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Two decades of experience with stenting to treat pulmonary vein stenosis in children at one of the foremost US centers for the procedure paints a sobering picture, one of short-term success against a backdrop of frequent recurrence and early death. The report, which was published online January 17, 2012, ahead of print in Circulation: Cardiovascular Interventions, suggests that use of larger stents and repeat interventions can help manage symptoms.

Investigators led by Doff B. McElhinney, MD, of Children’s Hospital Boston (Boston, MA), reviewed outcomes of stenting of 74 lesions in 47 pediatric patients with congenital or postoperative pulmonary vein stenosis at the institution between 1990 and 2010.

Median age at the time of implantation was 1.4 years. Most patients had undergone prior pulmonary vein intervention, including surgery in 53% of veins and transcatheter procedures in 59%. BMS were used in 57 veins of 39 patients, DES in 7 veins of 5 patients, and covered stents in 11 veins of 9 patients.

Stenting Improves Hemodynamics, MLD

Among patients with biventricular circulation, stenting decreased the median systolic right ventricular pressure from 69 mm Hg to 58 mm Hg (P = 0.03), while the ratio of right ventricular pressure to aortic pressure declined from 0.9 to 0.6 (P = 0.01).

Angiography showed that baseline minimum lumen diameter (MLD) improved after intervention for all stent types (table 1).

Table 1. Improvement in Vein Lumen Diameter by Stent Type

 
Importantly, because available DES are designed for use in coronary vessels and are smaller than BMS, postprocedural lumen diameter in DES-treated veins was smaller than in BMS-treated veins (P = 0.04).

Over a median follow-up of 3.1 years, 21 patients died. Estimated survival rates after first stent implantation were 62 ± 8% at 1 year and 50 ± 8% at 5 years. Complete occlusion occurred in 9 stented veins after a median of 4.2 months. Of 54 stents examined during repeat catheterization at a median of 3.9 months after implantation, 28 had already narrowed—8 severely and 9 moderately—typically along the entire stent length. Freedom from significant narrowing was 54 ± 9% at 6 months and 37 ± 10% at 1 year.

Overall, reintervention was performed in 32 stents. All repeat procedures succeeded in reducing stent narrowing. Freedom from reintervention was 62 ± 7% at 6 months and 42 ± 7% at 1 year.

Larger Stents Fare Better

Larger lumen diameter at the end of the implant procedure was associated with longer freedom from significant in-stent narrowing or occlusion (P < 0.001) and from reintervention (P = 0.017). Cox regression analysis showed that stent diameters at or above the threshold of 7 mm yielded longer freedom from significant in-stent narrowing or occlusion (P = 0.002) and from reintervention (P = 0.015).

The authors note that the great majority of stents used were BMS, and any comparison of different stent types is handicapped by the small number of alternative stents. On the other hand, DES proved ineffective, probably because most had small diameters, limiting expansion of the lumen, Dr. McElhinney and colleagues say. Moreover, any pharmacological benefit may have been masked by their smaller size, they speculate.

More Aggressive Follow-up

The investigators report that their approach to managing pulmonary vein stenosis has become more aggressive over time. Their current practice is to provide catheter-based reassessment—and reintervention if necessary—about every 4 to 8 weeks in addition to pharmacological therapy. In particular, they note, patients who have received smaller stents are more vulnerable and may benefit from more frequent follow-up.

In a telephone interview with TCTMD, Larry Latson, MD, of Joe DiMaggio Children’s Hospital (Hollywood, FL), said the paper confirms what most clinicians in the field believe—that transcatheter intervention is relatively safe and helps most patients in the short term, but a single procedure rarely resolves the problem. “Stents are not curative. There is a bad propensity for tissue to grow right back inside them,” he noted.

DES in particular have not lived up to their early promise, probably due to their relatively small diameters, Dr. Latson said.

“It’s all about real estate,” Ziyad M. Hijazi, MD, MPH, of Rush University Medical Center (Chicago, IL), told TCTMD in a telephone interview. “If you deploy a stent to about 5 mm and there is 1 mm of neointimal growth, you lose 20% of the lumen, but if the [larger] stent is expanded to, say, 10 mm, you lose only 10% of the lumen over the same period.”

Unfortunately, Dr. Latson added, there are significant technical obstacles to scaling up the current coronary-size DES to pulmonary size. As for covered stents, there is not enough experience with them to judge their efficacy,  he observed, but a major handicap is that available versions do not ‘grow’ with the patient, from a vessel size of 4 mm to 5 mm in babies up to10 mm to 15 mm in adults.

Persistence May Pay Off

Dr. Latson said he avoids using stents except in the subgroups for which the study indicates they are useful. “Putting a stent in a smaller-diameter vein doesn’t have much benefit over a balloon, and may have some downsides, especially in young children,” he noted, adding that repeated dilations generally achieve the best results. “If you keep going back, after a number of procedures, a much higher percentage of vessels eventually quit restenosing—they settle down and become fairly stable,” he explained.

One new technology of interest for pulmonary vein stenosis is drug-eluting balloons, Dr. Latson said, because they can be much larger than coronary DES, apply drug locally where it is needed, and leave nothing behind. Antirestenotic drugs have also been investigated, he added, but so far any benefit has not been great enough to outweigh the potential risk of using systemic medication in developing children.

Dr. Hijazi also sees promise in biodegradable stents. In fact, the Society for Cardiovascular Angiography and Interventions has been working with the US Food and Drug Administration to study such devices that are specifically designed for children, he reported, though manufacturers have shown little interest due to the rarity of the indication.

The bottom line is that over the past 2 decades, very little progress has been made in improving the prognosis for this disease, Dr. Hijazi said. Certainly, none of the current treatments are a “magic bullet,” Dr. Latson added.

The authors have a more judicious assessment. “Stent implantation does not appear to offer a long-term survival benefit . . . but may provide lasting relief of [pulmonary vein stenosis] in older patients and temporizing relief while a more comprehensive strategy is developed in patients with severe, aggressive disease,” they conclude.

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