ali r. rahimi, bobby wrights, md, hossein akhondi, md & christian m. richard, msc
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ALI R. RAHIMI, BOBBY WRIGHTS, MD, HOSSEIN AKHONDI, MD & CHRISTIAN M. RICHARD, MSC
Clinical Correlation Between Effective Anticoagulants & Risk of Stroke: Are We Using Evidence-Based Strategies
Trina LaPharmD. CandidateOct 20th, 2011
Southern Medical Journal 2004;97: 924-931
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
InclusionInclusion ExclusionExclusion
A diagnosis of AF requiring anticoagulation therapy
Hypercoagulable state
Hemorrhagic strokeCarotid stenosisPeripheral vascular
diseaseDilated
cardiomyopathy
Inclusion & Exclusion
Variables collectedVariables collected Data AnalysisData Analysis
AgeINRGenderRaceCo-morbiditiesManaging Physician
Specialty
Normal probability plots & 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
Nature of the variables collected
ResultsVariables Warfarin
(n=124)Non-Warfarin(n=166)
Statistical test P value
Age 72.95 ± 10.60 74.23 ± 11.92 0.232
Gender Male Female
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%
0.0170.6100.3420.5410.861
Managing physicianSpecialty Cardiology Neurology Internal Med Other
30.6%13.7%33.1%22.6%
16.9%10.8%39.2%33.1%
0.02
Stroke 19.4% 37.3% <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 dosagesConclusions
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 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
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