Anticoagulation in Atrial
Fibrillation
Dalia Hawwass PGY2
June 2015
Objectives
Determine when to anticoagulation is needed in patients
with non-valvular atrial fibrillation
Discussion of risk-based Antithrombotic Therapy (American
College of Cardiology recommendations)
When to use CHADS2-VaSc or CHADS2 score for stroke
risk assessment in non-valvular atrial fibrillation
Discussion of Different Anticoagulation Agents (including
newer forms of NOAGs)
Case Presentation
A 65 year old male with PMHx of preserved congestive heart
failure (LVEF 40%) and hypertension presents to ED with
palpitations and shortness of breath. At baseline, patient has very
active lifestyle, including cycling 2-3 times/week.
Hospital course notable for newly diagnosed atrial fibrillation
secondary to left atrial dilation. Workup was negative for
infection, thyroid disease or MI. Renal function is preserved. He
was started on rate control with beta blocker.
Currently, patient is asymptomatic and SOB resolved.
Should this patient be anticoagulated?
Anticoagulation in Afib
Risk of CVA in nonvalvular Afib is roughly 4.5%/yr
Afib is associated with increased risk for heart failure
and overall all cause mortality
Risk Based Antithrombotic Therapy based on
American College of Cardiology recommendations
CHADS2-VaSc or CHADS2 score used for nonvalvular Afib for stroke risk assessment
CHADS2
Acronym
Score
CHA2D2-VASc
Acronym
Score
CHF
1
CHF
1
Hypertension
1
Hypertension
1
Age≥ 75 yrs
1
Age≥ 75 yrs
2
Diabetes
mellitus
1
Diabetes
mellitus
1
Stroke/TIA/T
E
2
Stroke/TIA/T
E
2
Maximum
Score
6
Vascular
Disease
1
Age 65-74
1
Female Gender
1
Maximum
Score
9
Risk Stratification with CHADS2
Score
CHADS2 Acronym
Unadjusted ischemic stroke rate (%
per year)
0
0.6%
1
3.0%
2
4.2%
3
7.1%
4
11.1%
5
12.5%
6
13.0%
Risk Stratification with CHA2DS2VASc Score
CHA2DS2-VASc Acroynm
Unadjusted ischemic stroke rate (%
per year)
0
0.2%
1
0.6%
2
2.2%
3
3.2%
4
4.8%
5
7.2%
6
9.7%
7
11.2%
8
10.8%
9
12.2%
Class I Recommendations
• Selected Class I Recommendations
• In patients with non-valvular AF, calculate
CHA2DS2-VASc or CHADS2
• CHADS2-VaSc ≥2, oral anticoagulation
recommended
For patient with non-valvular AF with prior stroke, TIA or
CHADS2-VaSc ≥2, oral anticoagulation recommended with
warfarin (Evidence A) or newer agents (Evidence B)
Class II Recommendations
Class IIa selected recommendations
For patients with nonvalvular AF and CHADS2-VaSc=0,
reasonable to omit antithrombotic tx (Evidence B)
Patients with CHAD2-VaSc 1, can consider anticoagulation or
ASA
Pt with nonvalvular AF with CHADS2-VaSc ≥2 with end
stage CKD (CrCl<15mL/min) or on HD, reasonable to
prescribe warfarin (INR 2-3) (Evidence B)
Following coronary revascularization in patients with Afib
and CHADS2-VaSc ≥2, can use clopdiogrel with oral
anticoagulants but without ASA
Class III Recommendations:
Harm
Dabigatran, a direct thrombin inhibitor, should not be
used in patients with AF and a mechanical heart valve
(evidence B)
Direct thrombin inhibitors and factor Xa inhibitors are
not recommended in patients with AF and end-stage
CKD or on HD
Lack of evidence
Anticoagulation Agents
Aspirin
Warfarin (Coumadin)
Dabigatraban (Pradaxa)
Rivaroxaban (Xarelto)
Apixaban (Eliquis)
ASA + clopidogrel therapy
Aspirin
Irreversible inhibitor of COX, reduces prostaglandin and thromboxane A2
ASA shown to be beneficial in both primary and secondary prevention of stroke
Benefit to risk ratio in patients at low risk scores of 0 or 1 has not been well
studied
Recommendations for American College Chest Physicians, for CHADS=0, suggest
no therapy rather than antithrombotic therapy
If therapy is chosen, suggest ASA 81mg or 325mg
If CHADS=1, recommend oral anticoagulation or antiplatelet therapy
Plavix + ASA vs Warfarin was compared in the ACTIVE-W trial. Ended early due
to inferiority between these two groups in pts with CHADS2 = 2.
