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Tuesday, January 5, 2010
The Edwards SAPIEN transcatheter aortic heart valve is being studied in the PARTNER Trial to evaluate its safety and effectiveness in treating patients at high risk or who are unable to undergo conventional valve replacement surgery. The balloon-expandable valve is delivered while the heart continues to beat, without cardiopulmonary bypass.
For decades, open-heart surgery has been the gold standard for treating patients with aortic valve stenosis. Yet many patients do not qualify for surgery or are considered high-risk because of age, comorbid conditions, or other factors. In fact, nearly half of the 200,000 patients who require valve replacement every year in the United States do not have open-heart surgery.
Without intervention, severe aortic stenosis carries a poor prognosis, with the average patient survival as low as one to three years. Patients who do not have surgery have few options, often receiving palliative medical treatment to manage symptoms toward the end of life.
The PARTNER Trial
Physician-researchers at the Massachusetts General Hospital Heart Center are studying percutaneous aortic valve replacement as a treatment option for patients with severe aortic valve stenosis who are considered high-risk or are not candidates for traditional openheart surgery.
The research team is participating in a multicenter, randomized study called the PARTNER (Placement of Aortic Transcatheter Valves) Trial, designed to evaluate an alternative to open-heart surgery in patients with severe aortic valve stenosis. The Massachusetts General Hospital Heart Center is one of approximately 25 sites in the United States and Canada participating in the PARTNER Trial, which reached its target enrollment in Summer 2009.
In the trial, patients have been randomly assigned to receive either percutaneous aortic valve replacement, open-heart surgery, or, if they are not candidates for surgery, medical therapy. It is the first randomized controlled trial comparing percutaneous aortic valve implantation to conventional aortic valve replacement.
Transfemoral and Transapical Approaches
The procedure is performed on a beating heart, alleviating the need for cardiopulmonary bypass. The treatment involves the transfemoral or transapical delivery of a valve sewn into a frame, which is mounted and crimped onto a balloon delivery catheter. The replacement valve is similar to the bovine valves used in traditional open-heart valve surgery. However, instead of being mounted in a sewing ring that is attached surgically, this valve is mounted in a frame that can be delivered by catheter. The Sapien valve is available in two diameters, 23 mm and 26 mm, to accommodate different sizes in the aortic annulus.
In the transfemoral approach, the interventional cardiologist places a tube in the femoral artery in the leg and threads the device in a retrograde fashion up the iliac arteries and aorta to cross the diseased aortic valve.
This delivery method is similar to what is used in traditional cardiac catheterizations. But because these devices are larger than what is used in standard cardiac catheterizations, not every patient may have arteries suitable for this approach. This includes patients who may have developed peripheral artery disease. For such patients, an alternative delivery method is the transapical approach.
Transapical delivery requires a small left thoracotomy and a direct incision in the apex of the left ventricle to place the sheath and the device. Compared with the transfemoral approach, this delivery method is associated with fewer stroke risks and vascular complications. Compared with open-heart surgery, the transapical approach is less invasive and does not require the use of cardiopulmonary bypass.
Thousands of these valves have been implanted worldwide. Mortality data in high-risk patients has been reported at 8 percent at 30 days post-procedure.
Members of the interventional cardiology team at Massachusetts General Hospital believe the treatment has the potential to help many patients who are not favorable candidates for traditional open-heart surgery.
Ongoing Work to Study the Next-Generation Device
Based on feedback from the sites so far, the valve manufacturer has modified the replacement valve devices so that they are smaller and easier for the interventional cardiologist to advance across the valve. In addition, the newer device is composed of a different metal with a lower profile.
Researchers expect future studies of the next-generation device in patients with a moderate risk of surgery. The team is waiting to review the one-year primary end point of mortality, as well as complication rates in the PARTNER study patients. In the interim, the Heart Center will offer continued access of the device to patients who meet the inclusion criteria. These criteria include:
If this investigational treatment is approved for widespread use, it could represent a shift in how valvular diseases are managed, Massachusetts General Hospital researchers say. Rather than being managed primarily by surgeons, patients with aortic stenosis might be treated by a multidisciplinary team of cardiologists, interventional cardiologists, and surgeons who will work together to decide the best approach for the patient.
The Massachusetts General Hospital Heart Center is home to a multidisciplinary heart valve program that treats patients who have complex valvular diseases, including congenital, rheumatic, degenerative, and ischemic, and those related to valve endocarditis.
The program also offers balloon valvuloplasty for severe aortic stenosis. In addition, the Heart Center offers other clinical trials for valve diseases, including surgical options.
Massachusetts General Hospital Heart Center
For more information about the Massachusetts General Hospital Heart Center or to refer a patient, please call 866-MGH-8910 (866-644-8910) or visit the Heart Center website
The Massachusetts General Hospital Heart Center is a multidisciplinary program that integrates the experts and services of the divisions of Cardiology, Cardiac Surgery, Cardiac Anesthesia, Cardiac Imaging, and Cardiac Nursing to provide state-of-the-art care for patients with all types of cardiac disorders. Continuing its legacy as a pioneer in cardiac research, the Heart Center also conducts bench-to-bedside research aimed at improving the prevention, diagnosis, and treatment of heart disease worldwide.
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