Transcatheter Left Atrial Appendage Occlusion to Prevent Stroke
Abstract & Commentary
Synopsis: The first report of a percutaneously delivered device to occlude the left atrial appendage and prevent thrombus formation in patients with atrial fibrillation.
Source: Sievert H, et al. Circulation. 2002;105: 1887-1889.
In this interesting preliminary report, sievert and colleagues describe the first clinical experience with a new percutaneous catheter occlusion of the left atrial appendage device for preventing stroke and thromboembolism in patients with atrial fibrillation. The implant itself consists of a self-expanding nitinol cage that is covered with a polytetrafluoroethylene membrane. The membrane is laminated to the cage. When expanded, the cage is forced in tight contact with the endocardial surface of the left atrial appendage. Thus, the device should occlude the orifice of the left atrial appendage. The polytetrafluoroethylene membrane allows tissue growth into the device to help maintain its position and provide a nonthrombogenic interface with the bloodstream. There are also small anchors along the struts that pass through the membrane and assist with device anchoring early after implant. The device is delivered using a transseptal catheterization technique that was performed under transesophageal echo guidance. After the device was expanded in the left atrial appendage, its position was examined fluoroscopically after contrast ejection. If seating in the appendage was thought not to be adequate, the device could be collapsed and repositioned.
Left atrial appendage occlusion was attempted in 15 patients who ranged from 59 to 78 years of age. All patients had chronic atrial fibrillation and had contraindications to warfarin therapy. Three of the patients had suffered a thromboembolic event while on warfarin treatment. No patient had significant mitral or aortic valve disease. The left atrial appendage was successfully occluded in all 15 patients. The mean procedure time for an initial vascular access to removal of all vascular sheaths was 92.7 ± 43 min. In several patients, the initial device size was inappropriate and a second device was then inserted. Complications were infrequent. Hemopericardium was noted in 1 patient during the procedure but was relieved with percutaneous drainage. At early follow-up, repeat chest radiography and transesophageal echocardiography revealed stable implant position with no evidence of migration, erosion, or encroachment into the mitral orifice. Patients were maintained on aspirin, 300 mg/d, indefinitely and on clopidogrel, 75 mg/d, for the first 6 months after the procedure. After discharge, there were no late complications or thromboembolic events during follow-up.
In an addendum, Sievert et al report they have treated 16 additional patients. The only complication noted was a second case of hemopericardium, which was again successfully treated during the procedure.
Comment by John P. DiMarco, MD, PhD
The major complication associated with atrial fibrillation is the occurrence of thromboembolic events. It has been estimated that atrial fibrillation is responsible for 15-20% of all ischemic strokes. Although anticoagulation with warfarin markedly reduces this risk, a significant number of patients are not candidates or cannot tolerate chronic anticoagulation. The left atrial appendage is thought to be the source of many, if not most, emboli that occur in patients with atrial fibrillation. The novel device described in this early report is designed to eliminate risk associated with these left atrial appendage thrombi.
This early feasibility study demonstrates that a device that occludes the left atrial appendage can be implanted with a reasonable complication rate. However, further clinical studies will be needed to confirm the hypothesis that occlusion of the left atrial appendage with such a device actually reduces the incidence of ischemic strokes. If these clinical studies demonstrate efficacy, this device would then become an alternative to continuous anticoagulation in patients with absolute or relative contraindications to anticoagulation. However, any clinical trial to test this hypothesis will require a large number of patients who would be studied over a significant portion of time, since the stroke risk per year, even in very high-risk groups, is only 10-15%.
Dr. DiMarco is Professor of Medicine, Division of Cardiology, University of Virginia, Charlottesville.
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