Synopsis
Select and monitor antithrombotic therapy, recognise prosthetic dysfunction and act safely on thrombosis or bleeding.
- Every mechanical valve requires lifelong vitamin K antagonist therapy; a DOAC is not an acceptable substitute.
- The INR target is valve- and patient-specific: a modern bileaflet mechanical aortic valve commonly targets 2.5, while a mechanical mitral valve or added thromboembolic risk commonly targets 3.0; older high-thrombogenicity valves need higher targets.
- A low INR risks valve thrombosis and embolism; a high INR risks bleeding. Use the implant record, valve position/type and risk factors to document one target explicitly.
Key red flags
Acute dyspnoea, pulmonary oedema, shock, embolus, new murmur or a softer/absent mechanical click is an emergency.
Investigation priorities
Measure current VKA effect and time in therapeutic range.
Management branches
After valve replacement or when reviewing an established prosthesis.
- Identify valve type, manufacturer, position, implant date and separate indications for anticoagulation.
- For any mechanical valve, use lifelong warfarin with a written target INR; do not use a DOAC.
Key medicines
WarfarinSmPC typical induction 10 mg once daily for 2 days and usual maintenance 3-9 mg once daily, but prosthetic-valve dosing must be individualised to INR; common targets are 2.5 for a modern bileaflet aortic valve and 3.0 for a mechanical mitral valve or added risk.
Aspirin75 mg by mouth once daily.