A 68-year-old man undergoes successful mechanical prosthetic aortic valve replacement for severe aortic valve stenosis. After the procedure, he is started on an oral medication and instructed that he should take it for the rest of his life and avoid consuming large amounts of dark-green, leafy vegetables. Which of the following laboratory parameters should be regularly monitored to guide dosing of this drug?

Question

Quizplus · Accepted Answer

Eductional Objective: Prothrombin time (PT) should be regularly monitored in patients on warfarin. Warfarin inhibits synthesis of the vitamin K-dependent factors (factors II, VII, IX, and X, protein C, and protein S) by interfering with the activity of vitamin K epoxide reductase. It is used in patients with mechanical prosthetic heart valves to prevent thrombosis within the valve. The classic laboratory change seen in patients taking warfarin is a prolonged PT (often represented by the INR); routine monitoring of the PT is, therefore, used to guide therapy.

A 68-Year-Old Man Undergoes Successful Mechanical Prosthetic Aortic Valve Replacement