Abstract & Commentary
By John P. DiMarco, MD, PhD, Professor of Medicine, Division of Cardiology, University of New Mexico, Albuquerque. Dr. DiMarco is a consultant for Novartis and does research for Medtronic and Guidant.
Synopsis: This system may be an alternative therapeutic strategy for patients at risk of stroke who have contraindications for long-term warfarin anticoagulation.
Source: Ostermayer SH, et al. Percutaneous Left Atrial Appendage Transcatheter Occlusion (PLAATO System) to Prevent Stroke in High-Risk Patients with Non-Rheumatic Atrial Fibrillation: Results from the International Multi-Center Feasibility Trials. J Am Coll Cardiol. 2005;46:9-14.
Although anticoagulation with warfarin has been shown to be effective in preventing stroke in patients with nonrheumatic atrial fibrillation, many patients cannot tolerate warfarin therapy, and most would prefer not to take it. This has led to the development of innovative devices which may decrease the risk of stroke in these patients. In this paper, Ostermayer and colleagues report the early results using a new device designed to prevent left atrial appendage thrombus formation. The percutaneous left atrial appendage transcatheter occlusion (PLAATO) system consists of self- expanding nitinol cages in various sizes that are covered with expanded polytetrafluoroethylene. Anchors are positioned along the struts to help position and stabilize the PLAATO device in the left atrial appendage. The device is implanted using transseptal puncture from a femoral approach and positioned with transesophageal echocardiographic and fluoroscopic guidance in the left atrial appendage. Dye injections are used to assess the degree of left atrial appendage sealing by the device. The device can be repositioned if the initial deployment is not satisfactory. The major entry criteria for this feasibility trial required that patients have nonrheumatic atrial fibrillation of at least 3 months duration and have contraindications to chronic warfarin. In addition, patients were required to have either a history of a transient ischemic attack or stroke or other risk factors that put them at increased risk for thromboembolic events. The potential risk factors for consideration included congestive heart failure or systolic dysfunction, severe systolic hypertension, diabetes, age over 64 years, a history of myocardial infarction, or the presence of moderate or dense spontaneous echocardiographic contrast in the left atrial appendage. Patients with preexisting thrombi, as well as those with complex aortic plaques, mitral or aortic valve disease, left atrial diameters greater than 6.5 cm, recent acute coronary events and strokes, and symptomatic carotid disease were not eligible for participation.
After left atrial appendage closure, patients were placed on aspirin indefinitely. Some patients received clopidogrel for 4-6 weeks. A short peri-operative course of prophylactic antibiotic therapy was also prescribed to most patients. Follow-up was conducted at one week, one month, 3 months, 6 months, and 12 months. The primary end point of the study was a major adverse event including major or minor stroke, cardiac or neurological death, myocardial infarction, or a requirement for surgery related to the PLAATO procedure.
One hundred eleven patients were entered into the study. Eighty-four percent were over age 65 and 35% were over age 75. Using the CHADS2 index for stroke risk, 30% had a CHADS score of 2, 21% had a CHADS score of 3, 16% had a CHADS score of 4, and 7% had a CHADS score of 5 or 6. Percutaneous left atrial appendage occlusion was successful in 108 of 111 patients. Implantation was unsuccessful because of the presence of a left atrial thrombus at the time of the procedure in one patient and because of technical complications in 2 patients. The average procedure time was 68 ± 28 minutes. There was one periprocedural death associated with perforation and cardiac tamponade during the implant attempt. By echocardiographic criteria, 100% of patients had successful occlusion of the left atrial appendage at one month, and occlusion persisted in 49 of 50 patients studied out to 6 months. Device migration or dislodgement of the left atrial appendage was not observed. During a mean average follow-up of 9.8 months, there were 2 ischemic strokes 173 and 229 days after the procedure. Transient ischemic attacks were noted in 2 additional patients. This led to an observed annual stroke rate of 2.2%. There were 6 deaths in the 111 patients, but none were adjudicated as device or procedural related. Four patients died of cardiac or neurologic causes, one with secondary complications after gastrointestinal bleeding and one with an incarcerated abdominal hernia.
Ostermayer et al conclude that the PLAATO System can be inserted at acceptable risk with promising results, in terms of stroke prevention in a high-risk patient subset. Ostermayer et al propose that the system may be an alternative therapeutic strategy for patients at risk of stroke who have contraindications for long-term warfarin anticoagulation.
Stroke is the most worrisome common complication of atrial fibrillation. Although it has been well established that warfarin anticoagulation decreases the risk of ischemic stroke in patients with atrial fibrillation, many patients cannot take or are unwilling to take warfarin chronically. In the randomized warfarin trials, up to one-third of patients were excluded from participation because of definite contraindications to warfarin. In addition, major bleeding develops at about 2% per year during warfarin therapy in patients with atrial fibrillation, and about 25% will report problems with minor bleeding. This early report of a new catheter procedure for occluding the left atrial appendage is, therefore, quite promising. It must be remembered, however, that the left atrial appendage is not the only potential source of embolism in patients with atrial fibrillation. Risk of stroke is also linked to the presence of complex aortic and carotid atherosclerosis and thrombi can occur in other areas of the left atrium or left ventricle in patients with advanced heart disease. Despite these considerations, however, development of an effective and safe catheter procedure, which would markedly reduce the stroke risk without requiring systemic anticoagulation, would be a major benefit in many patients. From the standpoint of patient convenience alone, elimination of the frequent laboratory testing required during warfarin therapy would be a major advantage for patients. We can expect to see trials soon comparing therapy with either PLAATO or some comparable device, and warfarin in atrial fibrillation patients. If the devices prove to be safe and effective long-term, they may evolve to be attractive alternatives for many.