Poor TTR Switch to DOAC — RACP Adult Medicine MCQ

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EasyClinical PharmacologyPoor TTR Switch to DOACRACP Adult Medicine

A 62-year-old man with heart failure and AF is on warfarin. His INR has been labile with time in therapeutic range (TTR) of 40%. He has no contraindications to DOACs and no mechanical valve. His CrCl is 55 mL/min. What is the recommended action?

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Correct answer: C — Cease all anticoagulation

For patients on warfarin with poor TTR (<65%), switching to a DOAC is recommended as DOACs provide more consistent anticoagulation without routine monitoring. The SAMe-TT₂R₂ score can predict which patients will have poor TTR on warfarin and thus benefit more from switching to a DOAC. In this patient with no contraindications (no mechanical valve, no significant valve disease, CrCl >30), a DOAC is strongly preferred. Apixaban has the best safety profile for bleeding in elderly patients with CKD (ARISTOTLE trial). The 2018 Australian AF guidelines and 2025 ACS guideline support this approach.

Reference: NHF/CSANZ – 2018 – AF Guidelines; eTG – 2025 – Cardiovascular