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FOCUS ON NEUROLOGIC DISORDERS Jack J.
Chen, Section Advisor
Inadequate anticoagulation common in patients with AF at high risk
for stroke
Key point: An analysis of data from the Registry of
the Canadian Stroke Network revealed that the majority of high-risk
patients admitted with an ischemic stroke who had previously been
diagnosed with nonvalvular atrial fibrillation (AF) were either
suboptimally anticoagulated with warfarin or were not receiving warfarin
at the time of the event.
Finer points: Data from the Registry of the Canadian
Stroke Network, including 12 stroke centers, were analyzed to determine
the number of patients with nonvalvular AF presenting with an acute
ischemic stroke who were inadequately anticoagulated at the time of
admission. The investigators analyzed only patients with AF who were at
high risk for stroke, defined as patients with one or more of the
following risk factors: previous stroke, transient ischemic attack, or
systemic embolism; history of hypertension, heart failure, or pulmonary
edema; and older than 75 years. In addition, patients had to have no
known contraindications to warfarin therapy. The adequate use of
warfarin was analyzed for primary (n = 597) and secondary (n = 323)
stroke prevention.
Of patients presenting with their first stroke (mean age 77.6 years,
55.9% female), only 39.9% were receiving warfarin therapy, and 29.0%
were not receiving any antithrombotic therapies (i.e., aspirin). Of the
39.9% of patients who were taking warfarin, approximately three-fourths
(74.2%) had a subtherapeutic (< 2.0) international normalized ratio
(INR). The median INR at admission was 1.6. The investigators noted that
disabling strokes occurred in 60% of these patients and that 20% of
patients had fatal events. Of patients who had a history of ischemic
stroke or transient ischemic attack presenting with another event (mean
age 78.1 years, 53.7% female), only 57.3% were taking warfarin and 15.2%
were not receiving any antithrombotic therapies. Of the 57.3% of
patients who were taking warfarin, approximately two-thirds (68.3%) had
a subtherapeutic INR (median 1.6). The investigators concluded that
these findings are extremely “troublesome” and should
encourage clinicians to take greater steps “to prescribe and
monitor appropriate antithrombotic therapy to prevent stroke in
individuals with atrial fibrillation.”
What you need to know: A multitude of evidence and
current practice guidelines support the use of warfarin over aspirin
therapy for stroke prevention in patients with nonvalvular AF and
moderate or high risk factors. Results of this study and many others
highlight the fact that warfarin is being underutilized in this patient
population. The investigators cite various barriers to warfarin use,
such as the perceived increased risk of major bleeding events in the
elderly by prescribers, perceived inconvenience and responsibility
associated with INR monitoring, and the fact that prescribers may not be
fully aware of the proven benefits of warfarin. In an attempt to reduce
practice gaps, the investigators summarized numerous system-level,
prescriber, and patient strategies to increase appropriate
anticoagulation. System-level strategies include more anticoagulation
clinics, increased reimbursement for anticoagulation monitoring, and
pharmacist flagging of nonanticoagulated patients with AF. Prescriber
strategies include warfarin dosing and decision aids, and patient
strategies include increased, ongoing education and self-monitoring.
Pharmacists can make a substantial impact on stroke prevention by
identifying patients with AF who should be receiving warfarin and
actively managing these patients. Studies have proven the benefits of
“Coumadin clinics” in improving therapeutic outcomes of
patients treated with warfarin. Appropriately trained pharmacists have
demonstrated their ability to provide excellent care in these
settings.
What your patients need to know: Educate patients
with AF and at high risk for stroke on the importance of adherence to
warfarin therapy and routine blood tests. Tell them that failing to take
their warfarin as prescribed and get appropriate laboratory monitoring
substantially increases their risk for stroke.
Sources:
Related resource on www.pharmacist.com
Beth Farnstrom (bfarnstrom@aphanet.org)
Posted March 19, 2009
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