ASAP (ASA Plavix Feasibility Study With Watchman Left Atrial Appendage Closure Technology) Study (1)

ASA Plavix Feasibility Study with WATCHMAN™ Left Atrial Appendage Closure  Device


The PROTECT AF trial demonstrated that LAA closure with the  WATCHMAN Device was non-inferior to warfarin therapy. However, PROTECT AF only included patients that were candidates for warfarin, and even patients randomized to the LAA closure arm received concomitant warfarin for 6 weeks after WATCHMAN Device implantation.

AF patients who are contraindicated or intolerant of warfarin have few options for thromboembolic prophylaxis. Patients may be treated with aspirin and/or clopidogrel, but this treatment paradigm has a higher stroke risk than warfarin.

The ASAP study, a non-randomized feasibility study performed outside the US, was designed to assess the safety and efficacy of left atrial appendage closure (LAAC) in non-valvular atrial fibrillation (AF) patients ineligible for warfarin therapy.


150 AF patients contraindicated for long-term warfarin therapy were included in the ASAP Study. Patients were enrolled at 4 European centers.

  • Average CHADS2 was 2.8; Average CHA2DS2 -VASc score was 4.4
  • Mean age of the patient population was 72.5 (+/- 4.4 years) and the mean patient follow-up was 14.4 months

The reason for warfarin contraindication was:

  • Hemorrhagic/bleeding tendencies (93%)
  • Blood dyscrasias (7.3%)
  • Unsupervised senility/high fall risk (4%)
  • Other (5.3%)
  • A total of 61 patients (40.7%) had a prior stroke or TIA

Post procedure anti-platelet regimen

  • Clopidogrel through 6 months
  • Aspirin indefinitely

Patients were followed for up to 1 year

  • Follow-up was done at 3, 6, 12, 18 & 24 months
  • TEE at 3 and 12 months


The mean CHADSscore in the ASAP population was 2.8, which equates to a predicted ischemic stroke rate of 7.4% per year using data from a cohort of hospitalized AF patients, assuming no aspirin use 2. If this expected stroke rate of 7.4% per year is averaged with data in which aspirin was used, the expected ischemic stroke of the ASAP population is approximately 7.3%.3  It has also been reported in literature that the addition of clopidogrel can reduce this risk by up to 32%, bringing the expected rate down to 5.0% per year.4

The ASAP study demonstrated a 77% reduction in ischemic stroke in warfarin contra-indicated patients vs. aspirin alone and a 64% reduction vs. aspirin and clopidogrel.

All-cause stroke or systemic embolism occurred in 4 patients (2.3% per year); ischemic stroke in 3 patients (1.7% per year) and hemorrhagic stroke in 1 patient (0.6% per year). The strokes occurred in patients with a prior history of stroke or TIA. A total of 9 patients (5.0% per year) died during the follow-up period (cardiovascular, n=3; cancer, n=2; other, n=4); none were device or procedure related. The cardiovascular and non-cardiovascular deaths occurred at a median of 406 and 209 days post-implant, respectively.


Left atrial appendage closure with the WATCHMAN Device produced a significant reduction in the expected ischemic stroke rate for patients contraindicated to warfarin.