Anticoagulation in AF - Anja Drebes-SD

Anticoagulation in AF - Anja Drebes

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ADDr Anja Drebes

My name is Anja Drebes. I’m one of the Haematology Consultants at the Royal Free and the clinic lead for anticoagulation and thrombosis. And today I’ve talked about anticoagulation in patients with atrial fibrillation.

Non-valvular atrial fibrillation is the cause of about 50% of strokes and is an area where we can make a lot of impact with correct management. There is strong NICE recommendation now that patients with a CHA2DS2-VASc risk score of greater or equal one should be considered for anticoagulation therapy.

Anticoagulation options have widened now with the introduction of the newer direct oral anticoagulants and for me as a haematologist it’s important to help with safe introduction of these newer agents. So a switch to a newer direct oral anticoagulant should be considered if patients are intolerant to warfarin, if there is poor anticoagulation control on warfarin or if they have significant, technical or access difficulties with the monitoring.

When we talk about poor anticoagulation control, we are predominantly interested in patients with high INRs. So patients with an INR greater than eight or greater than five on two occasions over a six months period.

When we switch to the newer oral anticoagulants, there are several considerations. So in particular, these drugs are all renally excreted so it’s important so ensure that dosing is appropriate for renal function. And even though anticoagulant effect does not have to be monitored in these drugs, renal function has to be monitored on a regular basis. At least once a year for patients with good renal function, and more frequently for patients with impaired renal function.

With monitoring of the renal function, it’s important to use the calculated creatinine clearance based on the Cockcroft-Gault formulary rather than the estimated GFR which is available along with the U+Es because that might overestimate renal function.

Currently, warfarin is still the first-line anticoagulant in Camden, followed by rivaroxaban and dabigatran. Patients who refuse to be anticoagulated with warfarin, however, should be considered for one of the newer agents because they’re all NICE recommended and licensed for this indication and we have an obligation of care to our patients to ensure that they receive appropriate anticoagulation management.

There is prescribing guidance for rivaroxaban and dabigatran available on the intranet page and anticoagulation along with the NOAC referral proforma.

All anticoagulants are associated with an increased bleeding risk and that applies to warfarin as well as to the newer agents. So the main contraindications are conditions that would significantly increase the patient’s bleeding risk. And in addition, there are drug interactions with the newer agents, predominantly with azoles and HIV medication.

The newer agents have a much shorter half-life so adherence with the medication is important because missing doses can lead to treatment failure. And monitoring adherence will sit with primary care. Historically, anticoagulation management was a domain of secondary care. And with these new agents, it will be important that you develop integrated pathways across primary and secondary care to help with the safe management of these agents.

So prescribing advice for the newer agents along with the NOAC referral proforma and the clinical pathway guidance is available on the GP intranet under anticoagulation. In addition, you can contact the anticoagulation clinic at the Royal Free or myself directly if you have any further queries, and we are happy to help and advise.