Clinicians realized long ago that atrial fibrillation increases patients? chance of stroke and attempted to manage the risk medically. But a new device, the WATCHMAN left atrial appendage system, aims to eliminate the need for long-term anticoagulation therapy.
?Things like this can potentially make a difference in terms of patients? quality of life,? says Donna Whitman, RN, MS, clinical research coordinator for MedStar Research Institute at Washington Hospital Center in Washington.
The investigational device is implanted percutaneously during an interventional procedure. Washington Hospital Center recently joined a clinical trial to evaluate the effectiveness of the innovative treatment in 2007 and has begun screening candidates.
?It?s amazing what can be accomplished through a small, femoral access,? Whitman says.
The University of Virginia in Charlottesville, another clinical trial site, has implanted the device in three patients. All of them have come off the anticoagulant Coumadin (warfarin sodium) and have experienced no adverse events. About 645 people have received the device during the current multicenter trial.
Atrial fibrillation
Atrial fibrillation affects about 2.2 million Americans, according to the American Heart Association. The irregular cardiac rhythm causes the heart?s two atria to quiver. That allows blood to pool and clot. Clots can break off, enter the circulation, and cause a stroke.
Traditionally, patients take Coumadin to reduce the chance of stroke. ?Long-term Coumadin therapy has its own risks in terms of increased bleeding and bruising potential as well as hemorrhagic stroke potential,? says Whitman, adding Coumadin therapy can negatively impact patients? quality of life, making them fearful to live active lives and altering their diets.
The American Heart Association estimates 15% to 20% of all strokes occur in people with atrial fibrillation, and those strokes tend to be more severe because of the size of the clots. Device manufacturer Atritech indicates more than 90% of clots found in patients with atrial fibrillation are found in the left atrial appendage, a remnant of embryonic development.
The WATCHMAN system is a self-expanding, metal mesh cage covered with a permeable polyester material. It is designed to prevent clots from exiting into the heart and traveling to the brain.
?It?s like a basket that?s implanted in the appendage to keep clots formed there from entering the main portion of the left atrium and ultimately being allowed to travel,? Whitman says. ?It traps them, basically. The body forms a thin layer of tissue over the device to completely seal it off. When we?ve proved by echocardiogram it has sealed off, we take the patient off Coumadin therapy.?
The left atrial appendage can be removed during open-heart surgery and may be if the patient is undergoing an operation for a different reason, such as a bypass graft. However, an open surgery just to tie off the left atrial appendage is not warranted.
The device is delivered to the left atrium through a catheter, which passes through a small puncture in the septal wall separating the two upper chambers of the heart.
Transesophageal ultrasound follows its progession, and X-rays confirm proper placement. Patients stay on bedrest for six hours and are in the hospital overnight for monitoring.
Potential risk includes reaction to anesthesia, bleeding at the puncture site in the groin, and the chance of an accidental tear into the pericardial sac, which could result in an effusion or cardiac tamponade.
?Nursing care resembles that for other coronary procedures we do, both evaluating the groin site and monitoring the patient very closely for cardiac issues,? Whitman says.
Trials
Physicians initially implanted the WATCHMAN in a German patient in August 2002, and the first American received one in 2003. Atritech reported results of a pilot study, involving 66 patients, at the American College of Cardiology 2006 annual scientific session. Twelve of those patients had the device four or more years, and 32 had it for two years. All patients had the device for more than one year.
Ninety-seven percent of patients had stopped coumadin therapy at six months. There had been no reports of ischemic strokes, but two patients suffered from a transient ischemic attack. Ten of the patients in the pilot trial suffered adverse events, including two device embolizations, one delivery system problem requiring surgical intervention, five pericardial effusions, and two deaths, neither of which were device related.
The current PROTECTion in Patients With Atrial Fibrillation (PROTECT AF) multicenter study began in 2005. The phase 2/3 randomized clinical trial compares outcomes of people with atrial fibrillation treated with the WATCHMAN and those with long-term Coumadin therapy.
The study will assess whether the device makes a difference in the frequency of strokes, systemic embolism, and cardiovascular death. Secondary outcomes include technical and procedural success, major adverse events, and left atrial appendage coverage. Researchers also will evaluate safety.
Patients receive anticoagulation therapy post-procedure for 45 days and then take adult aspirin. If a transesophageal echocardiogram indicates no blood flow from the appendage, at 45 days, patients can come off coumadin. They are evaluated again at six, nine, and 12 months and semi-annually thereafter for up to five years.
The WATCHMAN remains investigational, and the U.S. Food and Drug Administration has not approved it for use outside a clinical trial. However, it holds promise for preventing this type of stroke without the risks of Coumadin.
?I think the opportunities that research has to offer can be so fascinating,? Whitman says. ?What this boils down to is quality of life for the patients.?
Debra Anscombe Wood, RN, is a freelance writer.
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