Plavix + ASA proved to be superior to ASA alone in ACTIVE-A trial.
Warfarin (Coumadin)
Vitamin K antagonist
For with CHADS2-VaSc ≥2 (sometimes also with 1 risk factor)
Goal INR 2-3
ARR 2.7% per year, NNT 37 in one year to prevent 1 stroke, NNT of 12
in pts with prior stroke.
Risk of stroke in pts with warfarin 1.66% annually
Pros: easy to monitor, easily reversible with Vitamin K, FFP, lower cost
compared to newer agents, once daily dosing, easy to use in patients
with CKD with CrCl <30 mL/min
Cons: multiple food-drug/drug-drug interactions; onset action is
typically 5-7 days, requires bridging, must monitor INR regularly, skin
necrosis
Dabigatran (Pradaxa)
Direct Thrombin Inhibitor-blocks both free and clot bound thrombin
RE-LY Trial established non-inferiority of dabigatran to warfarin
showed superior to warfarin in preventing ischemic and hemorrhagic CVAs with
reduced risk of major bleeding
Increased risk of GI bleeds
Dyspepsia most common side effect
Dabigatran at 150mg BID CVA risk/yr decreased from 4.5% to 1.1
CHADS=2, Dabigatran 150mg BID rather than adjusted-dose warfarin therapy
according to AT9 2012 Chest guidelines
Pros: no need for lab monitoring, No known drug-drug/food-drug interactions
Con: no reversal agent for major bleeding events, concern for renal impairment, BID
dosing, higher costs when compared to coumadin, unknown complete side effect profile,
need to use lower dose in pts with CrCl 15-30 mL/min
Rivoraxaban (Xarelto)
Selective/Reversible direct Factor Xa Inhibitor
Prevents conversion of prothrombin to thrombin
Rocket-AF trial showed similar major bleeding effect profile
overall to warfarin
Reduction in intracranial hemorrhage when compared to
warfarin
Pros: fast onset 2-4 hours, can reduce dosage in renal
impairment, daily dosing
Cons: no antidote, higher cost when compared to
coumadin, unknown complete side effect profile
Apixaban (Eliquis)
Direct Xa inhibitor
ARISTOTLE trial demonstrated superiority over
warfarin for major bleeding and overall outcome
Pros: can renally dose medication for CKD pts, fast
onset 3-4 hours
Cons: no antidote, BID dosing, higher cost when
compared to coumadin, unknown complete side effect
profile
Comparison of Agents
Case Revisited
Patient is a 65 yr old active male with HTN and CHF,
with a CHA2DS2-VASc score of 3 (HTN, CHF, age),
indicating his unadjusted yearly ischemic stroke risk of
3.2%
Class I recommendation to anticoagulate to prevent
CVA
Patient is healthy and no underlying renal impairment.
Discussion with cardiologist to initiate anticoagulation
with NOAG instead of coumadin based on active
lifestyle
Summary
CHADS2 and CHA2DS2-Vasc Scores are used for
calculation of stroke risk assessment in patients with
non-valvular Afib
When to initiate anticoagulation based on risk factors
Different types of Anticoagulation Agents used in
Atrial fibrillation
References
Uptodate.com: Topics: Anticoagulation in Atrial Fibrillation, Atrial fibrillation overview
Uptodate.com: Topics: Acute Management of Atrial Fibrillation
Uptodate.com: Topics: Rhythm Control vs Rate Control in Atrial Fibrillation
Uptodate.com: Topics: Surgical Management of Atrial Fibrillation
January, Craig T. et al. “2014 AHA/ACC/HRS Guideline for Management of Patient
with Atrial Fibrillation: Executive Summary." Journal of American College of Cardiology
(2014): n. pag. American College Cardiology Foundation. Web. 29 Sept. 2014.
http://content.onlinejacc.org/article.aspx?articleid
wmshp.org/sg_userfiles/Sarigianis_CE_10172013_handout.pptx
King, D, Dickerson, Sack J. Acute Management of Atrial Fibrillation: Part I. Rate and
Rhythm Control. Am Fam Physician. 2002 Jul; 66(2): 249-257.