Melody Valve Post-Approval Study Demonstrates Results Better than Originally Predicted

WASHINGTON, DC—In patients with right ventricular outflow tract (RVOT) conduit dysfunction, transcatheter pulmonary valve (TPV) replacement demonstrates high procedural success, excellent short-term function, and low reintervention rates at 1 year, according to results of a post-approval study presented March 30, 2013, at the American College of Cardiology/i2 Scientific Session.

Researchers led by Aimee K. Armstrong, MD of the University of Michigan C.S. Mott Children’s Hospital (Ann Arbor, MI), enrolled 120 patients (mean age 19.9 years, mean weight 59.4 kg) with a stenotic and/or regurgitant conduit from July 2010 to July 2012. Ultimately 99 patients were implanted with the Melody TPV (Medtronic, Minneapolis, MN) for at least 24 hours.

At 6 months, 96.7% of the implanted cohort with evaluable data (n = 90) had acceptable hemodynamic function (primary endpoint). Most of the implanted cohort overall (87.9%) also met the primary endpoint (P < 0.01 for both against the performance goal of 75%). At 1 year hemodynamic function remained high at 94.3% for the implanted cohort with evaluable data and 82.8% for the overall group.

RVOT mean gradient fell from 33.3 ± 14.1 mm Hg at baseline to 16.3 ± 7.1 mm Hg at discharge and 15.0 ± 9.9 at 6 months. Most patients (84.8%) had severe or moderate pulmonary regurgitation at baseline, but no evidence of this persisted at discharge or during follow up.

There were no instances of catheter reintervention at 1 year and 2 reoperations. Freedom from TPV dysfunction was 96.9% at 1 year, higher than the 93.5 ± 2.4% seen in the IDE trial. The rate of procedural serious adverse events was 13.3% including confined conduit tear, vascular complications, coronary compression, distal pulmonary artery perforation, arrhythmia, fever, paravalvular leak, and pulmonary edema. Within the first year, serious adverse events (8.1%) included endocarditis, sepsis, major stent fracture, pulmonary embolism, and arrhythmia/palpitations.

“This study confirms the strong performance of the Melody transcatheter pulmonary valve achieved by real-world providers with results comparable to the US IDE trial,” Dr. Armstrong concluded.

Pre-Stenting Reduces Stent Fracture

Evan M. Zahn, MD of Cedars-Sinai Medical Center (Los Angeles, CA) commented that “it’s encouraging that more than 10 years after this valve was introduced, we have proven transferability of this technology to the real world with results that are actually better than we were able to show in the IDE trial.” Given the better results, Dr. Zahn said, “I’d like to think we learned something perhaps related to stent fracture or pre-stenting.”

Dr. Armstrong confirmed that indeed her team has learned that “if we place the Melody valve inside in the intact pre-stent, usually made of stainless steel, the risk of fracture goes down significantly.” She said that 76% of patients in the current trial had an intact pre-stent as opposed to only 35% in the IDE trial. “So there was only 1 major stent fracture in the post-approval study. That patient did require reoperation and that patient did not have a pre-stent,” Dr. Armstrong explained, adding that it is now her practice to pre-stent virtually all patients.

With regard to risk factors, Dr. Armstrong said her team looked at characteristics including young age and hydration pre-procedure and found that the only independent variable associated with TPV dysfunction was a high right ventricular pressure pre-catheterization. “That was what was found in the IDE trial as well,” she reported. “I think that speaks to the fact that patients going into the procedure with a very stenotic conduit are probably more at risk for TPV dysfunction down the road.”

Dr. Zahn commented that “much has been made about endocarditis” in these patients, and Dr. Armstrong agreed that “it definitely requires further follow-up. The incidence of endocarditis was 3% during the first year, similar to what was seen in the IDE trial and it’s similar to what is seen in these patients who just have a RVOT conduit and never get a Melody valve,” she said.