Transcript Clinical Correlation Between Effective Anticoagulants & Risk of Stroke

Clinical Correlation Between Effective
Anticoagulants & Risk of Stroke: Are We
Using Evidence-Based Strategies
ALI R. RAHIMI, BOBBY WRIGHTS, MD, HOSSEIN
AKHONDI, MD & CHRISTIAN M. RICHARD, MSC
Southern Medical Journal 2004;97: 924-931
Trina La
PharmD. Candidate
Oct 20th, 2011
Introduction
 Atrial fibrillation (AF) can predispose patients to
blood clots that can cause stroke
 If untreated, one in three people with nonvalvular AF
will suffer a stroke
 The importance & efficacy of anticoagulation therapy
in preventing a stroke is a common knowledge & has
become the standard of care
Introduction
 Warfarin was reported to be substantially more
efficacious than aspirin
 Anticoagulant prophylaxis is effective as INR of 2 to
3, and is associated with a lower risk of bleeding
 However, despite extensive evidence &
recommendations for its use, anticoagulant
prophylaxis is underused in the management of AF
Study’s Objective
 Primary endpoint: To define correlation between
effective anticoagulant prophylaxis and risk of
thromboembolic stroke
 Secondary endpoint: To observe & investigate the
role of other factors, such as practice patterns in
different settings
Study Design
 Patients with a diagnosis of AF requiring
anticoagulation therapy & who were admitted
between years 1997 & 2000 to community-based
teaching hospital in Southeast Georgia were
identified through a retrospective chart review
 The sample consisted of 297 patients
 91 patients who suffered a stroke at any point during the study
period
 206 patients who did not suffer a stroke by the end of year
2000
Study design
 Patients demographics, clinical diagnoses, findings &
treating physicians were extracted from admission
records
 History of AF, duration of the disease, treatment
modalities, indicators for anticoagulation therapy, &
risk factors for comorbid diseases were obtained
from hospital charts
Study design
 Two study groups
 Warfarin: 124 patients
 No Warfarin: 166 patients
 No record of anticoagulation therapy: 7 patients
 INR
 Between 2.0 & 3.0 as therapeutic
 Prescribing physician specialties
 Neurologists
 Cardiologists
 General internists
 Others
Inclusion & Exclusion
Inclusion
 A diagnosis of AF
requiring
anticoagulation
therapy
Exclusion
 Hypercoagulable state
 Hemorrhagic stroke
 Carotid stenosis
 Peripheral vascular
disease
 Dilated
cardiomyopathy
Nature of the variables collected
Variables collected
Data Analysis
 Age
 Normal probability plots &
 INR
 Gender
 Race
 Co-morbidities
 Managing Physician
Specialty
the Shapiro-Wilks test to
assess the normality
assumption
 Chi-square test of
independence to compare
patients prescribed/not
prescribed warfarin for each
indicator variables
 The risk of stroke associated
with anticoagulation tx was
assessed using 2x2
contingency table & stratified
Mantel-Haenszel analysis
Results
Variables
Warfarin
(n=124)
Non-Warfarin
(n=166)
Statistical test
P value
Age
72.95 ± 10.60
74.23 ± 11.92
0.232
46.8%
53.2%
44.8%
55.2%
0.754
INR
2.51 ± 2.03
1.19 ± 0.45
<0.001
Comorbidities
CVA
CHF
CAD
HTN
Diabetes
24.2%
29.8%
22.6%
54.8%
25.0%
13.3%
27.1%
18.1%
58.4%
25.9%
0.017
0.610
0.342
0.541
0.861
Managing physician
Specialty
Cardiology
Neurology
Internal Med
Other
30.6%
13.7%
33.1%
22.6%
16.9%
10.8%
39.2%
33.1%
Stroke
19.4%
37.3%
Gender
Male
Female
0.02
<0.001
Results
 Higher warfarin dosages
 Larger values in INR (r=+0.395)
 Fewer strokes (r=-0.372)
 Prescribed by cardiologists (0.289)
 Greater occurrences of strokes are present in those
patients under the care of neurologist (r=+0.394)
 Average dosage of warfarin prescribed


Cardiologists: 2.94 mg
Neurologists: 1.76 mg
Odds of Warfarin Prescription
 Patients who were more likely to be prescribed
warfarin when


History of AF & stroke (P=0.013)
Care management by a cardiologists (P=0.035)
 Elderly patients were more likely to have additional
comorbidities that influenced the prescription of
warfarin
 Neurologists (P=0.308) & internists(P=0.77) have
similar patterns of prescribing warfarin when
compared with cardiologists
Odds of Stroke
 Patients who are not prescribed warfarin have
significantly higher risk of suffering a stroke
 Patients with diagnosis of CHF in addition to AF
were 6.8 times less likely to suffer a stroke when
compared with AF patients without CHF
 NNT: 50
Author’s comment
 Treatment of AF & anticoagulant prophylaxis are
complex & time consuming clinical undertakings
that requires long-term commitments
 This study’s result with regard to the risk of stroke in
patients with AF are consistent & in line with
previously published studies
 The elderly patients and the presence of co-morbid
diseases play a significant role in the decision
making process
Limitations & Conclusion
 Limitations
 Many patients’ records revealed the presence of internist in
addition to other specialists
 There were some overlaps between the primary providers in
ordering warfarin dosages
 Conclusions
 Despite extensive evidence supporting anticoagulation
therapy, both physicians & patients are less inclined to more
aggressive stroke prevention measures
 Cost, fear of bleeding complications, drug interactions, & time
are the factors influencing decision making
 educational opportunities & an aggressive public awareness
might be needed
Comments
 I think this is a very important study because it showed
the correlation between effective anticoagulant on stroke
prevention, and it raised the awareness of not fully use
evidence-based strategies per physicians
 However, the study did not document some essential
information
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History of compliance with warfarin
When patients started taking warfarin
How the physician adjust warfarin dosing
Record of all medications, including AF medications due to potential
drug interaction
History of adverse drug events and complications
Level of evidence