Soru

A $55$-year-old man is evaluated in the neurointensive care unit for right lower extremity swelling. Five days ago, he was admitted for a spontaneous subarachnoid hemorrhage. His past medical history is significant for a mechanical aortic valve replacement performed three years ago, for which he takes daily warfarin. Upon admission, his international normalized ratio (INR) was $3.2$, and his coagulopathy was appropriately reversed with four-factor prothrombin complex concentrate and intravenous vitamin K. A follow-up non-contrast computed tomography scan of the head obtained yesterday showed a stable hemorrhage with no expansion.

Today, physical examination reveals new-onset, non-pitting edema and tenderness of the right calf and thigh. Venous duplex ultrasonography of the right lower extremity demonstrates a non-compressible thrombus extending from the popliteal vein into the right superficial femoral vein. Vital signs are temperature $37.2^\circ\text{C}$ ($99.0^\circ\text{F}$), blood pressure $140/85$ mm Hg, heart rate $88$/min, and respiratory rate $16$/min. Oxygen saturation is $98\%$ on room air.

Which of the following is the most appropriate next step in management?