**Core Concept:** Antiphospholipid syndrome is a rare autoimmune disorder characterized by the production of antiphospholipid antibodies that can lead to pulmonary embolism and arterial thrombosis. Warfarin is a vitamin K antagonist used to prevent and treat thromboembolic events in patients with a history of antiphospholipid syndrome.

**Why the Correct Answer is Right:** In this scenario, the patient presents with a saddle embolus, deep vein thrombosis, dyspnea, hypotension, and tachypnea. The patient has been non-compliant with warfarin therapy, which highlights the importance of medication adherence in managing the underlying condition and preventing thromboembolic events. Although she initially responds poorly to heparin and fluids, these treatments are supportive measures and not specifically targeting the underlying condition.

**Why Each Wrong Option is Incorrect:**

A. Heparin is a short-acting anticoagulant that can be effective for treating acute thromboembolic events but is not a long-term therapy for antiphospholipid syndrome. Additionally, the patient's poor response to heparin and fluids further support the need for warfarin therapy.

B. Fluid therapy is supportive treatment for acute dyspnea and hypotension but does not address the underlying antiphospholipid syndrome and thromboembolic event.

C. Although the patient has RV hypokinesis on echocardiogram, this finding is nonspecific and does not directly address the antiphospholipid syndrome and its thromboembolic manifestations.

D. Warfarin is the appropriate therapy for antiphospholipid syndrome, as it is a long-term anticoagulant that helps prevent recurrent thromboembolic events.

**Clinical Pearl:** In patients with antiphospholipid syndrome, antithrombotic therapy with warfarin is essential to prevent recurrent thromboembolic events, despite the patient's initial poor response to heparin and fluid therapy. Echocardiography findings can be nonspecific and do not directly address the primary diagnosis.