The nurse is caring for a patient with the rhythm below who asks why she needs to take warfarin. Which statement best answers the patient's question?

Atrial fibrillation is characterized by uncoordinated atrial activity and a lack of effective atrial kick. This leads to blood stasis within the left atrial appendage, significantly increasing the risk of thrombus formation and subsequent embolic events, such as ischemic stroke or systemic arterial occlusion, necessitating long-term anticoagulant therapy for high-risk patients. A. Warfarin is an anticoagulant and does not possess inotropic or chronotropic properties that would directly increase cardiac output. Cardiac output is improved by controlling the heart rate or restoring sinus rhythm with medications like beta-blockers, calcium channel blockers, or through electrical cardioversion, rather than by thinning the blood. B. Warfarin does not influence the electrical conduction system of the heart and cannot prevent the transmission of atrial impulses to the ventricles. Its sole mechanism of action in this context is to inhibit the vitamin K-dependent synthesis of clotting factors, thereby reducing the physiological ability of the blood to form stable clots. C. In atrial fibrillation, the atria quiver instead of contracting forcefully, allowing blood to pool and stagnate. This stasis triggers the coagulation cascade, leading to the formation of mural thrombi. Warfarin provides systemic anticoagulation to prevent these clots from forming, which is the primary strategy for reducing the risk of a thromboembolic stroke. D. The ejection fraction is a measure of the percentage of blood leaving the heart each time it contracts and is largely a function of ventricular muscle health. Warfarin does not affect myocardial contractility or ventricular volume, and therefore has no direct clinical impact on increasing a patient's ejection fraction percentage.