- Dr. Mattias Berg MD CCFP(EM)
A. Fib: Do you know how to choose the right anticoagulant?
As it is estimated that up to 20% of strokes are the result of atrial fibrillation, it is important to consider the need for anticoagulation for your patients. That said, in the last few years a number of novel oral
anticoagulants (NOACs) have emerged onto the market providing therapeutic alternatives to that of warfarin in nonvalvular atrial fibrillation.
Valvular? Use Warfarin
Warfarin remains the only approved therapy in cases of valvular atrial fibrillation. The principal advantages of these agents lies in their lack of regular therapeutic monitoring and fewer interactions with diet or other medications. Relative downsides of these newer agents include increased cost, lack of long-term safety data, and lack of reversal agents in cases of severe or life-threatening bleeds.
ASA or Warfarin?
Prior to the initiation of any new therapies for your patients, it is always important to weigh the relative risks and benefits. Although a number of risk tools are available, the most widely recognized for estimating ischemic stroke risk in atrial fibrillation is the CHADS2 score (could you list these categories from memory?):
C - CHF
H - Hypertension
A - Age > 75
D - Diabetes
S2 - Stroke / TIA / Embolism
As the CHADS2 increases, the annual risk of ischemic strokes increases proportionally and hence a score greater than 1 would warrant consideration of anticoagulant therapy, whether it be warfarin or a NOAC.
Newer guidelines recommend that oral anticoagulants be used in patients age 65 and above.
Conversely, in low risk (CHADS2 = 0) patients antiplatelet agent such as ASA may be considered as an alternative.
Assess Bleed Risk
Finally, be sure to use a tool such as HASBLED to consider if the risk of anticoagulation outweighs the benefit.
H - Hypertension A - Abnormal renal and liver function S - Stroke
B - Bleeding L - Labile INRs E - Elderly D - Drugs or alcohol
EXAM TIP: Treat the patient, not the number
Don't forget that on an oral exam (and in real life) the most important consideration is what the patient wants. Provide them with information about the risks and benefits, and add your recommendation, but be sure to take the patient's goals and values into consideration if you want to prove you can be a capable and competent family physician.