Cutting Balloon Helps Treat Resistant Pulmonary Artery Stenosis

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In pediatric patients considered “untreatable” after failing low-pressure balloon angioplasty for pulmonary artery stenosis, treatment with a cutting balloon is more effective than high-pressure angioplasty and just as safe, according to findings from a randomized trial published online October 31, 2011, ahead of print in Circulation.

Researchers led by Lisa Bergersen, MD, MPH, of the Children’s Hospital Boston (Boston, MA), looked at 73 patients with 245 vessels marked by pulmonary artery stenosis. All of these received low-pressure (≤ 8 atm) balloon dilatation. Patients with vessels that failed to sufficiently dilate were then randomized to high-pressure angioplasty (15-22 atm; n = 66 vessels) or treatment with a cutting balloon (n = 107; Boston Scientific, Natick, MA) followed by additional low-pressure dilation. The hope was that the cutting balloon, which features microsurgical blades mounted longitudinally on the balloon’s outer surface, would facilitate dilation in these resistant obstructions.

More than half (52%) of the patients were under 4 years of age, with most of the remainder (57%) under 18. Over half (54%) also had tetralogy of Fallot.

Wider Lumens with Cutting Balloon

Cutting balloon therapy resulted in a greater percent increase in minimum lumen diameter (MLD, primary endpoint) immediately after intervention (85.1 ± 77.1% vs. 52.4 ± 66.0%; P = 0.004). In addition, the waist of the angioplasty balloon, representing incomplete resolution of the stenotic lesion, was eliminated in 97% of cutting balloon cases compared with 29% of high-pressure balloon cases (P < 0.001).

The absolute change in MLD was 1.3 ± 0.9 mm in the cutting balloon group vs. 0.8 ± 0.8 mm in the high-pressure balloon group, with a larger proportion of cutting-balloon vessels achieving a percent change in MLD greater than 50% compared with high-pressure balloon vessels. In addition, more than half (55%) of the vessels in the high-pressure balloon arm received cutting-balloon therapy after a crossover design was introduced in the trial. These vessels experienced an additional 48% increase in lumen diameter, with a final diameter after cutting balloon treatment 99% greater than the initial diameter.

There were no serious adverse events in any vessel studied, with low, equivalent rates of “somewhat” serious events in the cutting balloon (3%) and high pressure balloon groups (2%; P = 0.85). After angiographic core lab assessment, there were no significant differences in the appearance, presence of tears, or aneurysms after therapy. Nor were there any new aneurysms or vascular occlusions reported on follow-up angiography.

“The results indicate that [cutting balloon] therapy, followed by low-pressure dilation, is more effective than [high-pressure balloon] therapy for [pulmonary artery] obstructions resistant to initial low-pressure angioplasty,” the authors write, adding that in light of the low (29%) success rate of initial low-pressure angioplasty and the high crossover rate in the high-pressure dilation arm, cutting balloon technology should provide “a significant impact” for patients with resistant pulmonary stenosis, who represent “a population with previously untreatable disease.”

The study also represents one of the few randomized attempts to evaluate the performance of a device developed for adults but used in children, the authors note.

Cutting, Tearing, and Healing

In a telephone interview with TCTMD, Dr. Bergersen explained that “with regular balloons, you tear the muscle and then it heals in a larger diameter.” But, she added, “the cutting balloon allows you to make 4 linear cuts in the vessel that you can then propagate with a larger balloon. It’s a controlled dilation allowing you to at least make that initial cut in the vessel in areas that you can’t tear with a regular balloon. Then you make a larger tear, opening up the vessel.”

She indicated that the paper should provide good guidance for clinicians unfamiliar with using the cutting balloon in pediatric patients. “It’s a prospective study, so we used clear guidelines,” Dr. Bergersen said. “In our methods we clearly outlined how we choose balloons, what type of balloons we choose, and in what sequence. So interventionalists who have not previously used the technology will be able to look at that and adapt it to their practice.”

She estimated that interventionalists around the country started using the cutting balloon in pediatric patients between 2001 and 2003. “We found that some of these areas of obstruction [in the pulmonary artery] were resistant to regular balloons, so in these resistant lesions, the cutting balloon has been quite effective in opening up areas of obstruction.”

Taking the High Road

Just as important as the clinical implications are the regulatory ones, Dr. Bergersen noted. “It was always our intention to design the trial in a ‘high-road’ way to allow for a PMA application, so the study was designed and powered to support that,” she said. “Now, whether you move forward with a PMA, that’s a business decision. In pediatrics with low numbers, you can imagine it’s very difficult to make a financial argument to move forward. However, particularly when you have a study like this that shows benefits for children, the right thing to do is seek a pediatric indication.”

She added that over the past several months, Boston Scientific has been working on a PMA submission using the study data.

Dr. Bergersen expressed hope that the study has equally important long-range implications for studies in the field of congenital interventional medicine. “I think the real impact of this paper for my community is to demonstrate that it’s important to critically assess technology in children and to try to design studies that can support pediatric labeling indications,” she said. “There are a lot of challenges to doing that because of our small numbers, but with creative study designs and cooperation between multiple institutions, we’ve shown that it’s possible and that’s what we need to continue to do in the future.”

 

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Source:
Bergersen L, Gauvreau K, Justino H, et al. Randomized trial of cutting balloon compared with high-pressure angioplasty for the treatment of resistant pulmonary artery stenosis. Circulation. 2011:Epub ahead of print.

 

 

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