Percutaneous Pulmonary Valve Demonstrates Encouraging Short-term Results

A transcatheter pulmonary valve for use in patients with dysfunctional right ventricular outflow tract (RVOT) conduits has shown a high rate of procedural success and encouraging short-term function, despite some concern about reinterventions for stent fractures. The findings, which represent updated results from those presented to the US Food and Drug Administration, were published online July 19, 2010, ahead of print in Circulation.

In January 2010 the FDA approved the Melody valve (Medtronic, Minneapolis, MN) under the humanitarian device exemption (HDE) program. The device consists of a valved segment of bovine jugular vein sewn within a balloon-expandable stent. Prior to the approval, open surgery was the only means of treating complications with RVOT conduits. Approximately 1,000 patients per year in the United States are anticipated to be eligible for implantation with the valve, according to the manufacturer.

For the expanded US Melody trial, researchers led by Julie A. Vincent, MD, of Children’s Hospital of New York (New York, NY), implanted the valve in 124 patients (median age of 19 years) with dysfunctional RVOT conduits at 5 US centers (adding 2 centers from the original study) from January 2007 through August 19, 2009. The primary indication for treatment was either pulmonary regurgitation, conduit obstruction, or a combination of the 2.

There was 1 death from intracranial hemorrhage after coronary artery dissection, and 1 valve was explanted after conduit rupture.

Short-term Results

In terms of immediate results, transcatheter pulmonary valve placement resulted in reduction of median right ventricular (RV) systolic pressure from 65.3 mm Hg to 41.5 mm Hg, and median peak RVOT pressure gradient from 37 mm Hg to 12 mm Hg. In addition, the ratio of RV to aortic pressure was reduced from a median of 0.74 to a median of 0.42. Although additional interventions at the same catheterization were not permitted in the initial 35 implanted patients, procedures were performed in 51 of the subsequent 89 patients who underwent valve implantation. These included bare-metal stenting of the RVOT (n = 43), as well as branch pulmonary artery stenting or angioplasty (n = 8), coronary artery stenting (n = 1), inferior vena cava stenting (n = 1), and atrial septal defect closure (n = 1). Average procedure and fluoroscopy times were 174 ± 67 and 46 ± 25 minutes, respectively.

Improvements in NYHA class were observed at 6-month follow-up and were sustained through 2 years in most patients (there were 5 patients who declined in NYHA class). At 6 months, echo and MRI testing showed positive results in patients with paired data in terms of RV pressure, mean RVOT gradient, and RV end diastolic volume, although RV ejection fraction did not change (table 1).

Table 1. Paired Outcomes Pre- and Post-Pulmonary Valve Implantation

Survival free from RVOT reintervention was 95.4 ± 2.1% at 1 year and 87.6 ± 4.5% at 2 years. Freedom from a second transcatheter pulmonary valve was 96.9 ± 2.0% at 1 year and 90.4 ± 4.4% at 2 years. For freedom from valve dysfunction, rates were 93.5 ± 2.4% and 85.6 ± 4.7% at 1 and 2 years, respectively.

Overall, 11 patients underwent RVOT reintervention after transcatheter pulmonary valve implantation. Nine of them received a second valve for stent fracture and recurrent RVOT obstruction. Stent fractures of the valve were diagnosed in 25 patients, all but 1 of which were deemed minor, with no loss of stent integrity. One fracture was major (loss of stent integrity) at the time of identification and 6 progressed from minor to major during the course of follow-up. Freedom from diagnosis of stent fracture was 83.7 ± 3.7% at 7.5 months and 77.8 ± 4.3% at 14 months.

“In this updated report from the first prospective multicenter [transcatheter pulmonary valve] trial, we demonstrated an ongoing high rate of procedural success and encouraging short-term function of the Melody valve,” Dr. Vincent and colleagues conclude. “The addition of 2 sites to the original trial protocol supports the conclusion that this technology can be adopted safely and effectively by properly trained, experienced interventional pediatric/congenital cardiologists.”

They add that appropriate patient selection remains important, as does preventing or managing stent fracture.

Solving Stent Fractures

“Certainly from a clinical point of view, it’s encouraging that the implantation success rate was very high and the freedom from reintervention rate was very high,” commented Ziyad M. Hijazi, MD, MPH, of Rush University Medical Center (Chicago, IL), in a telephone interview with TCTMD. “The only concern, of course, was the incidence of stent fracture.”

Dr. Hijazi explained that at the beginning of the trial, the operators were not prestenting the outflow tract but instead directly implanting the valves, exposing them to extreme pressure and resulting in fracture rates of up to 30%.

“But since then, they started prestenting the conduit, and the incidence of fracture is much less,” he said. “So I think they solved the problem.”

No Cure, But Fewer Surgeries

Dr. Hijazi pointed out that this technology is not meant as a curative solution for these patients, in whom valves typically calcify every 5 to 7 years. “The goal of implanting a percutaneous valve in these patients between the RV and the [pulmonary artery] is to avoid at least one or two repeat open heart surgeries, which carry significant morbidity and mortality,” he said. “So instead of every 5 years needing surgery, maybe the next time you do a valve, and then five years later you do surgery, and then another valve, and so on.”

He indicated that the Edwards (Irvine, CA) Sapien pulmonic valve, modeled after the Sapien aortic valve, is also being studied for use in dysfunctional RVOT conduits. The COMPASSION (COngenital Multicenter trial of Pulmonic vAlve regurgitation Studying the Sapien InterventIONal THV) trial has just completed Phase I in the United States, with plans to expand to 7 or 8 centers, he noted.

Overall, Dr. Hijazi indicated that the technology for transcatheter pulmonary valve implantation is progressing, but not final yet. “It’s coming down the pipe,” he said. “We need to miniaturize it so that the smaller kids and children who need 4 or 5 or 6 repeat open heart surgeries can benefit.”