not obvious when they developed. There also may have been silent aneurysms that went undetected.

The Congenital Cardiovascular Interventional Study Consortium multicenter registry continues to track long-term outcomes among patients treated for aortic coarctation.