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The Aspirin vs. Warfarin conundrum in the treatment
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of Atrial Fibrillation for the protection of thromboembolism.
Joel R. Garcia, M.D. |
Over 2
million people in the United
States have Atrial
Fibrillation (AF) (1). As
the population continues to
age, the prevalence of this
disease continues to
increase. Almost 6% of those
over age 65 have AF (1). The
prevalence of the disease
increases sharply after the
7th decade of life. The
presence of atrial
fibrillation (AF) confers
significant mortality and
morbidity, with AF being the
most common cause of
cardioembolic stroke.
Because AF is so common as
is often highly symptomatic,
important therapeutic
decisions concerning the
need for antiarrhythmic and
antithrombotic therapy are
frequently faced by many
clinicians. The role of
aspirin versus coumadin for
the prevention AF related
thromboembolism is a
clinical conundrum that
remains a very difficult
subject for clinicians and
patients alike. This topic
will be the focus of this
review.
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Clinical Case: Mrs.
R, a 66 year old female with
newly diagnosed atrial
fibrillation presents to
your office for evaluation.
She has no history of TIA,
but has a history of well
controlled diabetes mellitus
type II. Her BP is 148/76
mmHg. She has no history of
heart disease.
Should this patient
be placed on coumadin or
aspirin for the prevention
of thromboembolism related
to her AF?
The annual stroke risk for patients older than 65 with non-rheumatic AF is at least fivefold greater than those patients of similar clinical characteristics. (2) This translates into a 5-7% yearly risk for stroke. A recent systematic review of the available medical literature found that the risk of stroke in a patient with AF was most significantly elevated by a prior history of stroke or a transient ischemic attack. (2) Other major risk factors for stroke include advanced age (> 75 years of age), history of hypertension, or diabetes mellitus. Interestingly enough, a history of heart failure or CAD were not conclusively linked with an increased risk of stroke. (2)
Current ACC guidelines recommend warfarin adjusted to achieve an INR between 2 and 3 to prevent stroke among patients with AF and a history of prior cerebrovascular disease, prosthetic heart valves, or mitral stenosis. (3) Warfarin therapy should also be considered for those patients age 75 years and older and those with hypertension, diabetes mellitus, heart failure or a documented left ventricular ejection fraction of less than 35%. Other patients with AF may receive aspirin for protection against stroke.
Pooled data from randomized trials show that warfarin reduces the risk of stroke from 4.5% to 1.4% per year in patients with non-rheumatic AF and no history of stroke or TIA. The current generalized consensus among many medical practioners and treatment guidelines recommend warfarin for AF patients at high risk of stroke, aspirin for patients at low risk for stroke, and either drug for patients at intermediate risk. It is this subset of patients that is the clinical conundrum for clinicians. There are a number of risk stratification schemes that help to predict stroke risk among patients with atrial fibrillation. An ACCP model and CHADS2 (named for components of the score: CHF, HTN (160/90mm Hg, Age (older than 75), Diabetes, and Stroke or TIA has been proposed to help in decision making for treating patients with nonvalvular AF (see table 1) below. (4, 5)
Singer DE, Albers
GW, Dalen JE, Go AS,
Halperin JL, Manning WJ.
Antithrombotic therapy in
atrial fibrillation: the
Seventh ACCP Conference on
Antithrombotic and
Thrombolytic Therapy
[Review]. Chest 2004; 126(3
suppl):429S-56S.
The risk of bleeding and
intracranial hemorrhage is
an obvious concern to
patients and physicians. In
pooled analysis (4) the
annual risk of intracranial
hemorrhage from controls to
those patients on warfarin
therapy rose from 0.1% to
0.3%. In “real world” terms
this translates into an
additional 2 intracranial
bleeds for every 1000
patients treated with
warfarin. Bleeding risks
should be discussed in
detail with patients. Major
risk factors for bleeding
include age > 65 years,
history of GI tract
bleeding, history of stroke,
history of recent MI,
hematocrit lower than 30 or
a creatinine of 1.5 or
greater. (6).
In our fictitious patient
described above, in applying
the ACCP risk criteria, the
patient would be a candidate
for warfarin given her 2
major risk factors of
diabetes and hypertension.
Using the CHADS2 criteria
she would fall into the
“moderate” risk for stroke
with 2 points for
hypertension and diabetes.
The use of both “rules” in
conjunction may be helpful
in giving treating
physicians and patients
alike more confidence in the
treatment decisions made.
There remains considerable
controversy in the medical
community and literature for
treatment of “moderate”
stroke risk patients with
AF. For the present time
being, a strategy of careful
clinical assessment and risk
stratification for atrial
fibrillation in which the
highest-risk groups for
stroke and thromboembolism
are targeted for
anticoagulation (with
warfarin) and low-risk
groups being treated with
aspirin appears to be most
clinically appropriate.
REFERENCES
1.
Feinberg WM, Blackshear JL,
Laupacis, A, Kronmal R, Hart
RG. Prevalence, age
distribution, and gender of
patients with atrial
fibrillation. Analysis and
implications. Arch Intern
Med. 1995; 155:469-473.
2. Stroke Risk in
Atrial Fibrillation Working
Group. Independent
predictors of stroke in
patients with atrial
fibrillation: a systematic
review. Neurology. 2007;
69:546-554.
3. Writing Committee
to Revise the 2001
Guidelines for the
Management of Patients with
Atrial Fibrillation.
ACC/AHA/ESC 2006 guidelines
for the management of
patients with atrial
fibrillation. Circulation.
2006; 114:e257-e354.
4. Singer DE, Albers
GW, Dalen JE, Go AS,
Halperin JL, Manning WJ.
Antithrombotic therapy in
atrial fibrillation: the
Seventh ACCP Conference on
Antithrombotic and
Thrombolytic Therapy
[Review]. Chest 2004;126(3
suppl):429S-56S
5. Pearce LA, Hart RG,
Halperin JL. Assessment of
three schemes for
stratifying stroke risk in
patients with nonvalvular
atrial fibrillation. Am J
Med 2000; 109:45-51.
6. Wells PS, Forgie
MA, Simms M, Greene A,
Touchie D, Lewis G, et al.
The outpatient bleeding risk
index: validation of a tool
for predicting bleeding
rates in patients treated
for deep venous thrombosis
and pulmonary embolism. Arch
Intern Med 2003; 163:917-20.
Bio:
Joel R. Garcia, MD is a
General and Invasive
Cardiologist at The Orlando
Heart Center, Sand Lake
office. A native of Reading,
Pennsylvania, he attended
the Pennsylvania State
University. He completed his
residency in Internal
Medicine at The Pennsylvania
State University College of
Medicine (LVH) program. He
then completed his
Cardiovascular Diseases
Fellowship at The
Pennsylvania State
University College of
Medicine, Milton S Hershey
Medical College Program. He
is board certified in
Internal Medicine and
Cardiology (BE). Dr Garcia
is proficient in all aspects
of invasive
(non-interventional)
cardiology, nuclear
cardiology, echocardiography
and coronary CT angiography.
He is available to see new
patients at the Orlando
Heart Center, Sandlake
office at 7236 Stonerock
Circle, Orlando Fl 32819.
Phone 407-370-5800.
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