Endobronchial Valve

Karla Harby                                                                                                                                                Medscape Medical News 2007. © 2007 Medscape                                      

September 17, 2007 (Stockholm) — An implantable endobronchial valve has been found to significantly improve lung function measures and quality of life for patients with emphysema. The valve is designed to block air flow to a diseased region of an emphysematous lung, thereby conferring the benefits of lung volume reduction surgery (LVRS) without the risks of major surgery.

The findings of the trial — known as the International Endobronchial Valve for Emphysema PalliatioN Trial (VENT) — were announced here at the 17th Annual Congress of the European Respiratory Society. The study started in December 2004, ended in April 2006, and involved 321 patients in 31 centers across the United States and Europe.

In this trial, patients with severe heterogeneous emphysema were randomly assigned to the treatment or control group in a ratio of 2:1. The primary study endpoints (forced expiratory volume in 1 second [FEV₁] and 6-minute walk test) were evaluated at 6 months, said Armin Ernst, MD, from Beth Israel Hospital and associate professor at Harvard Medical School, Boston, Massachusetts, during his presentation.

Among the 220 treated patients who received valve placements, at 6 months their FEV₁ had improved by 5.8%, whereas for the 101 controls, FEV₁ declined by 0.6% — a spread of 6.4% that was statistically significant (P = .0047), Dr. Ernst said. For the other primary study endpoint, the 6-minute walk test, treated patients improved their distance by 1.7% (about 15 meters) after 6 months, whereas the controls’ distance declined by 4.0%. This 5.7% spread was also statistically significant (P = .0073). Most secondary endpoints, including quality-of-life scales, also significantly improved.

As explained by Felix Herth, MD, professor at the University of Heidelberg’s Thoraxklinik in Germany, the bronchial implant — which is about the size of a pencil eraser — is a 1-way valve supported by a stent-like, self-expanding nickel titanium basket that holds the valve in place. To help create a seal with the surrounding bronchial tissue, the basket is encased in silicone. The 1-way valve allows gas to vent from the isolated lung section during exhalation but prevents air from refilling the area during inhalation. The valve also allows mucus to be expelled, which reduces the chance of infection.

Most patients require 3 valves to be implanted to isolate their most damaged lung section, and they cost approximately €2000 per valve, Dr. Herth told reporters at a news conference. Valve implantation currently requires an overnight hospital stay. Although the diseased lung no longer inflates, it remains perfused by blood, and no complications have been observed from leaving the deflated lung in the body, Dr. Herth told Medscape. Unlike surgical resection of diseased lung tissue, valve placements can be reversed.

Regarding safety, there was 1 death in the trial attributed to the procedure, said Charles Hugo Marquette, MD, professor at the University Hospital, Nice, France. Otherwise there was no significant difference in any safety measures between the treatment and control groups at 6 months. He told attendees that most complications resolve within 8 days of the procedure and may include shortness of breath, chest pain, and hypoxemia. In this trial 87 valves were removed from 31 subjects (14.1%), primarily for lack of efficacy or valve migration.

The underlying logic behind both valve placements and surgical resection is to “shrink the footballs in the chest that do nothing but take up space,” said principal investigator Frank Sciurba, MD, of the University of Pittsburgh (Pennsylvania) Medical Center, in his presentation. Inflated, diseased lung saps air from functioning lung and pushes the lungs down too far into the abdomen, where they impair normal mechanical function of the diaphragm.

The VENT findings appeared warmly welcomed by most congress attendees, but some questioned aspects of the methodology, especially the absence of blinded measurements and a sham control procedure. Christoph Bollinger, MD, PhD, professor at the University of Stellenbosch, South Africa, told Medscape that the trial clearly showed statistical significance regarding its stated endpoints, and about this, “there is nothing to criticize.” However, as someone who has performed LVRS in the past, he questioned the investigators’ claims that the implants are good for patients.

“The very important question is, is a statistical difference clinically relevant?” he said. For example, although the 6-minute walk test showed a 15-meter improvement, it is widely accepted that a minimum improvement of 50 meters is necessary to be noticed or appreciated by the patient. “They should have acknowledged these things,” Dr. Bollinger said.

This study was supported by Emphasys Medical Inc, Redwood City, California. None of the investigators report any relevant relationships.

European Respiratory Society 17th Annual Congress: Session 184. Presented September 17, 2007.