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Review cautions acceptance of Watchman device for left atrial appendage occlusion to prevent stroke in patients with atrial fibrillation

Henry I. Bussey, Pharm.D., FCCP, FAHA
July, 2009

Article Reviewed: Maisel WH. Left atrial appendage occlusion--closure or just the beginning? N Engl J Med. 2009 Jun 18;360(25):2601-3.

This concise review of the data regarding the new Watchman device presents the good news and appropriate cautions. The device is implanted in the left atrial appendage in order to block the main source of thrombi in atrial fibrillation. The implantation process is accomplished by transeptal venous catheter insertion.

Good news: When compared to warfarin therapy, the primary end point (absence of ischemic and hemorrhagic stroke, cardiovascular and unexplained death, and systemic embolism) was 32% lower in the Watchman group than in the warfarin-treated group; an outcome that met the non-inferiority criteria.

Cautions: The reviewer points out several key considerations that argue for caution in adopting this approach for preventing stroke in atrial fibrillation:

  • Thrombosis was identified on the device in 15 (3.7%) of patients and ischemic stroke was 50% higher in the device group (3% vs 2%)

  • The need for ongoing anticoagulation meant that device recipients received warfarin for at least 45 days followed by aspirin indefinitely and clopidogrel for 6 months. Warfarin was restarted for clinical reasons in 10% of patients. (Note that two recent trials have shown that aspirin or aspirin and clopidogrel is NOT safer than warfarin therapy. See clotcare.com/clotcare/aspirinclopidogrelwarfarinafib.aspx and clotcare.com/clotcare/warfarinvsaspirinforafib.aspx)

  • Cardiovascular surgery was required in 2.2% of procedures; an end point NOT included in the primary analysis.

  • Implantation was associated with several complications and implantation was successful in 408 of 449 (90.9%) attempts but 12.3% of patients had serious complications (pericardial effusion in approximately 5%, acute ischemic stroke in 1.1%, surgical removal due to embolization or sepsis in 4 patients.

  • Warfarin therapy in the control group was not ideal in that more than 25% of patients never took or discontinued warfarin, and INRs were in range only 55% of the time (below target 29.6% and above target 15.4%)

  • Nearly 30% of patients had a low CHADS2 stroke risk of 1 which may warrant therapy with aspirin only.

  • Fewer than 100 patients with the device were followed for 2 or more years and the relatively small size of the study resulted in a wide 95% confidence interval (relative risk of 0.68; 95% credible interval of 0.37 to 1.41).
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Wednesday, October 18, 2017