PARTNER Trial: Transcatheter aortic
valve implantation shows promise for patients too sick for conventional surgery
One-year data from the PARTNER clinical trial, published
in the New England Journal of Medicine, demonstrate that transcatheter aortic-valve
implantation, compared with standard therapy, resulted in significantly lower
rates of death among patients who cannot undergo surgery for aortic stenosis.
The trial studied the Edwards SAPIEN transcatheter heart valve for the treatment
of severe aortic stenosis. The results were presented as a Late Breaking Trial
at the 22nd annual Transcatheter Cardiovascular Therapeutics (TCT) scientific
symposium.
Transcatheter aortic-valve implantation (TAVI) is a new procedure in which
a bioprosthetic valve is inserted through a catheter and implanted within the
diseased native aortic valve. The Placement of AoRtic TraNscathetER valves (PARTNER)
trial is a multicenter, randomized clinical trial comparing TAVI with standard
therapy in high-risk patients with severe aortic stenosis. The co-principal investigators
are Martin B. Leon, M.D., and Craig R. Smith, M.D., at New York-Presbyterian Hospital/Columbia
University Medical Center. The data reflect a prespecified cohort of patients
who were considered to be unsuitable candidates for surgery.
The primary end point was the rate of death from any cause over the duration
of the study. A total of 358 patients with aortic stenosis who were considered
to be unsuitable candidates for surgery underwent randomization at 21 centers,
including 17 in the United States. Patients randomized for standard therapy received
a combination of watchful waiting, medications, and balloon aortic valvuloplasty,
which can provide transient clinical benefit but does not alter long-term outcomes.
At one year, based on the Hazard Ratio of 0.55, patients who underwent TAVI
showed a reduction in mortality from 50.7 percent to 30.7 percent. In addition,
there was a reduction in the combined endpoint of death from any cause or repeat
hospitalization from 71.6 percent with standard therapy to 42.5 percent with TAVI.
Among survivors at one year, the rate of cardiac symptoms was significantly lower
among patients who had undergone TAVI, as compared with those who had received
standard therapy (25.2 percent vs. 58.0 percent).
"Based on the reduction in mortality during the first year of the study,
balloon-expandable TAVI should be the new standard of care in patients who are
not suitable candidates for surgery," said Martin B. Leon, M.D., professor
of medicine and director of the Center for Interventional Vascular Therapy at
New York-Presbyterian Hospital and Columbia University Medical Center. Dr. Leon,
founder and chairman emeritus of the Cardiovascular Research Foundation, is the
co-principal investigator of the study.
At 30 days, TAVI, as compared with standard therapy, was associated with a
higher incidence of major strokes (5.0 percent vs. 1.1 percent) and major vascular
complications (16.2 percent vs. 1.1 percent). In the year after TAVI, patients
had no deterioration in the functioning of the bioprosthetic valve, as assessed
by evidence of stenosis or regurgitation on an echocardiogram.
"This study shows that transcatheter valve replacement is a safe and effective
option for this life-threatening illness in patients unsuitable for surgical valve
replacement," said Dr. Smith, study co-principal investigator and surgeon-in-chief
at New York-Presbyterian Hospital/Columbia University Medical Center. Dr. Smith
is also the Valentine Mott Professor of Surgery, the Johnson & Johnson Distinguished
Professor of Surgery, and chair of the Department of Surgery at Columbia University
College of Physicians and Surgeons. "Additional studies are needed to examine
the increased incidence of stroke following TAVI."
According to the study authors, research is already under way on the next generation
of TAVI devices that researchers hope will address the vascular complications
encountered in the trial.
In clinical practice, at least 30 percent of patients with severe symptomatic
aortic stenosis do not undergo surgery for replacement of the aortic valve because
of advanced age, left ventricular dysfunction, or the presence of multiple coexisting
conditions.
The replacement valve used in the PARTNER trial is made of pericardial tissue
leaflets hand-sewn onto a metal frame and implanted via a catheter into the left
ventricle. It is then positioned inside the patient's existing valve using a balloon
to deploy the frame, which holds the valve replacement in place. The procedure
is performed on a beating heart, without the need for cardiopulmonary bypass and
its associated risks.
The transcatheter valve procedure takes about 90 minutes, compared with four
to six hours for open-heart surgery. Open-heart surgery can require a two- to
three-month recovery period, compared with only a few days for the transcatheter
approach.
The multicenter PARTNER trial, which has more than 1,000 patients, began in
2007 and will be completed in 2014. The results reported today reflect only the
cohort of patients who are not considered candidates for surgery. The other arm
of the trial, which compares transcatheter valves with surgically implanted valves,
is ongoing. The executive committee of the trial includes two academic co-principal
investigators, three interventional cardiologists, and three cardiac surgeons.
|