[Is Atrial Fibrillation a Pre-Thrombotic State?]

Atrial fibrillation (AF) is said to be a pre-thrombotic state. In patients with AF, the left atrium is usually dilated and blood flow is sluggish, which enables the formation of a thrombus within the left atrium. This is consistent with two of Virchow's Triad, stasis of blood flow and endothelial injury, but the last of the Triad, hypercoagulability of blood, is difficult to explain in AF. There are reports that von Willebrand Factor (vWF), FVIII, fibrinogen, D-dimer, and Fragment 1+2 are elevated in AF patients. The important thing in the daily clinical setting is to identify high-risk AF patients who are prone to stroke and treat them with oral anticoagulants. Over the last 15 years, two well known criteria to predict the risk have been proposed. The first one is called CHADS2 and the second one is the CHA2DS2-VASc score. The CHADS2 score is a clinical prediction rule for estimating the risk of stroke in patients with non-valvular atrial fibrillation (NVAF). A high CHADS2 score corresponds to a greater risk of stroke, while a low CHADS2 score corresponds to a lower risk. The CHA2DS2-VASc score was proposed to complement the CHADS2 score by the inclusion of additional risk factors. These prediction rules are important because not all NVAF patients require oral anticoagulant therapy. There are disadvantages to taking oral anticoagulants, primarily bleeding complications. Therefore, even prediction rules of bleeding risks have been proposed to screen NVAF patients. In conclusion, it is difficult to predict a high-risk pre-thrombotic state among NVAF patients based only on laboratory findings. Practically, prediction rules will play a major role in the decision to start oral anticoagulant therapy.