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- prophylactic treatment for DVT (short-term)
- prophylactic treatment for hip surgery and surgery for femur fractures
(short to medium term)
- treatment of venous thromboembolism - deep vein thrombosis (DVT)
or pulmonary embolism (PE) (1)
- anticoagulation for 1 month is inadequate treatment after an episode
of VTE
- at least 6 weeks anticoagulation is recommended after calf vein thrombosis
and at least 3 months after proximal DVT or PE
- for patients with temporary risk factors and a low risk of recurrence
3 months of treatment may be sufficient
- for patients with idiopathic VTE or permanent risk factors at least
6 months anticoagulation is recommended
- target INR of 2·5 is recommended for long-term oral anticoagulant
(VKA) therapy for secondary prevention of VTE
- target INR of 2·5 is recommended for patients with DVT or PE associated
with antiphospholipid syndrome
- target of 3·5 is also recommended for patients who suffer recurrence
of VTE whilst on warfarin with an INR between 2·0 and 3·0
- cardioversion (1)
- target INR of 2·5 is recommended for 3 weeks before and 4 weeks after
cardioversion
- to minimise cardioversion cancellations due to low INRs on the
day of the procedure a higher target INR, e.g. 3·0, can be used
prior to the procedure
- peripheral arterial thrombosis and grafts
- antiplatelet drugs remain first line intervention for secondary antithrombotic
prophylaxis. If long-term anticoagulation is given to patients at high
risk of femoral vein graft failure a target INR of 2·5 is recommended
(1)
- coronary artery thrombosis
- if oral anticoagulant therapy is prescribed a target INR of 2·5 is
recommended (1)
- systemic embolism after MI
- mitral stenosis with embolism (long term)
- atrial fibrillation (long-term) - it may be safer to aim for an
INR of 2 in those aged over 75 years (3)
- risk of stroke is 3 times greater in patients with atrial fibrillation
with mitral stenosis than in those without valve disease - based on
its apparent effectiveness in non-randomized studies and its effect
in non-rheumatic atrial fibrillation, warfarin is usually given to maintain
an INR of 2.5 (5)
- treatment of recurrent DVT, PE (long term)
- target of 3·5 is also recommended for patients who suffer recurrence
of VTE whilst on warfarin with an INR between 2·0 and 3·0
- prosthetic heart valves (long-term)
- for patients in whom valve type and location are known specific target
INRs are recommended (1)
- bileaflet valve (aortic) 2·5
- tilting disk valve (aortic) 3·0
- bileaflet valve (mitral) 3·0
- tilting disk (mitral) 3·0
- caged ball or caged disk (aortic or mitral) 3·5
- otherwise a target INR of 3·0 is recommended for valves in the aortic
position and 3·5 in the mitral position (1)
Notes (1):
-
bioprosthetic valves:
- long-term warfarin not required in absence of atrial fibrillation
- oral anticoagulants are not required for valves in the aortic position
in patients in sinus rhythm, although many centres anticoagulate patients
for 3?6 months after any tissue valve implant
- patients with bioprostheses in the mitral position should receive
oral anticoagulants to achieve an INR of 2.5 for the first 3 months.
After 3 months, patients with atrial fibrillation should receive lifelong
therapy to achieve an INR of 2.5
- patients with bioprosthetic valves with a history of systemic embolism
and those with intracardiac thrombus should also be anticoagulated
to achieve an INR of 2.5
- patients who do not require oral anticoagulants after the first
3 months may be considered for antiplatelet therapy, e.g. aspirin
- INR values and risk of haemorrhage versus risk of thromboembolism in
treatment of DVT/PE
- risks of haemorrhage and thromboemboli are minimized at international
normalized ratios of 2-3. Ratios that are moderately higher than this
therapeutic range appear safe and more effective than subtherapeutic ratios
(6)
Reference:
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