Posted on by Alexandra Santamaria, PharmD,CDE, BCACP

Thromboembolism in AF

stroke journal
WebMD
  • Cardioembolism: due to blood stasis primarily in left atrial appendage
  • AF significantly increases risk of thromboembolic ischemic stroke 5 times compared to patients in sinus rhythm
    • 4 times greater risk of recurrent stroke
    • More severe disability
    • 2 times higher mortality

Most serious common complication of AF is arterial thromboembolism, most notably an ischemic stroke. Due to formation of atrial thrombi from blood stasis.

Thromboembolism occurring with AF is associated with greater risk of recurrent stroke, more severe disability, and mortality. Embolization of atrial thrombi can occur with any form of AF. Embolic risk leads to chronic oral anticoagulation.

Oral anticoagulants have been shown to lower the risk of clinical thromboembolism in nearly all patients with AF, at all levels of risk and irrespective of its classification

Estimation of Thromboembolism

CHA2DS2 VASc

January CT, et al. J Am Coll Cardiol. 2014;64:21  

In patients with nonvalvular AF, the CHA2DS2-VASc score is recommended for assessment of stroke risk

To assess stroke risk

0 = no antithrombotic therapy

1: no treatment or ASA

Oral anticoagulation recommended in score 2 or more

Antithrombotic Therapy

ACC/AHA Guidelines

Chest Guidelines

Anticoagulation: warfarin, dabigatran, apixaban, rivaroxaban, betrixaban

Other Factor Xa inhibitors (edoxaban, betrixaban) not approved at time of guidelines

CHADS 0: ASA may prevent 2 nonfatal strokes per 1000 pt

1: asa + clopidogrel for those unsuitable for/choose not to take AC for reasons other than bleeding (difficult maintaining stable INR, lifestyle limitations regular monitoring, costs)

HAS-BLED

Pisters R, et al. Chest. 2010;138:5

Bleeding risk scores to quantify hemorrhage risk

Other bleeding risk scoring systems: RIETE, HEMORR2HAGES, ATRIA

Helpful in defining patient at elevated bleeding risk, but clinincal utilily is insufficient for use as evidence for recommendations in guideline

Low risk: 0

Moderate: 1-2

A score >/3 indicates potentially “high risk” for bleeding and may require closer observation of a patient for adverse risks, closer monitoring of INRs, or differential dose selections of oral anticoagulants or aspirin

HAS-BLED > CHADS2 Score

  1. HAS-BLED score ≥3 indicates “high risk” of bleeding
    1. Caution and regular review needed following initiation of AC
    1. Address correctable bleeding risk factors (eg. uncontrolled hypertension, co-administration of NSAIDs or aspirin, etc).
  2. If HAS-BLED score exceeds CHADS2 score, the risk of major bleeding may outweigh potential benefit of AC
    1. Use in the Euro Heart Survey on AF population could have prevented 12.1% (4/33) of major bleeds (Pisters R, et al. Chest. 2010;138:1093).
  3. Requires validation in other cohorts of patients with AF
    1. Not yet adopted by the ACC/AHA/HRS AF guidelines AC = oral anticoagulation

Camm AJ, et al. Eur Heart J. 2010;31(19):2369-2429. Pisters R, et al. Chest. 2010;138:1093-1100.

Lip GY, et al. Am J Med.2010;123(6):484-488.

Why Is AF Undertreated from an Anticoagulation Standpoint?

•Patient intolerance or poor adherence

•Under-recognition of AF itself

•Physician treatment bias:

–Inclination to correlate burden of AF with stroke risk

–Belief that aspirin is an acceptable protective alternative to oral anticoagulants

–Medical liability: 27% of patients decline OAC based on shared decision-making (i.e., fear of complications)

De Breucker S, et al. Drugs Aging. 2010;27(10):807-813. Why Is AF Undertreated from an Anticoagulation Standpoint?

Percutaneous Left Atrial Appendage Closure (LAAC)

•Treatment strategy to reduce the risk of LAA blood clots from entering the bloodstream and potentially causing stroke in nonvalvular AF patients

•Randomized data only available for WatchmanTM procedure –Only FDA-approved device

•AmuletTM is being studied

•Lariat procedure is a commercially available closure device –FDA approval only for “approximation of soft tissue” but not LAA closure for stroke prevention Percutaneous Left Atrial Appendage Closure (LAAC)

Watchman Procedure

Watchman Device

Patient Selection

•Appropriate patients:

–Increased risk for stroke CHADS >1 or CHA2DS2-VASc ≥2

–Deemed suitable for warfarin

–Have appropriate rationale to seek nonpharmacologic alternative to warfarin

•Contraindicated:

–Do not use if thrombus visualized on TEE imaging

–Prior atrial septal defect (ASD) or patent foramen ovale (PFO) repair or closure device

–Contraindications to use of warfarin, aspirin, or clopidogrel

Additional Considerations

•Risks include bleeding, perforation, pericardial effusion, tamponade, stroke, and death

•Complication rate of 2-3%

•A shared medical consensus between 2 physicians and the patient is required to qualify for insurance coverage

PASS Criteria

•Position

–Position relative to the ostium of the left atrial appendage

•Anchor

–Are the fixation anchors engaged?

•Size

 –Device should be compressed 8-20% of original size

•Seal

–Device should span entire ostium and all lobes should be covered

Watchman device placement

Postprocedure Anticoagulation Protocol

Key Points

•Oral anticoagulation is the preferred therapy to reduce stroke risk in patients with AF…

•…but overall compliance with warfarin and DOACs is poor (~50%), especially among those at highest risk for stroke

•LAAC is a second-line therapy for stroke prevention in patients with AF and is reasonable alternative for patients. ineligible for long-term oral anticoagulation

Next article: Up next anticoagulation treatment