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Anticoagulation Therapy in Patients with Afib

Why: thrombotic embolization (clot formation) can occur with any forms of Afib (paroxysmal, persistent or permanent) due to blood stasis. The most likely clinical manifestation of Afib is ischemic stroke. Patients with Afib are generally put onto Anti-coag therapy to prevent the incidence of embolization and stroke

Impact of Anticoagulation:

Numerous trials have shown that for patients with moderate to high risk Afib, that warfarin significantly reduces the incidence of thromboemoblic events. For patients with low risk Afib, not enough studies have been done to determine if there is any added benefit to long term coagulation. Stroke risk decreases by ⅔ as compared to placebo.

Major Bleeding Risk:

The major risk to be concerned with with any form of anticoagulation is the increased risk of bleeding, especially with Intracranial hemorrhage which is the most serious complication of increased bleeding.

Risk Stratification of Afib patients for Major Bleeding Events

Condition Points
C Congestive Heart Failure 1
H Hypertension (140/90) 1
A Age >75 years 2
D Diabetes Mellitus Type 2 1
S2 Prior stroke or thromboembolic event 2
V Vascular disease (PAD, MI, Plaque) 1
A Age 65-75 1
Sc Sex (female) 1

Annual Stroke Risk

CHADS2-VASc Score Stroke Risk
0 0
1 1.3
2 2.2
3 3.2
4 4.0
5 6.7
6 9.8
7 9.6
8 ??
9 15.2

Anticoagulation Recommendations Based on CHADS2-VASc score

Score Risk Anticogulation Considerations
0 Low None or ASA ASA 75-325mg if using
1 Moderate Oral Anticoag or ASA Either Rivaroxaban or Dibigatran or Warfarin controlled to an INR of 2-3 or ASA 75-325mg per patient preference (weak recommendation for anticoag)
2+ High Oral Anticoag Either Rivaroxaban or Dibigatran or Warfarin controlled to an INR of 2-3 or ASA 75-325mg per patient preference (strong recommendation for Anticoag)

Most practitioners prefer the new modalities (rivaroxaban, dibigatran, apixaban) due to convenience, small decrease in the incidence of intracranial hemorrhage, and less dietary/drug interactions. However, the disadvantages include lack of an antidote and higher cost.

Aspirin Monotherapy: The controversy

ASA use in low risk patients has not been very well addressed. The study to address this did find a 20% reduction in the risk of stroke, but these results were not statistically significant nor did they have a large sample size. ASA has been repeated shown to be inferior to Warfarin therapy in the prevention of thromboembolic events. Same has been shown for ASA plus Clopidogrel and ASA plus low dose Warfarin.

What is the Optimal antiplatElet and anticoagulant therapy in patients with oral anticoagulation and coronary StenTing (WOEST) trial was a randomized controlled trial (RCT) that investigated the ideal antithrombotic strategy in patients on OAC undergoing PCI.6 Patients scheduled to undergo PCI with a prior indication to continue OAC for at least one year were randomized to two antithrombotic strategies: double therapy, consisting of warfarin and clopidogrel 75 mg, or triple therapy, consisting of warfarin, clopidogrel 75 mg, and aspirin 80 mg.

Double therapy, which saw a significant reduction in the composite of death, myocardial infarction (MI), stroke, systemic embolism, target vessel revascularization, and stent thrombosis when compared to triple therapy

Triple Therapy had significant increase in risk of minor bleeding when compared with Double Therapy (skin and GIT bleeding)

There was no difference in Major Bleeding or Intracranial bleeding when comparing the 2 therapies

Registry data and the WOEST trial, these recommendations note that “clopidogrel plus [a vitamin K antagonist] appears to be the most sensible combination early after PCI in AF patients.”10 For now, it is prudent to avoid changing practice until these results are confirmed by larger trials,

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