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      Is the Site of Thrombus Formation in the Left Atrial Appendage Associated with the Risk of Cerebral Embolism?

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          Abstract

          Atrial fibrillation (AF) is a risk factor for cerebral embolism, with the left atrial appendage (LAA) being considered as the source of emboli. However, the relationship between the histologic properties of LAA thrombi and the occurrence of cerebral embolism is not known. Seventy-six hearts from patients who died within 1 month after cerebral embolism were studied at autopsy. Patients were grouped according to the presence of AF and the presence of valvular disease (VD). We determined whether the LAA thrombi adhered to the trabecular region or the remainder of the LAA. LAA thrombi were grouped into three stages: a fresh stage in which thrombi consisted of fibrin and platelets, an organizing stage in which angiogenesis was observed in the thrombi, and an organized stage in which endothelial cells covered the surface of the thrombi. The AF+/VD– group included 19 patients (25.0%), the AF+/VD+ group 8 (10.5%), the AF–/ VD– group 37 (48.7%), and the AF–/VD+ group included 12 patients (15.8%). LAA thrombi were observed in 15 patients (78.9%) in the AF+/VD– group, and all of the thrombi adhered to the trabecular region. Thrombi in the fresh and the organizing stages were observed in 10 patients (66.7%). Patients in the AF+/VD– group accounted for about 25% of the cases of cerebral embolism. All of these thrombi were attached to the trabecular region, and about 70% of them could represent an embolic source.

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          Most cited references 2

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          Transesophageal echocardiographically facilitated early cardioversion from atrial fibrillation using short-term anticoagulation: final results of a prospective 4.5-year study.

          We sought to validate the safety of transesophageal echocardiographically guided early cardioversion in conjunction with short-term anticoagulation as a strategy for guiding early cardioversion in hospitalized patients with atrial fibrillation. Because atrial thrombi are poorly seen by conventional imaging techniques, several weeks of prophylactic anticoagulation is routinely prescribed before cardioversion. Transesophageal echocardiography is a superior test for identifying atrial thrombi; preliminary feasibility studies have supported its use to guide early cardioversion for patients in whom no thrombus is observed, but safety has not been validated in any large series. All patients admitted to hospital with atrial fibrillation during a 4.5-year period were screened. The inclusion criterion was a clinical duration of atrial fibrillation > 2 days or of unknown duration. Patients received anticoagulation with heparin/warfarin and underwent conventional transthoracic echocardiography followed by transesophageal study. Patients in whom transesophageal echocardiography revealed no atrial thrombus underwent pharmacologic or electrical cardioversion followed by warfarin therapy for 1 month. Cardioversion was deferred in patients with evidence of atrial thrombi, and they received prolonged warfarin treatment. Two hundred thirty-three patients (86% of those eligible) agreed to participate, and 230 underwent transesophageal echocardiography. Transesophageal echocardiography identified 40 atrial thrombi (left atrium 34, right atrium 6) in 34 patients (15%). One hundred eighty-six (95%) of 196 patients without thrombi had successful cardioversion to sinus rhythm, all without prolonged anticoagulation, and none (0%, 95% confidence interval 0% to 1.6%) experienced a clinical thromboembolic event. Eighteen patients with atrial thrombi underwent uneventful cardioversion after prolonged anticoagulation. Compared with smaller series that have shown only feasibility, this large prospective and consecutive study of patients undergoing transesophageal echocardiographically facilitated early cardioversion in conjunction with short-term anticoagulation validates the safety of this strategy. This treatment algorithm has a safety profile similar to conventional therapy and minimizes both the period of anticoagulation and the overall duration of atrial fibrillation.
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            Cardioversion from atrial fibrillation without prolonged anticoagulation with use of transesophageal echocardiography to exclude the presence of atrial thrombi.

            Because atrial thrombi are poorly detected by conventional noninvasive techniques such as transthoracic echocardiography, patients with prolonged atrial fibrillation usually receive several weeks of oral anticoagulation therapy before cardioversion is attempted. We wondered whether transesophageal echocardiography, an accurate method of detecting atrial thrombi, would allow early cardioversion to be performed safely if no thrombi were identified. A total of 669 consecutive patients admitted with the diagnosis of atrial fibrillation were screened. Patients were excluded if they were receiving long-term anticoagulation, if the duration of atrial fibrillation was two days or less, if they were not candidates for cardioversion, or if transesophageal echocardiography was contraindicated. Of 119 qualifying patients, 94 agreed to participate; the average duration of atrial fibrillation was 4.5 weeks. Participating patients underwent transthoracic echocardiography and transesophageal echocardiography followed by cardioversion if no thrombi were seen. Short-term anticoagulation with heparin was used in 80 patients before cardioversion, and 60 patients received warfarin for one month after cardioversion. Fourteen atrial thrombi were identified in 12 patients (13 percent), and 12 of the 14 thrombi were visualized only on transesophageal echocardiography. Cardioversion was deferred in all 12 patients. Two of these 12 patients died suddenly; 4 of the 10 surviving patients underwent uneventful cardioversion after prolonged oral anticoagulation. Seventy-eight of the 82 patients without thrombi underwent successful cardioversion to sinus rhythm (47 by means of antiarrhythmic drugs and 31 by electrical cardioversion), all without long-term oral anticoagulation. None of these patients (95 percent confidence interval, 0 to 4.6 percent) had an embolic event. In patients with atrial fibrillation of unknown or prolonged duration who are not receiving long-term anticoagulation, atrial thrombi are detected by transesophageal echocardiography in only a small minority (13 percent in our study). Our preliminary data suggest that if transesophageal echocardiography excludes the presence of thrombi, early cardioversion can be performed safely without the need for prolonged oral anticoagulation before the procedure.
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              Author and article information

              Journal
              CRD
              Cardiology
              10.1159/issn.0008-6312
              Cardiology
              S. Karger AG
              0008-6312
              1421-9751
              2002
              April 2002
              25 April 2002
              : 97
              : 2
              : 104-110
              Affiliations
              aFirst Department of Internal Medicine, and bDepartment of General Medicine and Clinical Investigation, Nara Medical University, Nara, and cDepartment of Pathology, National Cardiovascular Center, Osaka, Japan
              Article
              57681 Cardiology 2002;97:104–110
              10.1159/000057681
              11978958
              © 2002 S. Karger AG, Basel

              Copyright: All rights reserved. No part of this publication may be translated into other languages, reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying, recording, microcopying, or by any information storage and retrieval system, without permission in writing from the publisher. Drug Dosage: The authors and the publisher have exerted every effort to ensure that drug selection and dosage set forth in this text are in accord with current recommendations and practice at the time of publication. However, in view of ongoing research, changes in government regulations, and the constant flow of information relating to drug therapy and drug reactions, the reader is urged to check the package insert for each drug for any changes in indications and dosage and for added warnings and precautions. This is particularly important when the recommended agent is a new and/or infrequently employed drug. Disclaimer: The statements, opinions and data contained in this publication are solely those of the individual authors and contributors and not of the publishers and the editor(s). The appearance of advertisements or/and product references in the publication is not a warranty, endorsement, or approval of the products or services advertised or of their effectiveness, quality or safety. The publisher and the editor(s) disclaim responsibility for any injury to persons or property resulting from any ideas, methods, instructions or products referred to in the content or advertisements.

              Page count
              Figures: 6, Tables: 2, References: 23, Pages: 7
              Categories
              Cardiovascular Pathology

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