Therapeutics – Cardiovascular System Practice Test

The main idea is that mechanical heart valves are highly thrombogenic, so warfarin needs to be aimed at a higher INR to prevent valve thrombosis, whereas nonvalvular atrial fibrillation uses a lower INR target to balance stroke prevention with bleeding risk.

For most mechanical valves on warfarin, the therapeutic INR range is about 2.5 to 3.5. In some high-risk situations, clinicians may target up to 4.0, but 2.5–3.5 is the typical, widely accepted range. Nonvalvular atrial fibrillation generally targets an INR of 2.0 to 3.0, which provides effective stroke prevention while keeping bleeding risk reasonably manageable.

Thus, the combination of 2.5–3.5 for mechanical valves and 2.0–3.0 for nonvalvular AF aligns with standard practice and explains why that pairing is the best-fit answer.