ORLANDO, Fla.—A device percutaneously implanted in the left atrial appendage may replace anti-thrombotic drugs for stroke prevention in patients with nonvalvular atrial fibrillation (AF), according to research presented during the i2 Summit at the American College of Cardiology (ACC) 58th annual scientific sessions.
In the Embolic Protection in Patients with Atrial Fibrillation (PROTECT AF) trial, researchers compared the current standard of therapy, anticoagulation with warfarin, to a fabric-covered expandable nitinol cage known as the WATCHMAN (Atritech). The device occludes the left atrial appendage (LAA), preventing blood from entering. In patients with AF, blood pools in the LAA, because it is not being adequately pumped out, and often forms into clots.
Anticoagulation with warfarin is effective to prevent clot-related strokes in AF but it is used conservatively, largely because it can cause serious bleeding in some patients. It also necessitates regular blood tests and may require that patients restrict certain physical activities, as well as certain foods, according to principle investigator David R. Holmes, Jr., MD, Scripps professor of medicine at the Mayo Graduate School of Medicine, Rochester, Minn.
Researchers found that 87 percent of patients in the device arm (463) were able to discontinue warfarin after 45 days. The rate further increased at various time points: 92.5 percent at six months, 93.2 percent at 12 months and 94.1 percent at 24 months.
A total of 244 patients were in the long-term warfarin treatment arm.
The study found that in more than 900 patient-years of follow-up the combined rate of stroke (ischemic and hemorrhagic) and cardiovascular death-the primary measures of effectiveness-was 3.4 per 100 patient-years in the device group versus 5.0 per 100 patient-years in the warfarin group, a reduction of 32 percent.
"The device showed superiority for preventing hemorrhagic stroke and noninferiority for preventing ischemic stroke," Holmes said.
Six patients in the control arm had a hemorrhagic stroke and four died. One patient in the device arm suffered a hemorrhagic stroke and survived, but it occurred on day 15 while still on warfarin.
Holmes and colleagues found a higher rate of complications with the device early in the trial, which decreased as operator experience increased and with the development of a smaller device. The most common complication, pericardial effusion, dropped from an early rate of 5.5 percent to 1 percent over time.
In his commentary, John A. Camm, MD, from London, U.K., questioned the small number of participants in the trial (800) compared to over 8000 in trials assessing the efficacy of anti-thrombotic medications. But he complimented the trial's design, endpoints and statistical measures.
Because 68 percent of patients in the device arm had CHADS scores of 1 or 2, Camm suggested they might have been low risk to begin with.
Panelist Horst Sievert, MD, director of the Cardiovascular Center Frankfurt, Germany, whose facility was one of 57 in the U.S. and Europe to participate in the trial, said PROSPECT AF is a landmark study. He predicted that the device would first be used in patients who cannot tolerate warfarin, but will migrate to other patients quickly.