Aortic stenosis is becoming increasingly prevalent as the population of the United States ages. As many as 300,000 individuals in the U.S. currently have symptomatic aortic stenosis.
Surgical valve replacement, either with tissue or mechanical valve prostheses, has been the gold standard for treatment of extensive valve stenosis for many years. Improvements in surgical technique, durable valve prostheses, and better anticoagulation regimens have resulted in excellent patient survival and functional status. Recently, aortic valve repair has been offered to select patients with good results. Nevertheless, approximately one-third of individuals with symptomatic aortic stenosis are not candidates for open surgical replacement or repair because of their advanced age, severe comorbid conditions, or both.
The Placement of Aortic Transcatheter Valve (PARTNER) Trial is a multicenter, prospective randomized trial. It compares in parallel:
The trial is being conducted at 21 centers in the United States, Canada and Germany, including the Mayo Clinic campus in Rochester, Minn. The results of this second cohort of 358 patients (cohort B) have been released. The surgical arm of the trial (cohort A) is ongoing, and results are anticipated in 2011.
Although the 30-day rates of stroke and vascular complications were higher in the group treated with the investigational valve, survival at 1 year was dramatically higher in patients receiving the valve compared with those who received best medical therapy (69.3% vs 49.3%). Furthermore, patients who received the valve had fewer hospitalizations and better symptom relief than did those receiving standard medical care.
"The survival of the group receiving best medical care, including balloon valvuloplasty, was essentially the historical survival rate of patients with severe aortic stenosis," says Charanjit S. Rihal, M.D., chair of the Division of Cardiovascular Diseases and a principal investigator of the study at Mayo Clinic. "Medical therapy had no impact on survival."
Dr. Rihal also notes that some patients are not candidates for the valve because of characteristics of the valve annulus or because they have severe peripheral vascular disease. "Valve design and improved delivery systems should enable the deployment of percutaneous valves in more of these patients in the future, with a reduced risk of stroke, vascular damage, and major bleeding."
The results of this cohort should not be extrapolated to other patient groups. "The long-term durability of this investigational valve is as yet unknown," observes Thoralf M. Sundt III, M.D., a cardiovascular surgeon and also a principal investigator of the study at Mayo Clinic. "In patients with low operative risk, the standard approach to aortic valve replacement and repair may still be the best option. Nevertheless, it will be gratifying to have another option to offer high-risk patients."
The results of the surgical cohort will provide further insight. Ultimately, trials in other patient subsets and long-term patient follow-up will determine the role of percutaneous valves in the treatment of valvular disease.
For further information regarding the PARTNER Trial at Mayo Clinic, please contact Dr. Rihal at 507-255-2440 or
Dr. Sundt at 507-255-7064.