warfarin & DOAC'S for VTE

Question 1

If a DVT is ‘likely’ (2 points or more)
a proximal leg vein ultrasound scan should be carried out within 4 hours

if the result is positive?

Answer 1

a diagnosis of DVT is made and anticoagulant treatment should start

Question 2

If a DVT is ‘likely’ (2 points or more)
a proximal leg vein ultrasound scan should be carried out within 4 hours
if the result is negative?

Answer 2

a D-dimer test should be arranged.

A negative scan and negative D-dimer makes the diagnosis unlikely and alternative diagnoses should be considered

Question 3

if wells score 2 or more than 2 &
a proximal leg vein ultrasound scan cannot be carried out within 4 hours?

Answer 3

D-dimer test should be performed and interim therapeutic anticoagulation administered whilst waiting for the proximal leg vein ultrasound scan (which should be performed within 24 hours)

Question 4

what does interim anticoagulation mean and what is given in context of dvt suspicion?

Answer 4

using an anticoagulant that can be continued if the result is positive.

this means normally a direct oral anticoagulant (DOAC) such as
apixaban or rivaroxaban

Question 5

if
wells score 2 or more, scan is negative
BUT
the D-dimer is positive
what are the next 2 steps (assuming they are on interim anticoag)?

Answer 5

stop interim therapeutic anticoagulation
AND
offer a repeat proximal leg vein ultrasound scan 6 to 8 days later

Question 6

SAQ Question
list 5 situations in which warfarin may be preferred over direct oral anticoagulants (DOACs), considering its advantages and limitations.

Answer 6

Renal Impairment

Poor Compliance

Prothrombotic
Conditions

Mechanical Heart Valves

Experience

Question 7

why may warfarin be preferred in Renal impairment?

Answer 7

when there is significant renal impairment (e.g., Cockcroft-Gault Creatinine Clearance (CrCl) <15 ml/min or those on renal replacement therapy) *where DOACs are contraindicated *due to potential accumulation and increased risk of bleeding.

Question 8

why may warfarin be preferred when there are compliance issues?

Answer 8

its anticoagulant effect can be monitored through regular INR testing.

allows for adjustments to be made based on the INR results

Question 9

why may warfarin be preferred when a pt has prothrombotic rf’s?

eg, antiphospholipid syndrome or recurrent venous thromboembolism (VTE)

Answer 9

has a well-established role in managing these conditions
and
has a long history of efficacy and safety data.

Question 10

why may warfarin be preferred in pt with mechanical heart valve?

Answer 10

whereas DOACs are generally contraindicated due to insufficient data supporting their safety and efficacy , warfarin has that data

Question 11

list 3 limitations of warfarin ?

Answer 11

**Requires regular INR monitoring **to ensure therapeutic levels, and adjustments may be needed in response to changes such as bleeding events or interactions with other medications.

interactions with dietary vitamin K, alcohol, and various medications so need to manage these factors

require Initial Heparinization
patients typically require heparin cover to provide immediate anticoagulation until warfarin reaches a therapeutic level

Question 12

list the 4 DOAC’s licenced to treat VTE?

Answer 12

apixaban
dabigatran
edoxaban
rivaroxaban

Question 13

name 2 doac’s that don’t require heparin cover?

Answer 13

apixaban + rivaroxaban

Question 14

why are dabigatran and edoxaban not 1st line for suspected vte?

Answer 14

requirement for heparin therapy at treatment initiation
and
the need for an SCA

Question 15

Specific scenarios where Dabigatran and Edoxaban may be preferred and why?

Answer 15

• lactose intolerance
• high bleed risk- (dabigtran can be used as it has an antidote)

Question 16

Why is it generally advised to discontinue antiplatelet drugs during the initial and short-term treatment with anticoagulants?

Answer 16

Antiplatelet drugs significantly increase the risk of bleeding complications when used in conjunction with anticoagulants. Therefore, it is recommended to discontinue antiplatelet therapy during the initial and short-term treatment period (up to 6 months) to reduce the risk of severe bleeding.

The only exception is if the patient has a recent (<12 months) acute coronary syndrome or coronary intervention, in which case the risk-benefit balance should be assessed with a Cardiologist.

Question 17

What protective measures might be considered when concomitant antiplatelet therapy is required with anticoagulants?

Answer 17

using a proton pump inhibitor (PPI) like lansoprazole or a
histamine receptor antagonist (H2RA) like ranitidine
to reduce risk of GI bleed